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Influence of Elevated curing temperature on the Properties of Cement Paste and Concrete at the Same Hydration Degree

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Journal of Wuhan University of Technology(Materials Science) 2017年第6期32卷 1344-1351页

作者：王强 SHI Mengxiao WANG Dengquan Department of Civil Engineering Tsinghua University Beijing 100084 China

Three different curing temperatures（20 ℃, 40 ℃, and 60 ℃） were set, so that the nonevaporable water（w_n） contents of plain cement pastes cured at these three temperatures were measured to determine the hydration degree of cement. Tests were carried out to compare the pore structure and strength of cement paste, as well as the strength and permeability of concrete under different temperature curing conditions when their cements were cured to the same hydration degree. The experimental results show that either at a relatively low hydration degree（w_n=15%） or high hydration degree（w_n=16.5%）, elevated curing temperature has little influence on the hydration products of cement paste, while it has a negative influence on the pore structure and compressive strength of cement paste. However, this negative effect is weaker at high hydration degree. The large capillary pore（〉100 nm） volumes of cement pastes remain almost the same at high hydration degree, regardless of curing temperatures. As for the concrete, elevated curing temperature also has negative influence on its compressive strength development, at both low hydration degree and high hydration degree. And this negative effect is stronger than that on cement paste＇s compressive strength at the same hydration degree. On the whole, elevated curing temperature has little influence on the resistance of concrete to chloride ion penetration.

关键词： curing temperature compressive strength pore structure permeability

Effect of curing temperature on the Morphology and Hydration of MgO Expansive Material in Paste

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第4期36卷 675-679页

作者： ENG Tian Zi WANG Fu PENG Hailong YANG Weibo GAO Peiwei Department of Civil Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China Communication Plan Survey and Design Institute of Shanxi Province Taiyuan 030012P.R.China

The morphologies and hydration properties of MgO expansive material at different curing temperatures were investigated.When the curing temperature varies from 25℃to 50℃,the conductivity of MgO rises from 40 to 80μs/cm,the hydration product of MgO expansive material curing in water for 28 days is from 1.5—2 mm to 2—2.5μm in length through SEM observation,and the expansion of pastes with 5%of the magnesium oxide is from 0.36%up to 1.01%,it is increased by 2.78 times.When the content of cement paste increases to 95%and cured in water for 90 days,the brucite forms as hexaflaggy?shaped crystal,which is less than 0.1μm and tends to aggregates.The effect of curing temperature on the hydration of MgO expansive material is obvious.

关键词： MgO expansive material hydration curing temperature morphology expansion

Performances of Concrete under Elevated curing temperature

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Journal of Wuhan University of Technology(Materials Science) 2004年第3期19卷 65-67页

作者：谭克锋 John M Nichols Southwest University of Science and Technology Texas A&M University(USA)

The behaviors of concrete at elevated curing temperature were studied. The test results show that when concrete is cured at elevated temperature, a harmful consequence occurs.The later strength decreases significantly compared to that under normal curing condition. Incorporating silica fume, fly ash and slag or lowering w/c ratio can effectively alleviate this harmful consequence. Comparatively, incorporation of silica fume is the most efficient means to decrease the later strength reduction. The harmful consequence is not caused by the difference in degree of hydration since the degree of hydration is similar between elevated curing temperature and normal curing condition. The SEM analysis shows that it is the uneven distribution of hydration products caused by elevated curing temperature that leads to the later strength reduction of concrete.

关键词： curing temperature strength mineral admixture

Effect of curing temperature on Intermediate temperature Properties of Calcium Aluminate Cement Bonded Corundum Castables

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China's Refractories 2021年第3期30卷 33-36页

作者： LI Ye LIU Kun DING Dafei WANG Qingfeng FU Xiaohui YE Guotian Henan Key Laboratory of High temperature Functional Ceramics Zhengzhou UniversityZhengzhou 450001China Materials Engineering Department Luoyang Institute of Science and TechnologyLuoyang 471023China

In order to study the effect of the curing temperature on the intermediate temperature properties of calcium aluminate cement bonded corundum castables,the prepared castables were cured at 5,10,25,40 and 50℃,respectively,dried at 110℃ for 24 h and heat treated at 800 and 1100 ℃,respectively.Then the apparent porosity,the cold modulus of rupture and the cold crushing strength were measured.The phase composition of castable matrix specimens treated under the same conditions and the influence of the curing temperature on the intermediate temperature strength of the castables were also analyzed.The results show that with the increase of the curing temperature,the hydration degree of calcium aluminate cement increases,which promotes the uniform distribution of hydration products with AI203 after decomposition,thus enhancing the intermediate temperature strength of castables.

