Search

• Combined effects of extruded brick compositions with paper sludge and expanded perlite were characterized. • The use of additives in bricks has significantly affected their thermo-physical and mechanical properties. • The effects of process parameters on brick properties were investigated with a new mathematical modeling approach. • Fired brick samples showed good thermal insulation performance. • Produced exruded bricks have good potential for energy saving. Lightweight bricks produced with addition of different additive materials such as expanded perlite (EP) and recycling paper sludge (RPS) waste have been accomplished by a pug mill. Porous fired bricks were produced by using organic and inorganic additives such as paper waste and expanded perlite as pore-makers. In the experimental study, the seventeen mixture sets were prepared with Box-Behnken experimental design procedure of two additive ratios and firing temperatures. The brick samples were produced with shaping by extrusion method and firing at 850, 950 and 1050 °C for two hours after drying. Physical characteristics such as bulk density, apparent porosity and water absorption, and also, compressive strength, thermal conductivity and microstructural properties of brick samples were studied. Influences of process parameters on brick properties were investigated with a detailed neuro-regression analysis. In conclusion, the best brick composition (10 % EP + 10 %RPS by weight) in terms of thermal conductivity corresponding to acceptable mechanical properties was optimized. Accordingly, the compressive strength values of all samples are around 10 to 27 MPa. Also, the samples with high additive content (especially 10 %RPS + 5 %EP sample) exhibited the lowest thermal conductivity value (0.432 W/mK) due to the low firing temperature. [ABSTRACT FROM AUTHOR]

Abstract: Recycle paper mills (RPM) contribute 30% of total pulp and paper mill segment in India. With 85% average efficiency of RPM, 5% waste (RPMW) is produced annually. RPMW which otherwise is land filled has been utilized to make construction bricks that serves a purpose of solid waste management, new revenue generation and earning carbon credits. RPMW-cement combination low carbon foot print bricks with varying composition of cement (0–20%wt) have been prepared and tested as per ASTM C 67-03a standards. RPMW has been characterized using X-ray fluorescence (XRF), thermogravimetric and differential thermal analysis (TG–DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). TG–DTA confirms thermal stability till 280°C whereas SEM monographs show the pores and fibrous nature. From experimentation it is observed that waste-create bricks (WCB) prepared using RPMW-cement combination is light weight, shock absorbing and meets compressive strength requirements of ASTM C 67-03a. The brick making procedure being simple can be undertaken as rural entrepreneurship by unskilled labors of developing countries. [Copyright &y& Elsevier]

Abstract: This paper presents results of an investigation into the potential use of recycling paper mill waste-water to replace mixing water in cement mortar systems for manufacturing concrete masonry products. The physical and mechanical properties of mortar containing various amounts of de-inking waste-water were consequently investigated. A key finding of this study was that replacing mortar mixing water with waste-water significantly improved workability and consistency of cement mortar mixtures. In particular the flow of mortar mixtures increased with increase of waste-water content up to 50% and then levelled off when waste-water content exceeded 50%. Correspondingly, the flow of mortar mix with 100% waste-water replacement at water/cement ratio of 0.50 was found to be equivalent to that of the reference mortar mix with 100% potable water at water/cement ratio of 0.60, indicating potential use of de-inking waste-water as water reducing admixture. The enhanced workability arising from waste-water addition however induced changes in mechanical properties of the hardened material. Compared to reference mortar, replacing 10% and 100% potable water respectively resulted in 19% and 60% reduction of compressive strength, with a corresponding 5% and 16% drop in bulk density, and up to 19% increase in drying shrinkage. Also, water absorption and volume of permeable voids increased with increasing waste-water dosage, albeit marginally. The benefits derived from rheology improvements compared to compromises in mechanical properties due to de-inking waste-water addition strongly indicate clear potential of using de-inking waste-water in production of lightweight cementitious building and masonry elements. [Copyright &y& Elsevier]

• An innovative viscosity-modifying admixture (VMA) is produced from paper pulp. • The versatility of using milled paper pulp as a VMA in cement composites is validated. • The mechanism of viscosity modifying action of milled paper pulp is elaborated. • A new parameter is proposed to quantify nonlinearity induced by VMAs. In this paper, we report the performance of paper pulp as an innovative viscosity modifying admixture (VMA) for cement composites. Two different levels of fineness were obtained by mechanical milling of the same source of paper pulp. Their effects on viscosity modification, hydration kinetics, autogenous shrinkage, and compressive strength of cement grouts were measured, and their structural integrity at high pH was assessed. A new parameter was proposed to quantify nonlinearity induced by VMAs. Results showed that the hierarchical structure of paper pulp makes it possible to activate bridging flocculation and swelling mechanisms of hydrophile paper pulp fibers at different levels to produce versatile VMAs. The coarser milled paper pulp fibers mainly influences the plastic viscosity. By contrast, the milled paper pulp consisting of ultra-fine fibers significantly modifies both plastic viscosity and dynamic yield stress, induces more nonlinearity in the mixtures, and increases compressive strength of mortars at low dosages. [ABSTRACT FROM AUTHOR]

Abstract: The texture of the C–S–H gels formed in ternary cement blends containing thermally activated paper sludge (APS), fly ash (FA) from coal combustion and Ordinary Portland Cement (OPC) was studied by means of the specific surface area (SSA) and pore-size distribution (PSD), which were measured by the sorption isotherms of nitrogen gas and the BET method. Two differentiated zones in the PSD of the C–S–H gel at ∼10–20nm and ∼5nm were observed. The proportion of such zones depends on the age of hydration and amount of OPC replacement. The incorporation of the additions (APS and FA) clearly revealed an increase in both porosity and SSA. This effect decreased with the progress of hydration together with a refinement of the nano-porous structure of C–S–H. High correlations were found among these nanostructure characteristics of the C–S–H gel and mechanical strengths. [Copyright &y& Elsevier]

• Paper and pulp residues are used for manufacturing adobe bricks. • Compressive strength is increased up to 190% for 12.5% of replacement. • Thermal conductivity is reduced approx. 30% for 12.5% of replacement. • The water resistance complies with standards up to 12.5% of replacement. • Toxicity values meets the standards up to 20% of replacement ratio. Soil-based building material has been used since ancient times but lately it has been mainly considered for restoration purposes of traditional architecture instead of an eco-friendly construction material for new buildings. However, the promotion of a more sustainable architecture has recently led to look towards adobe or rammed earth, among others. Because of the high impact of concrete and the fired clay brick industry, mainly due to the use of clinker and the firing process, respectively, adobe may highly reduce the ecological footprint of conventional construction and building materials. In addition, the use of fibers for adobe reinforcement has been also highlighted as a key factor for improving adobe performance. Obviously, when residues successfully replace such fibers the ecological footprint may be reduced even more. Thus, this research focuses on the assessment of adobe reinforced with paper and pulp industry residues (PPR) with the aim of demonstrating the feasibility of this construction material. Several series have been made by varying the replacement percentage up to 20% and technological properties and toxicity have been assessed. It is concluded that compressive strength may be improved up to 190% while thermal conductivity is reduced approx. 30% for 12.5% of PPR replacement. Besides, adobe meets standards related to water resistance and toxicity values. [ABSTRACT FROM AUTHOR]

Abstract: This study was to develop a new building material, Wood-Crete, using sawdust, waste paper and Tradical lime. The paper presents the processing technologies, factors which affect the performance of the developed composites, and properties of Wood-Crete. The results showed that lightweight sustainable blocks can be produced with good insulating and other relevant properties for building construction with density ranging from 356 to 713kg/m3 and compressive strength from 0.06 to 0.80MPa. The properties were closely related to the composition of Wood-Crete with an addition of waste paper being a dominant influence on both strength and thermal conductivity, reflecting its effect on the structure of composite and contribution of self strength of paper fibres. The combined effect of sawdust and waste paper and Tradical lime had a direct effect on the strength properties of Wood-Crete. Of significant importance was the contribution of self strength of Wood-Crete due to the influence of the size of sawdust particles used. The developed Wood-Crete was able to withstand considerable amount of impact load and considered, like hempcrete, most suitable for wall panelling or other non- and semi-structural applications with good thermal insulating properties. [Copyright &y& Elsevier]

