Stabilization of Expansive Sub-Grade Soil Using Gypsum and Gypsum Blend with Brewery Spent Grain Ash

Abstract

Expansive soil problem is a serious problem due to a cause of damage for civil engineering structures and it influences the expansion of road construction in Ethiopia. Previously to reduce this problem, different stabilizer like cement, lime, flay ash, bitumen used to stabilize the expansive sub-grade soil but it requires high cost. Nowadays to be economical and due to the availability of material researcher use different innovative stabilizing agent from agricultural, industrial and agro-industrial waste like rice husk ash, molasses, groundnut ash, iron slag and Marble dust as a stabilizer. Brewery spent grain is one of agro-industrial waste which produces from beer factory. This solid waste seed coat is made from melting of barley, maze or wheat after processed which covers around 85% of the total waste (Gupta, et al., 2010). After converted to the ash characterize the pozzolanic property and elemental composition of BSG ash. However, it denies the pozzolanic according to ASTM D618 but it contains heavy cationic element which used for stabilization through cation exchange. Gypsum also used as a stabilizer but due to the availability, cost, applicability for other purpose requires high cost. The blending effect preferable than the individuals to modify the strength of expansive subgrade soil. The aim of this study is to compare the effect and reduce the amount of gypsum required for stabilization of expansive sub-grade soil through partially replace of BSG ash. After conducted the required laboratory analysis for gypsum and BSG ash stabilized subgrade by adding 5 – 20 percent with 5% interval. For gypsum stabilized the optimum effect happens at 20% which performed the high strength of sub-grade. PI, LS, OMC, MDD, CBR and CBR swell values for this percent were 24.93%, 11.43%, 30%, 1.475g/cm3, 5.51% & 3.87% respectively. The optimum effect of BSG ash stabilized for the strength of sub-grade happens at 5% with laboratory result of PI, LS, OMC, MDD, CBR and CBR swell were 36.3%, 15%, 29%, 1.472g/cm3, 4.97% & 4.08% respectively. The Blending stabilization conducted with the optimum percent of gypsum taken as the cumulative amount of the two additives for different (G: BSG ash) ratio of 1:1, 1:2, 1:3 and 1:4. The optimum blending effect on the strength of stabilized sub-grade happens at 1:2 ratio which contains 6.7% of gypsum and 13.3% of BSG ash with laboratory result of PI, LS, OMC, MDD, CBR and CBR swell were 29.84%, 14.29%, 33%, 1.32, 5.53% & 3.65% correspondingly. Therefore, at 1:2 ratio 13.3% gypsum was replaced by BSG ash which have equivalent effect on the strength of sub-grade due to optimum percent of gypsum stabilized.