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In this study, three hydration heat controlling materials (HHCMs), respectively, containing pure hydroxyl (polyvinyl alcohol, PVA), carboxylic (polyacrylic acid, PAA) and ester groups (maleic acid-ethylene glycol ester, P(MA-EG)) were synthesized and mixed with cement-based materials, and the hydration heat and setting time of cement pastes and the SEMI adiabatic temperature rise and strength of mortars were tested. The results showed that PAA and P(MA-EG) reduced the peak value of hydration exothermic rate by 77.45% and 62.28%, respectively, and prolonged 54.14 h and 15.56 h, respectively. Mechanism studies showed that HHCMs containing carboxylic or hydroxyl groups adsorbed on cement particles by Ca2+ complexation, while HHCMs containing ester groups hydrolyzed to carboxylic groups in alkaline cement pastes, which hydrolysis rate changed with the hydration temperature of cement-based materials to regulate the hydration process. This study aims to provide technical feasibility and theoretical basis for exploring new avenues of synthesizing HHCMs with different functional groups. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate how the addition of shrinkage-reducing polycarboxylate superplasticiser (SRPC) affected the shrinkage of cement-based materials (CBMs). SRPCs can significantly reduce the surface tension of cement solutions. In this work, a new molecular structure of SRPC was synthesised; its surface tension was reduced to 34·1 mN/m, which is lower than that of ordinary polycarboxylate superplasticisers (PCEs). Compared with mortars without additives, the shrinkage-reducing ratios of mortars containing SRPC at 7 and 49 d were about 33 and 22%, respectively, for an SRPC dosage of 0·2% by mass of cement. The results showed that the SRPC reduced the shrinkage of CBMs more effectively than an ordinary PCE. Furthermore, the shrinkage mechanism of CBMs containing SRPC was assessed regarding three aspects: the change in the pore size distribution of the cement pastes with pore size below 50 nm, the reduction of the capillary pore pressure in the hardened cement pastes after the addition of a low-surface-tension SRPC and the reduction in the evaporation rate of moisture through SRPC aggregation on the gas–liquid interface in cement pastes. [ABSTRACT FROM AUTHOR]

To make effective use of plant leaves as an environment-friendly heat-insulating building material, our research group has tested five poplar leaf modification methods to improve compatibility between leaf fibres and cement-based materials. The work involved testing water absorption of before and after modification of leaf fibres, the setting time and hydration heat of the fibre–cement paste, and analysed the mechanisms and effect of fibre modification methods on compatibility between fibres and cement-based materials. The results show that processing of fibres with surface coating and dipping methods improved compatibility between fibres and cement-based materials to some extent and in different aspects. Overall, the following three methods gave superior performance: pure acrylic polymer emulsion spraying, sodium silicate solution spraying and water dipping. [ABSTRACT FROM AUTHOR]

Sulphoaluminate cement has the advantage of low-temperature application performance, but its hydration mechanism at low temperatures is not yet clear. Anhydrous calcium sulfoaluminate (C4A3 S) is the main mineral in the composition of sulfoaluminate cement clinkers. In this paper, C4A3 S mixed with gypsum (CaSO4∙2H2O) to form a C4A3 S -C S H2 cement system; X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and mercury intrusion analysis (MIP) to clarify the effect of temperatures on the hydration properties of C4A3 S -C S H2 cement system. The results showed that hydration of the C4A3 S -C S H2 cement system could carry on at low temperatures, even at −15 °C. The main hydration product was ettringite. Low temperatures did not change the types of the hydration products, but the low temperature of 0 °C was more favorable for the formation of ettringite. The early hydration of the C4A3 S -C S H2 cement system was inhibited by the decrease in temperature. However, hydration of the cement at 0 °C continued at a high rate after one day. Morphologies of the ettringite for the C4A3 S -C S H2 cement system at −15 °C were needle-like structures, while they were of columnar structure at 0 °C. The compressive strength of samples at 0 °C reached 82 MPa, which is significantly higher than that at 20 °C. [ABSTRACT FROM AUTHOR]

