Properties Of Calcium Sulfoaluminate Cement Research Articles

Effects of calcined phosphogypsum replacement on hydration and properties of calcium sulfoaluminate cement at different curing temperatures

The present research aims to understand the cement hydration and microstructure formation mechanism of calcined phosphogypsum (CPG) supplemented calcium sulfoaluminate (CSA) pastes cured under hot-weather temperatures and to ensure the appropriate application and effective service of CSA cement-based materials, as well as to address the problem of overstocking of CPG. The effects of CPG dosage on the heat of hydration, electrical resistivity, hydration products, and bound water content of CSA cement pastes were investigated at curing temperatures of 20 °C, 35 °C, and 50 °C. Hydration kinetics was studied to elucidate the hydration mechanism, and thermodynamic modelling was performed to predict the phase assemblages. The results show that the incorporation of CPG facilitated the formation of ettringite and significantly reduced the transformation of ettringite to monosulfate, and these phenomena were enhanced with an increase in the CPG. The addition of CPG at elevated curing temperature (35 °C and 50 °C) significantly improved the compressive strength of CSA cement pastes. The growth rate and nucleation rate predicted by the BNG model for the CSA cement pastes cured at 50 °C were substantially higher compared to those at 20 °C.

Effects of AH3 and AFt on the Hydration-Hardening Properties of the C4A3S¯-CS¯-H2O System.

This study aimed to reveal the effects of the hydration products AH3 and AFt phases on the hydration and hardening properties of calcium sulfoaluminate (CSA) cement. In addition, the effects of anhydrite (CS¯) and gypsum (CS¯H2) on the properties of CSA cement were compared. Calcium sulfoaluminate (C4A3S¯) was synthesized with analytical reagents, and the C4A3S¯-CS¯-H2O system with different molar ratios of CS¯ and C4A3S¯ was established. The phase compositions and contents of AFt and AH3 were determined by X-ray diffraction (XRD), Rietveld quantitative phase analysis, and thermogravimetric analysis (TG). The effects of pore structure and hydration product morphology on mechanical properties were analyzed by mercury intrusion porosity (MIP) and scanning electron microscopy (SEM). The results showed that the compressive strength exhibited a correlation with the AH3 content. In the case of relatively sufficient anhydrite or gypsum, C4A3S¯ has a high degree of hydration, and the AH3 content can be considered to contribute more to the strength of the hardened cement paste. When anhydrite was selected, the combined and interlocked AFt crystals were covered or wrapped by a large amount of AH3. The mechanical properties of the hardened cement paste mixed with anhydrite were better than those of that mixed with gypsum.

Effect of particle size distribution on the pre-hydration, hydration kinetics, and mechanical properties of calcium sulfoaluminate cement

Effect of particle size distribution on the pre-hydration, hydration kinetics, and mechanical properties of calcium sulfoaluminate cement

Effect of the fineness of limestone powder on the properties of calcium sulfoaluminate cement

Effect of the fineness of limestone powder on the properties of calcium sulfoaluminate cement

Adding Effects of CaF<sub>2</sub> and TiO<sub>2</sub> as Mineralizers on the Sintering Temperature and Hardening Properties of Calcium Sulfoaluminate Cement

Adding Effects of CaF<sub>2</sub> and TiO<sub>2</sub> as Mineralizers on the Sintering Temperature and Hardening Properties of Calcium Sulfoaluminate Cement

Effect of Flue Gas Desulfurization Gypsum on the Properties of Calcium Sulfoaluminate Cement Blended with Ground Granulated Blast Furnace Slag.

This work aims to investigate the effect of additional flue gas desulfurization gypsum (FGDG) on the properties of calcium sulfoaluminate cement (CSAC) blended with ground granulated blast furnace slag (GGBFS). The hydration rate, setting time, mechanical strength, pore structure and hydration products of the CSAC-GGBFS mixture containing FGDG were investigated systematically. The results show that the addition of FGDG promotes the hydration of the CSAC-GGBFS mixture and improves its mechanical strength; however, the FGDG content should not exceed 6%.

Influence of Different Lithium Compounds on Hydration and Mechanical Properties of Calcium Sulfoaluminate Cement.

