关键词: 红黏土, 纳米氧化硅, 孔隙, 收缩, 填充

Abstract: The laterite may form cracks due to shrinkage for dehydration. These cracks not only reduce the overall strength, but also provide infiltration channel for rainwater, which intensifies the weakening of its bearing capacity. Therefore, how to inhibit laterite shrinkage is a key problem for engineering applications. The nano-silica particles are extremely fine in size and belong to the nano category. It is proposed to fully utilize the size advantage of nano-silica, so that nano-silica particles can enter the laterite aggregates and resist the shrinkage behavior of laterite caused by dehydration. Therefore, different dry mixing ratios (i.e. nano-silica: laterite = 0: 100, 2: 100, 3.5: 100, 5: 100, and 6.5: 100) were programmed, and nano-silica was mixed with laterite for compaction (dry density is 1.44 g/cm3 and 1.46 g/cm3 respectively). Shrinkage characteristics and pore distribution of compacted laterite-nano-silica mixture were compared. It was found that nano-silica could inhibit the shrinkage of laterite, and the shrinkage limit was also increased by the mixing ratio rising. Besides, plenty of nano-silica particles were found in the pores while the mixing ratio was greater than 5% by means of apparent morphology images. Meanwhile, the pore distribution curve also showed that the pores with diameter at 0.03 ?m reduced significantly, which indicated that nano-silica mainly filled the pores with diameter greater than 0.03 ?m. Adding nano-silica into laterite is a physical method to improve the shrinkage properties, which is different from the chemical methods such as lime treatment and has potential advantages to environmental protection.

Key words: laterite, nano-silica, pore, shrinkage, filling