Investigation of engineering properties of chemical grouted silty-fine sand mixtures

In this study, the groutability of sodium silicate-formamide and sodium silicate-glyoxal mixtures into the silty-fine sand mixtures and the engineering properties of the taken samples were successfully tested. Firstly, experiments were initiated on the sample of silt and fine sand using sieve analysis, hydrometer, specific gravity, maximum-minimum void ratios and permeability coefficient determination tests together with the gradations of silty-fine sand mixture samples to be used in grouting. Then, rheological property determination (gelling times, syneresis and viscosity) tests were performed on the sodium silicate-formamide and the sodium silicate-glyoxal solutions in order to determine the optimum mixing ratios to be used in the experiments. The most appropriate mixture ratios to be used in grouting experiments were; Sodium silicate-formamide mixtures with 70% and 50% sodium silicate ratios, sodium silicate-glyoxal mixtures with 53.76% and 60% sodium silicate ratios were selected. All grouting experiments, were successfull on all samples. In grouting tests with sodium silicate-formamide, the minimum grouting pressure values were between 0.20 and 3.00 bar, and in grouting experiments with sodium silicate-glyoxal, the minimum grouting pressure values were between 0.30 and 2.90 bar. As the particle size decreased and the percentage of sodium silicate increased, the minimum grouting pressure values increased. Unconfined compression tests were performed on 7th, 14th, 28th and 56th days under different curing conditions (air dried, stretch wrapped and cured tank). The strength values of the samples grouted with sodium silicate-formamide were between 0.26 and 6.90 MPa, and the strength values of the samples grouted with sodium silicate-glyoxal were between 0.44 and 2.14 MPa. The strength value increased with increasing sodium silicate ratio. In grouted samples, the maximum strength was observed in mixture 4 (70% fine sand - 30% silt), while the minimum strength was observed in mixture 5 (100% fine sand). Considering the curing conditions, the maximum strengths were observed in the samples stored in the air dried environment whilst the minimum strengths were observed in the samples stored in the curing tank. Finally, permeability coefficients (k) were determined on the samples that were successful in the grouting experiments by performing permeability tests on the 14th day without taking out the samples from the molds. Permeability coefficients of samples which were grouted with sodium silicate-formamide were between 6.08x10-6 and 4.18x10-5 cm/sec. Permeability coefficients of samples which were grouted with sodium silicate-glyoxal were between 2.29x10-6 to 1.48x10-5 cm/sec. Permeability values decreased with increasing silt percentage in fine sand-silt mixtures. Permeability coefficient values decreased between 10-3 and 10-2 order by grouting the sodium silicate-formamide into the fine sand-silt mixtures, while it decreased between 10-4 and 10-2 order by grouting of sodium silicate-glyoxal. Experimental studies have shown that the sodium silicate-formamide and the sodium silicate-glyoxal mixtures can easily be grouted into the pure silt samples and silty-fine sand mixtures.