• Potential of using a PSAS to improve the properties of sand for use as a backfill material. • Appropriate water content w of the PSAS-treated sand reduces the swelling potential of PSAS treated sand. • Significant lower strength development of PSAS-treated sand compared with OPC-treated sand under same mixing conditions. • PSAS-treated sand is a suitable replacement of OPC-treated sand. • XRD profiles show that the formation of CaCO 3 is dominant in the PSAS-treated. The aim of this study is to investigate the potential of using a paper sludge ash-based stabilizer (PSAS) to improve the properties of sand proposed to be used as a backfill material around underground pipes. The swelling potential and strength of the sand treated with PSAS are investigated by conducting a series of laboratory tests. Similar tests are conducted on sand treated with ordinary Portland cement (OPC). Swelling potential tests show that the PSAS-treated sand with a water content of 0% show significant expansion during soaking, similar to the OPC-treated sand. However, the test results reveal that an appropriate moisture content of the PSAS-treated sand reduces its potential for expansion, depending on the duration of its temporary placement at the construction site. Unconfined compression tests show that the compressive strength of the PSAS-treated sand is significantly lower than that of the OPC-treated sand under the same mixing conditions, even though the chemical composition of PSAS is relatively similar to that of OPC. The increase in compressive strength with the curing time is more gradual in the PSAS-treated sand than in the OPC-treated sand, suggesting that the former is easier to re-excavate. X-ray diffraction profiles showed that the formation of calcite is dominant in the PSAS-treated sand, and that berlinite may be an additional contributor to the increase in strength of PSAS-treated sand in the long term. [ABSTRACT FROM AUTHOR]

• Statistical models were developed for proportioning wastepaper sludge ash CLSMs. • The impacts on the properties of CLSMs of the mix design parameters were evaluated. • Parameters of the mix design are designed for satisfactory CLSM properties. • Robust mixtures of CLSM that meet DOT requirements are stated. • The proposed models are beneficial techniques for the design of practical applications for CLSMs. This study aims to create robust controlled low-strength material (CLSM) mixes of wastepaper sludge ash (WSA) binders and recycled fine aggregates (RFAs). A factorial design was carried out to mathematically model the effect of three main mix design parameters on the plastic and hardened properties of wastepaper sludge ash CLSM (WSA-CLSM) mixtures. The criteria were the ratio of water to cementitious materials (w/cm), the proportion of WSA replacement content, and the total cementitious material (cm) content. Flowability, bleeding, segregation, initial stiffening time, densities, water absorption, and unconfined compressive strength were the derived statistical models' responses. With the intention of extracting the statistical models, twenty mixes were prepared, and ten mixes were used to validate the precision of the produced models. The models are valid for mixtures of 2.53 to 2.73 w/cm, 50 to 100% of WSA (by total cm content) and 160 to 200 kg/m3 of total cm content. The regression methods were synthesised and analysed by classifying the key factors and their correlations to measure their properties in terms of the impacts of w/cm, WSA% and total cm content. Three optimum WSA-CLSM mixtures with significant positive desirability were formulated and tested using the established models. Robust WSA-CLSMs that meet the Department of Transportations (DOTs) specifications for CLSM backfill material classifications may be developed. [ABSTRACT FROM AUTHOR]

• Wood ash from Alberta's pulp and paper industry is used in lieu of Portland cement. • Cement-based foams are cast to achieve density ranging from 1000 to 1400 kg/m3. • Mechanical, thermal and acoustic properties are examined here. • Wood ash lowers thermal conductivity and noise, with minor drop in strength. • For indoor insulation, wood ash may replace cement at 10% for optimal effect. This study characterizes a Portland cement based cellular system prepared with a preformed foam. Wood ash, locally sourced from pulp and paper mills, was first characterized and later, blended at up to 20% of the binder. The resulting mixtures were cast at three densities between 1000 and 1400 kg/m3 and examined for mechanical, thermal and acoustic properties. A phase analysis was performed using X-ray diffraction to identify the components of the wood ash and again, in the hydrated system. The thermal constants were measured using the Transient Plane Heat Source (TPS) technique per ISO 22007-2. Sound absorption and noise reduction coefficients were evaluated using the impedance tube method per ASTM C384-04. The results show that although blending wood ash led to lower compressive strength and elastic modulus, the drop in strength was within 20%. While not as effective in reducing noise, the wood ash led to 20% lower thermal conductivity. These findings offer wood ash as a viable, replenishable and sustainable substitute for Portland cement in insulating foams. [ABSTRACT FROM AUTHOR]

Abstract: Kaolin, one of the materials of major importance for the ceramic and paper industry, is also used in the construction industry as a raw material for the production of white cement clinker and, in the form of metakaolin, as an artificial pozzolanic additive for concrete. Metakaolin is a vital component of high-performance and architectural concrete; however, its application in regular concrete is very limited due to relatively high production costs. This report evaluates the performance of a low-cost metakaolin-based additive called thermally activated kaolin (TAK), in cement. Due to its pozzolanic properties and the densification of cement matrix, the application of TAK provides a 15% improvement of the compressive strength. It was shown that TAK of optimal quality can be manufactured by the thermal treatment of raw kaolin with 74% of kaolinite at 750°C without the intermediate beneficiation stage. The application of a developed approach can significantly reduce production expenditures and make the application of such an additive feasible even in regular-grade cement and concrete. [Copyright &y& Elsevier]

Utilizing nano-SiO 2 (NS) to reinforce the old mortar and the weak interfacial transition zone (ITZ) in recycled coarse aggregate (RCA) is a productive approach to enhance the quality of RCA. Throughout this paper, RCA was immersed in NS solutions with different concentrations (2, 5, 10 and 30 wt%). Subsequently, a systematic evaluation of the crushing index and water absorption of the treated NS modified recycled coarse aggregate (SRCA) was conducted. In addition, the calcium hydroxide (CH) content of RCA before and after modification was analyzed by Thermogravimetric and Differential Thermal Analysis (TG-DTA) curves. This study finds that the performance of SRCA modified with 2% concentration achieves comparable modification effects to other concentrations. Additionally, this paper delves into the impact of NS powder on the slump characteristics and compressive strength of concrete. Considering the above research and economic costs, this study adopts 2% concentration of NS for RCA modification and further investigates the stress-strain relationship of NS modified recycled aggregate concrete (SRAC) with various SRCA replacement ratios. Moreover, this paper establishes mesoscopic models of SRAC for various replacement rates and proposes constitutive models corresponding to these rates. The results indicate that when the SRCA replacement rate is within 60%, the stress-strain curve shape of SRAC closely resembles that of natural aggregate concrete (NAC); when the replacement rate exceeds 60%, the descending segment of the SRAC stress-strain curve becomes more precipitous, showing a higher tendency towards fragility in the concrete. ● Nano-SiO 2 can be used to improve the properties of recycled coarse aggregates. ● NS powder affects the slump and compressive strength of recycled concrete. ● As the concentration of NS solution increases, the compressive strength of concrete increases. ● Mesoscopic models of modified recycled concrete were established and constitutive models were proposed. [ABSTRACT FROM AUTHOR]

This study proposed a procedure to optimize the mixture proportion of geopolymer using machine learning (ML) and multi-objective optimization (MOO) model, which enhances the compressive strength and minimizes the carbon emission and costs. The experiment was preliminary carried out to analyze the workability, compressive strength, microstructure, and pore characteristics of fly ash/slag-based geopolymer. The results showed that the higher replacement ratio of slag established positive effects on the hardening as well as porosity improvement due to the coexistence of C-S-H and NASH-type binders, especially for a ratio was no more than 60%. Considering the performance of geopolymers is often influenced by multiple factors such as material composition and curing conditions, which could not be solved by traditional methods. A database containing 836 samples was established to analyze the prediction performance of 7 ML models by using Bayesian optimization. The GPR model has good generalization ability, with R 2 being 0.99 (0.99) on the testing set (training set). Furthermore, the reliability of the ML models was evaluated by the tests conducted in this paper. The feature importance analysis utilizing SHAP method indicates that Age, HM, and SS are key parameters influencing the compressive strength of geopolymer. The proposed MOO model can effectively evaluate the trade-offs between compressive strength, carbon emission, and costs, and all Pareto solutions for bi-objective and three-objective provided the optimal mixture schemes. On this basis, the design procedure proposed in this paper can give the scheme of geopolymer materials with different requirements (given mixture scheme and given design strength). [Display omitted] • Working mechanism of different matrix on geopolymer are revealed. • SHAP method can explain the physical mechanism of parameter on the output variable. • Reliability of the intelligent prediction model is validated by experiment. • MOO model can evaluate the relationship between CS, CO 2 and costs of geopolymer. • Procedure of geopolymer mixture schemes with different design strength are proposed. [ABSTRACT FROM AUTHOR]

