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In the paper, the impact of paper production waste (primary sludge, or PS) on the properties of cement pastes and mortars is discussed upon. Some specimens were formed with fine PS fraction that replaced a part of cement content in them (5%, 10%, 15%, or 20%); in other specimens, coarse fraction of sludge (2/4) was used and a part of content of fine filler (sand) was replaced by PS. The properties of mixtures, such as water content required for cement paste of normal consistence, the setting time, exothermic temperature, flow diameter and plunger penetration, were established. In addition, the properties of hardened mortar, such as its density, flexural strength and compressive strength, were established. The microstructure of hardened specimens was examined as well. It was found that PS retarded hydration processes and reduced exothermic temperature; in addition, it reduced the flow diameter and the plunger penetration. While assessing the properties of hardened mortar, it may be stated that 5% PS waste might be used for replacement of a part of cement content. [ABSTRACT FROM AUTHOR]

Highlights • Lime sludge utilization in concrete, mortars, fired bricks, ceramics and cement. • 10–30% cement replacement in concrete and mortars by lime sludge is optimum. • 25–30% replacement of fine aggregates by lime sludge is optimum. • Bricks and ceramic production with lime sludge conserves less energy. • Lime sludge eco clinker synthesizes with less carbon footprint and temperature. Abstract This review paper encompasses the inclusive approach of lime sludge valorization in construction materials. Research studies based on cement and aggregate replacement by lime sludge concludes that 10–30% lime sludge is gainfully utilized in sustainable concrete and mortar. Additional prospect for lime sludge application in construction material is the production of cement and ceramics. Significant use of lime sludge in combination with supplementary cementitious materials such as silica fume, nanosilica and fly ash is recommended for the production of cement components and ceramics. The recommendations are also suggested in accordance with the outcome of the study. [ABSTRACT FROM AUTHOR]

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]

Highlights: [•] APS-FA blended cement mortars showed good resistance to freeze/thaw cycles. [•] Blended mortars perform better than OPC mortars in marine environments. [•] Resistance of blended and OPC mortars to Spanish’s plateau conditions are similar. [ABSTRACT FROM AUTHOR]

Abstract: Making use of industrial by-product or waste clay to partially replace cement in concrete has greatly contributed to sustainable development of environment. This study investigated the optimal activation condition for producing high reactivity metakaolin (MK) by using kaolin by-products (KB) from paper industry. Initially, the material properties of KB were analyzed in this study and the results indicated its great potential to be treated by calcination to be a very effective pozzolan. Afterwards, MK samples produced from different activation treatments of KB, including different calcining temperature, calcining duration, initial temperature rise rime and grinding particle size, were applied in mortar to determine their pozzolanic effect. Results indicated that the optimal activation condition for KB to high reactivity MK conversion is 2-h calcining duration at 750°C and with 7μm grinding particle size. Finally, compressive and flexural strengths of mortar samples produced by replacing cement with 0–25% MK content were tested and the results showed that 15% was the optimal cement replacement level of MK and the mortar so produced exhibited 20% improvement in compressive strength compared to control mortar. [ABSTRACT FROM AUTHOR]

Abstract: The use of paper de-inking sludge in pozzolanic material manufacture permits a disposable residue to be included in the cycle of the materials. A study on the reuse of paper de-inking sludge, undertaken in Spain, shows its potential as raw material for yielding a product with pozzolanic activity. This study establishes that an optimal condition for transforming paper de-inking sludge into a pozzolanic addition is achieved at 700°C maintained for 2h. Under these conditions, the organic matter disappears and the calcined sludge becomes active by transforming kaolinite into metakaolinite. The calcined product exhibits high pozzolanic activity. The present paper also analyses mechanical, physical and chemical properties of a blended cement containing 90% (in mass) standard Portland cement (CEM I-52,5N) and 10% of the pozzolanic addition obtained from controlled calcination of paper de-inking sludge (for 2h at 700°C). When the blended cement is compared with a cement containing 100% standard Portland cement, the following conclusions can be mentioned: a significant gain in compressive strength from 7 days on, a sooner initial setting time, as well as a reduction in SO3 percentage. In any case, the new blended cement complies with requirements set out in Spanish/European standard UNE EN 197-1-Part 1. [Copyright &y& Elsevier]

Highlights: [•] A beneficial reuse application for two industrial wastes, EPS and PSA, is reported. [•] Lightweight cement mortars containing PSA and EPS have low density and low thermal conductivity. [•] Ground EPS resulted in lower thermal conductivity than powdered EPS. [•] Mortars containing EPS and PSA meet the EU standards for rendering, masonry and plastering. [ABSTRACT FROM AUTHOR]

Highlights: [•] In TPC cement (APS/FA) predominates carboaluminate phase. [•] In OPC cement is formed ettringite as main phase. [•] Different morphologies and crystal sizes founding both cements. [•] The formation of non-expansive ettringite inside the pores is identified. [•] The TPC and OPC pastes can be catalogued as resistant to sulphate ions. [ABSTRACT FROM AUTHOR]

• Evolution of linear attenuation coefficient (LAC) regarding carbonation may vary via different CT. • X-ray energy level used for CT scan can reverse the LAC relationship between calcium carbonate and calcium hydroxide. • Hygral equilibrium and polymorphs of carbonation product can also affect the LAC of carbonated areas. A discussion on a recently published article authored by Kim et al. [Effect of carbonation on cement paste microstructure characterized by micro-computed tomography. Constr. Build. Mater. 263 (2020) 120079] is presented. [ABSTRACT FROM AUTHOR]

Abstract: Due to the growing extent of the sources of aggressive media, the concrete structures may be exposed to the action of organic species. The paper presents the results of the long-term study on the action of various organic substances on the cement-based material. The results obtained show the different aggressivity of the solutions of phenols, carboxylic acids and sulphonic compounds. Petroleum and mineral oil have been shown as unaggressive media. Observed increased expansions followed by crack propagation at the action of some media were adjudged to the cooperation of the mechanism of acidic attack and dispersive effect of surface activity of organic substances. [Copyright &y& Elsevier]

Lignosulfonates are water-soluble anionic polyelectrolyte polymers produced during industrial paper manufacturing. This study investigated concrete produced using lignosulfonates with various chemical contents at different concentrations. Therefore, concrete mixtures were produced using Ca-lignosulfonate (LSc), Na-lignosulfonate (LSn), Mg-lignosulfonate (LSm), and K-lignosulfonate (LSk) at concentrations of 0.4% and 0.8% by weight in the cement. Samples containing cements with different C 3 A, C 3 A + C 4 AF, and Na 2 O + K 2 O contents and variable fineness were tested to determine a compatible combination of cement and lignosulfonates. Results revealed that LSc was suitable for use in cements with greater C 3 A content and fineness and 0.8% was an appropriate usage concentration. [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]

