Freeze-thaw behavior of lime stabilized clay reinforced with silica fume and synthetic fibers

Several soil stabilization studies have been conducted in the literature with silica fume and fibers separately on coarse and fine grained soils. However, few studies have been conducted on freeze-thaw performance of soils modified with fibers or silica fume. This experimental study was conducted to investigate the effect of silica fume and polypropylene fiber modification on strength and freeze-thaw behavior of lime stabilized kaolinite clay. To observe the strength behavior, unconfined compressive strength tests were conducted. Strength losses were also measured after exposure to freeze-thaw cycles to investigate the durability of the modified samples. Control and modified samples were compacted at optimum moisture content and cured for 28 days. After curing, samples were inserted into the freeze-thaw chamber and after two, five and eight cycles samples were tested for compression. Synthetic polypropylene fiber content varied between 0.25% to 1% and silica fume content varied between 2.5% to 10% by dry weight of kaolinite in the prepared samples. Adding silica fume, fiber and mixtures having various silica fume-fiber ratios increased the compressive strength values and enhanced the freeze-thaw durability of the lime rich kaolinite specimens. Silica fume particles reacted with lime rich kaolinite as an extra silica source needed for hydration reactions. As a result, CSH gel products were formed, which surrounded the kaolinite particles. Fibers improved the friction resistance, interlock effect was created by cementation reactions between lime stabilized soil, fibers and silica fume. Silica fume and fiber modified lime rich clay reached the maximum strength at 0.25% fiber and 10% silica fume added specimens, strength values started to decrease with increasing fiber ratios. Silica fume, synthetic fiber and fiber-silica fume modified samples had an increase in compressive strength values with curing and modified samples exposed to freeze-thaw cycles had a lower strength loss compared to control specimens. Samples having higher strength values in unconfined compressive strength measurements were the most durable samples in the freeze-thaw tests with lower strength loss. The results indicated that fiber-silica fume modified kaolinite clay can be an economic and environmentally friendly alternative in soil stabilization projects by utilizing an industrial waste.