The development of ultra-high performance concrete (UHPC) with lower carbon emission has conducted by many researchers. However, there is a lack of quantitative comparison of carbon reduction efficiency, such as carbon emission and energy consumption values, of UHPC materials with various components. This paper reviews the trends toward lower-carbon UHPC based on Life Cycle Assessment related to the used materials, especially different binders, aggregates, and steel fibers. The environmental indicators, including embodied carbon emissions (EC), embodied energy consumption (EE), and embodied CO 2 index (CI) value, of UHPC mixtures in published paper are discussed. Since compressive strength is an important indicator, the minimum value of compressive strength of UHPC should be greater than 120 MPa in the assessment process. Moreover, the effectiveness of using various low-carbon alternatives is discussed and then ranked according to the reduction degrees of EC and EE. Results found that ultra-high performance geopolymer concrete (UHPGC) shows the lowest EC and EE and the highest CI. This indicates that UHPGC has decreased carbon emissions without compromising compressive strength. The use of supplementary cementitious materials and recycled powder obtained from waste aggregates to substitute cement is another effective way to reduce EE and EC. However, using waste aggregates or waste fibers to replace conventional aggregates or steel fibers is less efficient than cement replacement with supplementary cementitious materials (SCMs). Especially, the use of waste aggregate leads to negligible reductions in EC and EE. The study seeks to find out the most promising route for low-carbon UHPC in the circular economy through identifying low-carbon alternatives, which has great significance in designing low-carbon UHPC. • Multiple strategies to develop lower-carbon UHPC are reviewed. • The environmental impacts of different UHPC are systematically calculated based on LCA at a material level. • These strategies are discussed and ranked based on performances and environmental impacts. • The most effective strategy for developing lower-carbon UHPC is indicated. • Perspective for how to develop lower-carbon UHPC is given. [ABSTRACT FROM AUTHOR]

High-strength steel reinforced concrete (HSRC) columns configured with T63E/E/G rebar (whose yield strength is 630 MPa) have significant advantages such as less steel consumption and higher load carrying capacity. However, the compressive strength level of T63E/E/G rebar in HSRC columns under eccentric compression with a large eccentricity (LEC-HSRC) and the eccentric load carrying capacity calculation model is not precisely determined yet. In this paper, 11 LEC-HSRC columns were tested, then the test results and sectional stress state are discussed in depth. The results show that the compressive strength of T63E/E/G rebar could be fully utilized in LEC-HSRC columns, thus the compressive strength design value of T63E/E/G rebar in Technical specification for application of new heat-treatment high-strength ribbed bar in concrete structures DBJ 61/T 157–2019 was revised to 545 MPa accordingly, to the same level as the tensile strength design value. It's conservative to calculate the eccentric load carrying capacity of LEC-HSRC columns according to Code for design of concrete structures GB 50010–2010. A new eccentric load carrying capacity calculation model, which satisfies both the static equilibrium and strain compatibility condition, was proposed based on stirrup confined concrete constitutive relation, and it has higher accuracy compared with currently used models. The assumption that the strain at the edge of the compression zone of core concrete reaches the peak under ultimate load can suitably calculate the compressive stress of T63E/E/G rebars in LEC-HSRC columns. This paper offers experiment and theory support for the revision of DBJ 61/T 157–2019 and the engineering application of T63E/E/G rebar in China. • T63E/E/G high-strength rebar's compressive strength level in LEC-HSRC columns is experimentally and theoretically studied. • An eccentric load carrying capacity calculation mode based on the stirrup confined concrete constitutive relation is proposed. • The compressive strength design value of T63E/E/G rebar is revised from 435 MPa to 545 MPa in standard DBJ 61/T 157-2019. • The strain at the edge of the compression zone of core concrete reaches the peak under ultimate load. [ABSTRACT FROM AUTHOR]

Geopolymer concrete is a sustainable replacement to the Ordinary Portland Cement (OPC) concrete as it mitigates some of the associated problems of OPC manufacturing such as greenhouse gas emission and natural resource depletion. There has been significant recent research in the design of fly ash-based geopolymer concrete using advanced machine learning techniques which can address some of the problems with classical mix design approaches. However, practical application of geopolymer concrete is limited due to lack of standard mix design procedure. This comprehensive review summarizes the current literature on machine learning methodologies to predict the compressive strength of fly ash-based geopolymer concrete. Firstly, the input parameters used for the machine learning model development are categorized based on feature selection or feature extraction. Secondly, available machine learning approaches are categorized based on analysis methods namely, nonlinear regression, ensemble learning, and evolutionary programming. The effect of hyperparameters on the individual model performance, and model comparison based on the prediction performance are also discussed to identify potentially more suitable model type and hyper parameter ranges. Further, the paper discusses the input variable's sensitivity towards the model performance which provides guidance towards future model developments. Overall, this paper will provide an understanding of the current state of machine learning approaches to predict the compressive strength of geopolymer concrete and the gaps in research for the development of models and achieving the required performance. Hence, the summarized knowledge will be highly beneficial to design prospective research towards sustainable cement-free concrete using fly ash. • Artificial neural networks (ANN) predict geopolymer concrete strength well, offering reliable forecasts for new data. • Support vector machines and random forests offer ANN- like performance, serving as alternatives in machine learning (ML). • The success of ML model relies on proper selection of inputs and tuning hyperparameters for optimal performance. • The chemical, physical, and mineralogical characteristics of fly ash emerge as pivotal input variables in ML models. • Validating models through laboratory experiments is imperative, ensuring generalization for real-world applications. [ABSTRACT FROM AUTHOR]

• EOS of concrete specimens was determined from high pressure hydrostatic tests. • The effect of different mixtures at same compressive strength was examined. • Mix parameters were: water content, coarse aggregate amount and max aggregate size. • It was proven that EOS depends on mix properties and not on compressive strength. • The differences between hydrostatic and oedometric based EOS were determined. High intensity impact loading on a concrete structure induces three dimensional high intensity stresses, the analysis of which requires appropriate constitutive relationships describing the isotropic and deviatoric stress components. The isotropic component known as the hydrostatic relationship or the equation of state (EOS) is in the focus of this paper. The literature relates the EOS of concrete to its uniaxial compressive strength. This paper aims at refuting this relationship and validating the conjecture that the EOS depends on the concrete mixture. For that purpose, different concrete mixes of equal strength have been tested. The mixture parameters are the water content (with the same w/c ratio), the coarse aggregate content and the maximum aggregate size. Using a unique test setup, hydrostatic tests were carried out to extremely high pressures at the 1GPa level. The results clearly show the pronounced differences between EOS curves representing different mixtures having the same concrete strength, thus validating the above conjecture. As the EOS is sometimes derived from oedometric tests, the present investigation exploited oedometric tests results on exactly the same concrete mixtures and strength to compare the hydrostatic and oedometric resulted EOS curves. The comparisons show that for most cases the stress at a certain volumetric strain in the oedometric curves are somewhat lower than these in the hydrostatic EOS curves. However, for mixes with a large maximum aggregate size with a high aggregate content, the oedometric EOS merges with the hydrostatic EOS curves in the mid-to high pressure levels. Finally, statistical analysis using Analysis of Variance has been employed to identify the effect of different mixture parameters and their combination on the differences in the EOS. These new results enhance the insight on concrete behavior under triaxial high pressures and contribute to the development of a new generation of EOS curves. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hot water treatment resulted in significant improvement of wood-crete. [•] Addition of NaOH was able to extract soluble content of sawdust. [•] Linear correlation of waste paper reinforced wood-crete with boiling time of sawdust. [•] Higher percentage of waste paper gave rise to a higher compressive strength. [•] Geometry of waste paper had an influence on compressive strength of wood-crete. [ABSTRACT FROM AUTHOR]

[Display omitted] • The possibility of using waste plastic bags as a replacement in EPS insulation. • Two new composites were made with EPS and recycled plastic bags. • Both new samples reduced water absorption and increased fire resistance of EPS. • Replacing 25% of EPS volume with recycled plastic reduced its compressive strength to 82%. • The suitability of new composites as thermal and water insulation in the construction industry. In recent decades, there has been a significant rise in the production and consumption of plastics and polystyrene products (notably Expanded Polystyrene or EPS), and the reuse of their waste nowadays, due to their pollution potentials, has come to the forefront of attention. In this paper, new green building insulation is offered and examined, combining recycled plastic layers and EPS boards. The waste plastic bags turned into plastic sheets during the simple recycling process, and a monolithic EPS was divided into several boards with different thicknesses. Then, the recycled plastic bags were placed between EPS boards. Two composites of plastic sheets and EPS boards were prepared. The first composite consists of three layers (two layers of EPS with a thickness of 20 mm each, and a 10-millimeter plastic layer consisting of 36 recycled plastic bags). The second composite includes five layers (three layers of foam with a thickness of 10 mm each, and two layers of plastic paper, each consisting of 24 recycled plastic bags). All samples were similar in dimension, thickness, foam density, and type. The two new composites were then compared with the control sample in compressive strength, water absorption, and flame spread test. Even though a dramatic reduction of compressive strength has been observed, the results reveal the suitability of both three- and five-layer composites, which considerably improves fire and water resistance compared to the control sample. [ABSTRACT FROM AUTHOR]

