UFA道路混凝土早期自收缩及开裂敏感性研究

目的研究掺超细粉煤灰（Ultra-fine Fly Ash,简称UFA）的道路混凝土早期自收缩特征及UFA对混凝土早期开裂敏感性的影响规律.方法以UFA等量取代水泥配制UFA道路混凝土,采用自行改进设计的混凝土自收缩测试装置测试混凝土早龄期（72h以内）的自收缩变形,并利用平板式限制收缩开裂试验方法研究混凝土成型26h内的表面开裂特征;在试验基础上,评价UFA道路混凝土的早期开裂敏感性.结果随着UFA的掺入,混凝土的早期自收缩变形显著减小,在保持相同流动度条件下,明显低于基准混凝土,早期抗裂性能也优于基准混凝土,且随UFA掺量的增加,早期抗裂性能随之增强.结论掺入适量的UFA可有效地减小道路混凝土的早期自收缩,从而降低早期开裂敏感性,延长路面结构的服役寿命,并为UFA在实际工程中的应用提供了理论和技术支持.

Study on Early Autogenous Shrinkage and Cracking Sensitivity of Highway Concrete Containing Ultra-Fine Fly Ash

The early autogenous shrinkage of highway concrete containing ultra-fine fly ash(UFA) was investigated,and the influence of UFA on early cracking sensitivity of concrete was analyzed.UFA highway concrete was produced with UFA replacing equivalent cement added into concrete,and by means of the autogenous shrinkage test device designed and improved,early age(72 hours) autogenous shrinkage of UFA concrete was tested.Furthermore,method of flat plate restricted shrinkage and cracking was used for testing crack resistance of UFA highway concrete in 26 hours,and based on the tests,the early cracking sensitivity of UFA highway concrete was appraised.The results indicated that early autogenous shrinkage of concrete reduced conspicuously with the addition of UFA,which was smaller than ordinary concrete under the condition of similar workability.On the other hand,early cracking resistance of UFA concrete was better than ordinary concrete,and the more UFA was added,the better the crack resistance would be.This demonstrates that adding proper amount of UFA can restrain effectively the early autogenous shrinkage of highway concrete,reduce early cracking sensitivity and extend service-life of pavement structure.Moreover,this investigation also provides the theoretical and technical support for the application of UFA in the practical engineering.