纳米混凝土的制备及其干缩性能研究

采用试验研究与理论分析相结合的方法,在普通混凝土中分别掺入不同量的纳米二氧化硅(Nano-SiO_2)和纳米碳酸钙(Nano-CaCO_3),制备出新型纳米混凝土.通过微观电镜试验分析了不同纳米材料对混凝土内部结构变化的影响规律.通过干缩性能试验对比研究了不同纳米材料对混凝土干缩率的影响及作用机理,并确定出最佳掺入量.研究结果表明:Nano-SiO_2和Nano-CaCO_3均能改变混凝土的干缩率,但对干缩率改变的效果不尽相同;掺入Nano-SiO_2的混凝土试件,其干缩率随掺量的变化比掺入Nano-CaCO_3试件的干缩率变化更为明显,当Nano-SiO_2的掺量为0.5%或Nano-CaCO_3的掺量为2.0%时,混凝土试件的干缩率最小.研究还发现,混凝土的干缩与混凝土自身密实程度、弯月面产生的数量以及内部湿度存在着动态平衡的关系.

Preparation and Dry-Shrinkage Performance of Nano-Concrete

Based on experimental and theoretical analysis， new nano-concrete was made by adding different dosage of nano-SiO₂ and nano-CaCO₃ into ordinary concrete. The influence of nano-materials on the internal structure of concrete was analyzed by electron microscope observation. The impact of different nano-materials on the dry-shrinkage rate of concrete was compared through the dry-shrinkage tests， and the optimal dosage of nano-material was found. Results show that both nano-SiO₂ and nano-CaCO₃ can change the dry-shrinkage rate of the concrete， however， the changing rate of dry-shrinkage for concrete with nano-SiO₂ is more obvious than that with nano-CaCO₃. When the nano-SiO₂ content is 0.5% or when the nano-CaCO₃ content is 2.0%， the dry-shrinkage rate is the minimum. It is also found that there exists dynamic equilibrium relationship between the concrete shrinkage， the dense degree of concrete and the number of meniscus and internal humidity.