• Paper presents economic and environmental benefits of concrete made with IBWA. • Fine aggregate replaced with 0%, 5%, 10%, 15% and 20% Incinerated Biomedical Waste Ash. • Strength, permeability, water absorption and sorptivity properties investigated. • Use of 5% IBWA improves strength and reduces permeability. • Cement stabilization reduces the leaching of metals from IBWA concrete. Biomedical waste is combination of medical waste from various sources like hospitals, research centers, clinics etc. and that presently or in the future poses a significant risk to human, plant or animal life. As it is produced in abundance and therefore cannot be treated or disposed of without special precautions. Generally biomedical waste is burned in incineration plant and produce Incinerated Biomedical Waste Ash (IBWA). It is considered dangerous or lethal because it may contain toxic substances such as heavy metals (hazardous waste). Typically, IBWA is dumped in a landfill to limit its spreading in the environment. But as none of the landfills is 100% leak-proof. This paper presents the influence of incinerated biomedical waste ash as fine aggregate replacement on the strength and permeation properties of concrete. For this purpose, a control concrete mix was made and four concrete mixes were made with four different percentages (5, 10, 15, and 20%) of IBWA. Results from the experimental study show that the incorporation of 5% IBWA as a partial sand replacement advances the strength and durability performance of the concrete. Compressive and split tensile strength test were performed upto age of 56 days and rapid chloride penetrability test (R.C.P.T.), water absorption, sorptivity and leachate analysis were performed upto age of 28 days. Toxicity characteristic leaching procedure (TCLP) test was performed and results indicates that it is non-hazardous. [ABSTRACT FROM AUTHOR]

• The optimal calcination temperature of MFPSA is 800 °C and the dosage is 4%. • MFPSA can increase the 28d flexural strength of fiber cement by 11.5%. • MFPSA can increase the compressive of fiber cement strength by 5.7%. • MFPSA decreases the 28d capillary water absorption of fiber concrete by 31.9%. • MFPSA promotes hydration and introduces hydrophobic groups. The modified Fenton paper sludge ash (MFPSA) was employed to replace cement in different proportions to prepare fiber cement products. The mechanical and hydrophobic properties of the MFPSA/fiber cement and concrete were studied. When the calcination temperature is 800 °C and the dosage is 4%, the MFPSA increases 28d flexural strength of fiber cement by 11.5%, compressive strength by 5.7%, and decreases water absorption by 2.6%. The MFPSA also decreases the 28d capillary water absorption of fiber concrete by 31.9%. The XRD, SEM/EDS, FTIR were employed to reveal how the MFPSA affects the hydration mechanism, and microstructure of MFPSA/fiber cement products. [ABSTRACT FROM AUTHOR]

• This current research paper is focused on the toughness and impact resistance of hybrid fiber reinforced self-compacting concrete. • Compressive strength made this suitable for structural elements. • Using SEM images, the SCC's failure mechanisms were assessed and fibre-aggregate interface was evaluated. • In digital image processing, the cross sections inspected and fiber segregation coefficient values were evaluated. This research paper presents the results of extensive experimental investigations and analytical results on the fresh and hardened properties of self-compacting concrete reinforced with hybrid hooked end fiber (HF) and crimped steel fiber (CF) in different fiber volume fractions. In this present investigation, the mixes were reinforced with different fiber combinations of hooked end fiber (0.25, 0.5 and 0.75%) and crimped fiber (0.25 and 0.5%). The fresh state properties of the mixes were characterized by using slump flow diameter, T 50cm , and V-funnel test. The hardened properties of self-compacting concrete (SCC) mixes were assessed by using compressive strength, flexural strength and impact resistance test. Regression analysis was carried out in order to correlate the fresh and hardened state on the extensively large volume of collected experimental data. The results reported that adding hybrid hooked end-crimped steel fiber significantly improves the compressive strength, flexural strength and impact resistance. Addition of hooked end steel fiber led to improve the compressive strength when compared to crimped end fiber. Moreover, increasing the crimped fiber content decreased the effect of hooked end steel fiber in flexural strength improvement. [ABSTRACT FROM AUTHOR]

• Nano-TiO 2 is more efficient than nano-SiO 2 for reducing the harmful pore. • Nano-particles, especially nano-SiO 2 , can accelerate the cement hydration. • Reinforcing efficiency of nano-SiO 2 is strongly dependent on its size and content. Although it has been verified that nanomaterials can improve the properties of cement-based materials, the research on the characteristics and mechanism of different types of nanomaterials is still inadequate. Two typical types of nanomaterials, nano-SiO 2 (pozzolanic material) and nano-TiO 2 (non-pozzolanic material), are utilized in this paper to investigate the combined effects of reactivity, size, and content on the efficiency of nanomaterials in cement-based materials. The experimental results indicate that the size and content effect of nano-SiO 2 is obvious. Small size and large content of nano-SiO 2 can significantly improve the compressive strength of cement paste. However, the size effect of nano-TiO 2 is much weaker than that of nano-SiO 2 , and the content effect of nano-TiO 2 is only obvious at the early age. For the late age compressive strength, the small content of nano-TiO 2 shows a similar obviously improving effect as the big content of nano-TiO 2. The pore structure analysis shows that both nano-SiO 2 and nano-TiO 2 can reduce the total porosity of cement paste, but nano-TiO 2 is more effective than nano-SiO 2 at reducing the harmful pores. Therefore, the small content of nano-TiO 2 is more effective to enhance the impermeability of cement-based materials. The results of this paper show that nano-SiO 2 and nano-TiO 2 have different effects and they should be selected based on the properties requirement of cement-based materials. [ABSTRACT FROM AUTHOR]

• A pregelatinized starch-binding gypsum was prepared to mimic the historic binders. • The gypsum strength is enhanced by pregelatinized starch-binding gypsum structure at high w/c ratios. • The contact points stress enhancement promotes macro strength enhancement. • Hydrogen bonding plays a key role in constructing the pregelatinized starch–binding gypsum structures. Minimizing gypsum powder usage by increasing water to gypsum (w/c) ratios has both economic and environmental benefits. However, gypsum is limited in application by its poor mechanical strength at high w/c ratios. To enhance the strength of hardened gypsum at high w/c ratios, this paper proposes a pregelatinized starch–binding gypsum structure. The mechanical strength, working abilities, and microstructure of pregelatinized starch–binding gypsum samples at high w/c ratios were evaluated. And the micro-nano structure and enhancement mechanism of pregelatinized starch–modified gypsum was investigated. The results show that at high w/c ratios from 0.8 to 1.0, pregelatinized starch significantly improved the mechanical properties of gypsum, where the flexural and compressive strength of 3 d modified drying sample were 3.3 MPa and 6.6 MPa in comparison to pure gypsum samples tending to 0 MPa. Pregelatinized starch participates in the overlapping structure of gypsum crystals and bind to them without affecting the crystal structure and morphology of single particles. The nanostructure of modified contact points involved strong adsorption of pregelatinized starch onto the (1 2 0) face by hydrogen bonding, which enhanced binding adhesion at contact points. And pregelatinized starch effectively reduced separation of the (1 2 0) face under x– and z– tensile stretching, and slipping along the (0 1 0) face under y– tensile stretching. This paper presents a modification that enhances mechanical properties of gypsum at high w/c ratios, and provides deeper understanding of crystal overlapping mechanisms at the nanoscale. [ABSTRACT FROM AUTHOR]

• Mechanical characterization of lime mortars by means of the Drilling Resistance Measuring System (DRMS). • Influence of penetration and rotational speed on drilling results. • Influence of penetration and rotational speed on correlations between UCS and drilling results. • Correlations between the mean of the drilling forces and the depth of cut per revolution. • Comparison between regression models developed using DRMS at a constant and variable depth of cut. The paper investigates the influence of the user-controlled variables on the results of the drilling test (DRMS) performed on lime mortars used for ancient buildings restoration. In particular, the ratio of the penetration and rotational speed (δ), namely the depth of cut per revolution, is considered. The experimental results show a relevant variation in the shapes of the drilling profiles with δ, especially in mortars with lower strengths. The efficacy of the regression models between the uniaxial compressive strength (UCS) and the drilling results changes with the depth of cut. An optimal range of δ to perform the DRMS test is identified for the analyzed mortars. The paper also investigates the possibility of performing the DRMS test according to another procedure poorly studied in the literature to evaluate the UCS of materials. It consists of making more holes in the same material at different values of δ. This method is based on the analytical and experimental results obtained with another scratching technique, the scratch test. The statistical analysis of results shows that the correlation between the mean of the drilling forces and δ can be described by linear regression in a limited range of δ. The slope of the linear regression has a high correlation with UCS. The obtained positive results move to deepen the experimental research on this topic. [ABSTRACT FROM AUTHOR]