The slag obtained in the process of pig iron smelting has been widely used, but the variational hydration activity always is a significant factor affecting its quality. In this experiment, the laboratory simulated slag was prepared by adjusting the chemical composition and cooling method. The experiment primary characterized the structure and hydration process with different types of slag by using MAS NMR, XRD, compressive strength, ICP, SEM, and hydration heat, then obtained the influence of the composition of the network former S/A (the mass ratio of SiO2 and Al2O3 in chemical composition) and amorphous phase content on its structure and hydration activity. The result shows that lowering the S/A value can reduce the degree of vitreous polymerization in the slag; reducing the S/A value of the slag can make the slag hydration time advance, and consequently, the cumulative exotherm increases, the liquid phase Ca/Si and Al/Si ionic ratio increases, and the hydration product changes from C–S–H gel to C–A–S–H gel, which ultimately leads to an increase in compressive strength. In the high S/A value slag, the formation of the trace crystal phase of gehlenite is beneficial to reduce the degree of polymerization of the amorphous. [ABSTRACT FROM AUTHOR]

Although the side chain ionizability (the adsorption group density and adsorption space are changed) of polycarboxylate superplasticizer (PCE) serve as the key structural parameter in affecting the cement hydration, its effect on cement hydration is unclear. Based on PCE with nonionizable side chain (NSC-PCE) and the PCE with ionizable side chain (ISC-PCE), the influence of the side chain ionizability of PCE on the hydration behavior of cement was studied. Compared with NSC-PCE, ISC-PCE has a stronger ability to change the migration of water and ions, thus delaying the crystal nucleation and growth of cement hydration (better morphology and distribution, the crystal size was reduced by more than 20 %), increasing the crystal growth index (tendency toward spherical growth), prolonging the phase boundary reaction (reduce micro-cracks), which was conducive to the formation of more uniform and dense crystals (good strength, ISC-PCE: 50.0 MPa > NSC-PCE: 49.2 MPa > Blank: 48.7 MPa). These findings provide the design basis and theoretical guidance for the innovative development of PCE. [Display omitted] • ISC-PCE decreases the hydration rate and hydration degree of cement. • The effect of PCE on the hydration process was studied by the hydration kinetics model. • ISC-PCE has a stronger ability to change the migration of water and ions. • Proposes working mechanism in viewpoints of dissolution-precipitation equilibrium. • Tailoring the side chain ionizability was a new strategy to tune the performance of PCE. [ABSTRACT FROM AUTHOR]

In this study, the impacts of CO 2 -absorbed triethanolamine solutions (TEA-CO 2) on the mechanical property, phase composition and micro-structure of cement mortars were investigated. The results showed that TEA-CO 2 addition increased the 1d, 3d, and 28d compressive strength by 47%, 19%, and 4%, respectively, which suggests a synergistic effect of triethanolamine and absorbed CO 2 on strength development of cement mortars. The enhancement is due to TEA-CO 2 accelerates hydration of aluminate and silicate phases in early age. TEA-CO 2 facilitated CaCO 3 formation to increase cement hydration degree and modify the pore structures. However, the hydration of silicate phases was delayed slightly by TEA-CO 2 at 28d. The above results provide theoretical support for further utilization of CO 2 in cementitious materials. • Effect of TEA-CO 2 on strength development of mortars was investigated. • TEA-CO 2 addition increases flexural and compressive strength of mortars. • TEA-CO 2 accelerates the hydration of aluminate phase and silicate phase at early age. • A synergism of cement hydration and carbonation in the presence of TEA-CO 2 was proposed. [ABSTRACT FROM AUTHOR]

• The hydration of glass is heterogeneous due to phase-separation structure; • The heterogeneous hydration of glass impact the formation of calcium hydroxide; • The hydration rate advantage of calcium-rich and silicon-rich phase can be reversed; • The heterogeneous hydration is suitable for thermodynamic simulation of cement paste; Supplementary cementitious materials (SCMs) affect the hydration process and long-term properties of cementitious systems. Since a large percentage of SCMs belong to alkaline-earth aluminosilicate glasses that possess a phase-separated structure, further research into their hydration characteristics is essential. This study investigated the effects of the hydration characteristics of synthetic glasses with various phase-separated structure on the phase evolution of cementitious systems by combining simulations with experiments. The results showed that with the increasing degree of phase separation, the hydration of synthetic glass transitions from homogeneous to heterogeneous hydration. The phase evolution of hardened paste, particularly for calcium hydroxide, is influenced by the difference in hydration rates among each separated glassy phase. Compared to homogeneous hydration, the rapid hydration of the Ca-rich phase reduced the consumption of calcium hydroxide, while the rapid hydration of the Si-rich phase accelerated calcium hydroxide consumption. For glasses exhibiting phase separation characteristics, the consistency between thermodynamic simulations employing a heterogeneous hydration model and experimental results exhibits a notable enhancement. [ABSTRACT FROM AUTHOR]