This paper investigates the influence of temperature on autogenous deformation and early-age stress (EAS) evolution in ordinary Portland cement paste using a recently developed Mini Temperature Stress Testing Machine (Mini-TSTM) and Mini Autogenous Deformation Testing Machine (Mini-ADTM). In the Mini-TSTM/ ADTM, CEM I 42.5 N paste with a water-cement ratio of 0.30 was tested under a curing temperature of 10, 15, 20, 25, 30, and 40 °C. X-Ray diffraction (XRD) tests were conducted to measure the amount of ettringite and calcium hydroxide, which reveals the micro-scale mechanisms of autogenous expansion. The applicability of the Maturity Concept (MC) for the prediction of autogenous deformation and relaxation modulus under different temperatures was also examined by the experimental data and the viscoelastic model. This paper leads to the following findings: 1) The autogenous deformation of ordinary Portland cement paste is a four-stage process comprising the initial shrinkage, autogenous expansion, plateau, and autogenous shrinkage; 2) Higher temperature leads to higher early-age cracking (EAC) risk because it accelerates the transitions through the first three stages and causes the autogenous shrinkage stage to start earlier. Moreover, higher temperatures also result in increased rates of autogenous shrinkage and EAS in the autogenous shrinkage stage; 3) Autogenous expansion and plateau are attributed to the crystallization pressure induced by CH. Temperature-dependent CH formation rates determine the duration of the plateau stage; 4) Low-temperature curing can delay but not completely prevent the EAC induced by autogenous deformation; 5) The MC cannot predict the autogenous deformation at different temperatures but can be used to calculate the relaxation modulus, which in turn aids in EAS prediction based on autogenous deformation data. • The effects of temperature on early-age cracking risk induced by autogenous deformation is systematically analysed. • The autogenous deformation and the stress evolution were tested by a mini–Temperature Stress Testing Machine. • The effects of calcium hydroxide on autogenous expansion were found. • A viscoelastic model combined with maturity concept was developed to predict the stress evolution. [ABSTRACT FROM AUTHOR]

• A innovative way to obtain realistic traction-separation curves is investigated. • Fluid-solid coupling model based on cohesive unit cracking behaviour is developed. • Evaluation of sealing capacity of cementing interface by fluid–solid coupling model. • Factors affecting the sealing capacity of cementing interfaces are investigated. Estimating the sealing property of the cementing interface is vital for judging the quality of well cementing construction. The main methods currently used to evaluate the sealing property of the cementing interface (hydraulic cementing strength method and shear cementing strength method) are susceptible to the effects of specimen geometric regularity, interfacial cementing condition, and shear damage pressure source, and the measurement results are not stable, making it difficult to use them as effective methods to evaluate the real cementing interface sealing performance. In this paper, based on the cracking behavior of cohesive units, a method to evaluate the sealing performance of the cementing interface by simulating the cracking process of fluid breaking through the cementing interface in ABAQUSTM FEA software was investigated. The research process includes two parts: first, using a self-designed holding stretching device after eliminating the errors caused by non-interface displacement in the conventional stretching method by repeated stretching and subtraction. The real interfacial traction-separation curve and formation cohesion unit parameters were obtained. Secondly, the cohesive unit parameters obtained in the first step were input into ABAQUSTM FEA software to build a fluid–solid coupling model to simulate the cracking process in the interface region when the fluid breaks through the cementing interface, in which obtaining the solid interface cracking sealing pressure and evaluating its sealing performance are finished. And the accuracy and feasibility of this method were verified by a homemade physical sealing model of the cementing interface. In addition, the factors affecting the fluid pressure at the breakthrough of the cemented interface were investigated in this paper, and it was concluded that changing the elastic modulus of sandstone and cement sheath had a more significant effect on the fluid pressure at the breakthrough of the cemented interface than their Poisson's ratios. Furthermore, the results of this paper also indicate that when the permeability of cement sheath and sandstone is in the range of 0.001 mD–10 mD, the fluid pressure at the time of breaking the cemented interface decreases as the permeability of cement sheath and sandstone increases, and beyond this interval, the effect of the sudden change in permeability of cement sheath and sandstone on the fluid pressure at the time of breaking the cemented interface is no longer obvious. [ABSTRACT FROM AUTHOR]

• Hydration mechanism and hydration products of MPC are introduced. • Effects of temperature, mixing proportion and raw material properties on the setting time of MPC are discussed. • Effects of retarders and mineral admixtures on the setting time of MPC and mechanisms of reaction are analyzed. As a low-carbon and good-performance cementitious material, magnesium phosphate cement (MPC) has been widely studied in recent years. However, excessively rapid setting and hardening has been the main reason limiting the engineering applications of MPC. Therefore, this paper presents a comprehensive literature review of 146 papers published from 1970 to 2023 in which we analyzed the effects of raw material properties and ratios, temperature variations, retarder and admixture contents on the setting time of MPC-based materials, and we summarized the approaches to regulating the solidification and hardening of MPC. More importantly, this paper focuses on the mechanism of the effects of mixing proportion and the admixtures on the solidification and hardening of MPC. Finally, this paper suggests research directions about MPC's setting that are worth investigating in the future. This review enables scholars and engineers to have a clearer understanding of the solidification process of MPC. As such, this review serves as a valuable reference for advancing the field of MPC. [ABSTRACT FROM AUTHOR]

• The tire-pavement mechanism and the measurement methods of pavement friction coefficient are reviewed. • The pavement surface characteristics and the measurement methods of pavement texture are provided and discussed. • The anti-skid evaluation models are summarized and discussed. • The anti-skid overlays are overviewed. Deep insight on the skid resistance of highway tunnel pavement is vital to driving safety of vehicles. This paper presents a review on the skid resistance of cement concrete pavement in highway tunnel. Firstly, this paper summarizes the pavement working environment in highway tunnel. Secondly, tire-pavement friction mechanism, friction measurement methods and the pavement skid resistance inside and outside highway tunnel are reviewed and discussed. Then, the pavement surface texture and the measurement methods are provided and discussed. The anti-skid evaluation models are also reviewed. Finally, the anti-skid methods of cement concrete pavement including resurfacing techniques, and anti-skid overlays are overviewed. Research results show that hysteresis and adhesion can be considered as the main effects contributing to the overall friction force. But the interface contact issues of rubber are also significant for the tire-pavement friction mechanism, which are recommended for further study. Friction measurement methods have different application conditions and indicators. There remains a need to further conduct normalization research on different friction measurement methods. For pavement texture measurement methods, non-contact measurement methods exhibit greater potential for application in pavement texture measurement. Compared with the traditional empirical models, the finite element models can not only provide higher accuracy and reliability in evaluating tire-pavement interaction, but also be more cost-effective and efficient. However, the pavement texture morphology, in particular, pavement micro-texture takes a significant role in investigating the micro-contact, which requires more attention. For tire dynamics models, adaptive models possess substantial potential in tire dynamics modeling and simulation. Compared with resurfacing techniques, anti-skid overlays can provide higher skid resistance and longer service life. The Novachip ultra-thin wearing layer presents a more promising outlook for application in highway tunnel pavement compared to other anti-skid overlays. [ABSTRACT FROM AUTHOR]