Construction and demolition wastes (CDW) are promising sources for geopolymer production; however, the great variability of CDWs arising from their origin causes an abstention from implementation. As one of the key challenges in the CDW management and recycling practices, origin-depended variations in the waste materials and their reflection on the final product performance can be overcomed through in-depth waste characterization and design optimization. To this end, this paper aims to characterize CDWs collected from five different demolition zones with regard to their physical-, chemical-properties and the mechanical performance of geopolymer pastes produced with them. The compressive strength of geopolymer pastes was found to be significantly influenced by the chemical composition, crystalline nature, and fineness of CDWs. Optimization of precursor characteristics resulted in consistent mechanical performance ranging from 54.5 to 68.0 MPa after curing at 115 °C for 48 hours, regardless of the CDW origin. The aluminosilicate and calcium content of the precursor heavily influenced the ultimate gel structure in a positive manner, which determined material strength. The optimized use of CDWs from the same source increased the compressive strength of geopolymer pastes by up to 64%. • CDWs from different demolition zones were characterized. • Physical, chemical and crystalline properties of CDWs were examined. • CDWs from 21 different origin were used to produce geopolymers. • Aluminosilicate content and fineness were dominant in mechanical performance. • Precursor-based optimization resulted in 54.5–68 MPa compressive strength. [ABSTRACT FROM AUTHOR]

The establishment of a lunar base is crucial for lunar studies, resource extraction, and advancement in deep space exploration. Considering the limitations of rocket capacity and Earth-Moon transportation costs, lunar regolith is regarded as the most practical material for lunar base construction. Consequently, the in-situ additive manufacturing technology for simulated lunar regolith has been widely studied in recent years. This paper proposes a novel additive manufacturing approach for lunar regolith simulants. The simulants and several resins were mixed into a paste with high simulant content of 86 wt%, which was suitable for extrusion-based additive manufacturing process. To fully leverage the lunar environment, the feasibility of the ultraviolet (UV) and thermal curing of the resins was first verified, which was followed by the validation of the lunar regolith paste with the solid content of 86 wt%. After the characterization of the ultraviolet and heat curing properties, the paste was further 3D printed via the extrusion-based device. The extruded paste underwent preliminary curing in a UV environment and was then heated to approximate the daytime lunar conditions, achieving complete curing of the printed component. The cured parts exhibited a compressive strength of 9.83 ± 1.07 MPa, meeting the requirements for infrastructure construction in the low-gravity lunar environment. This work offers significant implications for future in-situ construction on the Moon using extrusion-based additive manufacturing of lunar regolith. • Pastes with high regolith content of 86 wt% is prepared. • UV- and thermal-curing properties of resins and pastes are investigated. • Additive manufacturing of lunar regolith structures is successfully achieved. • Compressive strength of cured structures reaches 9.83±1.07 MPa. [ABSTRACT FROM AUTHOR]

The porous hydrophilic nature of cement-based material is susceptible to water and corrosive media, severely reducing the durability. In this paper, methyl siloxane-based hydrophobic powder was prepared, and its effect on the physicochemical and anti-corrosion properties of mortar with different water-cement ratios were investigated. The results show that the addition of hydrophobic powder significantly improved the hydrophobic properties of mortars. Especially for the mortars with w/c ratios of 0.2 and 0.4, it showed superhydrophobicity with a water contact angle up to 156.5 ° and 152.3 ° respectively. Lower w/c ratio mortar has a denser microstructure, which reduces the water absorption rate of the mortar, and the hydrophobic powder enhances the hydrophobic effect of low w/c ratio mortar more significantly. The methyl siloxane groups in the hydrophobic powders will bind to the C-S-H gel in the mortar through Si-O bonding, preventing the C-S-H gel connections from forming a continuous network structure. This increased the pore volume and reduced the compressive strength by 14.6%-22.7%, but the total hydration degree was increased, and significant corrosion protection of the steel rebar was demonstrated. [Display omitted] • Super hydrophobicity of mortar was achieved by modification of hydrophobic powder. • Hydrophobic mortar with lower w/c ratio exhibits better anti-corrosion performance. • Methylsiloxane groups combine with C-S-H gel by Si-O enhancing hydrophobic properties of mortar. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP), an emerging technique recently, has been investigated in extensive studies for its ability to improve or enhance the properties of materials. This paper mainly explored the effect of MICP on the early strength and hydration products in fly ash blended cement paste (FABC) under different MICP treatment measures. Firstly, the influence of different environment on the growth of microorganism and three calcium source (CaCl 2 , Ca(CH 3 COO) 2 and Ca(NO 3) 2) on the production of calcium carbonate precipitation were investigated. The experimental results presented that the efficiency of CaCO 3 precipitation in the Ca(NO 3) 2 sample by adding bacterial solution is higher than other groups. Compared to untreated specimens, the mechanical properties of FABC paste are adversely affected by direct mixing with bacterial solution (MICP1) due to the fact that the hydration reactions of C 3 S and Ca(OH) 2 (CH) in FABC system were negatively affected as indicated by the hydration heat measurement. In contrast, the early performance of drying-immersing sample in bacterial solution (MICP2) was improved, with a maximum efficacy of 52.03%. The hydration process was facilitated in FABC paste treated with MICP2 treatment, further leading to increased formation of CH, C-S-H and AFt. Furthermore, Nanoindentation showed the HD C-S-H gel and CH were the dominant phases in MICP2 samples, and the matrix became denser with more hydration products, which also confirmed the increase in macroscopic compressive strength. The findings of this work can provide a guidance for the application of FA based on MICP method for enhancing the early strength in cementitious materials. • Compared with Ca(CH 3 COO) 2 and CaCl 2 , the efficiency of CaCO 3 precipitation in the Ca(NO 3) 2 sample is highest. • The hydration process of FABC is negatively affected by MICP1 treatment. • The MICP2 treatment can improve the early compressive strength of FA blended cement. • Nanoindentation detects more HD C-S-H gel and fewer porosity percentage. • More hydration products enhance the macroscopic and microscopic mechanical properties. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) members are subject to map cracking owing to the delayed ettringite formation (DEF) by excessive core temperature during the first few days of hydration. Studies on the mechanical properties of concrete with DEF expansion have been conducted to identify the variation in moduli and strength of the material. This paper provides a comprehensive review of the mechanical properties of plain concrete with DEF expansion to examine the degradation characteristics compared to the experimental conditions. The dynamic moduli, static moduli, and compressive strength of the plain concrete decreased up to 60%, 85%, and 65%, respectively, owing to large swelling, where the damage process showed colossal expansion. The reduction amount depends on the aggregate-to-cement ratio, chemical composition of the cement, aggregate type, water-to-cement ratio, and the mix. The static moduli is more sensitive to expansion in the initial expansion stage than other mechanical properties. The structural performance of DEF-affected RC members was also investigated, reviewing the relevant studies to include the structural performance of alkali-silica reaction (ASR) affected structures. The structural performance cannot be appraised using the mechanical properties of plain concrete. It was indicated that the DEF expansion of concrete core can be significantly confined by surrounding reinforcement in RC members. This inhibits the reduction in mechanical properties of concrete and results in maintaining the load-carrying capacity of RC members. Chemical prestress developed in concrete due to the swelling restraint by reinforcement, and anisotropic damage improves the stiffness of the RC members. • Comprehensive review of mechanical properties of DEF-affected plain concrete. • Structural performance of DEF-deteriorated RC members was studied. • Structural performance depends on DEF- induced stress in reinforced concrete. • DEF expansion confinement should be considered to assess structural performance. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on based the universal morphology of recycled coarse aggregates in reality, an idealized model of recycled coarse aggregates was prepared using stones. Axial compressive strength tests were conducted on prism-shaped specimens of Modeled Recycled Coarse Aggregate Concrete (MRCAC), which were prepared with different old cement mortar coverages and aggregate arrangements. Through comparison with experimental data, the reliability of the finite element analysis model was determined. It was found that the arrangement of MRCA had a significant impact on the failure characteristics and elastic modulus of MRCAC. Thus, different arrangement modes affected the stress distribution within the specimens, resulting in significantly different axial compressive strength. • Studied the influence of aggregate arrangement on the stress characteristics of MRCAC. • Studied the influence of old cement mortar on the mechanical properties of MRCAC under different internal force transmissions. • Revealed the influence characteristics of old mortar on the stress-strain relationship in recycled concrete. [ABSTRACT FROM AUTHOR]