In this paper, star -like polycarboxylate superplasticizer (SPCE) and comb -like polycarboxylate superplasticizer (CPCE) were prepared via atom transfer radical polymerization (ATRP) to study the mechanism of the effectiveness enhancement resulting from this transformation of topological structure. It was found that SPCE molecules acted higher adsorption amount and more Ca2+ complexes, and formed a lower and more compact adsorbed layer and larger surface coverage with a flat conformation on cement surface, depending on more anchored points per unit volume. Through this mechanism, cement particles adsorbed by SPCE showed stronger dispersible capability and colloidal interaction forces (the steric force was dominant), resulting in lower yield stress and plastic viscosity of the cement paste containing SPCE which behaved as an ideal Bingham fluid. The aim of this study is to clarify the mechanistic correlation between topological structure evolution and effectiveness promotion for PCE. [Display omitted] • Topological transformation of PCE helps to enhance effectiveness via more adsorbed points per unit volume. • SPCE molecules adsorb as a flat conformation to present a low and compact layer on cement surface. • Rheological properties of cement pastes depend on the interparticle steric force which plays a dominant role. • Good agreement is shown among the measured adsorbed layer thickness, R h value and surface coverage. • Novelty changing to dense topological structure is proved as a promising way to obtain highly effective PCE. [ABSTRACT FROM AUTHOR]

• A certain dosage of DEA or TEA helps to increase the application performance of accelerator. • The complexation effect of DEA and TEA in accelerator have a significant difference. • DEA in accelerator promote the C 3 S hydration in the initial stage of hydration. • High dosage of TEA in accelerator increases the formation rate of AFt and inhibit the hydration of C 3 A and C 3 S. • Transformation of DEA-Al to DEA-Ca occurred in the cement hydration when accelerator containing DEA. In this study, diethanolamine (DEA) and triethanolamine (TEA) were used to prepare a series of liquid alkali-free accelerators to investigate the different effects of complexation of DEA and TEA in accelerators towards the initial stage of cement hydration. Two types of accelerators respectively containing DEA (dosages of 0, 6, 8, 10, 12%) and TEA (dosages of 0, 0.25, 0.5, 0.75, 1, 8%) were prepared, and after addition, the setting time of cement pastes and compressive strength of mortars were tested. The result showed that the optimum dosage of DEA and TEA in accelerators was 8% and 0.25% respectively, and the early-strength effect of TEA was stronger than that of DEA. The mechanisms of DEA and TEA in accelerators were further revealed in terms of complexation capacity, concentration of Ca2+, and hydration products and microstructure morphology of cement pastes. DEA and TEA complexed with Al3+ in accelerators and promoted the formation of ettringite (AFt) in cement pastes, and the complexation capacity of TEA to Al3+ was stronger than that of DEA, causing that high dosage of TEA in accelerator promoted the formation of AFt more than DEA and covered at the surfaces of C 3 A and C 3 S, which inhibited the hydration. DEA in accelerator could promote the hydration of C 3 S in the initial stage due to the transformation of complex DEA-Al to DEA-Ca. This study aims to interpret the different influences of complexation effects of DEA and TEA in accelerators on the properties of cement-based materials and their working mechanisms. [ABSTRACT FROM AUTHOR]

In the synthesis of functional polycarboxylate superplasticizers (PCEs), ester monomer was usually used as small monomer or macromonomer. However, there were few studies on the co-introduction of small ester monomer and ester macromonomer into one PCE molecule and its effects. In this study, it was found an interesting behavior of competitive hydrolysis between these two ester monomers in diester PCE, which performed higher fluidity of cement paste, greater adsorption amount and shorter prolongation of the induction period of cement hydration due to the competitive hydrolysis. Furthermore, the kinetics of hydrolysis and adsorption of the diester PCE were probed, and the rate order was: ester macromonomer < small ester monomer < diester monomers. This study aims to innovatively reveal the special behavior and mechanism of competitive hydrolysis of PCE using diester monomers in cement-based materials and to provide a theoretical basis for enriching molecular design and innovative application of functional PCEs. [Display omitted] • First study on the competitive hydrolysis behavior of PCE having complex diester. • Competitive hydrolysis occurred between small ester monomer and ester macromonomer. • The kinetics of hydrolysis and adsorption of the diester PCE were established. • Better performances in adsorption and dispersibility of diester PCE in cement paste. • Competitive hydrolysis helped reduce the prolongation of hydration induction period. [ABSTRACT FROM AUTHOR]

