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Permeable concrete is an innovative type of concrete that provides a sustainable solution for stormwater management by allowing water to seep through and be filtered naturally. This study focuses on the preparation and performance investigation of an epoxy resin-based permeable concrete containing ceramsite. In this study, ceramsite, a lightweight aggregate, is used as a substitute for conventional aggregates in the concrete mixture. The epoxy resin is then added to improve the strength and durability of the concrete. A series of tests, including compressive strength, water permeability, and freeze-thaw resistance tests, are conducted to evaluate the performance of the epoxy resin-based permeable concrete. The results show that with an increasing epoxy resin binder–aggregate ratio, the compressive strength of the epoxy resin-based permeable concrete significantly increases while the permeability coefficient decreases. Different types of aggregates have varying effects on the compressive strength and permeability coefficient of epoxy resin-based permeable concrete, with high-strength clay ceramsite providing the highest compressive strength and lightweight ceramsite having the highest permeability coefficient. In addition, the discrete element simulation method effectively and feasibly determines the ultimate load and accurately simulates the compressive strength of the permeable cement-based mixture, consistent with the measured compressive strength. A quadratic polynomial regression analysis yielded an R2 value of around 0.93, showing a strong relationship between durability and freeze-thaw cycles. The findings contribute to the development of sustainable construction materials for stormwater management and offer potential applications in various infrastructure projects. [ABSTRACT FROM AUTHOR]

This paper presents the performance of a multifunctional generic compound, 4-Aminobenzoic acid (4ABA) as migratory inhibitor applied on hardened concrete surface to curb corrosion due to combined chloride and carbonated environment. Electrochemical techniques (LPR and EIS), gravimetric analysis were applied to evaluate the corrosion performance and the inhibition mechanism of 4ABA. Chloride and carbonation profiles were developed to investigate the dominant cause of corrosion during the exposure. Visual and microscopic analysis of concrete surface and rebar surface was also done. Compressive strength test was performed to study the effect of corrosion inhibitor on strength property of hardened concrete. Results confirm that 4ABA prolonged the passive state of rebar when used as preventive measure and restrained the on-going corrosion process when employed as repair strategy. Combined exposure by chlorides and CO2 leads to redistribution of chloride ions in concrete matrix. The results also conclude that during the combined exposure, chloride ions initiate the corrosion process and carbonation aggravates this process. Application of 4ABA does not influence the strength properties of concrete. ABA has performed the inhibition by protective layer development and shield formation against the negatively charged corrosive ions. Blended cement concrete system which was observed to be more vulnerable to corrosion was seen to attain similar corrosion resistance as OPC concrete after inhibitor application. [ABSTRACT FROM AUTHOR]

Admixtures used in concrete have been produced for conventional concrete and the behavior of these additives in geopolymer/alkali‐activated systems is still complicated. In this study, the effects of different types of water‐reducing admixtures on the fresh and mechanical properties of Class F fly ash‐based geopolymer mortars and alkali‐activated slag mortars were investigated. For this purpose, flow diameter, rheological examination, compressive and flexural strength tests were carried out. The data obtained showed that the admixtures used in the study did not have a positive effect on the fresh properties of geopolymer/alkali‐activated mortars, and the improvements in the flow properties were due to the extra water contributed by the admixture. The flow diameters of the mixtures containing the same amount of water with the mixture containing plasticizer were generally higher than those of the mixtures prepared with the admixture up to 10.3% in the fly ash‐based mortars and 15.4% in the slag‐based mortars. Addition of plasticizers reduced the compressive strength of fly ash‐based geopolymer and slag‐based alkali‐activated mortars up to 31.7% and 29.7%, respectively. [ABSTRACT FROM AUTHOR]

Self‐compacting concrete (SCC) is a type of flowable, high‐strength and high‐performance concrete in the construction field, which can flow and compact under its own weight. The damage of concrete is often caused by internal microstructural defects. Nano silica (NS) has excellent pozzolanic properties, and with an appropriate content of NS as auxiliary cementing material, it can promote the generation of C‐S‐H gels in addition to serve as internal filler, thus improves the micro‐scale defects in concrete. This paper extracts data from studies published over the last decade which focus on the application of NS in SCC and discusses the similarities and differences between the studies. Ultimately, a systematic review of the physical and chemical characteristics of NS, and the effect of NS on the workability, mechanical and durability properties of SCC is presented. Based on the review, the most common NS content is 0%–6%, where the negative effect of 0%–6% NS on the workability of SCC can be controlled by increasing the dosage of superplasticizer. The NS content of 2%–3% is optimum for improving the mechanical strength and the ability of SCC to resist water permeability, corrosion, acid and sulfate attacks, elevated temperature as well as shrinkage. [ABSTRACT FROM AUTHOR]

The swift growth of urban areas and industries has resulted in a rise in concrete production and subsequent depletion of resources as well as environmental pollution. In light of environmental considerations, it has become imperative to discover and advance alternative binding construction materials that can substitute conventional Portland cement. Geopolymers have emerged as a viable solution to this issue. Geopolymer composites can benefit from unique attributes and improved performance through the use of nanomaterials. This is achieved by augmenting the composite's microstructural features, creating additional C-S-H, N-A-S-H, and C-A-S-H gels, and filling in nanopores within the matrix. In this paper, extensive experimental laboratory works have been conducted to investigate the effects of adding different dosages (1, 2, 3, and 4%) of nano-silica (NS) particles on the setting times, compressive strength, splitting tensile strength, resistance to elevated temperatures, electrical resistivity, bulk electrical conductivity, thermogravimetric analysis and scanning electron microscopy of geopolymer concrete composites. As a result of the addition of NS, the mechanical strength, electrical conductivity, and thermal behavior of geopolymer concrete all improved by 21%, 36%, and 26%, respectively, in comparison to the control GPC mixture. Furthermore, according to SEM observations, the addition of NS improved the microstructural characteristics of the GPC specimens due to the formation of additional geopolymerization products. Finally, it was discovered through statistical and multivariate analysis that the developed model codes, such as ACI 318, ACI 363, AS3600, and CEB-FIP, are not suitable for predicting splitting tensile strength, electrical resistivity from their tested compressive strength values. [ABSTRACT FROM AUTHOR]

