Effect of high temperature environment on water absorption and microstructure evolution of strain hardening cementitious composites
-
摘要: 在高温环境下,应变硬化水泥基复合材料(Strain hardening cementitious composites,SHCC)微结构发生破坏,进而导致其力学与抗渗性能及微结构的劣化。对比研究20℃(常温)、105℃、200℃、400℃、600℃及800℃高温作用后,不同纤维掺量的SHCC试件力学与吸水性能的演化规律,并利用低场核磁共振等技术从微观角度分析了材料宏观性能劣化机制。结果表明:当受热温度由20℃升高至105℃时,试件的动弹性模量有所下降,但抗压强度及抗折强度有所提高。当受热温度升至200℃时,SHCC抗压强度和动弹性模量变化不大,但受热温度高于400℃后,二者均迅速下降;受热温度由105℃升至200℃时,SHCC试件抗折强度显著降低;高于400℃后,抗折强度进一步劣化。纤维掺量对高温作用后的SHCC试件残余力学性能没有明显规律性的影响。另外发现,当受热温度低于200℃时,SHCC毛细吸水性能较差,具有一定的抗毛细入渗性能;400℃以上时,高温损伤能够显著促进SHCC试件的毛细吸水速度和吸水量。低于200℃时,较高纤维掺量的SHCC试件初始毛细吸水系数增加更为迅速,毛细吸水能力更强。加热温度不高于200℃时,SHCC试件的微结构较为密实;超过400℃后,SHCC试件内部纤维熔化、裂纹生成与扩展导致其力学性能显著劣化,毛细吸水性能提高。同时,高温后SHCC试件内部裂纹体积分数随纤维掺量的增加而升高。
-
关键词:
- 应变硬化水泥基复合材料(SHCC) /
- 高温 /
- 力学性能 /
- 吸水性能 /
- 微观结构
Abstract: At high temperature, the microstructure of strain hardening cementitious composites (SHCC) was damaged, which leaded to the deterioration of mechanical properties, impermeability and microstructure. The evolution of mechanical properties and capillary water absorption law of SHCC specimens with different fiber contents exposed to 20℃ (normal temperature), 105℃, 200℃, 400℃, 600℃ and 800℃ were studied, and the degradation mechanism of macroscopic properties of materials was analyzed from the perspective of microstructure by using low-field nuclear magnetic technology. The results show that when the heating temperature increases from 20℃ to 105℃, the dynamic elastic modulus decreases, but the compressive strength and flexural strength increase. When the heating temperature rises to 200℃, the compressive strength and dynamic elastic modulus of SHCC change little, but when the temperature is higher than 400℃, both of them decrease rapidly. When the heating temperature is increased from 105℃ to 200℃, the flexural strength of SHCC specimen decreases significantly, and when the heating temperature is higher than 400℃, the flexural strength further deteriorates. The fiber content has no obvious regular effect on the residual mechanical properties of SHCC specimen after high temperature. In addition, when the heating temperature is lower than 200℃, SHCC has poor capillary water absorption performance and has a certain capillary infiltration resistance. Above 400℃, the high temperature damage can significantly promote the capillary water absorption rate and the water absorption capacity of SHCC specimen. When the temperature is lower than 200℃, the initial capillary water absorption coefficient of SHCC specimen with higher fiber content increases more rapidly, and the capillary water absorption capacity is stronger. The microstructure of SHCC specimen is relatively dense when the heating temperature is lower than 200℃. When the temperature exceeds 400℃, the melting of fibers inside the SHCC specimen and the generation and propagation of cacks lead to significant deterioration of mechanical properties and improvement of capillary water absorption. In the meantime, the volume fraction of cracks in SHCC specimens increases with the increase of fiber content after high temperature. -
表 1 不同聚乙烯醇(PVA)纤维掺量的应变硬化水泥基复合材料(SHCC)配合比
Table 1. Mix proportions of strain hardening cementitious composites (SHCC) with different polyvinyl alcohol (PVA) fiber contents
Sample mw/mc Material/(kg·m−3) Cement Fly ash Silica sand Water PVA fibers SP 1.5vol%PVA/SHCC 0.25 550 650 550 301 19.5 8 1.8vol%PVA/SHCC 0.25 550 650 550 301 23.5 8 2.0vol%PVA/SHCC 0.25 550 650 550 301 26.0 8 Notes: 1.5vol%PVA/SHCC, 1.8vol%PVA/SHCC and 2.0vol%PVA/SHCC—Fiber accounts for 1.5vol%, 1.8vol% and 2.0vol% of the total volume of the cementitious material; mw/mc—Mass of water and cementitious material; SP—Superplasticizer. 表 2 不同PVA纤维掺量的SHCC初始毛细吸水系数