A novel star-shaped polycarboxylate superplasticizer (SPCE) was synthesized through a simple two-step method. 1 H Nuclear Magnetic Resonance ( 1 H NMR) and Infrared Spectroscopy (IR) measurements were used for structural characterization. SPCE and comb-shaped polycarboxylate superplasticizer (CPCE) with same molecular weights were designed and synthesized. The cement paste containing SPCE exhibited better fluidity, fluidity retention, water reduction, 25% lower saturated dosage of PCE, 10% longer setting time, lower hydration heat, more delayed hydration heat evolution and lower amount of hydration products at early ages. Furthermore, the adsorption behavior of SPCE and CPCE in cement pastes and the zeta potential were investigated, and then the working mechanism of SPCE was theoretically explained. It is interesting that changing topological structure from comb-shape to star-shape can achieve the optimization of dispersion effect, and further improve the working effectiveness. The aims of this study are to provide a new avenue to synthesize superplasticizer with novel structure achieving the chemical diversity of superplasticizer structure, and to verify the contribution of optimizing molecular shape. This new type of superplasticizer can be used as a rheology modifying agent in fresh cement-based materials. [ABSTRACT FROM AUTHOR]

Effects of disodium EDTA (EDTA-2Na) on hydration and mechanical properties of calcium sulphoaluminate-belite cement (CSBC) were investigated systematically. Results show that EDTA-2Na addition leads to visible changes in CSBC strength development. 0.50 % EDTA-2Na significantly enhances the compressive strength by 18 % and 23 % compared with the blank specimens at 7 d and 28 d, while reducing the strength at 8 h and 1 d. The content of the main hydration product (AFt) determines the strength development. At the early hydration stage, EDTA-2Na delays hydration of ye'elimite to form AFt, thus decreasing the early hydration degree of CSBC and increasing the porosity to reduce strength. In the presence of EDTA-2Na, the morphology changes of amorphous aluminum hydroxide (AH 3) facilitate the AH 3 -C 2 S-CaSO 4 reaction to increase AFt content and form a more condensed structure, thus enhancing the late strength. In this way, the strength development of CSBC mortars can be modified and regulated by EDTA-2Na. [ABSTRACT FROM AUTHOR]

This study was conducted based on the ISO 14040/14044 standards to analyze the environmental impact caused by blast furnace slag utilization for ordinary Portland cement production in typical plants in Beijing. In addition, sensitivity analysis of resource consumption, transport distance, the allocation methods and life cycle impact assessment model were discussed in detail. The results showed that global warming potential and acidification potential were the most significant environmental impacts resulted by slag-based cement production, accounting for 58.5% and 21.7% of the total environmental impact, respectively. Moreover, the cement production and energy generation phases accounted for 66.6% and 29.6% of total environmental loads of slag-based cement from cradle to gate, respectively. Sensitivity analysis showed that the comprehensive environmental impact of slag-based cement was sensitive to the consumption of limestone and energy, as well as the allocation methods and life cycle impact assessment model; but was insensitive to the consumption and transport distance of blast furnace slag. Compared with traditional Portland cement, except for the approximately 9% increase of human toxicity potential, the other impacts of slag-based cement decreased to a certain extent. In particular, abiotic depletion potential and land use potential significantly reduced by 72% and 41%, respectively. Therefore, producing cement with blast furnace slag would slightly increase electricity consumption, but significantly improve the benefits of land resource and materials conservation and significantly decrease the comprehensive environmental impact of cement. [ABSTRACT FROM AUTHOR]

Highlights: [•] Amide-PCE was synthesized successfully and the optimal conditions were determined. [•] The structure of amide-PCE and its sufficient amidation reaction were confirmed. [•] Amide-PCE has better application performance than the conventional PCE in concrete. [•] The dispersion mechanism of amide-PCE in cement–water system was illustrated. [•] It can provide electrostatic repulsion, steric hindrance, complex and lubrication. [ABSTRACT FROM AUTHOR]

