纤维和聚合物对水泥砂浆早期开裂的防治及作用研究

研究了砂浆早期(0~6 h)的收缩变形特性,测试了其收缩变形量及变形稳定后裂缝的长度与宽度。采用名义开裂面积、首次开裂时间、收缩应变等评价纤维(碳纤维及聚丙烯纤维)、聚合物(丁苯乳液)对砂浆早期塑性收缩开裂的作用效果,并对纤维和聚合物对砂浆抗裂作用机理进行了分析。研究认为:纤维对砂浆的增强效应和空间效应与聚合物的成膜、微纤维以及减缓水泥水化放热速率作用相结合,使得砂浆早期的抗裂性能随着聚合物和纤维的掺入得到了改善,作用效果主要与纤维的掺量、纤维的弹性模量等有关。相同体积掺量下,碳纤维对砂浆早期的抗裂作用效果优于聚丙烯纤维。

Effect and Mechanism of Fiber and Polymer on the Early Shrinkage of Cement Mortar

The early(0~6h) shrinking property of mortar is studied.The shrinkage strain,crack length and width are measured when the shrinking of mortar becomes stable.The following parameters such as nominal crack area,first crack time,shrinkage strain to appraise the effect of fiber(polypropylene and carbon fiber) and polymer on the early shrinking of mortar,the crack mechanism of fiber and polymer on the early shrinking of mortar are also studied.The result indicates that fiber plays reinforcement effect and space effect on mortar,while polymer plays forming film,micro-fiber effect and at the same time it lowers the hydration heat.The effect of fiber together with polymer greatly improves the early shrinking performance of mortar,which is related to the content and elastic module of fiber.With the same content of fiber,carbon fiber shows better effect than polypropylene in restricting early shrinking crack of mortar.