Lime is one of the main raw materials necessary for the production of autoclaved aerated concrete (AAC). The preparation of lime by calcining limestone directly and indirectly emits a large amount of CO2 due to the limestone decomposition and energy consumption. In this study, AAC was made using modified carbide slag (MCS) instead of lime, which effectively can utilize solid wastes and reduce the CO2 emission. Results showed that in the first 2 h of hydration, the heat release rate of MCS was higher than that of lime, and the cumulative hydration heat of lime and MCS within 30 h was 206.1 and 204.3 J/g , respectively. MCS not only can improve the fluidity of slurry, but also can enhance the gas-foaming rate. Cumulative pore volume increased with the increase of MCS content in AAC. Tobermorite, quartz, katoite, anhydrite, and calcite were the main minerals in the AAC. With the increase of MCS content, the density and strength of AAC decreased and the thermal insulation performance increased. When the MCS content was 100%, the AAC density was 594 kg/m3 , the compressive strength was 3.6 MPa, and the thermal conductivity was 0.141 W·m−1·K−1 , which meet in the requirements of the Chinese standard. [ABSTRACT FROM AUTHOR]

In today's world, enhancing the performance of recycled aggregate concrete is an essential need, as it ensures the effective utilization of demolished construction waste. The advantages of fly ash and polypropylene fiber in conventional strength concrete are well known. However Further research is required to evaluate the impact of using fly ash, silica fume and polypropylene fiber in case of RA and its effect on the properties of recycled aggregate concrete (RAC). This study evaluates the effects of using 50%, 75%, and 100% recycled aggregate (RA) and 1%, 2%, and 3% polypropylene fiber with a fixed amount of fly ash and silica fume 87 kg/m3 and 21.75 kg/m3. The objective is to determine how these combinations affect concrete strength and durability properties (compression, tensile strength, acid resistance and water absorption). This study also investigates the reliability of non-destructive tests, ultrasonic pulse velocity and rebound number, in the presence of polypropylene (PP) fibers and fly ash with recycled aggregate. The experimental investigation showed that the combination of RA based concrete, fly ash (FA), and polypropylene fiber (PPF) improved concrete durability and strength. The concrete compressive strength made with 50% RA was 13% lesser than that of control concrete, but with the incorporation 3% PP fiber the same mix achieved 5% higher strength than control mix. On the other hand, the concrete compressive strength made with 75% RA and 100% RA was experimentally found 19% and 22% lower, respectively than control mix. The combinations containing constant fly ash and PPF, in addition to 50% recycled concrete aggregate (RCA), demonstrate greater resistance when exposed to sulfuric acid (H 2 SO 4) environments, in comparison to the control mixture. However, the worst performance is shown by mix (100% RA). [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using ordinary Portland cement (OPC) in concrete has significant environmental and sustainability concerns. Notably, in the production of OPC, large volumes of greenhouse gases are produced, which contribute to global warming, and large amounts of natural raw materials are used, which can lead to the depletion of nonrenewable resources with time. In addition, OPC production is highly energy-intensive. To mitigate these concerns, it has become common practice to reduce the amount of OPC used in concrete production by partially replacing OPC with a supplementary cementitious material (SCM). Most of the SCMs used have pozzolanic properties and react with free lime in OPC to provide more cementitious material, which increases the long-term strength of concrete and also densifies the pore structure, resulting in improved durability in harsh environments. This study explored the effect of OPC on the resistance to sulfuric acid attack and drying shrinkage when OPC is partially replaced by processed bagasse ash (PBA) at dosages of up to 50%, together with 5% silica fume. Both materials are pozzolanic and are expected to react with free lime in OPC concrete to increase the strength and densify the concrete; however, with increased PBA dosage, the cement is diluted, and a reduction in strength can be expected. This study explores the benefits that can be realized, focusing primarily on sulfuric acid resistance and the reduction of drying shrinkage. [ABSTRACT FROM AUTHOR]

Recently, the usage of a cold-bonded method in the production of artificial green geopolymer coarse aggregates (GCA) has been crucial from an economic and environmental perspective because the sintering method consumes an enormous quantity of energy and generates a significant quantity of pollutants. This research investigated the manufacture of GCA via cold-bonded pelletization using two distinct industrial byproducts (GGBFS and FA) via a new and simpler pelletization technology. Three different binders were used to produce three distinct types of GCAs as partial replacements for natural coarse aggregate (NCA) at varying replacement rates (0%, 25%, 50%, and 75%). The first group used ground-granulated blast furnace slag, while the second used GGBFS with perlite, and the third used FA with perlite. An alkaline activator was commonly used with all three groups. The physical and mechanical properties of three distinct varieties of GCA were recorded. The results indicated that the mechanical and chemical properties of three different types of GCAs were nearly identical to those of natural aggregate, with the exception of their increased water absorption. According to the findings, the recommended mixtures were suitable for usage in the construction industry. The results indicated that the ratio of all investigated attributes declined as the number of GCAs increased. In contrast, lightweight concrete can be obtained at a ratio of GCA (FA with perlite) equal to 75%, where unit weight, compressive, splitting tensile, flexural, and water absorption strengths were 1.87 gm/cm3, 20.2 MPa, 1.8 MPa, 8 MPa, and 6.0%, respectively (FA with perlite). [ABSTRACT FROM AUTHOR]

The concrete of the main structure of subway stations is highly constrained, so the temperature effect and shrinkage effect generated during the construction process often cause large restraint stress, thus causing the problem of structural cracking. Therefore, low-heat-of-hydration cements are usually used in such construction work to reduce the temperature during the aging of concrete. Therefore, based on the hydration heat release subprogram of concrete, an effective numerical simulation was carried out, and compared with the semi-adiabatic temperature rise test, a method of numerical calculation and parameter fitting to solve the influence coefficient of the hydration heat model was proposed, and the sensitivity of the hydration heat release model and the influence coefficient for several concrete mixtures with additives was studied. The main conclusions are as follows: (1) Combined with the measured temperature curves of several types of mineral-admixed concrete, the composite exponential exothermic model of several types of mineral-admixed concrete can be obtained by adjusting the parameter fitting to solve the influence coefficient of the exothermic hydration model proposed in this paper. (2) One can adjust the influencing coefficient a to control the maximum temperature of concrete. Similarly, the temperature curve of concrete can be adjusted by modifying the influencing coefficient b. [ABSTRACT FROM AUTHOR]