• Experimental investigation of bonded-in dowel connections of screw and rods in TCC. • Analysis of the effect of an interlayer and an adhesive with the use of lightweight concrete. • Comparison of the models given in the current design codes with the experimental analysis. With the need of renovation in the current timber structures, use of a cement based layer is a popular solution, which improves the structural integrity and increases the structural mass. In this paper, the use of a lightweight concrete with dowel type connections is investigated since such a combination can serve for both new and existing structures. Two types of dowel connections are experimentally tested, screws and bonded-in rods, to observe their limits and the contribution of an adhesive. To extend the application to an existing structure where a wood-based flooring may be present (such as OSB), which acts as an interlayer in the composite solution, the connections are tested with an interlayer as well. To overcome this challenge, in this paper, the predrilled hole at the wood based material (timber and interlayer) is filled with an adhesive to form a bond to the connection. The experimental results indicate that the addition of an adhesive lead to a positive contribution in mechanical properties. The experimental results are compared with the analytical approaches given in the current codes. The difference in comparisons are justified and further supported with the literature. [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]

• 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]

Highlights • Shrinkage and expansion of various glass aggregate mortars are presented in this paper. • Crushed glass, glass beads, and expanded glass were used to replace natural sand. • Crushed glass and glass beads in mortar improved plastic and drying shrinkage. • Mortar bar tests confirmed deleterious nature of glass, except for expanded glass. Abstract This paper presents the effect of various glass aggregates on plastic and drying shrinkage and alkali silica reaction (ASR) expansion of cement mortar. The study was done by substituting a portion of sand with expanded glass, crushed glass, and glass bead aggregates. The low absorption capacity of glass, except expanded glass, enhanced the dimensional stability of the mixtures, minimizing volumetric contraction associated with shrinkage. Presence of finer glass particles in the mortar resulted in a large benefit in ASR expansion. The study found that cement mortar with glass aggregates can be beneficial if aggregate type and amount is chosen appropriately. [ABSTRACT FROM AUTHOR]

• A simulation model for autogenous deformation based on solidification theory is proposed. • The role of creep on autogenous shrinkage is considered. • The effects of additions of fly ash and silica fume are investigated. The addition of supplementary cementitious materials (SCMs), which is an effective method to reduce the CO 2 emission during the cement production, will change the autogenous shrinkage of early-age hydrating cementitious systems. In this paper the effect of different SCMs, i.e., silica fume and fly ash, on the physical properties and autogenous shrinkage of cement paste is studied, both experimentally and numerically. The experiment results show that autogenous shrinkages of cement pastes reduce significantly with the increase of water-binder ratio. The addition of fly ash will lead to smaller autogenous shrinkage while the influence of the dry densified silica fume on the autogenous shrinkage is not pronounced. A numerical simulation model, in which autogenous shrinkage is split up into an elastic part and a time-dependent part is proposed in this paper. The two parts are calculated separately. The simulation of the visco-elastic response of the cement paste to the internal driving force was performed by using a solidification theory model that takes the aging into consideration. The physical properties of different kinds of cement paste are experimentally investigated and the measured results are taken as input parameters of the simulation model. The simulated autogenous shrinkage of different kinds of cement pastes are compared with the measured results to verify the prediction of the proposed model. [ABSTRACT FROM AUTHOR]

Unmodified thermal-activated recycled cement (RC) paste has unfavorable properties like fast setting. This paper intends to modify RC by adding phosphogypsum (PG) and ground-granulated-blast-furnace-slag (GGBS). A comprehensive experimental program combining isothermal calorimetry, mechanical tests, TG, XRD, MIP, 29Si NMR and SEM of modified RC (PG-GGBS-modified-recycled-cement) pastes was conducted. The results show that GGBS and PG not only effectively modified the setting time but also contributed to a more compact skeleton. The final setting time was extended from 12 mins to 84 mins. The 28d and 90d compressive strength reached 29.8 and 36.9 MPa, increaseing by 21.1 % and 39.9 %, respectively. It is shown that PG acted as a sulfate excitation to the active Al 2 O 3 in the GGBS and RC to generate AFt. Rehydrated C-S-H gel could both wrap and protect the CaSO 4 ·2 H 2 O crystals and crystalline contact points, and effectively filled the pores of the hardened paste, thus promoting the generation of C(-A)-S-H and Ca 5 (SiO 4) 2 (OH) 2. The rehydration of modified RC was associated with a remarkable amount of AFt and AFm intergrowing with the reformed C-S-H gel and generating a compact network skeleton. • Modification of recycled cement with phosphogypsum and GGBS was investigated. • GGBS and PG not only effectively modified the setting time but also contributed to a more compact skeleton. • Rehydrated C-S-H gel could effectively fill the pores, thus promoting the generation of C(-A)-S-H and Ca 5 (SiO 4) 2 (OH) 2. • The final setting time of recycled cement was extended from 12 mins to 84 mins. • The 28d and 90d compressive strength reached 29.8 and 36.9 MPa, increased by 21.1 % and 39.9 %. [ABSTRACT FROM AUTHOR]

Polymer emulsion impregnation is a common method for strengthening recycled fine aggregate (RFA). By mixing Nano carbon black (NCB) into the polymer emulsion, highly conductive modified RFA (MRFA) can be simultaneously obtained. In this paper, highly conductive and self-sensing concrete was prepared by using the MRFA impregnated with the NCB and polydimethylsiloxane (PDMS) solution. The microstructure of MRFA and MRFA concrete physico-mechanical properties were studied. The effects of replacement ratio of MRFA, temperature, water content, and loading rate on the conductivity and self-sensing of prepared MRFA concrete was explored. The results show that the PDMS fills the pores of the RFA surface. The water absorption decreases by 2.53%, the apparent density and fineness modulus increased by 1.5% and 8.3%, respectively. With the increase of MRFA replacement ratio, the resistivity of concrete gradually decreases, and a sharp decline appears from 60% to 70%. The percolation threshold of concrete is calculated to be 3.37 vol% of NCB. Meanwhile, the MRFA concrete has good temperature sensitivity and humidity adaptability. Under the stress cycle loading, the stress sensitivity of the MRFA concrete with 70% replacement ratio MRFA is as high as 4.45%/MPa. Besides, the stress sensitivity of MRFA concrete decreases as the loading rate increases. • Recycled fine aggregate was treated with carbon black and polydimethylsiloxane. • Self-sensing concrete resistivity was measured by four-electrode method. • Self-sensing concrete piezoresistivity was studied. [ABSTRACT FROM AUTHOR]

