等强条件下机制砂混凝土收缩徐变试验研究

Experimental Study on Shrinkage and Creep of Manufactured Sand Concrete Under the Condition of Equal Strength

以4种不同岩性的机制砂、水泥、粉煤灰等为原料,在不同养护龄期下,制备强度等级为C30、配筋及砂率不同的机制砂混凝土试件,通过钢制加载架对试件提供稳定荷载,利用机械千分表对试件变形进行双面测量,研究等强条件下机制砂混凝土收缩徐变性能,找出干扰机制砂混凝土收缩徐变性能的指标。试验结果显示:4种机制砂混凝土干燥收缩值比较类似,4种岩性的机制砂混凝土在测试前30 d干燥收缩值增加的速度较快,30 d后增长较慢;4种机制砂混凝土徐变应变和徐变系数从小到大的顺序依次是:凝灰岩<砂岩<花岗岩<石灰岩,收缩徐变性能最好的是石灰石机制砂;普通砂混凝土的收缩值低于石灰岩机制砂混凝土的收缩值,且养护龄期影响混凝土的收缩性能,收缩性能与养护龄期成正相关;机制砂混凝土的徐变系数和徐变挠度随配筋增大而降低,配筋为4∅14时试件的徐变性能最好;荷载为6 kN时徐变性能最好,荷载为2 kN时徐变性能最差;徐变挠度随着温度的增加而增加,随着湿度的增加而降低;石粉含量同机制砂混凝土的收缩性能成正相关,且当石粉含量低于12%时,收缩值变化不大。

With four different lithology mechanism sand,cement,fly ash as raw materials,such as under different curing ages,preparation of C30 strength grade,reinforcement sand and sand ratio of different mechanism of concrete specimens,by steel loading of specimens to provide stable load,using mechanical dial gauge measuring the specimen deformation,experimental study on the mechanism of strong conditions such as sand concrete shrinkage and creep performance,The indexes of shrinkage and creep of sand concrete with disturbance mechanism are found out.The experimental results show that the drying shrinkage values of the four types of mechanized sand concrete are similar.The drying shrinkage values of the four kinds of lithology of the mechanized sand concrete increase rapidly 30 days before the test,but grow slowly after 30 days.The creep strain and creep coefficient of the four kinds of mechanized sand concrete from small to large are in the order of tuff<sandstone<granite<limestone,and the limestone mechanized sand has the best shrinkage and creep performance.The shrinkage value of ordinary sand concrete is lower than that of limestone made sand concrete,and the curing age affects the shrinkage performance of concrete,and the shrinkage performance is positively correlated with the curing age.The creep coefficient and creep deflection of the reinforced concrete decrease with the increase of the reinforcement,and the creep performance of the specimen is the best when the reinforcement is 4∅14.The creep performance is the best when the load is 6 kN and the creep performance is the worst when the load is 2 kN.Creep deflection increases with the increase of temperature and decreases with the increase of humidity.There is a positive correlation between the content of stone powder and the shrinkage property of the concrete,and when the content of stone powder is less than 12%,the shrinkage value changes little.