This study investigates a novel method of recycling end-of-life reverse osmosis (RO) membranes to enhance the mechanical properties of concrete. Reverse osmosis (RO) is a widely used technology for water purification and desalination, but it has various environmental problems that require attention. RO membranes have a short service life, resulting in the generation of end-of-life (E-o-L) RO membrane trash in thousands of tons each year, which is typically disposed of in landfills, polluting land resources. The RO membrane primarily comprises a thin-film composite of polyamide (TFC PA) as a filter medium. The material properties of TFC PA are studied and added to the concrete as an additive in the cement volume at 1 to 20%. The optimum mix is identified at 3.4% of TFC PA, and the mechanical properties are nearly 17% greater than the control mix. SEM/EDX shows a higher bonding between TFC PA and the concrete, and TGA results exhibit the mass loss increasing with the increase in TFC PA. MIP analysis shows that the volume of cumulative pores and intruded volume is increased with increasing TFC PA. A sustainability study was carried out to evaluate the energy consumed and embodied CO2 in the mixes and compared them with the control mix. The mathematical model for compressive strength at 7 days, 14 days, and 28 days is done using response surface methodology (RSM) with the independent variables of TFC PA, slump, and superplasticizer. The adopted regression illustrates a significant relationship between the response and variables, proving a higher R2 for all the models and optimal p-values for the responses. They show that TFC PA influences the enhancement of properties of concrete. The residual also proves to be very minimal in the model. [ABSTRACT FROM AUTHOR]

This study examined the feasibility of producing colored geopolymer concrete using slag as the binder and investigated the effects of pigment on various properties of geopolymer concrete. The geopolymer concrete was supplemented with two varieties of pigment, namely iron oxide hydroxide in the shades of "red" and "yellow", then the following tests of compressive strength, rebound number, density, and ultrasonic pulse velocity were carried out on it. The highest compressive strength value was achieved when adding 1% of pigments, which increased the red and yellow values from the reference value by 2.7 percent and 1.8 percent, respectively. The best rebound number values can be obtained by adding 1% yellow and 3% red, which increased the red and yellow values from the reference value by 8% and 15%, respectively. The density increases as the proportion of the additional pigment rises. The maximum density values were achieved by incorporating 1% of red and yellow pigment, with a respective increase of 1% and 3% for red and yellow. The highest values of ultrasonic pulse velocity when adding 1% of yellow and red color pigments increased by 1.7% for yellow and 2% for red. The optimal addition is 1.2% as it enhances properties and reduces expenses when utilizing smaller pigments [ABSTRACT FROM AUTHOR]

This study aimed to develop accurate models for estimating the compressive strength (CS) of concrete using a combination of experimental testing and different machine learning (ML) approaches: baseline regression models, boosting model, bagging model, tree-based ensemble models, and average voting regression (VR). The research utilized an extensive experimental dataset with 14 input variables, including cement, limestone powder, fly ash, granulated glass blast furnace slag, silica fume, rice husk ash, marble powder, brick powder, coarse aggregate, fine aggregate, recycled coarse aggregate, water, superplasticizer, and voids in mineral aggregate. To evaluate the performance of each ML model, five metrics were used: mean absolute error (MAE), mean squared error (MSE), root mean squared error (RMSE), coefficient of determination (R2-score), and relative root mean squared error (RRMSE). The comparative analysis revealed that the VR model exhibited the highest effectiveness, displaying a strong correlation between actual and estimated outcomes. The boosting, bagging, and VR models achieved impressive R2-scores in the range of 86.69%–92.43%, with MAE ranging from 3.87 to 4.87, MSE from 21.74 to 38.37, RMSE from 4.66 to 4.87, and RRMSE between 8% and 11%. Particularly, the VR model outperformed all other models with the highest R2-score (92.43%) and the lowest error rate. The developed models demonstrated excellent generalization and prediction capabilities, providing valuable tools for practitioners, researchers, and designers to efficiently evaluate the CS of concrete. By mitigating environmental vulnerabilities and associated impacts, this research can significantly contribute to enhancing the quality and sustainability of concrete construction practices. [ABSTRACT FROM AUTHOR]

Tumushuke, a significant node of "the China–Pakistan Economic Corridor" and "the Silk Road Economic Belt", is strategically located in the southern region of Xinjiang. Due to the widespread distribution of its salty soils, concrete construction safety is significantly compromised. The construction of this project used sulfate-resistant cement, which was costly to construct. Six groups with varying sulfate immersion concentrations were set up to perform sulfate erosion tests and sulfate freeze–thaw coupling tests, respectively, based on the survey of the distribution of sulfate concentration in the area. The Tumushuke area's concrete erosion kinds were classified using a microanalysis of the degraded concrete. The findings indicate that the concrete primarily exhibits gypsum-type erosion when the sulfate concentration is greater than 20,000 mg/kg, ettringite–gypsum-type erosion when the sulfate concentration is between 15,000 and 20,000 mg/kg, and ettringite-gypsum-type erosion when the sulfate concentration is less than 15,000 mg/kg. The erosion product, carbon–sulfur silica-calcite, also occurs under sulfate freeze–thaw coupling. In the Tumushuke area, ettringite-type erosion damage is primarily found in low-sulfate areas in the southwest and a small portion of the northeast. In contrast, higher-sulfate areas in the central northward area are primarily affected by ettringite–gypsum and gypsum-type erosion damage. The results of this study can provide a basis for adopting different anti-sulfate erosion measures for engineering construction in different regions. [ABSTRACT FROM AUTHOR]