In order to realize the resource utilization of coal gasification fine ash (CGFA) in cement fields, a key is to solve the problem of low activity of CGFA. This paper studied the performance of CGFA as supplementary cementitious materials in cement. Furthermore, to enhance the activity of CGFA, targeted chemical activators were employed, with triethanolamine (TEA) and simulated high salinity wastewater (SHSW) chosen as representatives of organic and inorganic agents, respectively. It was found that CGFA had a synergistic effect with cement at a low dosage, while the inhibition effect on cement hydration was dominant at a high dosage. TEA promotes the strength development of the CGFA-cement system by promoting early hydration of cement and dissolution of active minerals in CGFA. However, the promoting effect of TEA on cement hydration will change to an inhibiting effect with the development of time, which will have an adverse effect on the development of strength. In general, the optimal dosage of TEA is 0.03 %, which can increase the 28-day activity index of CGFA from 69.1 % to 75.6 %. SHSW accelerates the strength development of the CGFA-cement system by promoting the hydration of cement and facilitating the dissolution and hydration of active minerals in CGFA. In addition, X-ray diffraction results show that a new hydration product, Friedel's salt, is formed under the excitation of SHSW. But this new hydration product will gradually dissolve as the pH decreases. The 28-day activity index of CGFA can be increased to a maximum of 83.3 % under the excitation of 2 % SHSW. [Display omitted] • The direct use of CGFA has adverse effects on the properties of cement. • Activity index of CGFA can be increased to a maximum of 83.3 % by chemical activators. • Activators promote the dissolution and hydration of active minerals in CGFA. [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach to synthesize highly mono-dispersed in situ grown NS (INS) on Fly Ash (FA). The uniform particle size (41 ± 3.5 nm) and mitigation of the agglomerations tendency of INS were accomplished without any surfactant by utilizing the surface properties of acid-treated FA. INS's growth and adsorption mechanisms were proposed by employing the findings of FTIR and zeta potential investigations. SEM and TEM were used to evaluate the structure and INS dispersion. The impacts of synthesized INS and commercial NS (CNS) on cement pastes' cementitious properties were comparatively investigated using equal dosages of INS & CNS (0.5%, 1.0%, 1.5%). The experimental results revealed that even the highest dosage (1.5%) of INS exhibited better fluidity and rheological behavior than the lowest dosage (0.5%) of CNS in cement pastes. Moreover, compared to CNS, excellent dispersion of INS engendered prominent hydration kinetics of cement pastes and showed more efficient early and long-term strength development. QXRD cement pastes' findings further endorsed INS's prominence over CNS by indicating a significant increase in amorphous content and a notable reduction in CH content. Furthermore, INS refined the pores in the hardened cement pastes efficiently by decreasing the porosity more remarkably. • Surfactant-free NS has been grown in situ (INS) for the first time on the fly ash. • Phosphoric acid aid polycondensation & deter agglomerations in INS formation. • The content of NS in INS@FA is 15.5%. • Growth and adsorption mechanisms of INS formation have been proposed. • INS outperformed CNS by proving itself a better nano-reinforcement option. [ABSTRACT FROM AUTHOR]

Excessive void content is an essential reason for the poor road performance of cement emulsified bitumen mixture (CEBM), while incorporating steel slag with high microwave responsiveness into CEBM and followed by microwave heating may be an effective method to reduce void content. To verify this hypothesis, this paper investigated the effect of microwave heating on the void characteristics of CEBM using X-ray computed tomography. The study mainly focused on the distribution characteristics of different-sized voids, the distribution uniformity of voids, and the shape characteristics of voids. The results revealed that the number of different-sized voids decreased significantly after microwave heating, especially the number of small-sized voids decreased the most. The reduction in void number improved the distribution uniformity of longitudinal and radial voids. However, it reduced the distribution uniformity of voids between the inner and outer sections of the specimen. Through the analysis of aggregate movement characteristics, it was found that the increase in the separation degree of inner and outer voids was due to the larger-sized aggregates being more efficiently distributed on the outer section of the specimen. Additionally, microwave heating reduced the complexity of void shapes. The reduction of void number and the improvement of void characteristics by microwave heating are expected to enhance the structural durability of CEBM, thereby improving its road performance. [Display omitted] • The effect of microwave heating on the void distribution of CEAM was analysed. • A new object uniformity index, the Separation Index (S E) was proposed. • The influence of aggregate particle motion characteristics on void distribution was analysed. [ABSTRACT FROM AUTHOR]

The release of heavy metal elements in heavy metal tailings ponds not only causes environmental pollution but also poses potential hazards to human health. Therefore, it is of great significance to stabilize heavy metals and apply anti-seepage treatment to tailings ponds. In this paper, the tailings in the Shenxiandong lead-zinc tailings pond in Yunnan Province, Southwest China, were analyzed. The adsorption effects of different natural stabilizing agents on lead (Pb) and zinc (Zn) in tailings were investigated. Orthogonal and modification experiments were used to identify the most effective stabilizing agent. This agent was then combined with a high-pressure rotary jet cement slurry to investigate the properties of the resulting consolidation body and its effect on heavy metal solidification. The results show that the tailings are more likely to release heavy metal elements into the environment. The results of the orthogonal experiments show that the stabilizing agent CCA, which is a combination of fly ash, attapulgite, and Na-bentonite in a 2:1:2 ratio, effectively adsorbs Pb and Zn elements in the tailings. The stabilizing agent CCAPT is created by modifying CCA with 7% H 3 PO 4 at pH of 12 and heat treating at 200 °C. CCAPT demonstrates a 97.2% improvement in stabilization efficiency for Pb and a 94.1% improvement for Zn compared to CCA. The combination of CCAPT and cement slurry resulted in a 25.6% increase in compressive strength and a 29.5% decrease in permeability coefficient compared to the cement slurry formed consolidation body. The core-flooding experiment shows that the residual leachate after consolidation of "5% CCAPT + cementitious slurry" contains only 35.6 μg/L of Pb and 29.2 μg/L of Zn. These concentrations are significantly lower than the national emission requirements. This study presents an experimental foundation for further investigation into the use of high-pressure jet grouting technology to seal tailings ponds. ● An economical stabilizing agent CCAPT was developed which has a significant adsorption effect on Pb and Zn. ● The adsorption mechanism of CCAPT on the Pb and Zn from the tailing sand was analyzed. ● Hydrophobicity can reduce the permeability coefficient of cement consolidation body. ● CCAPT can improve the compressive strength and decrease the permeability coefficient of the cement consolidation body. ● CCAPT and cement slurry can effectively improve the stabilization effect of the cement consolidation on Pb and Zn. [ABSTRACT FROM AUTHOR]