• The accelerated self-healing of cracks in cement mortars containing TEA was investigated. • The size of portlandite are greatly decreased by the addition of TEA in cement mortars. • The accelerated formation of CaCO 3 is responsible for the accelerated crack healing in TEA containing mortars. Mechanism of accelerated self-healing behavior of cement mortars incorporating triethanolamine (TEA) was investigated. The crack width in cement mortar specimens and the healing efficiency of cracks during immersion in water were quantitatively measured according to the Poiseuille's law. To reveal the working mechanism of TEA in the accelerated self-healing of cracks in cement mortars during water immersion, multi-techniques including X-ray diffraction (XRD), thermogravimetry (TG), nitrogen sorption isotherm and scanning electron microscopy (SEM) were employed to determine the changes in composition and microstructure of hydration products in the presence of TEA before and after water immersion. In addition, carbonation process of synthesized CH powder was studied. Results show that self-healing of the cracks in cement mortars during water penetration is a result of the continuous formation of CaCO 3 on the fractured surfaces. TEA addition visibly enhances the self-healing performance of cement mortars and a higher dosage of TEA leads to a higher self-healing efficiency, because of the accelerated precipitation of CaCO 3 on the fractured surface in mortars. TEA addition results in great morphological changes and increasing the surface area of portlandite as the second major hydration product of cement. Thus the carbonation process is notably accelerated in the mortars containing TEA. Moreover, the TEA-Ca2+complexation may promote the decalcification of C-S-H. [ABSTRACT FROM AUTHOR]

The application of self-healing property to cement-based materials promoted a long-term service time in engineering. In this study, dimethyl thio-toluene diamine (DMTDA) microcapsules were synthesized successfully through melting-dispersion-condensation techniques, and enabled crack closure thus recovering the mechanical property. The as-fabricated DMTDA microcapsules showed a core-shell structure and well-dispersed properties with a tailorable core fraction and diameter, (e.g., a diameter of 312.7 ± 97.6 μm and a shell thickness of 15.2 ± 2.6 μm under agitation rate of 300 RPM). It was found that DMTDA microcapsules had a high core fraction and good thermal stability. The introduction of microcapsules decreased the flowability of cement paste but remained integral structures during the mechanical agitation. The increase of microcapsule concentrations led to a significant drop in porosity but a slight decrease in compressive strength of cement paste. Most importantly, the addition of DMTDA microcapsules and isocyanates microcapsules in the cement paste could repair the early hydration cracks with a size less than 100 μm, thereafter achieving a satisfying recovery of the compressive strength. [ABSTRACT FROM AUTHOR]

• A novel sulfonate-modified PCE was synthesized based on innovative molecular design. • Sulfonate modification on the side chains of PCE can enhance the sulfate tolerance. • Effects of competitive adsorption, ionic strength and conformation were studied. • Good performance retention and stability were shown for solving compatibility problem. • Many quantitative evaluation indexes for sulfate tolerance of PCE were established. A novel polycarboxylate superplasticizer (PCE) was synthesized by graft copolymerization between acrylic acid (AA) and end-functionalized poly (allyl sulfonate) (PALS) to produce comb polymer, i.e. PAA-g-PALS. The molecular structure was confirmed by Infrared Spectroscopy (IR) and 1H Nuclear Magnetic Resonance (1H NMR), and the molecular properties were characterized by Gel Permeation Chromatography (GPC). The conventional PCE with comb structure using isobutenyl polyethylene glycol (IPEG) as side chains (i.e. PAA-g-IPEG) was also synthesized to explore the effect of the side chain on the PCE performances. The fluidity and its retention, rheological properties, hydrodynamic radii (R h), adsorption behavior and zeta potential of the cement pastes containing PAA-g-PALS or PAA-g-IPEG were comparatively tested. It was found that this designed "sulfonate modified PCE" exhibited stronger dispersing stability and sulfate tolerance to cement paste and less sensitive to the sulfate competitive adsorption and the increase in ionic strength. Based on the above results, the evaluation method (the sulfate resistance index of PAA-g-PALS was increased by 24% as compared to that of PAA-g-IPEG) was innovatively established and the mechanism of sulfate resistance was clarified in detail. The purpose of this research is to offer an avenue with great potentials to synthesize a novel PCE with excellent workability retention and sulfate tolerance in fresh cement pastes. This sulfonate-modified polycarboxylate superplasticizer has great potentials as a viable alternative to conventional PCE, especially in some harsh cement systems. [ABSTRACT FROM AUTHOR]