Performance of Steel Slag and Fly Ash Added Soil as Subbase Materials

Abstract

The steel industry, which is an indicator of the developed countries with its production, also brings the problem of waste together. This waste product, that differs depending on the production process and is called slag, is generally referred as solid waste. Many researchers to use for different purposes are examining this type of wastes, which are difficult to store and dispose. It is also investigated about the usability as a filling material in civil engineering. The possibility of using such materials as an alternative to soil stabilization solutions, especially in the areas close to the industries producing these wastes, in the filling of such structures as the roads, railways, airport runways comprise of the basis of the surveys. In this study, the impact of steel slag and fly ash, another waste product released because of combusting lignite coal with low energy at the power plants, on the bearing ratio after blending with kaolin grade clay at different rates was observed. Keeping the 5% clay rate stable in weight, steel slag and fly ash with varying rates were added to prepare the test samples, which were cured for 0, 7, 28 and 56 days under stable conditions and subjected to California Bearing Ratio tests. The results showed that when steel slag and fly ash are used with clay, there were significant increases in their bearing ratios compared to the reference clay sample. While the wet California Bearing Ratio (CBR) was around 15% for the normal clay sample, when it is blended only with steel slag the wet CBR increased up to 70%, and when blended with fly ash the wet CBR went up to 130%. The used materials had very weak and weak binding properties when used alone while their binding properties increased by gaining pozzolanic property within the mix.