This work investigated the influence of three different lithium compounds, lithium carbonate (Li2CO3), lithium sulfate (Li2SO4) and lithium chloride (LiCl), on the hydration and mechanical properties of calcium sulfoaluminate (CSA) cement mixtures. Five concentrations of Li+, 0, 0.05, 0.11, 0.16 and 0.22 mmol/g of cement, were chosen, and then the proportions (by mass) of three lithium compounds were determined. Compressive strengths at 8 h, 24 h and 28 days were tested. Meanwhile, an early hydration heat test, thermogravimetric (TG) analysis, X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques were performed to study the influences of different lithium compounds on properties of CSA cement mixtures. The experimental results show that three lithium compounds can all accelerate the early hydration process of CSA cement. There is not a remarkable difference on the properties of CSA cement pastes with a different content of Li+. The anion of lithium compounds can also affect the properties of CSA cement pastes, the accelerating effects of LiCl and Li2SO4 are more significant than that of Li2CO3, but there is not a distinct difference between LiCl and Li2SO4.

Effect of ground granulated blast furnace slag on the properties of calcium sulfoaluminate cement

In order to make a good understanding of the properties of calcium sulfoaluminate cement (CSAC) blended with ground granulated blast furnace slag (GGBFS), the effect of GGBFS on the hydration heat, setting time, mechanical strength, pore structure and hydration process of CSAC was investigated using isothermal calorimeter, MIP, XRD, SEM, thermal analysis and so on. Results show that the hydration rate and total hydration heat are reduced with the addition of GGBFS, meanwhile, the initial and final setting time has obvious increase. The compressive strength of mortars with GGBFS ≤ 10% is close to that without GGBFS when they are cured for 28d, 56d and 120d, however, it decreases obviously when the GGBFS content is more than 10%. The pore size of hardened cement paste shifts to larger diameter with the GGBFS content increasing from 0% to 30% and the total porosity increases from 26.1% to 35.4%. The addition of GGBFS has no obvious effect on the formation of hydration products, while the total amount of hydration products is reduced. Besides, the number of micro-cracks in the hardened cement paste reduces with the GGBFS content increasing.

Properties of calcium sulfoaluminate cement made ultra-high performance concrete: Tensile performance, acoustic emission monitoring of damage evolution and microstructure

Abstract The properties of early age strength ultra-high performance concrete (ES-UHPC) made with calcium sulfoaluminate (CSA) cement, including tensile performance, damage evolution monitored by acoustic emission (AE) and microstructure were evaluated in this work. Results show that the ultimate tensile strain eUtu of ES-UHPC can reach to 0.199% at 1 d, which is 4.23 times larger than that of normal UHPC (N-UHPC) at the same testing age. AE testing results indicate that both types of UHPCs exhibit multiple cracking behavior at 28 d. With the tensile strain developing, the two UHPCs show a similar damage evolution trend and multiple microcracks with crack-width smaller than 0.01 mm generated after 0.046% strain reached. Microstructure tests demonstrate that ettringite presented after 4 h and the content increased significantly from 4 h to 3 d, which contributed to the early mechanical properties for ES-UHPCs.

Influences of ethylene-vinyl acetate and methylcellulose on the properties of calcium sulfoaluminate cement

Calcium sulfoaluminate (CSA) cement is widely used in architecture engineering and emergency repairs. However, it still exhibits several disadvantages, such as low flexural strength and strength regression during the late curing age. Ethylene-vinyl acetate (EVA) copolymer is useful in improving the flexural strength of Portland cement. Methylcellulose can improve the water retention properties of cement-based materials to ensure homogeneity during hydration and to improve the stability of hydration products. The effects of EVA and methylcellulose on the setting time, strength, and pore structure of CSA cement mortar were investigated in this study. Both polymers evidently prolong setting time and enhance flexural strength, but decrease compressive strength. The regression of strength after 7 days of curing was well controlled using methylcellulose. The hydrates and mechanism of the polymer-modified CSA cement were investigated via X-ray diffraction analysis and scanning electron microscopy.

