Effects of Rubber and Bottom Ash Inclusion on Geotechnical Characteristics of Composite Geomaterial

This paper investigated the effects of including crumb rubber and bottom ash on the geotechnical characteristics of composite geomaterial (CGM) in which dredged soils, crumb rubber, and bottom ash are reused for recycling. Several series of test specimens were prepared at five different percentages of rubber content and three different percentages of bottom ash content. The mixed soil specimens were subjected to unconfined compression, elastic wave, and California bearing ratio (CBR) tests to investigate their strength, stiffness, small strain properties, and CBR values. The test results indicated that rubber and bottom ash affected engineering properties of the CGM. The addition of bottom ash to the soil mixture contributed to increases in unit weight, unconfined compressive strength, secant modulus, shear modulus, and CBR at a given rubber content. However, increasing rubber content resulted in decreased bulk unit weight, unconfined compressive strength, elastic wave velocity, and CBR value of CGM. The results of elastic wave tests indicated that higher rubber content resulted in reduced elastic wave velocity and a lower shear modulus. Of the samples tested in this study, those with lower rubber content exhibited sand-like behavior and a higher shear modulus. Samples with a higher rubber content exhibited rubber-like behavior and a lower shear modulus. The CBR of CGM with bottom ash was much greater than that of CGM without bottom ash.