Supersulfated cement (SSC) incorporates a significant amount of ground granulated blast-furnace slag (GGBS) and phosphogypsum (PG), which contributes to low carbon emissions and offers for extensive application. This paper investigated the evolution characteristics of performance and microstructure of SSC and Portland slag cement (PSC) pastes under Na 2 SO 4 solution attack and Na 2 SO 4 -HCl solution compound attack, including visual appearance, compressive strength, hydration products, pore structure and morphology. The results show that SSC group demonstrates superior resistance to Na 2 SO 4 solution compared to PSC group, which is reflected in no change in visual appearance over immersion time, a continuous increase in strength and stable hydration products. The pore volume (＜50 nm) of SSC increased after 270 days of erosion, while PSC experienced a sharp increase in pore volume (＞50 nm), which is also reflected in the compressive strength, with PSC (52 MPa) significantly lower than SSC (67 MPa). Na 2 SO 4 -HCl solutions significantly deteriorate both SSC and PSC groups. The strength of SSC remained 45 MPa from 28 to 180 days, decreasing rapidly thereafter, while PSC strength decreased rapidly after 90 days. Compound solution reduced alkalinity, resulting in the decalcification of C-S-H gel and ettringite decomposition. After 90 days of erosion in compound solution, the total pore volume of both SSC and PSC increased from 0.15 to 0.17 mL/g, while the pore volume (＜50 nm) of SSC was higher than that of PSC. Additionally, the strength and strength retention rate of SSC group were higher than PSC after 28 days of erosion. Therefore, SSC exhibits superior resistance to compound chemical attacks compared to PSC, especially for long term attack. • Supersulfated cement (SSC) exhibits better resistance to sulfate solutions compared to Portland slag cement. • Formed ettringite with high content and more stable in SO 4 2− ions environment elevates the properties of SSC. • The resistance to compound chemical attack of SSC is superior than Portland slag cement, especially for long term attack. [ABSTRACT FROM AUTHOR]

This study investigated the changes in three characteristics, including phase compositions, microstructure, and microhardness, in the interfacial transition zone (ITZ) of high-ferrite cement (HFC) products when subjected to different curing systems. In addition, we explored the underlying mechanisms through which supplementary cementitious materials (SCMs) influence the ITZ under steam curing conditions. The characterization was performed through the application of test techniques such as X-ray diffraction analysis, backscattered electron, scanning electron microscopy, energy dispersive X-ray spectrometry, and microhardness. The findings demonstrated that the increase in the curing temperatures promoted the HFC mortar to generate an excellent ITZ performance compared to Portland cement and ground granulated blast furnace slag (GGBFS) showed an improvement in steam-cured HFC-ITZ better than. Specifically, optimal enhancement of the ITZ in steam-cured HFC cement-based materials was achieved through the 40% replacement of GGBFS where the calcium hydroxide (CH) content and orientation growth were reduced while the hydration product formation was increased, resulting in declined porosity. Furthermore, the incorporation of 20% replacement of fly ash (FA) led to the decrease in the CH content and porosity of the ITZ. However, due to the lower reaction activity, unreacted FA persisted in the paste even after 28 days of curing. Additionally, the uneven distribution of hydration products resulted in diminished microhardness. On the other hand, a 40% replacement of FA marginally improved the properties of the ITZ. Finally, the test data and conclusions in the paper can provide some evidence for the application of GGBFS and FA in HFC and HFC-based concrete. • At elevated curing temperatures, the ITZ in high-ferrite cement exhibits a denser microstructure. • The steam curing process, combined with a 40% addition of GGBFS, promotes the hydration to enhance the structure of ITZ. • The "filling effect" of FA reduces the porosity of HFC-ITZ, but the lower activity results a lower degree of pozzolanic reaction. [ABSTRACT FROM AUTHOR]

This paper studies the use of municipal solid waste incinerator bottom ash as a supplementary cementitious material in concrete products using an innovative chemical treatment approach. The primary objective is to address emissions associated with waste-to-energy facilities and the heavy reliance on ordinary Portland cement as the primary binder in concrete. The proposed method involves the removal of metallic aluminium from the bottom ash and the subsequent use of the treated bottom ash as a partial cement replacement to produce concrete. Concrete specimens were produced with varying proportions of treated or untreated municipal solid waste incinerator bottom ash, replacing 20%, 35%, and 55% of ordinary Portland cement according to EN 197 European standard for common cement. Moreover, class F fly ash was incorporated in equivalent percentages as a reference supplementary cementitious material, and a control mix was prepared using solely Portland cement. The evaluation encompassed multiple visual and analytical techniques, including scanning electron microscopy, X-ray diffraction, X-ray fluorescence, and setting time analyses on pastes made with Portland cement, fly ash, and bottom ash. All specimens were evaluated in terms of mechanical performance, namely compressive strength. The chemical treatment process facilitated the release of a significant quantity of hydrogen, a by-product of aluminium oxidization. Consequently, this resulted in significantly reduced formation of gas bubbles in concrete in the fresh state and, therefore, diminished expansion during the setting process. As the proportion of cement replacement with bottom ash increased, a decline in strength was observed. However, this decline was less pronounced when using treated bottom ash, particularly with lower levels of incorporation. • Municipal solid waste incinerator bottom ashes as partial cement replacement. • Novel NaOH-based chemical treatment for incinerator bottom ashes. • Mixes with untreated ashes present extensive expansion due to aluminium oxidization. • Treatment led to overall performance enhancement due to lower gas generation. [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]

The blending of steel slag powder with cement can mitigate the carbon footprint of cementitious composites. The rheological properties of cement pastes are well known to be related to interparticle forces. However, the magnitude of the interparticle force depends on many physico-chemical factors. The influence of various factors on interparticle forces is not yet clear, making it difficult to control the rheological properties. In this paper, the interparticle force of steel slag powder blended cement paste was quantified and its relationships with dynamic rheological properties and basic physico-chemical parameters were explored. By means of this, the interparticle force was confirmed to could explain the effect of steel slag powder on the dynamic rheological properties of cement paste within 1 h. Moreover, how physico-chemical parameters affect the interparticle forces was clarified. A cement paste with large particle size and apolar surface energy, as well as small potential square, Debye length and small polar surface energy, can exhibit large interparticle force and high dynamic yield stress and plastic viscosity. A simple formula calculating interparticle force from basic parameters was proposed, which is believed to effectively and practically regulate the interparticle force. The relationships between interparticle forces, physico-chemical parameters, and rheological properties provide an effective reference for regulating the dynamic rheological properties of cement paste through fundamental parameters. • The interparticle force can explain the effect of steel slag powder on the dynamic rheological properties within 1 h. • How physico-chemical parameters affect the interparticle force is clarified. • A simple formula calculating interparticle force from basic physico-chemical parameters is proposed. [ABSTRACT FROM AUTHOR]

The X-ray spectrum changes while traveling through specimen, and this phenomenon, known as the beam-hardening effect, breaks the linear relationship between the intensity variety on radiographs and material thickness. In the detection of water transport in cement-based materials, this effect leads to inaccurate results of the quantitative moisture distribution inside the sample, and it is difficult to eliminate this effect by gravimetric calibration. To solve this problem, this paper proposed a calibration strategy for the attenuation coefficient curve of cement-water two-phase specimens, and provided a heuristic mathematical model for fitting the 2D attenuation coefficient surface of cement paste specimens. The experiments showed that for zones close to saturation, beam-hardening leads to an overestimation of moisture content, while for a zone with a low water content, the X-ray radiography results without correction tend to underestimate it. After correction, the method showed a quantitative result close to that of the gravimetric method, and maintained a good stability in samples of different thickness. • An X-ray beam-hardening correction method for quantitying moisutre content in cement paste was proposed. • The effective attenuation coefficient in two-phase materials comprising water and cement has been obtained. • The quantitative error due to beam-hardening effect was reduced from 26.9% to less than 5.65%. [ABSTRACT FROM AUTHOR]