Applying conductive cement-based anode is one of the commonly used methods to achieve uniform electrochemical protection for concrete structures. However, anodic acidification is a critical challenge limiting the effectiveness of electrochemical protection in concrete. Therefore, carbon fiber (CF) and expanded graphite (EG) were used in the current study as conductive materials to reduce the resistivity of cement-based anode by creating a "multi-scale" conductive grid within the anode, while slag powder was employed to enhance the anode resistance to chloride intrusion. This paper investigated the influence of slag powder on the mechanical properties, resistivity, and hydration products of carbon fiber-expanded-graphite conductive mortar (CECM) anodes. The results indicated an inverse relation between the slag powder content and the mechanical properties and resistivity of cement-based anodes. In general, the optimal dosage of slag powder is 20%, at which the compressive strength and resistivity of CECM decrease by 14.8% and 2.75%, respectively. Furthermore, a cubic function relation could be applied to correlate the slag powder content to the mechanical properties and electrical conductivity of the anodes. CF, EG, and slag powder created a composite structure within the hardened cement paste, and formed a multi-scale conductive grid that reduced the cement mortar's resistivity. Through XRD and FT-IR tests, it was found that during the testing period, the pozzolanic effect of slag powder was insufficient to compensate for the loss of strength resulted from the reduced amount of cement clinker. In addition, TGA-DTG results showed that the total amount of C-S-H in Group A increased from 14.31% to 22.86%, while in the Group B this amount increased from 20.74% to 25.94%. The optimal group had an increase from 20.21% to 24.59% in C-S-H content. These results confirm the similar hydration effect of slag powder on EG cement slurry compared to that on ordinary cement. It also indicates that the chloride ion resistance of cement-based anodes can be enhanced through the pozzolanic effect of slag powder, ultimately achieving long-term stable operation of cathodic protection system. • Slag powder is used to modify CECM. • Slag powder particles distributed in multi-scale conductive grids interlaced with EG and CF. • Quadratic surface can reflect the relation of Slag powder content and CECM's compressive strength and resistivity. • Slag powder's "secondary hydration" does not compensate for the strength loss caused by its "dilution effect". [ABSTRACT FROM AUTHOR]

This paper presents experimental and analytical study results to evaluate the uniaxial compression behavior of concrete columns actively confined with Fe-based shape memory alloy (Fe-SMA) spirals. For the study A total of 16 concrete columns were fabricated for the study. Ten of the columns were actively confined by Fe-SMA spirals through electrical resistance heating, while four columns were passively confined by deactivated Fe-SMA spirals. Finally, the remaining two columns were unconfined specimens without lateral reinforcement. The experimental variables included the pitch of the Fe-SMA spiral, confinement type, and heating temperature. The Active confinement due to activation of the Fe-SMA spiral resulted in improved ductility of the confined concrete columns compared to passive confinement. The effects of activation status and heating temperature were more prominently observed in specimens with smaller spiral pitches and lower concrete compressive strength. Particularly, the compressive strength of columns actively confined with a 30 mm pitch spiral was enhanced by over 100% compared to unconfined concrete. Furthermore, an analytical stress-strain model for concrete actively confined with Fe-SMA spirals was proposed in this study. The proposed model accurately predicted the experimental results of columns confined with external SMA wires reported by other researchers. • Activated Fe-SMA spiral distributed the damage area of the concrete column. • The pitch of the Fe-SMA spiral affected the maximum compressive strength and ductility of the concrete. • Active confinement by the activated spiral improved the compressive strength. • The uniaxial compressive behavior of a concrete column confined with Fe-SMA spiral was predicted through the proposed model. [ABSTRACT FROM AUTHOR]

Ensuring the integrity of oil and gas wellbores critically hinges on cement binding. This paper presents findings of the untapped potential of Tanzanian natural pozzolans, namely, kaolin and pumice, as a feasible option for geopolymer cement, specifically tailored to enhance the structural integrity of oil and gas wellbores. Results from XRF, XRD and FTIR analyses confirmed that kaolin, modified kaolin (metakaolin), and pumice powder are composed mainly of SiO 2 and Al 2 O 3 , while modified quartz with NaOH (metasilicate) is primarily composed of SiO 2 and Na 2 O. The results revealed that 21% of metasilicate in a mixture of kaolin activated at 800 °C and pumice resulted in geopolymer pastes with the best compressive strengths. Compressive strengths of 35.94 ± 0.93 and 33.71 ± 0.37 MPa were obtained at 70 and 90 °C respectively, after 28 days of curing in brine baths (40 g/L NaCl and 40 g/L Na 2 SO 4). XRD results on crystallinity showed that the formulated geopolymer pastes had amorphous phases (70.73%), indicating the presence of irregular, non-repeating atomic structure. The AFM results strongly supported the presence of amorphous phases and further revealed that the geopolymer pastes have few pores and no cracks. TGA results revealed that the formulated pastes were thermally stable up to 900 °C. MP-AES results showed an increase in the concentration of dissolved metal ions from the geopolymer pastes from the 7th to 21st days of curing that remained relatively constant until the 28th day. This observation suggests that the chemical stability of geopolymer paste increased with curing time due to the formation of more geopolymerization chains facilitated by the consumption of unreacted metal ions during curing. These results concurred with the compressive strength findings of this study. The water absorption result was 0.81%, implying that the geopolymer pastes were water-resistant. The overall results contribute to developing sustainable and eco-friendly cement options for the oil and gas industry, ensuring the integrity and longevity of wellbores. • Utilizing kaolin and pumice significantly improves structural stability. • A 21% metasilicate geopolymer cement mix exhibits superior compressive strength, ideal for challenging wellbore environments. • Developed pastes demonstrate amorphous structure, minimal porosity, and crack resistance, indicating high durability. • The pastes show outstanding thermal stability up to 900 °C and increased chemical resilience over time. • The water-resistant nature of these geopolymer pastes aligns with sustainable oil and gas wellbore applications. [ABSTRACT FROM AUTHOR]

Cementitious concrete is considered potentially the largest avenue to utilize the captured carbon dioxide (CO 2). Its capacity is significantly influenced by various parameters, including the CO 2 introduction method for sequestration. This paper attempted to study the variation in carbon sequestration potential of ordinary Portland cement (OPC) based concrete and paste when the CO 2 is introduced to the samples during mixing, curing and both. The carbonated samples obtained using the abovementioned methods have been compared in terms of CO 2 uptake capacity, microstructural densification, porosity reduction, and strength variations. A maximum CO 2 Uptake Capacity of about 25% was achieved under Standard Ambient Temperature and Pressure (SATP) conditions, with a maximum CO 2 Conversion of 70.35% and 93.80% obtained at the surface for CO 2 Mixing and CO 2 Curing, respectively. Further, carbon-sequestered concrete (CSC) resulted in enhanced compressive strength, and reduced the size of pores in addition to making them uniform in size. • A CO 2 Uptake Capacity of 13.9% was obtained using the CO 2 Mixing regime. • A CO2 Uptake Capacity of 19.75% was achieved using the CO 2 Curing regime. • A CO 2 uptake of 25.17% was observed using the CO 2 mixing + CO 2 curing regime. • A maximum CO 2 Conversion rate of 70.35% was achieved in the CO 2 Mixing case. • A maximum CO 2 Conversion rate of 93.80% was achieved for the CO 2 Curing case. [ABSTRACT FROM AUTHOR]

