摘要
为了促进工业副产品在水泥混凝土中的再生利用,在自密实混凝土中掺入再生骨料,并设置了两种循环变温条件,研究再生骨料自密实混凝土在循环变温作用后的抗压强度、弹性模量、超声脉冲速度和硬化密度宏观性能,并分析了抗压强度损失量与无损测试方法中结构损伤特性指标的相关性。最后通过混凝土内部结构微观形貌表征,揭示了冷、热变温作用下的结构损伤机理。试验结果表明,循环变温作用后,混凝土抗压强度下降程度最高,其在冷变温循环后下降了15%~35%。温度应力损伤造成混凝土内部的微裂缝扩展,增加了水泥石基质的不连续性,导致超声脉冲速度大大降低。随着抗压强度损失量的增大,各项结构损伤特性指标损失量均有所增加。混凝土内部温度应力损伤主要是由于集料与胶凝基质的热变形能力不同,导致在界面过渡区中出现微裂纹,或微裂纹在微孔等应力集中处萌生,然后在胶凝基质中扩展,从而造成结构的不可逆损伤。合理控制再生骨料掺量和级配,将有利于改善混凝土的温变稳定性。
In order to promote the recycling and utilization of industrial by-products in cement concrete, the recycled aggregate is added to self-compacting concrete, and two kinds of cyclic temperature variation conditions are set. The macroscopic properties of compressive strength, elastic modulus, ultrasonic pulse velocity and hardening density of the self-compacting concrete of recycled aggregate after cyclic temperature variation are studied, and the correlation between compressive strength loss and structural damage characteristics indicators in non-destructive testing methods is analyzed. Finally, the microstructure characterization of the internal structure of concrete reveals the mechanism of structural damage under the action of cold and hot temperature variation. The test results show that, the compressive strength of concrete decreases the most after cyclic temperature variation,with a decrease of 15% to 35% after cold temperature variation cycling. Thermal stress damage causes the microcracks to expand inside the concrete, increasing the discontinuity of the cement paste matrix, and leading to a significant reduction in ultrasonic pulse velocity. As the loss of compressive strength increases, the loss of various structural damage characteristics indicators increases. The internal temperature stress in concrete is mainly due to the different thermal deformation capabilities of aggregates and cementitious matrices, leading to the occurrence of microcracks in the interface transition zone, or the initiation of microcracks at stress concentration such as micropores, and then the expansion in the cementitious matrix, and resulting in the irreversible damage of the structure. The reasonable control of the content and gradation of the recycled aggregate will be beneficial to improving the temperature stability of concrete.
作者
刁光雷
Diao Guanglei(Liaoning Provincial Transportation Planning and Design Institute Co.,Ltd.,Shenyang 110166,China)
出处
《北方交通》
2023年第5期30-33,37,共5页
Northern Communications
关键词
再生骨料
自密实混凝土
循环变温
结构损伤
微观分析
Recycled aggregate
Self-compacting concrete
Cyclic temperature variation
Structural damage
Microanalysis