Fractures in rocks have significant effects on the stability of rock mass structures. Physical model testing is an effective approach for investigating the failure mechanisms of fractured rocks. In this paper, a new binder jetting (BJ) 3D printing technology using magnesium phosphate cement (MPC) is proposed to fabricate rock models with isotropic and brittle matrices and complex fractures. A self-developed BJ 3D printer is used to perform the printing and investigate the effects of different layer thicknesses, molar ratios of magnesium oxide to phosphate (M/P), and borax retarder contents on dimensional accuracy, mechanical anisotropy, and brittleness. The test results show that the layer thickness and M/P exert significant influences on the dimensional accuracy and mechanical anisotropy by regulating the binder's diffusion and penetration into the powders. The degree of hydration, and thus the brittleness of the specimens, is also influenced by different M/P values. The borax retarder prolongs the setting time, and thus provides a longer hydration time, resulting in better interlayer bonding and lower mechanical anisotropy. The optimized specimens exhibit a much lower anisotropy index in compressive strength compared to that of the counterpart commercial sand and gypsum BJ printed specimens, and the high brittleness index of the 3D printed specimens indicates it can achieve the rating of brittle rocks. The crack initiation angles and failure patterns of printed specimens with single and double fractures are consistent with those of practical rock specimens, which demonstrates that the proposed BJ 3D printing method using MPC is promising for reproducing highly accurate rock-like models with complex fractures. • Binder jetting 3D printer for MPC cement is developed. • Accuracy, anisotropy and brittleness are optimized to fabricate rock-like models. • Binder jetting 3D printing using MPC cement is feasible to fabricate rock analogs. [ABSTRACT FROM AUTHOR]

This paper presents a simple polynomial model predicting the alkali concentration in concrete pore solution as a function of the cement composition, the total alkali content and the water-to-cement ratio. The model was designed to assess the risk of alkali-silica reaction (ASR) in concrete rubble from the decommissioning of nuclear power plants. The influence of various factors on alkali concentration in the cement pore solution, such as the origin of the binder (ordinary Portland cements from different sources), the water-to-binder ratio, and the amount of ground granulated blast furnace slag was investigated. The polynomial model was derived and validated using experimental data. Further validation was based on literature data which confirmed its predictive accuracy. The model provides valuable insights into the alkali concentration of concrete pore solution and its potential impact on ASR. • An easy-to-use tool for predicting alkali concentrations in concrete structures. • Valuable insights into material property interactions for designing and assessing concrete structures, including applications in radioactive waste disposal. [ABSTRACT FROM AUTHOR]

Superabsorbent polymers (SAPs) have emerged as promising additives to regulate cement hydration via their intrinsic water absorption/desorption characteristics. This paper aims to investigate the influence of SAPs with different functional groups on the development of cement hydration and growth of calcium hydroxide (CH). The current experiment firstly uncovered the active control mechanism of CH in cement paste by SAPs, especially for the nucleation site and crystallization orientation. Specifically, the pores left behind SAPs after water release usually processed higher w/c ratio, Ca2+ concentration and smaller crystallization pressure, which jointly triggered the in-situ nucleation and crystallization of CH along (0 0 1). However, the hydration degree of cement paste was reduced by 0.1∼4.4% with addition of SAPs, especially in the early stage, which was attributed to that less free water can be used for cement hydration due to the strong water absorption property of SAPs. These insights provide a valuable foundation for deploying SAPs in an active control strategy for CH growth position and crystal form in cement-based materials. • The nucleation site and crystallization orientation of CH can be controlled by SAPs. • Higher w/c ratio, Ca2+ concentration triggers the formation of CH around SAPs. • The addition of SAPs reduced the hydration degree of cement paste by 0.1 ∼ 4.4%. • The addition of SAPs primarily affects hydration during the early stage. [ABSTRACT FROM AUTHOR]

Bayer Red mud (BRM) and phosphogypsum (PG) are known as two main industrial wastes around the world. Previous studies have demonstrated the contribution of BRM and PG in cement-based hydration reactions, but their collaborative role is still pending in cement-stabilized dredged soil. In this study, the collaborative role of BRM and PG was examined by comparing micro-macro properties of stabilized clay with different initial water contents, cement contents and BRM/PG proportions. The chemical and microscopic results are found highly complementary, indicating existence of alkali-activation effects, pore-filling effects and cementation damage effects in stabilized clay. The pH of 8% cement-stabilized clay increases by about 0.5 after addition of 10% alkaline BRM, which activates clay mineral in dredged soils and results in more sufficient pozzolanic reactions. In addition, the pore-filling effect of ettringite is much more contributory in soils with a higher water content of 140%. Such positive effects significantly weaken as the water content decreases to 80%, the cementation damage effects come into picture instead. The unconfined compressive strength (UCS) after 7 days curing nearly triples with an optimal proportion of BRM and PG, demonstrating effectiveness of the proposed approach. As the water and cement contents increase, the optimal proportion of BRM and PG evolves from R7.5P2.5 into R5P5. • This paper examines the role of RM and PG in cement-stabilized dredged soil with different water and cement contents. • The contribution of alkali-source from RM is significant at a low cement content and an early curing stage. • The pore-filling effect of ettringite is more important at a high water content. • The optimal proportion of RM and PG evolves from R7.5P2.5 to R5P5 as the water and cement contents increase. [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]

Highlights • This paper investigate the effect of Poly AMPS grade SAPs on the properties of cement paste material for the first time. • In addition, this paper compares the effect of Poly AMPS grade SAPs and Commercial ones on the hydration process of cement based materials too. Abstract Preparation and characterization of superabsorbent polymers (SAPs) of poly (2-acrylamido-2 methyl propane sulfonic acid) with different ratios of cross-linker/monomer (0.0043, 0.0086, 0.014, and 0.028) and swelling capacity on Portland cement properties and its hydration were investigated. The comparison between poly (AMPS) and commercial samples (agriculture and hygienic grade of SAP) was studied too. Synthetic and commercial grade SAPs were studied with FTIR (Fourier transform infrared spectroscopy), swelling (in distilled water and saline solution (0.9% NaCl, with pH 7)) and AUL (absorbency under load) were measured completely. As a result, poly (AMPS) with 0.03 g of cross-linker has the highest swelling capacity (425.52 g/g and 66.18 g/g in distilled water and saline solution respectively) and poly (AMPS) with 0.06 g of cross-linker shows the highest AUL (13.2 g/g) among the synthetic and commercial samples. The hydrations of cement paste were investigated by means of XRD (X-ray diffraction) and FTIR spectroscopy in combination with thermo analytical method (TGA/DTG) (Thermo gravimetric Analysis). To determine the crystal size and porosity, SEM-EDX (Scanning electron microscope-Energy-dispersive X-ray spectroscopy) was used and also, rheology was used to determine the workability and efficiency of cement paste. As it is concluded, the hydration of cement paste with agricultural SAP is better than the others. TGA shows that the intensity at 7 day hydration time is the most. The cement paste contains poly (AMPS) based SAP with higher amount of cross-linker (0.2 g) and low swelling content has the best workability. And the cement paste contains poly (AMPS) with low amount of cross-linker (0.03 g) and highest swelling had the lowest porosity and the best distribution. From viewpoint of workability A4 is the best and from viewpoint of swelling and microstructure of cement A1 is the best. [ABSTRACT FROM AUTHOR]