Basaltic rocks are the main source of local crushed rock aggregate for concrete in their region. Basaltic rocks are also potential rocks for alkali–silica reaction (ASR). ASR is a complex mechanism that deteriorates concrete via creating volumetric expansion over time between the reactive silica in the aggregate and the alkali components in Portland cement. However, due to the multi-scale nature of this long-term phenomenon, understanding its mechanism in concrete structures remains difficult to assess. In this study, the morphology and analytical composition of three groups of concrete prepared with basalt aggregate, basalt aggregate with 20% fly ash substitution of cement, and limestone aggregate were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX); it was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) and compared with the ASR structure. The (Na + K)/Si and Ca/Si ratios in SEM/EDX analysis and the water peaks in FT-IR and TGA analyses will help to determine the footprint of ASR. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The subject of this research is sustainable construction and energy saving, which is most reflected in the technological aspects of building construction. This article focuses on single-family buildings, and the subject of this research is hollow blocks (blocks) created as a result of hydrothermal treatment, in this case, autoclaved aerated concrete (AAC) and autoclaved cellular concrete (ACC), both traditional and modified plastics (HIPS). There are two types of materials resulting from hydrothermal treatment: autoclaved sand-lime bricks and autoclaved concrete. Both in the case of ACC and silicates bricks, the basic substrates used during their production are lime, sand and water (cement is also added to cellular concrete). This article presents the methodology of testing the porous structure of autoclaved materials with the use of computed tomography. Aerated concrete (light autoclaved concrete) has a compressive strength of 2–6 MPa. The tests included aerated concrete modified with high-impact polystyrene, commonly known as HIPS. HIPS high-impact polystyrene is a thermoplastic polymer that is obtained by block suspension polymerization of styrene with the addition of synthetic rubber. As a result of polymerization, small particles of polybutadiene remain in the polystyrene male, changing its physical and mechanical properties. The results from the content of air voids in the autoclaved concrete sample were, on average, 52.53%. [ABSTRACT FROM AUTHOR]

In recent years, the increased use of heavy commercial vehicles with higher axle weights has required the development of innovative technologies to improve the mechanical properties of asphalt concrete conglomerates, such as fatigue resistance and rutting. This study offers a comprehensive comparative analysis of different types of asphalt concrete tested in four trial sections (S1, S2, S3, S4) of the SP3 Ardeatina rural road in Rome, under actual traffic and operational conditions. More precisely, the pavement technologies applied include modified asphalt concrete with graphene and recycled hard plastics for S1, asphalt concrete modified with styrene–butadiene–styrene (SBS) for S2, asphalt concrete with a standard polymeric compound for S3, and traditional asphalt concrete for S4. The evaluation approach involved visual inspections in order to calculate the pavement condition index (PCI) and falling weight deflectometer (FWD) tests. In addition, back-calculation analyses were performed using ELMOD software to assess the mechanical properties. The laboratory tests revealed superior properties of M1 in terms of its resistance to permanent deformations (+13%, +15%, and +19.5% compared to M2, M3, and M4, respectively) and stiffness (10,758 MPa for M1 vs. 9259 MPa, 7643 MPa, and 7289 MPa for M2, M3, and M4, respectively). These findings were further corroborated by the PCI values (PCIS1 = 65; PCIS2 = 17; PCIS3 = 28; PCIS4 = 29) as well as the FWD test results after 5 years of investigation, which suggests greater durability and resistance than the other sections. [ABSTRACT FROM AUTHOR]

Beam-column joints are crucial load transmission zones because they face concentrated forces from both the beams and the columns. High shear and axial stresses caused by these concentrated forces in the area of the joint may result in decreased joint strength. This article proposes a new beam-to-column connection developed for precast concrete-resisting frames. Concrete mixtures are enhanced mechanically by adding nano silica as it increases compressive strength, flexural strength, and abrasion resistance. Within the concrete, it creates a solid, gel-like matrix that fills voids and strengthens the whole construction. In this study, three reinforced concrete beam-column joint specimens were cast with fly ash, the other three with nano-silica and fly ash, and one sample with nano-silica and a control mix without admixtures was cast. Specimen cast using fly ash and nano-silica is subjected to cyclic loading after 28 days of curing. A load capacity of 100 kN was imposed on the column during testing. It was observed that a gradual increase in fly ash decreased the compressive and flexural strength of the beam-column joints. This decrease in strength was addressed by adding 2.5% nano-silica. Nano silica acts as a nucleus to bond tightly with cement particles during hydration. The results showed that the flexural strength equivalent to that of a controlled specimen can be achieved by adding nano-silica at 2.5% and fly ash at 60%. The highest loading of 38.1 kN can be applied to the specimen with nano-silica without fly ash. Although a higher axial compression ratio can improve the bearing capacity and initial stiffness, it can also reduce deformation capacity and flexibility. [ABSTRACT FROM AUTHOR]

The current study reports on the long-term structural performance of novel reinforced marine geopolymer concrete beams under accelerated weathering conditions. The study covers the flexural performance of 40 geopolymer concrete beams reinforced with basalt fibre-reinforced polymer (BFRP) bars, including 12 beams under sustained loading when exposed to 3, 6 and 12 months of accelerated marine environment consisting of tidal cycles of seawater at a temperature of 50°C. The experimental results revealed that the novel marine geopolymer concrete reinforced with BFRP bars reported minimal micro- and macro-mechanical degradation compared to geopolymer concrete or ordinary concrete beams under the same exposure environment, with and without sustained loading. The BFRP-reinforced self-compacting geopolymer concrete (SCGC) beams reported 87% residual ultimate load after 12 months of exposure to marine environments, while the sustained loaded BFRP-SCGC beams reported a residual strength of 79%. In addition, microstructural assessment using scanning electron microscopy and energy dispersive X-ray spectroscopy analysis revealed that after 12 months of exposure there was a trace of chloride salts, indicating the chemical ingress over time; however, the impact on structural properties is not distinct. [ABSTRACT FROM AUTHOR]

This study investigates the performance of recycled aggregate concrete incorporating different sizes and concentrations of coarse aggregate under sodium sulphate and normal water curing. Ten mixes were produced, having two control mixes of 12 to 20 mm and 5 to 12 mm coarse aggregate size. The rest of the mixes have supplementary cementitious material with 0%, 15%, 30%, and 45% substitution of respective sizes normal aggregate by recycled aggregate. The fresh recycled aggregate concrete mixes were assessed through the slump, ball penetration, and compacting factor test, which exhibited a falling trend with the percentage increase of recycled aggregate. Moreover, compressive strength and ultrasonic pulse velocity drop with the percentage of RCA increases at 7, 28, and 91-days normal curing and 5% Na2SO4 solution curing at 91 days. The compressive strength and ultrasonic pulse velocity of 5-12 mm coarse aggregate concrete showed improvement over 12-20 mm coarse aggregate concrete of the same replacement for both curing. However, 5% Na2SO4 solution curing specimens exhibit around 5-11% decrease in compressive strength and higher penetration depth than normal curing . Furthermore, the outer face of the silica fume included samples have received fewer white patches after sodium sulphate immersion. [ABSTRACT FROM AUTHOR]

