Low dosage nano-silica modification on lightweight aggregate concrete

Abstract

Although the nano modification has been considered as a promising approach to enhance the mechanical properties of cement-based concrete, the investigation of low dosage nano modification on lightweight cement-based concrete is still very limited. In this study, the lightweight concrete, which was modified with low dosage nano-silica particles, were investigated. Non-prewetting and prewetting methods were used to prepare the lightweight concrete samples. The compressive and flexural strengths were tested to evaluate the modification effects of low dosage nano-silica on lightweight concrete. The microstructure analyses demonstrate that the hydration process of the cement paste can be changed with addition of nano-silica, and new types of hydration products have been observed in nano modified cementitious matrix. The interface between the lightweight aggregates and the cement paste can be reinforced by low dosage of nano-silica due to the new types of hydration products. However, relatively high dosage of nano-silica will reduce the modification effect because of the internal stress, which is resulted from the volume expansion of the new types of hydration product, at the interface of the lightweight aggregates and the cement paste. This study not only shows the possibility of low dosage nano modification on the mechanical properties enhancement of lightweight concrete but also provides potential modification mechanisms, which help to design and fabricate high-performance lightweight concrete materials.