关键词： curing temperature calcium aluminate cement corundum castable intermediate temperature strength

Performance development of styrene-butadiene copolymer-modified calcium sulfoaluminate cement mortar under different curing conditions

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2021年第12期22卷 1005-1026页

作者： Ru WANG Yu-sheng FAN Zhao-jia WANG Tian-yong HUANG Tao ZHANG Key Laboratory of Advanced Civil Engineering Materials(Tongji University) Ministry of EducationShanghai 201804China School of Materials Science and Engineering Tongji UniversityShanghai 201804China State Key Laboratory of Solid Waste Reuse for Building Materials Beijing Building Materials Academy of Science ResearchBeijing 100041China

The purpose of this study was to investigate the change in the physical and mechanical properties of styrene-butadiene copolymer(SB)dispersion-modified calcium sulfoaluminate(CSA)cement mortar as it aged from 28 to 360 d,and cured at different temperatures and relative humidities.The results show that the mechanical properties of reference mortar(RM)of CSA cement,including its flexural,compressive,and tensile bond strength,showed a reduction after a certain time,but its water capillary absorption was hardly affected by age.When SB dispersion was added,there was no reduction in mechanical strength.The amount of SB added did matter.Addition of 5% SB had a negative effect on most properties compared with RM,except for tensile bond strength.However,the properties of SB-modified mortar(SBMM)were enhanced significantly as the amount of SB was increased from 5% to 20%.temperature change had different effects on the properties of RM and SBMM.High temperature was beneficial to early flexural and compressive strength development of RM,but caused serious strength reduction at later stages.High temperature enhanced the development of tensile bond strength of RM.Increasing temperature enhanced properties of SBMM,including flexural,compressive,and tensile bond strength.Higher relative humidity improved all measured properties of all mortars.Scanning electron microscope(SEM)observations of the morphology of RM and SBMM at 360 d cured under different conditions accounted well for the changes in mechanical properties.

关键词： Calcium sulfoaluminate(CSA)cement Styrene-butadiene copolymer(SB)dispersion Mortar Properties curing temperature Relative humidity(RH)

Effect of curing Regime on the Distribution of Al^(3+) Coordination in Hardened Cement Pastes

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Journal of Wuhan University of Technology(Materials Science) 2013年第5期28卷 927-933页

作者：丁庆军 HU Chenguang FENG Xiaoxin HUANG Xiulin School of Materials Science and Engineering Wuhan University of Technology School of Materials Science and Engineering Hebei United University School of Materials Science and Engineering Hubei University

The effect of curing regime on the distribution ofAl3＋ coordination in hardened cement pastes within 28 d were investigated by 29Si and 27Al magic angle spinning （MAS） nuclear magnetic resonance（NMR） with deconvolution technique. The results indicate that the tetrahedral coordination Al3＋ incorporated in C-S-H structure mainly originate from the AP＋ incorporated in the alite and belite phases in the Portland cement. The curing regime of constant temperature of 20 ℃ is beneficial to the octahedral coordination Al3＋ transforming to tetrahedral coordination AP＋ incorporated in C-S-H structure. However, at curing regime of variable temperature, the temperature rising process is more advantageous to the transformation from ettringite to monosulphate, substitution of Al3＋ for Si4＋ in the C-S-H structure and the formation of the third aluminate hydrate （TAH） than that at constant temperature of 20 ℃. The high temperature of 60 ℃ in the holding temperature process promotes the decomposition of ettringite, and enhances the consumption of the Al3＋ incorporated in C-S-H phases and the Al3＋ in TAH for the monosulphate forming. The temperature decreasing promotes the transformation from monosulphate to ettringite, and increases the consumption of the Al3＋ incorporated in C-S-H phases, and then increases the quantity of the TAH.