Effect of ternesite on the hydration and properties of calcium sulfoaluminate cement

Ternesite is an intermediate phase formed during clinkering of calcium sulfoaluminate (CSA) cement. This paper presents an experimental study on the feasibility of using ternesite as an additive of CSA cement in order to improve cement properties. Properties including setting time, mechanical strength, dimensional stability and hydration kinetics are investigated. The results indicated that the incorporation of ternesite can decrease the setting times and the strength development at early ages. The hydration of ternesite at later ages can increase the strength after 28 days of hydration, and 5% of ternesite is most favorable. The use of ternesite as an additive in CSA cement is harmless to the volume stability. The addition of ye’elimite to the pure ternesite promotes the hydration of ternesite and the formation of ettringite. XRD results show that the addition of ternesite can promote the formation of ettringite at later ages.

A comprehensive study on the relationship between mechanical properties and microstructural development of calcium sulfoaluminate cement based self-leveling underlayments

In this study, the mechanical properties of calcium sulfoaluminate cement based self-leveling underlayments (SLU) prepared with various amount of anhydrite were evaluated through setting times, flowability, compressive strengths and linear shrinkage tests. Meanwhile, to optimize the workability and cost, a high percent of limestone powder was added in all the blends. Influences of CSA cement clinker variety and anhydrite dosage on the hydration of SUL were investigated in terms of the phase assemblage and microstructural development between 1 h and 56 d. Results show that the main hydrates of the control SUL samples made with neat CSA cement clinker and limestone powder are hemicarbonate, monosulfate, aluminium hydroxide and minor amounts of ettringite; massive ettringite and aluminium hydroxide are observed once anhydrite is further added. The SLU containing neat CSA1 cement clinker exhibits higher compressive strengths and drying shrinkage compared with those of neat CSA2 cement clinker. But such differences among different CSA cement clinkers based SLU are getting narrower with increasing anhydrite dosage. Those SLU samples made with 30% anhydrite yield the highest strength but the lowest drying shrinkage. The formation of ettringite at early term mainly contributes to strength development, while the formation of ettringite at later hydration stage favors to decrease the late-term drying shrinkage.

Effect of coral filler on the hydration and properties of calcium sulfoaluminate cement based materials

In this research, the feasibility of using coral filler in Calcium sulfoaluminate (CSA) cements based materials is investigated, targeting at reducing transportation cost for the marine construction. Properties including setting time, mechanical properties and hydration kinetics are investigated. Two blended materials groups with and without anhydrite are tested. Then, their properties are compared with the plain CSA cement clinker samples (with and without quartz filler). The obtained results indicate that coral filler decreases the hydration heat and generates hemicarbonate instead of monosulfate. Moreover, the replacement of CSA cement clinker by coral filler can slightly decrease the setting time and improve the strength development of sulpho-aluminous cement based materials with limited anhydrite. However, the activity of coral filler decreases with the addition of anhydrite. In the group with sufficient anhydrite, the replacement of CSA cement clinker by coral filler has limited effect on the CSA cement hydration, and can decline the long-term mechanical properties of CSA cement based materials.

Micro-mechanical properties of calcium sulfoaluminate cement and the correlation with microstructures

To investigate the micro-mechanical properties of calcium sulfoaluminate cement and the correlation with the microstructures, we apply a variety of advanced techniques of microstructural and micro-mechanical characterization, including scanning electron microscopy with backscattered electron and energy-dispersive X-ray spectroscopy detectors, X-ray fluorescence, X-ray diffraction and nanoindentation. For the first time, the micro-mechanical properties of material microstructures present in a calcium sulfoaluminate cement are estimated. In the calcium sulfoaluminate cement used in this research, two type of hydration product microstructures with the differentiable microstructural morphologies, compositions and micro-mechanical properties are identified and investigated. The correlation of the micro-mechanical properties with the microstructures shows that the hydration product microstructure containing more ettringite has lower indentation modulus and hardness than that containing more aluminum hydroxide.

Influence of polyether polyol on the hydration and engineering properties of calcium sulfoaluminate cement

The aim of the present paper was to investigate the efficiency of polyether polyol as shrinkage-reducing admixture on pastes and mortars prepared with calcium sulfoaluminate cement (CSA). CSA was prepared by mixing CSA clinker and re-crystallized gypsum in different proportions. Three types of polyether polyol were added at a dosage of 1.5 wt% of CSA when hydrating pure pastes and standard mortars. The engineering properties of mortars (compressive strength, drying shrinkage) and the microstructure of pastes were investigated. The results show that polyol reduces drying shrinkage of CSA-based mortars without affecting the nature of hydrates formed. The effect of polyol mainly depends on its molecular weight.