Recent advancement in construction practices demands the utilisation of construction materials in a sustainable way which promotes the use of industrial by-products as Supplementary Cementitious Materials (SCMs) and alternative aggregates to protect diminishing natural resources. The present study proposed the utilisation of high-volume fly ash in the production of Self-Compacting Concrete (SCC) made with varying proportions of coarse and fine recycled aggregates. Natural Aggregates (NA) of both coarse and fine type in high-volume fly ash SCC were replaced with the respective type of recycled aggregates at the dosage of 0%, 50% and 100% by volume and their hardened state behaviour was studied in terms of compressive strength, chloride ion permeability, initial rate of water absorption, sorptivity coefficient and sulphate resistance. Results of the investigation recommends uses of Silica Fume (SF) at 10% dosages in ternary blends of cement along with high-volume fly ash for the production of SCC at 50% replacement level of both coarse and fine recycled aggregates, without compromising the hardened state properties of concrete. [ABSTRACT FROM AUTHOR]

In this paper, firstly, the effects of graphene oxide on the mechanical properties of concrete were investigated. Secondly, the degradation and mechanism of the mechanical properties of graphene oxide concrete (GOC) under sulfate attack and a freeze–thaw environment were investigated. In addition, the dynamic modulus of elasticity (MOEdy) and uniaxial compressive strength (UCS) of the GOC were measured under different environmental conditions. According to the test results, the incorporation of graphene oxide in appropriate admixtures could improve the mechanical properties of concrete in these two working environments. It is worth noting that this effect is most pronounced when 0.05 wt% graphene oxide is incorporated. In the sulfate attack environment, the MOEdy and UTS of the GOC0.05% specimen at 120 cycles decreased by 22.28% and 24.23%, respectively, compared with the normal concrete specimens. In the freeze–thaw environment, the MOEdy and UTS of the GOC0.05% specimen at 90 cycles decreased by 13.96% and 7.58%, respectively, compared with the normal concrete specimens. The scanning electron microscope (SEM) analysis showed that graphene oxide could adjust the aggregation state of cement hydration products and its own reaction with some cement hydration crystals to form strong covalent bonds, thereby improving and enhancing the microstructure density. [ABSTRACT FROM AUTHOR]

The goal of this paper is to investigate the impact of nano-materials on the mechanical and electrochemical properties of self-cleaning concrete. Nano-titanium dioxide and nano-zinc oxide were used as additives for this purpose. Additionally, a comparative study on the effect of using these materials on the self-cleaning concrete's characteristics was conducted. The dosages of nano-titanium dioxide (nps-TiO2) and nano-zinc oxide (nps-ZnO) used were 0, 0.5, 1, 1.5, 2, and 2.5% and 0, 1, 2, and 3% of the weight of the cement, respectively. The results showed that the optimum compressive strength and the lowest corrosion rate were fulfilled at 2.5% of nps-TiO2 and 1% of nps-ZnO, and using 2.5% of nps-TiO2 achieved the highest improvement in the corrosion rate. However, 1% for nps-TiO2 mixtures and 1% for nps-ZnO mixtures were the best ratios for flexural strength. On the other hand, for the corrosion rate, the samples were tested at 2 and 6 months. When nps-TiO2 and nps-ZnO samples were compared to the control sample, 2.5% and 1% of nps-TiO2 and nps-ZnO, respectively, showed the largest improvement in resistance to corrosion. Also, the self-cleaning property of the samples containing nano-materials (nps-TiO2 and nps-ZnO) was tested. As the results illustrated, the self-cleaning property of the samples was increased over time due to photocatalytic degradation. Furthermore, the results of the photocatalytic tests showed that nps-TiO2 samples outperformed nps-ZnO samples overall. [ABSTRACT FROM AUTHOR]

This paper presents experimental results on the influence of concrete composition factors on the criterion characterizing the ratio between the compressive strength of activated low-cement concrete and clinker consumption. The investigation was carried out using mathematical planning of the experiments. Experimental and statistical models describing the influence of the fly ash, activating additive (microsilica), consumption of cement and aggregates, as well as the superplasticizer on the strength of low-cement concrete under normal hardening conditions and after steaming were obtained. The values of the clinker efficiency criterion and the mineral additive cementing efficiency coefficient were calculated, and models of these parameters were obtained for the investigated concrete compositions. It was shown that the activating effect of microsilica yields an increase in ash cementing efficiency and clinker efficiency criterion in concrete. Using the obtained models, an example for calculating the ash cementing efficiency coefficient is given. [ABSTRACT FROM AUTHOR]

Concrete is vital for the development of modern buildings. However, they suffer from the high viscosity problem in their application process due to the use of a low water–cement ratio in order to maintain their high strength. Developing PCEs with the presence of ester functional groups in their molecular structure is one of the most effective measures to improve the flowability of concrete. Here, three PCEs with different alkyl densities of acrylic acid ester: PCE-M, PCE-E, and PCE-B were designed to explore their viscosity-reducing effect on the performance of cement and concrete. The structures of the three PCEs were characterized via Fourier transform infrared (FTIR) spectra, proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC). Their properties were also determined via zeta potential, surface tension, and rheological experiments. It was found that PCE-M had the best performance, with the lowest surface tension, highest zeta potential, and therefore highest charge density on the cement particles, lowest viscosity, and highest flowability of cement paste, and exhibited the best performance of concrete in terms of workability. The best performance of PCE-M in reducing the viscosity of cement and concrete can be ascribed to the smallest amount of water-repellent alkyl groups, enhancing the electrostatic repulsion and reducing the viscosity, thereby boosting the dispersion and stabilization of cement pastes and concrete. This study shed lights on designing other PCEs with high viscosity-reducing effects via an ester group control. [ABSTRACT FROM AUTHOR]

