纳米氧化硅充填红黏土团粒内孔隙的收缩响应

Shrinkage behavior responses to nano-silica filling pores in aggregate laterite

红黏土易失水收缩开裂,不仅降低了其整体强度,还为雨水入渗提供了通道,加剧了其承载能力的弱化。因此,如何抑制红黏土收缩,成为解决问题的关键。纳米氧化硅颗粒尺寸极其细小,隶属纳米范畴。充分发挥纳米氧化硅的尺寸优势,以期纳米氧化硅微粒能够进入红黏土团粒内,抵抗红黏土的失水收缩行为。为此,选用不同干质量掺入比(纳米氧化硅:红黏土分别为0:100、2:100、3.5:100、5:100、6.5:100),将纳米氧化硅混入红黏土后压实成型(干密度1.44 g/cm^(3)和1.46 g/cm^(3))。比较压实红黏土-纳米氧化硅混合物的收缩特性与孔隙分布情况。试验发现,纳米氧化硅可以抑制红黏土的收缩行为;而且随着掺入量增加,其缩限值也逐渐提高。红黏土-纳米氧化硅混合物的表观形貌照片显示,纳米氧化硅掺量大于5%时,红黏土团粒内孔隙赋存有大量纳米氧化硅颗粒。同时,孔隙分布曲线还表明,分布于孔径0.03μm的孔隙明显减少,说明纳米氧化硅主要充填孔径大于0.03μm的孔隙。纳米氧化硅改善红黏土的收缩性属于物理方法,有别于石灰处治等化学方式,更具有环境友好的潜在优势。

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/cm^(3) and 1.46 g/cm^(3) 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 μm reduced significantly, which indicated that nano-silica mainly filled the pores with diameter greater than 0.03 μm. 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.