Buildings
·
2022
·Vol. 12
·期 4
·422
·
IF 3.324
Jinqing Jia,Yimu Wang
The interaction effects of four chlorine-free admixtures such as calcium formate (CF), triethanolamine, (TEA), triisopropanolamine (TIPA), and sodium sulfate (SS) on the compressive strength development of Portland cement mortars were investigated based on the design of experiment (DoE). The results showed that both the addition of CF and SS contributed significantly to the strength of cement mortars at early curing age. However, the interaction of CF and SS could hinder their respective positive effect on the strength of cement at 1 d. At later curing ages, CF was still beneficial in improving the late strength of cement, but SS had a negative effect on the strength of cement at 28 d. A negative effect of TIPA on the strength of cement was found at 3 d. However, the positive interactive effect of TIPA and CF was sufficient to offset the negative effect of TIPA on the strength of mortars at 3 d if the dosage of CF exceeded 2%. In addition, TEA had a positive influence on 7 d strength until a turning point was reached and the optimum dosage of TEA was approximately 0.013%.
研究领域:
土木工程
·
材料科学
✓ 已验证
DOI
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2020
·
IF 4.419
Feng Zhang,Yin Bai,Yuebo Cai
Under low temperature environment, the concrete strength develops slowly, which will seriously hinder the construction progress. Traditional early-strength components can not meet the requirements of green and high-performance concrete, combined with the research and application of early-strength accelerators under low temperature is relatively few, and its low-temperature early-strength performance is limited, the early strength development rate of specimens is far lower than that of blank samples at 20 °C, so it is urgent to develop new early-strength component to promote the strength development rate of concrete at low temperature. In this paper, calcium bromide (CaBr 2 ) was used as an early strength component to test the 1-, 3-, 7-, and 28-d compressive strengths of the mortars and cement pastes mixed with 0–1.0% CaBr 2 under 5 °C curing. CaBr 2 had a significant effect of early strength at low temperature (5 °C), and the strength of the specimens mixed with 1.0% CaBr 2 at each age was close to or even exceeded that of the contrast samples cured at 20 °C. The equilibrium method (gravimetric method) was used to study the effect of 1 mol/L of CaBr 2 in water on the dissolution of the single ores C 3 S at different ages. CaBr 2 could promote the dissolution of C 3 S at a low temperature of 5 °C, and the solubility of C 3 S had an obvious tendency to increase. Further, X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) and energy-dispersive spectrometry (EDS) analysis and mercury infusion porosimetry (MIP) analysis were used to perform microscopic characterization (e.g., product composition, morphology, pore structure, etc.) of the hydration products of the cement single ores or mortars mixed with CaBr 2 . On this basis, the early-strength mechanism of CaBr 2 was discussed. CaBr 2 could promote the initial hydration of cement at low temperature (5 °C) and significantly increase the degree and rate of hydration of C 3 S and C 3 A single ores, and also generated new type of products, bromine-containing C–S–H gels and bromoaluminate calcium hydrate (Ca 4 Al 2 O 6 Br 2 ·10H 2 O), and the Ettringite and Ca(OH) 2 crystals were mostly formed on the surface of gel products or inside the pores. Large amounts of hydration products were generated, which refined the pore diameter of samples by reducing the most probable pore size and total porosity, thus making the microstructure of samples denser and enhancing the strength of specimens.
研究领域:
建筑材料学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED POWDER TECHNOLOGY
·
2024
·
IF 4.2
Chen Jixi,Jia Jinqing,Zhu Mengyu
Water film thickness (WFT) has been discovered to significantly affect the performance of cement-based materials in previous studies. The purpose of this study is to apply the WFT theory to cement-based materials with early-strength agents. To this end, calcium chloride (CaCl 2 ) and triethanolamine (TEA) were used to prepare 32 groups of fresh pastes with varying water-cement ratios and different dosages of CaCl 2 /TEA. These pastes were tested for flow performance, setting time, and hardening performance. The comprehensive effects of WFT and early strength agents on the mobility and hardened properties of cement-based materials were discussed from the obtained results. Results show that WFT is still one of the main elements affecting the performance of cement-based materials in the presence of early strength agents. CaCl 2 increased the packing density of the paste, enhancing the excess water between particles and enlarging the WFT, which positively impacted the performance of the paste. In contrast, TEA decreased the WFT, increased the cohesion between particles, and declined the fluidity. Furthermore, as the water-cement (w/c) ratio raised, the WFT of the paste also increased. This caused cement particles to be enveloped in excess water, improving slip capacity and consequently increasing fluidity but reducing strength. Overall, WFT and admixture dosage can effectively predict the fluidity and mechanical properties of the paste.
