硬石膏对超高性能混凝土性能的影响及机理研究

Study on the influence and mechanism of anhydrite on the properties of ultra-high performance concrete

超高性能混凝土(UHPC)是一种具有超高力学性能和超高抗渗性能的水泥基复合材料,具有胶材用量大、收缩大的特点。为了有效调控UHPC收缩应变,通过波纹管法、接触法、电通量法、RCM法和NEL法分别研究了不同掺量硬石膏对UHPC体积稳定性和耐久性能的影响。结果表明:随着硬石膏掺量的增加,UHPC的体积收缩率逐渐减小,抗氯化物渗透性能逐渐提高。当硬石膏掺量为6%时,7 d收缩率仅为145.2με,与对照组相比减小了69%;此时氯离子扩散系数最小,为3.9×10^(-14)m^(2)/s;SEM分析可知,此时UHPC基体界面过渡区(ITZ)的密实度更高。

Ultra-high performance concrete(UHPC)is a kind of cement-based composite with ultra-high mechanical properties and ultra-high impermeability.It also has the characteristics of large amount of glue and large shrinkage.In order to effectively regulate the shrinkage strain of UHPC,in this paper,the effects of different content of anhydrite on the volume stability and durability of UHPC are studied by five test methods:bellows method,contact method,electric flux method,RCM method and NELmethod.The results show that with the increase of anhydrite content,the volume shrinkage of UHPC decreases gradually.When the content of anhydrite was 6%,the shrinkage rate at 7 days was only 145.2με,which decreased by 69%compared with the control group.At the same time,with the increase of anhydrite content,the ability of UHPC to resist chloride penetration is also gradually enhanced.When the anhydrite content is 6%,the chloride ion diffusion coefficient reaches the minimum value,which is 3.9×10^(-14) m^(2)/s.SEM analysis shows that the compactness of UHPC matrix interface transition zone(ITZ)in the test group with anhydrite content of 6%is higher.