To facilitate the use of geopolymer materials in shotcrete applications, this study presents the development of a geopolymer mortar and explores its flowability and early-stage mechanical properties. Firstly, 15 groups of geopolymer mortar specimens with 3 liquid-binder ratios (0.70, 0.75 and 0.80) and 5 binder-aggregate ratios (0.225, 0.250, 0.275, 0.300 and 0.325) were developed. Secondly, the P-wave velocity, slump, early-age compressive strength and compressive strength were obtained by ultrasonic pulse velocity test, slump test and uniaxial compressive test. Thirdly, discussion on the effect of liquid-binder ratio and binder-aggregate ratio on P-wave velocity, flowability, compressive strength and early-age compressive strength of geopolymer mortar were carried out. Finally, an optimal mix proportions rang of geopolymer mortar materials that meet the requirements of wet shotcrete technology were proposed. The results show that P-wave velocity, slump, early-age compressive strength and compressive strength increase as the increasing of liquid-binder ratio. The slump, compressive strength and P-wave increase as the increasing of binder-aggregate ratio. Moreover, the optimal binder-aggregate ratios were proposed as 0.244 - 0.321, 0.228 - 0.298, and 0.209 - 0.241 for geopolymer mortar with a liquid-binder ratio of 0.70, 0.75 and 0.80, respectively. Geopolymer mortar in these mix proportions achieves compressive strengths ranging from 28.4 MPa to 41.1 MPa after curing for 1 day and 44.2 MPa to 55.4 MPa after curing for 28 days. The mix proportion of geopolymer mortar proposed in this paper can simultaneously meet the standard requirements for mechanical properties and flowability, demonstrating potential for wet shotcrete applications. • A mortar for shotcrete application has been developed using geopolymer as the primary material. • The effects of liquid-binder and binder-aggregate ratios on mortar properties were investigated. • Flowability and early-age mechanical properties of the developed mortar were comprehensively analyzed. • An optimal mix proportion range was proposed for effective use in geopolymer shotcrete applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • In this paper, a new method for preparing biochar-modified vegetation concrete is presented. • The porosity, permeability and planting capacity of vegetation concrete were studied. • Different biochar contents have different effects on physical properties and planting capacity. • According to the growth of ryegrass, an optimal mix proportion of biochar-modified vegetation concrete was recommended. Abstract Vegetation concrete is an effective material to beautify the landscape, reduce pollution and protect the environment. To further improve the plant compatibility of vegetation concrete, this paper recommends an improved method of adding biochar particles to vegetation concrete. In this research, different masses of biochar were mixed into concrete to study the trend in porosity, permeability and plant compatibility. According to the growth status of three types of common grass species, ryegrass was selected as the best grass species in this study. As the content of biochar increased, the porosity and permeability coefficient of vegetation concrete continued to decrease, while the effect of biochar on plant growth promotion at first showed an increase to the maximum and then a gradual decrease. When the biochar content was 5 kg/m3, ryegrass showed the best growth. Compared with the experimental group of vegetation concrete without biochar, the plant height, root length and germination rate increased by 22.2%, 21.1% and 12%, respectively, on day 25, and the compressive strength also increased slightly. Therefore, adding a suitable amount of biochar can improve the characteristics of vegetation concrete. Furthermore, the optimum mix proportion of biochar-modified vegetation concrete was recommended. [ABSTRACT FROM AUTHOR]

Highlights • The introduction of EAF dust in concrete is gaining attention in civil engineering. • Concrete with EAF dust showed an increase of the compressive strength. • Lixiviation of all the studied concretes was practically the same than traditional concrete. Abstract One of the problems of steelworks, referring to the steel manufacture, is the generation of secondary products, resulting in recent years in new types of industrial waste that, depending on the sustainability of the environment, must be reused or treated. This paper analyzes the mechanical behavior of concrete samples with the addition of an industrial waste, such as ferritic fume dust produced by electric arc furnaces (EAF) when the materials are melted and makes a comparison using other types of additions of concrete such us silica fume. At the same time this paper studies the capacity of the matrix to encapsulate this residue that eventually ends up deposited in a landfill. The results show that, besides giving the concrete a greater resistance as it happens with silica fume, the use of this type of waste as an addition to concrete is suitable since the material remains encapsulated in the concrete matrix, thus not producing leaching of heavy metals which can be harmful to the environment and therefore to the health of the human being. [ABSTRACT FROM AUTHOR]

Highlights • Effect of column size on axial compressive behavior of FRP ring-confined concrete is studied. • The effect of column size is negligible for FRP ring-confined concrete. • The axial and hoop strains distributions are presented. • A new design-oriented stress-strain model for FRP ring-confined concrete is proposed. Abstract This paper presents the results of an experimental program aiming to investigate the effect of the specimen size on the axial compressive behavior of circular concrete columns wrapped with spaced FRP rings. A database consisting of the up-to-date test results on FRP ring-confined concrete in the literature is established, and it is used for proposing a new design-oriented stress-strain model for FRP ring-confined concrete. The accuracy and reliability of the new model are validated by comparing the test results presented in this paper with the predictions by the new model. The comparisons show that the new model provides close predictions with test results. [ABSTRACT FROM AUTHOR]

Highlights • 87 research articles on lightweight self-compacting concrete have been reviewed. • Physical properties of LWA which affect the LWSCC performance are reviewed. • Fresh and hardened properties of LWSCC are reviewed. • Features and limitations of 6 LWSCC mixture methods are presented. Abstract The utilization of natural and artificial lightweight aggregates in lightweight self-compacting concrete (LWSCC) is gaining popularity in research field. Extensive research has been carried out in the past decade all over the world to utilize lightweight aggregates (LWA) in self-compacting concrete (SCC). LWSCC, which uses renewable aggregates, has great potential to become an alternative material to conventional concrete. The paper is aimed to review the more recent research of physical properties of lightweight aggregates used in developing mix design of lightweight self-compacting concrete. In design, the mix proportion of LWSCC is a crucial factor to achieve the desired fresh and hardened concrete properties. The methods to develop LWSCC mix design with anticipated fresh and hardened concrete are reviewed. Research shows that the mix design LWSCC is preferably proportioned by aggregates packing concept. In addition, discussion on the fresh and hardened concrete properties is made and summarized in this paper. Studies indicate that there is a promising future for the use of lightweight aggregates in SCC as it shows satisfactory filling ability, passing ability, segregation resistance and compressive strength. Research gaps recommendations are then identified through this review to further discover lightweight self-compacting concrete in several aspects, particularly in term of sustainability. [ABSTRACT FROM AUTHOR]

Highlights • Compressive strength at high temperatures of fibre concretes studied. • Influence of the high temperatures on the physical and chemical changes of the concrete studied. • Behavior of the new Dramix 5D steel fibre concretes in fire studied. • Model for compression strength at high temperatures of fibre concrete proposed. Abstract The high temperatures of fires affect the physical and chemical properties of the concrete and thus influence its mechanical properties. This paper presents the results of an experimental investigation on the compressive strength at high temperatures of high-strength fibre concretes. The influence of the high temperatures on the physical and chemical changes of the concrete was also analysed by Thermo Gravimetric Analysis/Differential Thermal Analysis (TGA/DTA), X-Ray Diffraction (XRD) and Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM/EDS). Five concrete compositions with different steel fibre contents and types have been tested: one without steel fibres (reference composition), two with Dramix 3D steel fibres and two with Dramix 5D steel fibres (45 and 75 kg/m3). This new type of steel fibres, the Dramix 5D, presents a double curvature at its ends, allowing a more efficient anchorage in the cementitious matrix. The behaviour at high temperatures of concretes made with these 5D fibres has been compared with the one of concretes made with the Dramix 3D steel fibres. Therefore, the impact of the high temperatures on the compressive strength and morphology of the high-strength fibre concretes made with the Dramix 3D and 5D steel fibres has been evaluated. The paper proposes also models for the compressive strength at high temperatures of the studied high strength fibre concretes. [ABSTRACT FROM AUTHOR]

Highlights • Modifying cement based adhesive for bond between CFRP and concrete using magnetized water. • Studying mechanical properties of magnetized cement based adhesive. • Prediction of magnetized mortar properties using genetic programming. Abstract Cement-based adhesive (CBA) is used as a bonding agent in Carbon Fibre Reinforced Polymer (CFRP) applications as an alternative to epoxy-based adhesive due to the drawbacks of the epoxy system under severe service conditions which negatively affect the bond between the CFRP and strengthened elements. This paper reports the results of, an investigation carried out to develop two types of CBA using magnetized water (MW) for mixing and curing. Two magnetic devices (MD-I and MD-II), with different magnetic field strengths (9000 and 6000 Gauss) respectively, were employed for water magnetization. Different water flows with different water circulation times in the magnetizer were used for each device. Compressive and splitting tensile strength tests of the magnetized CBA (MCBA) were conducted for different curing periods (3. 7, 14, 21 and 28 days) using MW. It was found that MW treatment increases the strength of CBA. The highest strength was obtained for MCBA samples when MD-I was used at a low flow rate (F = 0.1 m3/hr) for 15 mins of circulation time (T). The latter was found to positively affect MCBA properties when T was increased from 15 min to 60 mins. Prediction of the compressive and tensile strength values are also studied in this paper using genetic programming, the models showed good correlation with the experimental data. [ABSTRACT FROM AUTHOR]

Highlights • The paper presents the in situ compression test-XCT scan of foamed concrete. • The meso-scale modelling is directly reconstructed from XCT images. • Failure mechanism of foamed concrete is elucidated by XCT scan and the meso-scale modelling. • The meso-scale simulation shows a good agreement with the observation from XCT scan. • The paper provides a comprehensive framework to understand the behaviour of foamed concrete. Abstract Foamed concrete has been widely used in infrastructure construction and poses new challenges to design and modelling. This paper investigates the behaviour of foamed concrete with the help of X-ray Computed Tomography (XCT), which is capable of characterising the microstructure of foamed concrete. An in situ compressive test-XCT scan is carried out to observe the failure mechanism of foamed concrete by XCT when subjected to compression load. A meso-scale simulation based on XCT images is conducted to simulate the behaviour of foamed concrete. An algorithm that directly reconstructs the meso-scale model from XCT images is developed. The experimental and numerical results show that foamed concrete exhibits a significant change in mechanical behaviour; it is less brittle compared to the response of dense samples. However, the reduction in the level of brittleness is accompanied by a significant decrease in compressive strength. Failure development inside samples is successfully captured by the XCT scan and the meso-scale modelling. The topology of foamed structures, in particular the chain of interconnected pores, influences the failure mechanism of foamed concrete. The combination of XCT scan and meso-scale modelling provides a comprehensive framework to understand the mechanical behaviour of foamed concrete. [ABSTRACT FROM AUTHOR]

