快速修补混凝土的收缩性能及其评价方法研究

主要研究了快速修补混凝土的干缩、早期收缩、自收缩性能以及初长测试时间对混凝土收缩性能评价的影响。研究结果表明,快速修补混凝土的收缩比普通混凝土大,且快速修补混凝土的收缩是以自收缩为主;快速修补混凝土的收缩在3 d龄期内的发展非常迅速,3 d龄期以后快速修补混凝土的收缩与普通混凝土相当;初长测试时间对快速修补混凝土收缩性能的评价有重要影响,如果按照普通混凝土收缩试验方法,在混凝土成型后的2~3 d龄期后开始测初长,将会严重低估快速修补混凝土的收缩性能,低估程度达20%~40%。因此,本文建议当进行快速修补混凝土的收缩试验时,在快速修补混凝土的抗压强度达到5~7 M Pa时进行拆模,并立即送入恒温恒湿室放置1 h后即可测初长。

A Study on Shrinkage Property and Evaluation Method of Rapid Repair Concrete

The properties of early shrinkage,autogeneous shrinkage,dry shrinkage and the effects of test time of original length of specimen on the evaluation of shrinkage of rapid repair concrete(RRC) are studied in this paper.The results show that the autogenous shrinkage is the main part of shrinkage of RRC,and the increasing speed of shrinkage of RRC is quick than that of ordinary Portland cement concrete(OPC) before 3 d age,but equivalent to OPC after 3 d age,so the shrinkage of RRC is serious than that of OPC.The test time of original length of specimen effects on the evaluation of shrinkage of RRC significantly.The shrinkage of RRC would be estimated lowly if testing the original length of specimen at 2 d or 3 d age.Therefore,it is suggested that the demoulding of specimens are carried out when the compressive strength of RRC arrives at 5 to 7 MPa,and then the original length of specimens is tested immediately after the specimens are kept in the constant temperature and humidity room for 1 h.