不同龄期混凝土砖墙体收缩变形的试验研究

EXPERIMENTAL INVESTIGATION ON CONCRETE PERFORATED BRICK WALL SHINKAGE AT DIFFERENT AGES

由于收缩大、含水率高,施工规范不允许使用未达到龄期的混凝土砖,然而由于种种原因,工程中尚有未达到标准龄期的混凝土砖大量使用的现实情况,需要工程技术人员认识这种材料的特性,并对已经上墙的材料提出修复措施。对不同龄期混凝土砖墙体的收缩变形规律进行试验研究。首先对单块砖进行了含水率、抗压强度等指标的测定;然后对不同龄期砌筑的墙体进行了持续测试,包括墙体端部位移和即时应变;最后进行分析和估算,并提出工程限制措施建议。试验表明:部分未达到标准龄期混凝土砖块体在不同湿度环境下表现出初期湿胀的特点;墙体收缩表现出现干缩和湿胀循环,墙体的初期收缩率在1.6×10-4～2.0×10-4;测试得到的墙体即时应变初期表现为受压状态,随后转为受拉状态并趋于稳定;不同龄期混凝土砖墙体的初期即时应变与时间的关系近似服从指数下降规律。得出的结论为控制干缩裂缝和未到龄期混凝土砖上墙后的修复提供依据,对于正确认识不同龄期混凝土砖墙体的特性、指导工程实践具有现实意义。

It is forbidden to use concrete perforated brick（CPB）wall at early ages for its big shringkage and high water content,Nevertheless,there are still many applications in engineering practice due to various reasons.Engineers should recognize their characteristics,then decide how to repair the walls.Experimental investigation is carried out in this study including bricks and walls.Firstly bricks are tested with water content,compressive strength,and etc;then whole walls at diffirent ages are tested with walls＇ end deformations and instantaneous strains;at last analysis and estimations are done and engineering restrictions are proposed.It is concluded that some early-age CPB bricks have wet inflations,whereas CPB walls have wet inflation and dry shrinkage circulations.Its shinkage rate is about 1.6~2.0×10-4.Walls＇ instantaneous strains show a pressure characreristic at beginning and then to tensile,and tend to be stable at last.Relationship between instantaneous strain and time（age）has an exponential decay trend.Results obtained in this study help engineers to control cracks and repair walls,It reflects the basic characteristics of walls at different ages,and thus has relevant engineering significance.