Highlights • CNTs and CNFs are both the nano-structured fibrous materials with excellent properties. • The dispersion of CNTs/CNFs is the decisive factor affecting the performance of composites. • The incorporation of CNTs and CNFs affects the variety performance of cement-based materials. • CNTs/CNFs-modified cement-based composites have broad application prospects. Abstract CNTs and CNFs are drawing widespread attention due to the unique structure and excellent properties, such as the mechanical property and the electrical property. It will significantly improve the cement-based composites' properties when adding CNTs/CNFs into composites. This paper briefly introduces the CNTs'/CNFs' basic properties and dispersion methods, and elucidates the properties of cement-based composites recombining CNTs/CNFs, including the mechanical property, the deformation property, the durability property, the thermal conductivities and electrical conductivities. This paper also summarizes the problems existing in present research, and gives some proposes for future study. [ABSTRACT FROM AUTHOR]

Highlights • Waste marble slurry used as an important resource in concrete and reducing the carbon footprint of cement. • Long-term strength and durability performance of concrete on partially replacing cement by weight by dried waste marble powder slurry assessed. • Both Mechanical and durability parameters of hardened concrete tested for a period of 1 year after exposing samples to adverse environmental conditions. • Marble slurry replacement percentages kept as 10%, 15%, 20%, 25% and water binder ratios as 0.35, 0.40 and 0.45. • Surface mesh for variation in all the properties with different replacement levels, curing conditions and water binder ratios plotted. • Relationship between mechanical and durability properties with compressive strength derived for marble slurry incorporated concrete. Abstract Present study assesses and evaluates the long-term strength and durability performance of concrete on partially replacing cement by weight by dried waste marble powder slurry. Four different replacement percentages (0, 10, 15, and 20 and 25%) and three water-binder ratios (0.35, 0.40 and 0.45) have been tested in the paper. The main reason for the study is to check whether use of dried marble slurry affects the properties of concrete in long term as the amount of binder is reduced, when cement is partially replaced. Long-term impact is analyzed by testing the concrete samples for 28, 56, 90, 180 and 360 days after curing the specimens in water for 28 days and exposing the samples to adverse environmental conditions in the state of Rajasthan, India where the temperature ranges from 0 °C in winters to as high as 47 °C in summers. The concrete mixes were tested for strength parameters mainly compressive, tensile and flexural strength, also durability parameters water permeability, abrasion resistance and water sorptivity. Surface mesh for variation in all the properties with different replacement levels, curing conditions and water binder ratios are plotted in the paper. Based on the analysis of concrete with various replacement levels of marble slurry, it can be concluded that for up to 15% replacement, an enhanced physical strength and durability of concrete blocks was observed across testing periods of 28 days to 360 days. It was observed that marble dust generated an effective dense mix for higher replacement ratios, thus improving the properties in long-term duration. Finally, relationship between strength and durability properties with compressive strength are derived for marble slurry incorporated concrete. [ABSTRACT FROM AUTHOR]

Highlights • Self-consolidating concretes (SCCs) incorporating volcanic materials in a sodium sulfate environment. • It intends to use volcanic materials as a cement replacement of binary and ternary concrete mixtures. • SCCs incorporating volcanic materials would allow to obtain ternary SCCs that meet the qualification criteria for sulfate resistance. Abstract This paper examines the performance of self-consolidating concrete incorporating volcanic materials in a sodium sulfate environment. The volcanic materials used as a cement replacement of binary and ternary concrete mixtures in this research were Tolima, Puracé and Boyacá. The results were compared to those of standard SCC. The physical properties (density, absorption and porosity) and sorptivity of water were determined. The degree of sulfate attack was evaluated using dimensional variation, visual examination and compressive strength change of SCC specimens immersed in two exposure media (reference medium and sodium sulfate solution (5% Na 2 SO 4)) for different ages exposure. The microstructure was studied using Scanning Electron Microscope (SEM) coupled to EDS and X-ray Diffraction (XRD) analysis. This paper shows that the use of inert (Tolima) and pozzolanic (Puracé and Boyacá) volcanic materials results in SCCs with good sodium sulfate resistance. [ABSTRACT FROM AUTHOR]

Highlights • The near surface mounted (NSM) strengthening technique is attractive and efficient. • Recent research has focused on the use of cementitious adhesives for NSM. • The paper shows 22 bond pull-out tests at ambient temperature on concrete prisms. • Both epoxy resin and cementitious grout bonding agent are investigated. • Effect of position of the bar in the groove, bar surface and bond length is shown. Abstract The near surface mounted (NSM) fiber reinforced polymer (FRP) strengthening technique is a demonstrated, attractive and efficient alternative to externally bonded reinforcement (EBR) strengthening systems. NSM strengthening can be used to enhance the stiffness and the strength of deficient reinforced concrete members, with high utilisation of the FRP's mechanical properties (at ambient temperature) when epoxy is used as bonding agent. However, owing to epoxy adhesives' sensitivity to elevated temperature exposure, recent research has focused on the use of cementitious adhesives, which are less sensitive to elevated temperature, in NSM FRP applications. This paper presents results from 22 bond pull-out tests at ambient temperature on concrete prisms with an embedded carbon FRP bar NSM strengthening system. Different bonding agents (i.e. epoxy resin or cementitious grout), positions of the bar in the groove (i.e. in the centre or at the top of the groove), bar surface treatments (smooth and ribbed) and bond length (300 and 400 mm) are investigated. [ABSTRACT FROM AUTHOR]

