STABILIZING CINDER GRAVELS FOR HEAVILY TRAFFICKED BASE COURSE

Abstract

Investigation into the improvement of natural cinder gravels with the use of stabilization techniques was made using samples collected from quarry sites near Alemgena and Lake Chamo. Mechanical and cement stabilizations were investigated in two subsequent phases. In the first phase, optimum amount of fine soils that makes up the deficiency of fine particles of natural cinder gravels was found to be 12 %. In the second phase, natural cinder gravel samples without, and with 12% fine soils were stabilized with 3, 5, 7, and 10% of cement by mass. The results of the investigation indicated that the optimum amount of cement required to achieve the minimum UCS of 3.0 MPa as specified in ERA and AACRA pavement design standards for heavily trafficked base course without adding fine soils is found to be 7 % cement. However, this high cement requirement was reduced to 5% cement which is a practical value by mechanically stabilizing cinder gravel with 12 % of fine soils before cement stabilization. Nevertheless, the performance of cement stabilized cinder gravel should be investigated in a full-scale road experiment against cracking due to stresses induced by thermal, shrinkage, and traffic.