钢纤维超高强混凝土的收缩变形及开裂研究

Research on shrinkage deformation and cracking of very high strength concrete with steel fiber

超高强混凝土的抗压强度虽然很高,但其致命缺陷是高脆性和高的自收缩变形,从而极易产生裂缝。通过研究在超高强混凝土中掺入钢纤维,测试不同基体、不同钢纤维掺量及不同长径比条件下的钢纤维超高强混凝土的收缩变形及开裂规律。试验研究表明：在本试验条件下,钢纤维长径比大对抑制混凝土收缩有利,长径比小的钢纤维对混凝土的抗裂性有益。微钢纤维掺量在0.3%~0.9%范围内时,对超高强混凝土自收缩减小幅度为26.3%~28.8%,对干缩减小幅度为19.5%~43.7%,掺量0.6%和0.9%的微钢纤维超高强混凝土干缩比普通混凝土还小。掺入钢纤维能大幅度减小超高强混凝土的收缩变形,增强超高强混凝土的早期抗裂性能。

With high compressive strength,very high strength concrete has a fatal defect of high brittleness,which causes concrete cracking easily.In this study shrinkage deformation and cracking of very high strength concrete mixed with steel fibers were tested under the conditions of different matrix,amount of steel fiber,and length-diameter ratio of fiber,respectively.The test results show that,in this experiment,the autogenous shrinkage of very high strength concrete was decreased 26.3%~28.8%,and the dry shrinkage was reduced 19.5%~43.7% when 0.3%~0.9% amount of steel fiber were added.The dry shrinkage of very high strength concrete is lower than that of ordinary concrete in case of 0.6% or 0.9% amount of steel fiber mixed.It is also presented that larger length-diameter ratio of steel fiber is benefit to inhibit shrinkage development,but smaller L-D ratio is favorable to control concrete cracking.