研究领域:
土木工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS AND STRUCTURES
·
2024
·Vol. 57
·期 5
·1-12
·
IF 3.4
Zhang Wan,Wu Zhihong,Huang Wang,Liu Jiayuan,Zhou Huafeng,Qiu Junlong
It is insufficient to enhance the strength of shotcrete by simply relying on the early strength component aluminum sulfate in the liquid accelerator. The introduction of organic additives can effectively compensate for this deficiency. In this study, three different structures of organic ethers, 18-crown-6 (ECS), tetraethylene glycol monomethyl ether (Tg), and ethylene glycol monomethyl ether (Eg), were added to an aluminum sulfate alkali-free liquid accelerator, and their effects were comprehensively investigated. The results revealed that these organic ethers were capable of bolstering the strength of the mortar after 28 d. The efficiency of these ether organics on the strength of cement mixed with the accelerator followed the order: ECS > Tg > Eg. Specifically, when the ECS content reached 0.3%, the compressive strength of the mortar at 1 d was measured at 8.07 MPa. In addition, changes in the phase composition and micromorphology were scrutinized through X-ray diffraction and scanning electron microscopy, culminating in the establishment of a mechanistic model elucidating the hydration process of organic ether accelerator cement.
研究领域:
建筑材料学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION
·
2020
·Vol. 35
·期 3
·611-619
·
IF 0.64
Zhang Feng,Bai Yin,Cai Yuebo,Chen Bo,Ning Fengwei
Triisopropanolamine (TIPA) was used as an early strength component to study its effects on mortar strength, cement paste setting time and early hydration characteristic of cement. And the early strength mechanism of TIPA at low temperature of 5 °C was also discussed. The results showed that, at 5 °C, the incorporation of TIPA promoted the condensation of cement paste, shortened the initial and final setting time, and accelerated the strength development of specimens at all ages, among which the strength after 3 d increased significantly. The 1, 3, 7, and 28 d compressive strength ratios of the mortars mixed with 1% TIPA could reach 196%, 179%, 160% and 110% respectively, and the mortar strength after 3 d exceeded that of the contrast sample cured at 20 °C. Under low temperature condition, TIPA could promote the hydration reaction of cement, shorten the induction period and advance the acceleration period. Furthermore, the maximum heat release rate and cumulative heat release quantity would be all increased, and the cumulative heat release of the cement mixed with TIPA hydrated for 12 h and 7 d increased 73% and 38% respectively. TIPA could shorten the nucleation and crystal growth (NG) stage and increase its hydration degree significantly, so it promoted cement hydration reaction. Additionally, the hydration reaction rates in phase boundary reaction (I) phase and diffusion reaction (D) phase were increased, and the duration of I process was prolonged, thereby the development of specimen strength would be accelerated. TIPA did not obviously change the types of hydration products, but increased the content of Ca(OH) 2 in the samples and the degree of cement hydration. After hydration to 7 d, large amounts of hydration products, whose surface was smooth, were formed and bonded into sheets, and the structural density of samples improved significantly.
研究领域:
建筑材料学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION
·
2025
·Vol. 40
·期 1
·130-140
·
IF 1.1
Liu Jian,Chen Meiting,Ji Xiaoli,Xu Chao,Wang Chunmei
A ternary early-strengthening agent consisting of calcium formate + triethanolamine + lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early strength. The optimum ratio of the three early-strengthening agents was determined as 0.5% calcium formate + 0.04% triethanolamine + 0.4% lithium sulfate by response surface methodology. The effects of the ternary early-strengthening agent composed of calcium formate + triethanolamine(TEA)+ lithium sulfate on cementitious pore sealing materials under the synergistic effect of quercetin were studied by means of the performance tests of compressive strength, fluidity, and setting time, and the microstructural characterizations of X-ray powder diffractometer(XRD), thermogravimetry (TG-DSC) and scanning electron microscopy (SEM). The study shows that the synergistic effect of ternary early-strengthening agent and quercetin forms a multiperformance composite admixture for cementitious materials. The best performance was obtained with the compounding scheme of 0.5% calcium formate + 0.04% triethanolamine + 0.4% lithium sulfate ternary early-strengthening agent and 0.05% quercetin. The compressive strength of 1, 3, 7, and 28 d are 94.8%, 39.8%, 42%, and 28% higher than those of the blank group, respectively. The initial time and final setting time are 41 and 57 minutes, respectively. According to the microscopic analysis, the network and fibrous C-S-H gels generated by ternary early-strengthening agents are attached to the surface promoted by quercetin, which forms skeleton support while thickening and solidifying the cement slurry, which enhances the early compressive strength of the cement-based materials.
研究领域:
建筑材料学
·
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Environmental Earth Sciences
·
2018
·Vol. 77
·期 6
·1-7
·
IF 1.435
Wang Huaqing,Zhang Shuguang,Wu Beining
The early-strength characteristics and mechanism of eight kinds of early-strength agents in low-strength cementitious materials prepared with manganese tailings were studied, and then the optimum mixing amount was obtained by means of progressing and superimposing optimization. The phase composition and morphology of hydration products were characterized through X-ray diffraction and scanning electron microscopy. The results indicated that there existed good superimposing effect among triethanolamine, ferric chloride and lithium carbonate. When the mixing amount of triethanolamine, ferric chloride and lithium carbonate were 0.04, 0.3 and 0.7%, the compressive strength of 3- and 7-day net paste samples increased by 105.5 and 34.5%, while the porosity of 3- and 7-day decreased by 8.3 and 7.4%, respectively. The initial setting time shortened from 130 to 65 min. Therefore, the combination of early-strength agents could accelerate the dissolution of tailings, shorten hydration cycle, increase the amount of ettringite and calcium silicate hydrate, compact the internal structure further, reduce the porosity, which could achieve the compressive strength improved in short time.
研究领域:
材料科学
·
土木工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）