Significant efforts have been made to improve concrete mix design for shrinkage reduction and crack control, including reduction of cement content and selection of cement type with less heat of hydration, maximizing aggregate contents, and introduction of discrete fibers in concrete to increase internal restraint. Although high-performance concrete (HPC) mixes including fibers [e.g., steel fibers, polypropylene fibers, or polyvinyl alcohol (PVA) fibers] have reduced the level of shrinkage cracking, they have not eliminated it. Thus, understanding the level of tensile strain the fibers take in the concrete could provide valuable information to aid engineers to make an informed decision on the need for fibers in tension demand in the concrete and determine the appropriate fiber detailing and concrete mix additives. As such, this study aimed to explore a multiscale, hierarchical fiber gradation through a combination of nanoscale nanofabrillated cellulose (NFC) with microscale sisal fibers and macroscale steel fibers in concrete to mitigate the causes of concrete shrinkage cracking at an early age. A total of 22 mixtures were designed and tested. The results show that nanofabrillated cellulose, sisal fiber, and steel fiber can play an excellent synergistic effect to inhibit the early-age shrinkage of concrete. The test data reveal that, when steel fiber is partially replaced by sisal fiber, the early shrinkage of steel fiber concrete is significantly reduced by 26.91% at maximum. Meanwhile, when the NFC content reached 0.15%, the 7-day shrinkage value of concrete reinforced by steel fiber, sisal fiber, and NFC was the lowest, and the shrinkage strain value decreased by 25.03% compared with N0. Compared with the experimental group in which sisal fiber partially replaced steel fiber, the 7-day shrinkage value of the experimental group in which sisal fiber mixed with NFC, sisal fiber mixed with NFC and steel fiber decreased to a certain extent, among which SF1.1FF0.4NFC0.15 showed the best shrinkage inhibition performance, and the shrinkage strain value decreased by 82.56% and 45.39% compared with N0 and SF1.1FF0.4, respectively. [ABSTRACT FROM AUTHOR]

In this study, the effect of colloidal nano-silica replacing a fraction of cement and recycled concrete fine aggregate replacing natural sand on the post-fire mechanical features and durability of concrete was explored. To achieve this goal, 189 concrete samples were manufactured in total, with key variables being the volume of fine aggregate at 0, 50, and 100% replacing natural fine aggregate, the volume of nano-silica at 1.5, 3, 4.5, and 6% replacing the cement weight, and the exposure temperature at 20, 300, and 600 °C. Parameters selected for consideration in the concretes consisted of compressive capacity, splitting tensile capacity, elastic modulus, ultrasonic pulse velocity (UPV), and weight loss. Furthermore, using scanning electron microscopy (SEM) imaging, the microstructural condition of different sample groups was investigated. According to the findings, as the content of the recycled fine aggregate (RFA) replacing natural fine aggregate increased, the compressive capacity of the unheated and heated concretes declined, and the rate of this drop became greater as the replacement volume increased. On the other hand, the presence of the nano-silica and an increase in its content replacing the cement content in recycled aggregate concrete improved the compressive strength relative to the reference concrete for all the exposure temperatures, with the greatest improvement for the replacement percentage of 4.5%. In addition, the heat-induced compressive capacity drop was more pronounced at higher replacement levels of nano-silica. With a rise in the exposure temperature of the samples with only the recycled fine aggregate, fewer microcracks formed compared with the samples containing both recycled fine aggregate and nano-silica. The maximum weight loss occurred in the recycled sample containing the highest contents of nano-silica and recycled aggregate. Afterward, it was attempted to estimate the mechanical features of concrete by developing several empirical formulas as a function of temperature and volume fractions of recycled fine aggregate and nano-silica. These formulas were evaluated against the test data of this study and others, which showed an acceptable correlation. Finally, the findings of the tests were evaluated against the predictions of ACI 216, EN 1994–1-2, EN 1992–1-2, and ASCE. [ABSTRACT FROM AUTHOR]

The polycarboxylate superplasticizer (PCE) has been widely used in concrete products, tunnels, bridges and water conservancy projects due to its excellent characteristics. With the rapid development of the construction industry and the depletion of high-quality raw materials for concrete, sand and gravel containing clay have been used in concrete, which reduces the properties of PCEs. Recent studies have found that many PCEs structures without PEG/PPG or polyamine side chains have been developed due to the influence of montmorillonite (MMT) in clay on the fluidity of concrete. However, the influence mechanism of clay minerals in concrete on PCEs and the improvement methods are not summarized, and this paper has systematically overviewed this aspect. Firstly, HPEG-PCEs and APEG-PCEs in the PCEs market have superior cost effectiveness for concrete, while specific efficient PCEs such as zwitterion PCEs are suitable for calcination of clay cement mixtures to reduce anthropogenic CO2 emissions. Secondly, the chemical adsorption of clay to PCEs in concrete leads to a sharp decline in concrete fluidity, in which montmorillonite has the greatest effect, followed by illite and kaolin. Finally, methods such as modifying clay, increasing or reducing the steric resistance of PCEs, introducing special functional groups and adding sacrificial agents are discussed to improve the fluidity of concrete containing clay by changing the structure of clay layers and PCEs, thus saving the construction cost caused by the amount of raw materials and PCEs. In addition, the efficient application and future research of clay minerals and PCEs are also prospected. [ABSTRACT FROM AUTHOR]

Nowadays low calcium fly ash-based geopolymer concrete can be replaced with cement-based concrete to avoid the adverse effect of manufacturing cement on the environment. Utilization of geopolymer concrete instead of traditional concrete using low calcium fly ash and nano silica reduces a significant amount of CO-2 emission towards the atmosphere. However, the performance of geopolymer concrete is less than that of Portland cement concrete. To improve the performance of geopolymer concrete nano silica was used in the present study. In this work, geopolymer concrete was made utilizing fly ash, ground granular blast furnace slag (GGBS), and sugarcane bagasse ash. In the first instance, binary combinations i.e. fly ash and GGBS were employed as cementitious materials for the production of geopolymer concrete. In the second instance, a ternary mixture of pozzolanic material was prepared by taking 25% GGBS, 65% Fly ash, and 10% bagasse ash. In the third instance, varying percentages of nanoparticles were used for the above ternary mixture. The mechanical and durability properties of the geopolymer composite that was made earlier were tested. The compressive strength and split tensile strength of geopolymer composites were assessed for mechanical properties and a rapid chloride permeability test, water absorption test, and acid attack test were done to know about the porosity of concrete. Results showed that, with a dose of 4% nanoparticles, the durability and strength properties of the concrete had improved the most. The GCBA-N4 mixture had the highest split tensile and compressive strength was measured to be 2.91 MPa and 41.33 MPa and the rapid chloride permeability test, water absorption rate, and percentage of mass loss due to sulfate attack were found as a minimum for GCBA-N4 specimen. [ABSTRACT FROM AUTHOR]