Highlights • Coal gangue is silicon-aluminium materials, which can be used to prepare geopolymer after high-temperature calcination. • Coal gangue geopolymer has a high early strength, higher than that of OPC.45 cement paste specimens. • The generation of the zeolite facies crystallization plays an obvious role on the compressive strength of coal geopolymer. • This paper provides experimental and theoretical basis for the development and wide application of coal gangue cementitious materials. Abstract This paper explores the impacts of sodium hydroxide modulus, alkali lye amount and liquid–solid ratio on the strength and microstructure of coal gangue geopolymer materials, involving a total of five sodium hydroxide moduli, four NH/NS mass ratios and seven liquid–solid ratios. To characterize the morphology and structure of coal gangue geopolymer materials, we carried out XRD, TG-DTG, FT-IR and SEM analysis on the specimens respectively. The results show that NH concentration has no impact on paste fluidity and has significant impact on compressive strength of geopolymers. Both paste fluidity and compressive strength of geopolymers increase with the increase in liquid–solid ratio. However, it should be noted that the compressive strength decreases with the increase in liquid–solid ratio when the liquid–solid ratio is greater than 0.32. The optimal NH/NS mass ratio is 1:1.5 ∼ 1:2. In comparison with P.O42.5 cement specimens, coal gangue geopolymers have higher initial strength and lower 28 d compressive strength. The analytical results of microstructure are consistent with those of compressive strength, which demonstrates that the polymerization products of coal gangue geopolymers are N-A-S-H gels and some other aluminosilicate zeolite crystals. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) is an innovative engineering wood panel product made from gluing layers of solid-sawn lumber at perpendicular angles. Owing to the excellent structural rigidity in both orthogonal directions, CLT becomes a preferred construction material for shear walls, floor diaphragms, and roof assemblies. CLT is normally made of Spruce-pine-fir (SPF) lumber or Douglas fir-Larch lumber. Recently, attempts have been made to manufacture CLT with Canadian hemlock. This paper investigates the out-of-plane bending properties and compressive properties of CLT panels made from Canadian hemlock. The mechanical properties of the CLT panels in the major/minor strength directions were obtained through experimental tests, and numerical models were developed to predict bending stiffness and ultimate load resisting capacity of the CLT panels. Moreover, theoretical bending stiffness of the CLT panels was calculated according to the equations provided in different code provisions, and the calculated values were compared with the experimental data. Results show that CLT panels made from Canadian hemlock perform as well as those made from other common used lumber species (i.e. SPF or Douglas fir), and the bending stiffness and ultimate load resisting capacity of the CLT panels can be predicted by the developed numerical models. In addition, in the major strength direction, the global bending stiffness of the panels can be predicted using the theoretical bending stiffness. In the minor strength direction, the local bending stiffness of the panels can be predicted using the theoretical bending stiffness calculated according to the Shear Analogy theory. The results presented in this paper can provide fundamental basis for supporting the potential engineering application of CLT panel products made from Canadian hemlock. [ABSTRACT FROM AUTHOR]

This paper aims to study the resistance of magnesium potassium phosphate cement (MKPC) paste to seawater erosion. MKPC paste specimens were prepared and their compressive strength, mass change, hydration temperature and water absorption were measured. The phase composition and microstructure were also analyzed. The results show that the initial hydration age of the reference sample M1 under natural curing condition has a significant effect on its compressive strength development in seawater. The residual ratios of the compressive strengths of M1(3d) and M1(28d), hydrated for 3 and 28 days, respectively, under natural curing condition, are 76.6% and 91.1% at 360-day seawater immersion age, respectively. This also indicates that early-age M1 has poor resistance to seawater erosion. Adding some limestone (LS) powders and silica fume (SF) can significantly improve the strength of early-age MKPC paste. The 3-day compressive strength of M2 with LS and SF is about 50% higher than that of M1. After immersion for 360 days in seawater, the residual ratios of the compressive strength of M2(3d) and M2(28d) are both close to 93%. This implies that initial hydration age of M2 under natural curing condition has almost no effect on its compressive strength development in seawater. Compared with M1, M2 has higher resistance to seawater erosion, which is attributed to the higher hydration degree and more compact structure of M2. This paper might be useful for preparing MKPC-based materials that can meet the requirements of marine concrete. [ABSTRACT FROM AUTHOR]

Long-term durability of concrete has been of interest for researchers in past decades, and throughout their numerous research endeavors, they have tried to improve durability with the application of different methods. One technique is the integration of a new material into the concrete. One material that has attracted great attention of researchers is nano-SiO 2 (NS). Its considerable performance in the enhancement of durability properties of concrete and mortar provides reasonable specifications satisfaction for scholars. In this paper, important durability characteristics of concrete, including the chloride ion penetration, electrical resistivity, water penetration, water absorption, the pore size distribution, the carbonation, the sulfate resistance, frost resistance, shrinkage, and thermal properties were explored. Additionally, the effects on the microstructure of concrete and mortar in the previous studies were discussed. Mechanical properties, such as compressive strength, flexural strength, tensile strength, and abrasion resistivity were also investigated in the past and most recent papers. [ABSTRACT FROM AUTHOR]

The lightweight expanded polystyrene (EPS) concrete has the characteristics of vibration energy absorption and can be used to conduct the metro track of vibration reduction and isolation. But the workability and compressive strength of the lightweight EPS concrete need to be improved in the engineering application of vibration energy absorption when EPS beads are mixed in concrete. To improve the workability and compressive strength, this paper investigated the effects of viscosity modifying admixture (VMA) on the workability, segregation resistance, compressive strength and failure mode of a class of structural lightweight EPS concrete, prepared by controlling a certain water-binder ratio and fly ash replacement. The dosage of VMA in the mixtures was 0.02%, 0.04%, 0.06%, 0.08% and 0.10% by weight of the total cementitious materials (TCM), respectively. Workability was investigated through a multi-index of slump, slump flow, T50 and inverted slump cone time while segregation resistance was evaluated by a density test. The concept of anisotropy was employed to evaluate the compressive strength and failure mode. Results showed that VMA had significant negative effects on the fluidity of structural EPS concrete. From the density test results, VMA significantly enhanced the resistance to segregation and the segregation degree of EPS concrete exhibited a negative linear correlation with the dosage of VMA according to the definition of segregation index (SI). The compressive strength decreased substantially with increase of VMA and the anisotropy of the strength was shown to be inhibited gradually with increase of VMA, resulting from the improvement of resistance to segregation. As the elimination of anisotropy, the failure modes were altered consequently. In terms of the effectiveness to inhibit the segregation and the anisotropy, 0.10% by weight of TCM was recommended as the most effective dosage for VMA in this paper. [ABSTRACT FROM AUTHOR]

This paper examines the relation between strength and elastic modulus of high performance concrete (HPC) tailored from various heavy and normal weight aggregates coupled with the effect of micro-silica as a supplementary cementitious material (SCM). Elastic modulus of concrete is an important mechanical property and plays an important role for the calculation of deformations in the structural components. Experimentation was conducted in precise laboratory environment and all other parameters were kept constant in the mixtures. This investigation was prompted to supply the construction industry with appropriate information on how specific properties of HPC mixtures can be improved using local normal and heavy weight aggregates and incorporating supplementary cementitious materials. In other words, this paper will encourage the local aggregate consumption in mega projects that to be constructed for special purposes. In this investigation, dissimilar types of normal and heavy weight coarse aggregates were used. It was found that it is worthy to study experimentally the relation between strength and MOE of HPC when different types of coarse aggregates are used for an indicated HPC mixture with a corresponding combination of supplementary cementitious material. The comparison of experiment results with the ACI prediction models showed that the models should be enhanced for accurate prediction for the effect of aggregate type with and without the use of micro-silica as supplementary cementitious material. An assessment of the need for an aggregate and micro-silica based modification to the ACI models is also proposed. The experimental work conducted in this investigation confirmed that the type of aggregate and its combination with a supplementary cementitious material would have important influence on the HPC characteristics. Hence, the use of appropriate values for the strength-MOE relation for a HPC mixture based on the nature of used aggregates and SCM is recommended. However, such values might be not available in some cases, if so the experimental trend lines presented in this study can be used to calculate them. [ABSTRACT FROM AUTHOR]