机制砂钢筋混凝土梁的徐变特性

Creep characteristics of reinforced concrete beams made with manufactured sands

为缓解混凝土用砂供需矛盾,用高品质机制砂代替天然砂是大势所趋。徐变作为钢筋混凝土的一个重要性能,是制约机制砂在工程结构中应用的关键因素之一。对比了天然砂和机制砂的四种骨料的颗粒级配、石粉含量和亚甲蓝值等材料指标,研究了机制砂的细观指标特性。设计了天然砂和机制砂钢筋混凝土梁长期持载试验,基于850 d的混凝土梁跨中截面应变和跨中挠度的长期观测数据,发现亚甲蓝值与跨中截面的混凝土表面应变发展具有一定的相关性,随着亚甲蓝值的增大,跨中截面混凝土表面的应变量随时间发展增加。同时,随着时间的增长,机制砂混凝土梁的挠度值逐渐明显大于天然砂混凝土梁的,亚甲蓝值是影响机制砂混凝土梁长期挠度的主要因素之一,挠度发展随亚甲蓝值的增大而增大。

In order to resolve the contradiction between demand and supply of sand for concrete,it is a general trend to replace natural sand with high quality manufactured sand.As an important property of reinforced concrete,creep is one of the key factors restricting the application of manufactured sand in important engineering structures.This paper first presented a comparison between four types of aggregate in terms of their material indexes such as the material indexes of gradation,stone powder content and Methylene blue(MB)value.The meso-index characteristics of manufactured sand were also presented.Based on the long-term observation data of strain and deflection at the midspan of concrete beams in 850 days,it is found that the MB value has a certain correlation with the development of concrete surface strain at the midspan of concrete beam.With the increase of MB value,the strain on the concrete surface at the midspan increases with the time.At the same time,with the increase of time,the deflection value of concrete beams made with manufactured sand gradually becomes significantly greater than that of concrete beams made with natural sand.The MB value is one of the main factors affecting the long-term deflection value of concrete beams made with manufactured sand,and the development of deflection increases with the MB value.