A Study on the Effect of Replacing Coarse Grains in Sub-Base Materials with Concrete Residues on their California Bearing Ratio

Abstract

California Bearing Ratio (CBR) values are critical to the properties of granular subgrade materials and play a significant role in determining the design variables of several flexible pavement design methods. Concrete waste is considered an environmental problem in many regions of Iraq. Therefore, its removal is of significant environmental value when used to improve the properties of certain materials, such as the granular sub-base examined in this study. This research examined the impact of substituting particles measuring 19 mm to 12 mm in granular sub-base materials, class C and D, with crushed concrete waste at replacement rates of 25%, 50%, 75%, and 100% while preserving their gradation characteristics, on the CBR value. The CBR examination results showed that the most significant improvement in the CBR value was observed at a 100% replacement ratio, attaining 55.84% and 57.22% at a 1 mm penetration for the unsoaked C and D samples, respectively, and 63.32% and 48.11% for the soaked condition at a 1 mm penetration for the C and D samples, respectively. The increase in CBR was correlated with an increase in Optimum Moisture Content (OMC) and a decrease in maximum dry unit weight (γdry max), demonstrating that the percentage increase in CBR is non-linear. An increase in CBR may be helpful in the foundation base for many projects.