高温后混凝土强度与孔隙结构变化规律试验研究

Experimental Research on Transformation Law of Mechanical Properties and Pore Structure of Concrete after High Temperature

针对高温后混凝土力学性能衰弱特性,运用氮气吸附原理,分析高温后混凝土比表面积、孔径分布等结构损伤特征,从微观孔隙角度阐释宏观力学性能衰弱特性。结果表明:①混凝土的抗压强度随温度的升高逐渐降低,且呈线性变化;②混凝土微孔启裂扩展的阀值温度是200℃,此时混凝土的比表面积最大;混凝土大孔启裂扩展的阀值温度是600℃,此时混凝土的比表面积最小;③影响高温混凝土力学性能的微观孔隙直径与温度呈现正相关分布;200℃时,混凝土微孔增多,微孔占总孔比为34.6%;400℃时,混凝土中孔增多,中孔占总孔比为53.97%;600℃时,混凝土大孔缓慢增多,大孔占总孔比为36.3%;800℃时,混凝土大孔急剧增多,大孔占总孔比为72.26%。

Aiming at the weak mechanical property of concrete after high temperature,the characteristics of structural damage such as concrete specific surface area and pore size distribution after high temperature were analyzed by using nitrogen adsorption principle,and the macroscopic mechanical properties of the weakening characteristics were explained from the perspective of microscopic pores. The results show that:①the compressive strength of concrete decreases with the increase of temperature,and changes linearly;②the threshold temperature of concrete microporous crack initiation is 200 ℃,and at this time the concrete has the largest specific surface area. The threshold temperature of the crack expansion of concrete large hole is 600 ℃,and at this time the specific surface area of concrete is the smallest;③the microscopic pore diameter and the temperature affecting the mechanical properties of high temperature concrete show a positive correlation;200 ℃,the concrete microporous increased,micropore accounts for 34.6% of the total hole;400 ℃,the concrete middle hole increased,the middle hole accounts for 53.97% of the total hole;600 ℃,macroporous concrete slowly increased,macroporous account for 36.3% of the total hole;800 ℃,macroporous concrete increase rapidly,accounting for 72.26% of the total hole.