纳米二氧化硅对再生骨料混凝土性能影响的研究

Effects of Nano Silica Additions on Properties of Recycled Aggregate Concrete

再生骨料混凝土是一种环保材料,然而由于再生骨料的固有缺陷,导致其很难在结构工程中推广应用。纳米二氧化硅作为一种混凝土辅助胶凝材料,已经在普通混凝土中得到了充分的研究,但其用于改性再生骨料混凝土的研究较少。利用万能试验机、扫描电镜及X射线衍射仪,从工作性能、抗压性能、抗拉性能和微观形貌等方面,分析了不同掺量纳米二氧化硅对再生骨料混凝土改性的影响,深入探讨了利用纳米二氧化硅对再生骨料混凝土进行改性的可行性。试验结果表明:纳米二氧化硅具有高活性和填充效应,促进了水泥的水化反应,对再生骨料混凝土早龄期抗压性能提升明显;此外,纳米二氧化硅由于其颗粒尺寸较小,填充了再生骨料的微裂纹和孔隙,降低了再生骨料混凝土的脆性,对再生骨料混凝土后龄期抗拉性能提升显著。值得注意的是,纳米二氧化硅具有团聚效应,需要采用减水剂和预拌的方法提升其工作性能,从而推广其适用性。

Recycled aggregate concrete(RAC) is an environmental friendly material. However,due to the inherent defects of recycled aggregate(RA), it is difficult to popularize its application in structural engineering. As an auxiliary cementitious material for concrete,nano silica(NS) has been tremendously studied in ordinary concrete,but there are few studies on its use in modified recycled aggregate concrete. In this paper,using universal testing machine,scanning electron microscope and X-ray diffractometer,the effects of different additions of nano-silica on the modification of recycled aggregate concrete were analyzed from the aspects of working performance,compressive performance,tensile performance and microscopic morphology. The feasibility of using nano-silica to modify recycled aggregate concrete was discussed in depth. The test results showed that nano-silica has high activity and filling effect,which promotes the hydration reaction of cement and significantly improves the compressive performance of recycled aggregate concrete at the early age. In addition,due to its small particle size,nano-silica fills the micro-cracks and pores of recycled aggregate, reduces the brittleness of recycled aggregate concrete, and significantly improves the tensile properties of recycled aggregate concrete at the later age. It is worth noting that nanosilica has agglomeration effect,and it is necessary to use water reducing agent and pre-mixing method to improve its working performance,thereby promoting its applicability.