Table 2. Initial capillary water absorption coefficients of SHCC with different PVA fiber contents
Temperature/℃ 1.5vol%PVA/SHCC/(g·cm−2·min−0.5) 1.8vol%PVA/SHCC/(g·cm−2·min−0.5) 2.0vol%PVA/SHCC/(g·cm−2·min−0.5) 20 0.007 0.009 0.007 105 0.008 0.009 0.008 200 0.010 0.014 0.019 400 0.019 0.020 0.025 600 0.117 0.062 0.119 800 0.323 0.326 0.357 表 3 不同温度下不同PVA纤维掺量SHCC的孔隙度
Table 3. Porosity of SHCC with different PVA fiber contents under different temperatures
Temperature/
℃1.5vol%PVA/
SHCC1.8vol%PVA/
SHCC2.0vol%PVA/
SHCC105 0.069 0.088 0.104 200 0.158 0.159 0.160 400 0.230 0.239 0.228 600 0.282 0.290 0.261 800 0.309 0.308 0.296 -
[1] WANG X S, WU B S, WANG Q Y. Online SEM investigation of microcrack characteristics of concretes at various temperatures[J]. Cement and Concrete Research,2005,35(7):1385-1390. doi: 10.1016/j.cemconres.2004.07.015 [2] VODAK F, TRTIK K, KAPICKOVA O, et al. The effect of temperature on strength-porosity relationship for concrete[J]. Construction and Building Materials,2004,18(7):529-534. doi: 10.1016/j.conbuildmat.2004.04.009 [3] CHAN Y N, LUO X, SUN W. Compressive strength and pore structure of high-performance concrete after exposure to high temperature up to 800°C[J]. Cement and Concrete Research,2000,30(2):247-251. doi: 10.1016/S0008-8846(99)00240-9 [4] NOUMOWE A. Mechanical properties and microstructure of high strength concrete containing polypropylene fibers exposed to temperatures up to 200℃[J]. Cement and Concrete Research,2005,35(11):2192-2198. doi: 10.1016/j.cemconres.2005.03.007 [5] 高贯鹏. 高温后PVA-SHCC的力学性能与抗渗性能试验研究[D]. 青岛: 青岛理工大学, 2012.GAO Guanpeng. Experimental study on the mechanical properties and anti-permeability of PVA-SHCC after high temperature[D]. Qingdao: Qingdao Technological University, 2012(in Chinese). [6] PENG Z, DAI Y, DING X, et al. Self-healing behaviour of multiple microcracks of strain hardening cementitious composites (SHCC)[J]. Construction and Building Materials,2018,169:705-715. doi: 10.1016/j.conbuildmat.2018.03.032 [7] LIU L X. Fire performance of high strength concrete materials and structural concrete[D]. Florida: Florida Atlantic University, 2009. [8] YAN L, XING Y M, LI J J. High-temperature mechanical properties and microscopic analysis of hybrid-fiber-reinforced high-performance concrete[J]. Magazine of Concrete Research,2013,65(3-4):139-147. doi: 10.1680/macr.12.00034 [9] YU J, LIN J, ZHANG Z, et al. Mechanical performance of ECC with high-volume fly ash after sub-elevated temperatures[J]. Construction and Building Materials,2015,99:82-89. doi: 10.1016/j.conbuildmat.2015.09.002 [10] 林建辉, 余江滔, VICTOR C L. 超高韧度水泥基复合材料经亚高温处理后的性能[J]. 硅酸盐学报, 2015, 43(5):604-609.LIN Jianhui, YU Jiangtao, VICTOR C L. Performance of engineered cementitious composites after treated at sub-high temperatures[J]. Journal of the Chinese Ceramic Society,2015,43(5):604-609(in Chinese). [11] 高丹盈, 赵亮平, 杨淑慧. 纤维矿渣微粉混凝土高温中的劈拉性能[J]. 硅酸盐学报, 2012, 40(5):677-684.GAO Danying, ZHAO Liangping, YANG Shuhui. Splitting tensile properties of fiber reinforced ground granulated blast furnace slag concrete at high temperatures[J]. Jour-nal of the Chinese Ceramic Society,2012,40(5):677-684(in Chinese). [12] 褚洪岩, 孙伟, 蒋金洋. 高温作用下牺牲混凝土的损伤演化[J]. 