关键词： curing temperature distribution Al3＋ coordination cement pastes

Early Hydration and Setting Process of Fly Ash-blended Cement Paste under Different curing temperatures

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Journal of Wuhan University of Technology(Materials Science) 2020年第3期35卷 551-560页

作者：张文华 WU Fan ZHANG Yunsheng Civil Engineering Department Nanjing Forestry UniversityNanjing 210037China Department of Materials Science and Engineering Southeast UniversityJiangsu Key Laboratory of Construction MaterialsNanjing 211189China

A specially developed ultrasonic measurement apparatus (UMA) was used to in situ monitor the setting process of fly ash blended cement paste. Combined with the results of Vicat Needle tests, isothermal calorimetric measurement, XRD analysis, SEM morphology and compressive test, the influence of curing temperature (20, 40, 60, and 90 ℃) and fly ash content (0,10%, 20% and 30%) on the setting and hydration process of fly ash blended cement paste was analyzed. The results show that setting and hardening process of fly ash blended cement paste at elevated temperature can be clearly identified into three stages including dormant stage, acceleration stage and deceleration stage. The increasing of curing temperature greatly accelerates the setting and hardening process. However, the content of fly ash does not have significant effect on the setting in condition of 90 ℃. Besides, the initial and final setting time of cement paste is correspondent with the time of duration of dormant stage and the time of UPV value is 1500 m/s (T1500), respectively. Thus, the UMA can be used to determine the initial and final setting time of cementitious material under different curing temperatures. The compressive test results indicate that the paste with 20% fly ash presents higher compressive strength than the plain paste at curing temperatures of 90 ℃. Therefore, appropriate amount of fly ash is beneficial for concrete in the high temperature curing conditions.

关键词： ultrasonic setting and hardening process curing temperature fly ash microstructure

Effect of curing Regime on Polymerization of C-S-H in Hardened Cement Pastes

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Journal of Wuhan University of Technology(Materials Science) 2013年第4期28卷 715-720页

The effect of two different curing regimes on the polymerization degree of C-S-H in hardened cement pastes within 28 d were investigated by measuring the chemical environments of 29Si with magic angle spinning （MAS） nuclear magnetic resonance （NMR） and by analyzing the 29Si NMR spectra with deconvolution technique. The experimental results indicate that, at curing regime of constant temperature of 20℃, the polymerization of C-S-H increases and then decreases with curing age, and the A1/Si ratio increases gradually with curing age, furthermore, the two non-bridging oxygen bonds of bridging silicate tetrahedra in C-S-H structure mainly bond to H＋. At curing regime of variable temperature, the polymerization of C-S-H firstly increases then changes slightly and subsequently decreases with the temperature from low to high and then to low, and the A1/Si ratio firstly increases then keeps invariant and subsequently slightly decreases. Moreover, the temperature decreasing is advantageous for the Ca2＋ to be bonded to the bridging silicate tetrahedra and entering into the interlayer of C-S-H structure. The polymerization of C-S-H at curing regime of variable temperature is higher than that cured at constant temperature, but the curing regime of constant temperature is more beneficial to the substitution of AP for Si4＋ than that of variable temperature.

关键词： curing temperature cement C-S-H polymerization A1/Si ratio

Application of silver nanoparticles in electrically conductive adhesives with silver micro flakes

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China Welding 2022年第2期31卷 23-28页

作者：刘昊马瑞赵丁伟崔志远张微微王建强 Harbin Institute of Technology(Shenzhen) Shenzhen 518054China Academy of Defense Technology China Aerospace Science and Industry Corp.Beijing 100854China

This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a filler loading of 78 wt.%,83 wt.%and 88 wt.%and cured at 150℃and 180℃,respectively.The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature.Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%,because the segregation of NPs enlarged the average distance of silver flakes;while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%,probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes,especially when curing at high temperature of 180℃.

关键词： electrically conductive adhesives silver nanoparticles mass fraction curing temperature