Highlights • The long-term behavior of cement paste is studied experimentally and analytically. • An analytical scheme is developed to estimate the chloride diffusion coefficient. • The analytical scheme is verified with eight sets of experimental data. Abstract The intention of this paper is to estimate the steady-state chloride diffusion coefficient of mature cement paste through laboratory test and theoretical analysis. In the test, the chloride diffusion coefficient of cement paste with water/cement ratios of 0.3, 0.4, 0.5, and 0.6 is measured at curing ages from 28 to 1800 days. The test results show that, for cement paste cured for smaller than 360 days, the chloride diffusion coefficient reduces quickly with the increase of curing age. For cement paste cured for larger than 360 days, however, the chloride diffusion coefficient decreases slowly with increasing the curing age. In view of the multi-phase and multi-scale characteristics of cement paste, a three-step scheme is developed to derive the chloride diffusion coefficient analytically. In the scheme, the chloride diffusion coefficients of the inner and outer hydration products and the solid phase are formulated with a two- and three-phase composite sphere models, respectively. Finally, for the bi-continuous cement paste system composed of a solid phase and capillary pores, the effective medium method is adopted to deduce the chloride diffusion coefficient. Eight sets of experimental data, obtained in this paper and collected from the literature, are used to verify the analytical scheme. It is concluded that the developed three-step analytical scheme can evaluate the chloride diffusion coefficient of mature cement paste with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Patch repairs are widely used for local damage in RC columns. • 15 patch-repaired RC columns were tested at the ICITECH. • The paper analyses the effectiveness of patch repairs on RC columns. • Patch repair is compared with: all-four-sides and one-side repair. Abstract This paper describes an experimental study on patch-repaired reinforced concrete columns subjected to axial loads until failure. The behaviour of four series of columns repaired with Class R3 and R4 cement-based mortar was analysed both with and without a bonding agent. The results obtained were compared with control series of undamaged and damaged but unrepaired columns to determine the effectiveness of the repairs and the subsequent improvement in the behaviour of the columns. The results of this study were compared with those of previous work by the authors on the analysis of all-four-side repairs and one-side repairs. The conclusion reached was that patch repairs are highly effective as compared to the other techniques studied and that using Class R3 mortar achieves better results on damaged columns made with low-quality concrete. It was also concluded that applying a bonding agent does not improve the results, although this element was found to be necessary to prevent the premature detachment of the repair when there is a substantial difference between the stiffness of the column concrete and that of the mortar used in the repairs. [ABSTRACT FROM AUTHOR]

Durability is one of the primary concern in new buildings and also for the old existing infrastructures. This paper deals with the durability properties of concrete containing sandstone slurry as a filler material. A significant quantity of sandstone slurry gets deposited, and their disposal problem becomes acuter. In order to utilize these wastes and to practice a sustainable construction, the ultimate solution is to use these types of sandstone slurry in concrete. Since durability plays an enormous role in maintaining the infrastructure for years, various tests such as compressive strength, flexural strength, water absorption, sulfate attack, acid attack, carbonation, DIN-Permeability, sorptivity are done to get the durability of the sandstone slurry mix in concrete. This paper presents the result of experimental research to examine the suitability of sandstone slurry as a partial replacement of total aggregates in cement concrete. It was observed that up to a certain level of substitution, compressive and flexural strength show a comparable result to that of control concrete. Also, it shows a good result with a controlled replacement towards acid-attack as well as sulfate attack and are equivalent to that of Portland cement concrete. Similar effect were also observed towards carbonation and permeability. From the results, it can be said that there is a promising future for the use of sandstone slurry as a partial replacement of total aggregate, which can lead to more significant environmental and sustainable benefits. [ABSTRACT FROM AUTHOR]

Dissolution and leaching mechanism of the calcium ions in cement based material has an important influence on its service performance. In this paper, the mechanism of the dissolution and leaching process of cement based materials was analyzed. The results showed that early dissolution and leaching behavior of cement-based materials was different with the later period, and therefore this paper was just focus on the early dissolution. At the early period of dissolution and leaching, it was mainly due to the chemical dissolution process by discussing the mechanism of this period; moreover, mathematics mechanism of early dissolution of calcium in cement based materials was determined by using chemical kinetics combined with mathematic calculated, and the chemical mechanism model was then verified by using the literature data. [ABSTRACT FROM AUTHOR]

Around the world flexible pavement is the most favored pavement structure to build road and highways. A massive amount of non-renewable materials and industrial products like aggregates, bitumen, cement, lime, and other additives are consumed during construction and maintenance of this pavement system. Extraction and production of these virgin materials is an unsustainable practice. Wastage of materials, environmental deterioration, depletion of resources, and the spike in material cost led researchers to search for alternative materials that can be used in flexible pavement. This paper provides an overview of such recycled materials that have been successfully used in different layers of flexible pavements. Studies have established that the use of secondary material not only provide an efficient waste disposal technique but also reduce demand for conventional material and reduce overall construction cost. Through this paper, an attempt has also been made to identify the reason because of which, despite having essential studies, their field implementation has been limited and suggest possible remedies by which use of recycled material in the flexible pavement can be promoted. [ABSTRACT FROM AUTHOR]

Research on quantification of the size and porosity of the interface between the reinforcing steel and concrete is limited in the current published literature. This paper presents a reliable and accurate method for quantification of steel-concrete interface using the technique of Backscattered Electron (BSE) imaging. Details of sample preparation procedure designed to minimize the damage to the steel-concrete interface due to grinding and polishing are presented. A new thresholding method to separate porous band at the interface from steel and cement pastes is proposed. It is found that there is a relatively wide porous band with large pores and voids near the steel-concrete interface. It is also found that the size of porous band around the steel bar is not uniform, and that the water to cement ratio can significantly affect the size and distribution of porous band at the interface. Quantification of steel-concrete interface as proposed in this paper is of importance in crack prediction of corrosion-affected reinforced concrete structures. [ABSTRACT FROM AUTHOR]

The heterogeneity of a cement-based material results in a random spatial distribution of carbonation depth. Currently, there is a lack of both experimental and numerical investigations aiming at a statistical understanding of this important phenomenon. This paper presents both experimental and numerical supercritical carbonation test results of cement mortar blocks. The carbonation depths are measured along the carbonation boundary by the proposed rapid image processing technique, which are then statistically studied by calculating, e.g., their probability density and power spectral density (PSD). The results indicate that the distribution of the carbonation depth can be approximately represented by a lognormal distribution function and the PSD has quantitative correlation with some of the statistic parameters used in the simulations. In particular, the effects of the autocorrelation lengths and the coefficient of variation of porosity, which are used to define the random porosity field, on the irregularity of carbonation depth are analyzed numerically in details and validated by experimental results. The study has shown that using a random field of porosity with due consideration of spatial correlation and variance, the irregularity of carbonation depth can be realistically captured by the numerical model. The numerical results confirm that lognormal distributions represent the random nature of carbonation depth well and the average and variance of the irregular carbonation depth increase with the increase of carbonation time, autocorrelation length and coefficient of variation of porosity. The study also offers a potential method to numerically calibrate some of the statistic parameters required by a numerical carbonation model through comparing the PSD with that from experimental tests. Overall the methodology adopted in the paper can provide a foundation for future investigations on probability analysis of carbonation depth and other similar work based on multi-scale and -physics modelling. [ABSTRACT FROM AUTHOR]