硅酸盐学报, 2016, 44(2):211-217.CHU Hongyan, SUN Wei, JIANG Jinyang. Damage evolution of sacrificial concrete subjected to elevated temperatures[J]. Journal of the Chinese Ceramic Society,2016,44(2):211-217(in Chinese). [13] STELZNER L, POWIERZA B, OESCH T, et al. Thermally-induced moisture transport in high-performance concrete studied by X-ray-CT and 1H-NMR[J]. Construction and Building Materials,2019,224:600-609. doi: 10.1016/j.conbuildmat.2019.07.065 [14] NOUMOWE A N, SIDDIQUE R, DEBICKI G. Permeability of high-performance concrete subjected to elevated temperature (600°C)[J]. Construction and Building Materials,2009,23(5):1855-1861. doi: 10.1016/j.conbuildmat.2008.09.023 [15] LIU J C, HAI T K. Mechanism of PVA fibers in mitigating explosive spalling of engineered cementitious composite at elevated temperature[J]. Cement and Concrete Composites,2018,93:235-245. doi: 10.1016/j.cemconcomp.2018.07.015 [16] KALIFA P, GREGOIRE C, CHRISTOPHE G. High-temperature behaviour of HPC with polypropylene fibers: From spalling to microstructure[J]. Cement and Concrete Research,2001,31(10):1487-1499. doi: 10.1016/S0008-8846(01)00596-8 [17] ZHANG D, DASARI A, TAN K H. On the mechanism of prevention of explosive spalling in ultra-high performance concrete with polymer fibers[J]. Cement and Concrete Research,2018,113:169-177. doi: 10.1016/j.cemconres.2018.08.012 [18] ZHAO H T, DING J, HUANG Y Y, et al. Experimental analysis on the relationship between pore structure and capillary water absorption characteristics of cement-based materials[J]. Structural Concrete,2019,20(5):1750-1762. doi: 10.1002/suco.201900184 [19] 谢恩慧, 周春圣. 利用低场磁共振弛豫测孔技术预测水泥基材料的水分渗透率[J]. 硅酸盐学报, 2020, 48(11):1808-1816.XIE Enhui, ZHOU Chunsheng. Prediction of water permeability for cement-based material from the pore size distribution achieved by low-field nuclear magnetic resonance relaxation technique[J]. Journal of the Chinese Ceramic Society,2020,48(11):1808-1816(in Chinese). [20] ZHOU C S, REN F Z, ZENG Q, et al. Pore-size resolved water vapor adsorption kinetics of white cement mortars as viewed from proton NMR relaxation[J]. Cement and Concrete Research,2018,105:31-43. doi: 10.1016/j.cemconres.2017.12.002 [21] 陶高梁, 陈银, 袁波, 等. 基于NMR技术及分形理论预测SWRC[J]. 岩土工程学报, 2018, 40(8):1466-1472.TAO Gaoliang, CHEN Yin, YUAN Bo, et al. Predicting soil-water retention curve based on NMR technology and fractal theory[J]. Chinese Journal of Geotechnical Engi-neering,2018,40(8):1466-1472(in Chinese). [22] 薛维培, 刘晓媛, 姚直书, 等. 不同损伤源对玄武岩纤维增强混凝土孔隙结构变化特征的影响[J]. 复合材料学报, 2020, 37(9):2285-2293.XUE Weipei, LIU Xiaoyuan, YAO Zhishu, et al. Effects of different damage sources on pore structure change characteristics of basalt fiber reinforced concrete[J]. Acta Materiae Compositae Sinica,2020,37(9):2285-2293(in Chinese). [23] 中国国家标准化管理委员会. 钢丝网水泥用砂浆力学性能试验方法: GB/T 7897—2008[S]. 北京: 中国标准出版社, 2008.Standardization Administration of the People's Republic of China. Test methods of mechanical properties of mortar for ferrocement: GB/T 7897—2008[S]. Beijing: Standards Press of China, 2008(in Chinese). [24] LI Y, ZHANG Y, YANG E H, et al. Effects of geometry and fraction of polypropylene fibers on permeability of ultra-high performance concrete after heat exposure[J]. Cement and Concrete Research,2019,116:168-178. doi: 10.1016/j.cemconres.2018.11.009 [25] 张彬. 水泥基材料的高温特性及其再水化修复的研究[D]. 武汉: 武汉理工大学, 2012.ZHANG Bin. Study on the high temperature characteristics and rehydration repair of cement-based materials[D]. Wuhan: Wuhan Technological University, 2012(in Chinese). [26] LI Y, TAN K H, YANG E H. Influence of aggregate size and inclusion of polypropylene and steel fibers on the hot permeability of ultra-high performance concrete (UHPC) atelevated temperature[J]. Construction and Building Materials,2018,169:629-637. doi: 10.1016/j.conbuildmat.2018.01.105