混凝土点状爆裂原因探究及机理分析

针对建筑工程中混凝土构件表面出现的点状爆裂现象，对出现爆裂的混凝土构件进行采样，通过XRD分析确定了样品的主要组成有CaO、C₃A、C₁₂A₇、Ca(OH)₂等矿物，结合样品的DSC/TGA定量分析数据，确定了导致混凝土点状爆裂的主要原因是CaO水化生成Ca(OH)₂体积膨胀导致的；此外，混凝土中的C₁₂A₇与找平材料(主要指石膏)中的CaSO₄·2H₂O会水化生成AFt，也会导致混凝土开裂，因此，在混凝土抹面后点状爆裂现象会集中出现。采用乙二醇-EDTA化学滴定法测定样品游离总钙，结合DSC/TGA定量分析结果，发现爆裂中心底层未粉化骨料中f-CaO含量依然较高，解释了工程中采用当前修补方式修补后混凝土继续爆裂的原因。

Study on cause and mechanism analysis of concrete punctate burst

This article focused on punctate burst on the surface of concrete members in an actual concrete engineering,the concrete members with burst were sampled.Through the XRD,it was determined that the main mineral composition of those samples contain CaO,C₃A,C₁₂A₇and Ca(OH)₂and other minerals.Combined the DSC/TGA quantitative analysis of those samples,concluded that the main reason of concrete punctate burst was that the volume expansion when the CaO hydrated to Ca(OH)₂.In addition,C₁₂A₇ can react with CaSO₄-2H₂O to form AFt,which will also cause concrete cracking.Therefore,concrete punctate burst appeared after plastered.Combining results of DSC/TGA quantitative analysis and EDTA chemical titration,which concluded that the content of free-calcium in the specimen is still high and this is the reason of the concrete still burst after repaired by the current way.