Due to an incessant upsurge in the construction industry and the steep increase in the cost of raw materials, researchers are focusing on various resources that can be replaced with cement as a construction material. One such material that is rich in Silicon and Aluminium is Flyash. Flyash as an additive to concrete made a way for a contemporary material that was coined as Geopolymer Concrete (GPC). In Geopolymer, alkaline activators such as sodium hydroxide or potassium hydroxide are mixed with sodium silicate so as to form geo-polymerization with products like GGBS, flyash etc. and which as a result binds the aggregate. This paper mainly emphasizes on role of Crumb Rubber (CR) in the formation of GPC replacing the fine aggregates by various percentages (5% - 15%) of CR. The Geopolymer mix design is proposed for M40 grade. Compressive and tensile strength tests were carried out on concrete modified with Flyash and GGBS (Ground Granulated Blast Furnace Slag) in 60:40 ratios. At a molarity of 14M, ratio of sodium silicate to sodium hydroxide is maintained as 2.5. The samples were placed in an ambient condition and were tested for strength on 7, 14 and 28 days. Based on the experimental results, it was observed that use of CR in GPC does not enhance the strength properties and cannot be used in high-end structural applications only. [ABSTRACT FROM AUTHOR]

The incorporation of waste glass and glass fiber, as replacements for fine aggregate and cement respectively, offers a sustainable strategy to mitigate landfilling and virgin aggregate extraction. The present study delves into the influence of these waste derivatives on the mechanical and thermal attributes of concrete. Fine aggregate was substituted by crushed glass shards in a weight-to-weight ratio ranging from 5% to 30%, and cement was replaced by glass fiber in a weight-to-weight ratio of 1%. Mechanical attributes such as compressive, flexural, and splitting strength were evaluated, along with thermal characteristics of the concrete. A concrete mix ratio of 1:2:4 and a water/cement ratio of 0.45 were employed. The results revealed that concrete designated as Mcf20% demonstrated superior mechanical properties compared to the reference concrete. After 28 days, compressive strength of 51.2 MPa, flexural strength of 6.5 MPa, and splitting tensile strength of 3.78 MPa were recorded for Mcf20% concrete, signifying the beneficial effects of the combined use of glass fiber and crushed glass. Furthermore, an inverse relationship was observed between the percentage of waste additives and thermal conductivity. This investigation underscores the potential of recycling glass and glass fiber as eco-friendly additives in concrete, improving both mechanical properties and thermal performance, thus endorsing their use in structural and architectural concrete applications. [ABSTRACT FROM AUTHOR]

Only in Europe, every year around 29 million tons of plastic waste are generated and only about 35% of such waste is collected for recycling. This results in huge amounts of plastic waste threatening the environment. One of the possible solutions for disposal can be represented by the concrete industry. Several research works have already studied the use of plastic waste in concrete mix as partial replacement for aggregates, showing that this use of plastics can contribute to reducing the environmental impact of concrete production by saving non‐renewable resources. At the same time, lightweight concrete can be produced but at a non‐negligible cost of a mechanical strength reduction. This work aims at investigating the effects on concrete physical and mechanical performances resulting from the introduction of recycled plastic aggregates in combination with another kind of waste used as filler, namely biochar. Biochar, which is the solid carbonaceous by‐product resulting from wood‐waste pyro‐gasification, can have the role of carbon sequestrating additive in concrete, being able to fix carbon in a stable form in buildings for decades. The experimental findings obtained in this work show that the combination of biochar and recycled plastic waste, which was never investigated before, can help to obtain concretes with satisfactory mechanical performance, which promote circular economy principles. Thanks to biochar addition, the reduction in mechanical properties due to the presence of plastics is extremely limited with respect to control; moreover, these concretes demonstrate better behavior in terms of fracture energy and ductility. [ABSTRACT FROM AUTHOR]

Through this study, an attempt was made to produce concrete beams from self‐compacting concrete (SCC) contain expanded polystyrene (EPS) beads as coarse aggregate and waste plastic fibers (WPFs) produced from cutting disposed packing straps in site. The beams were designed according to ACI‐318‐14, where three different reinforcement ratios were chosen for the purpose of checking the conductance of thresholds made of this type of environmentally friendly concrete under bending loads. The use of EPS with WPFs had a significant positive effect in reducing the density of concrete, and the highest percentage of reduction was equal to (38.46%). Using WPFs had a positive effect in increasing the flexural toughness of concrete prisms, and the maximum increment was equal to (180%) compared with these made from the reference mix. The results proved the possibility of producing lightweight concrete from the use of EPS waste and WPFs, three of which are structurally can be classified as lightweight concrete combination of normal weight and lightweight aggregates according to specifications requirements of ASTM330/330M‐14. Reinforced lightweight SCC beams behaved under flexural loads similar to the reinforced concrete beams made from normal weight concrete counterparts under flexural loads. [ABSTRACT FROM AUTHOR]

Concrete is known as one of the most important materials in the world. Concrete composites consisting of cement, water, aggregates, and some additives are used to improve the properties of concrete. These concrete have a certain compressive strength that can be increased depending on the type of concrete. In line with these ideas, high-performance concrete (HPC) has been produced, which can have high compressive strength by adding materials such as fly ash, silica fume, etc. This type of concrete is used in bridges, dams, and special constructions. However, obtaining the mixture design of HPC is problematic and complex, for this reason, the machine learning methods can make it easy to achieve the output by saving time and energy. This study has used support vector regression (SVR) to predict the compressive strength of HPC. Moreover, this study provided two meta-heuristic algorithms for obtaining suitable and optimized results, which are contained the artificial hummingbird algorithm (AHA) and Sine Cosine Algorithm (SCA). The model by coupling with algorithms created the hybrid method in the framework of SVR-AHA and SVR-SCA. Furthermore, some criteria indicators have been used for determining the most desirable hybrid model, which is included coefficient of correlation (R2), root mean square error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and weight absolute percentage error (WAPE). As a result, the AHA algorithm could have a more satisfying association model with the SVR model, and the results were RMSE = 2.00 (MPa), R2 = 98.59%, MAE = 0.717 (MPa), MAPE = 1.22 (MPa), and WAPE = 0.114 (MPa). [ABSTRACT FROM AUTHOR]

The application of waste tire rubber in the concrete industry is one of the most effective and environmentally friendly ways to solve the problem of so-called black pollution. However, the application of rubber particles (RP) in the concrete industry is hindered by their low stiffness and poor bonding performance with the cement matrix. In this paper, a novel modification method of polydopamine (PDA) modification was used to enhance the hydrophilicity of the RP surface. The surface morphology, element content, and hydrophilicity of RP treated with PDA and KMnO4 were analyzed through scanning electron microscope and energy dispersive spectrometer (SEM-EDS) and sedimentation methods. The unit weight, ultrasonic pulse velocity (UPV), compressive strength, compressive toughness, toughness index, and flexural strength were taken to determine the mechanical properties of ultrahigh-performance rubber concrete (RUHPC). The results showed that the adhesion between paste and RP and the sedimentation rate of RP with PDA or KMnO4 treatment methods exhibited a remarkable improvement. Compared with unmodified RUHPC, the basic mechanical properties of KMnO4 -modified RUHPC were improved slightly, and its toughness index was improved greatly. SEM and EDS results confirmed that PDA was deposited on the surface of RP, eliminating the gap of interface transition zone and significantly enhancing UPV, compressive strength, and flexural strength of RUHPC by 4.1%–5.8%, 17%–20%, and 6.1%–9.8%, respectively. In addition, the compressive toughness of unmodified and KMnO4 -modified RUHPC decreased, whereas that of PDA-modified RUHPC increased significantly. It can be concluded that the mechanical properties of RUHPC with treated RP have improved significantly and the application of RP in ultrahigh-performance composites (UHPC) offers more opportunities for recycling RP. [ABSTRACT FROM AUTHOR]

This research examines the effects of using a combination of Ground Granulated Blast furnace Slag (GGBS) and Hydrated Lime (HL) as alternative cement ingredients on the mechanical and microstructural properties of ternary mixed concrete (Ordinary Portland Cement (OPC)+GGBS+HL). The OPC was replaced with GGBS in increments of 10% from 10% to 70%, while HL was substituted at levels ranging from 0% to 20% in increments of 10%. The results showed that the highest compressive strength (56.20 MPa), split tensile strength (4.25 MPa), and flexural strength (5.58 MPa) were observed for the ternary concrete mixture containing 60% OPC, 30% GGBS, and 10% HL with 0.36 water binder ratio after 28 days of curing. [ABSTRACT FROM AUTHOR]

A haunch system improves the performance of a beam-to-column structure, in combination with a geopolymer haunch, the green-concrete concept is supported by reducing the Portland cement use. The energy dissipation, load‒deformation behavior, failure mode, residual deformation, and plastic hinge formation under a loading‒unloading scheme were studied based on experimental full-scale specimens. The responses of the loading‒unloading protocol were compared to the monotonic loading results. A geopolymer and conventional concrete haunch having similar compressive strengths were analyzed. It was shown that the geopolymer haunch performed excellently and that a concrete haunch remarkably improves the performance of a structure regardless of the haunch material. The geopolymer haunch enhanced the load level at first cracking for 10%, and the formation of plastic hinges 0.7% and 4.5% for the monotonic and loading–unloading, respectively, but slightly reduced the ultimate load by 1%. The loading‒unloading protocol had a negative impact of 3% to 7% on the overall performance, the reduction was lower for the geopolymer haunch underlining the superiority of this material. The loading–unloading scheme resulted in a monotonic strength degradation and deviation in failure mode. A finite element model was constructed to generate and analyze the relation of the haunch's concrete strength to the load‒deformation response. It was found that the haunch's compressive strength had no influence on the behavior of the beam-to-column joint, even for a haunch with a compressive strength as low as 25 MPa. [ABSTRACT FROM AUTHOR]

In this work, the self-catalyzed kinetics to produce glycerol, diglycerol, and polyglycerol-4 maleate esters were experimentally determined from 60 ºC to 80 °C. These esters can be used as intermediates in the production of partially bio-based admixtures that can replace petroleum-derived polycarboxylate ethers, which are traditionally used as concrete superplasticizers. The obtained experimental data were used to adjust the kinetic model parameters for the three reactions, including the effect of temperature. The model adequately predicted the behavior of the three proposed reactions, which was statistically validated using the Fisher-Snedecor test. The activation energies of glycerol, diglycerol, and polyglycerol-4 maleate were 29.5, 85.5, and 68.9 kJ/mol, respectively, with frequency constants of 7.93 × 102, 2.02 × 1011, and 4.48 × 108 min−1. The highest activation energy was obtained for the esterification of maleic anhydride (MAH) with diglycerol, indicating that this reaction is more temperature dependent. The kinetic constants at 70 °C were 2.56 × 10−2 min−1, 1.92 × 10−2 min−1, and 1.46 × 10−2 min−1 for the esterification of MAH with glycerol, diglycerol, and polyglycerol respectively, showing a greater reaction rate for the esterification with glycerol. • The self-catalyzed kinetics to produce glycerol, diglycerol, and polyglycerol-4 monomaleates were experimentally determined. • A first-order model predicts the behavior of the reactions, and it was statistically validated by the Fisher-Snedecor test. • Activation energies for glycerol, diglycerol, and polyglycerol-4 reactions were 29.5, 85.5, and 68.9 kJ/mol, respectively. • For all the reactions studied, conversion and yield of monomaleates were higher than 98% and 93%, respectively. [ABSTRACT FROM AUTHOR]