Engineering properties of recycled Calcium Carbide Residue stabilized clay as fill and pavement materials

Reuse of waste materials for pavement applications is of great international interest. This paper presents basic and engineering properties of the recycled Calcium Carbide Residue (CCR) stabilized clay. Scanning electron microscopic images show that the recycled CCR stabilized clay particles are larger than the CCR and clay particles due to the attached pozzolanic products. The large grains reduce linear shrinkage and free swell ratio of the recycled CCR stabilized clay. For the same compaction energy and CCR content, the unit weight of the recycled CCR stabilized clay is lower than that of the CCR stabilized clay because the harder attached pozzolanic products resist the compaction. The strength development and the reduction in void ratio with time confirm that the pozzolanic reaction still prevails even after remolding. This implies that the pozzolanic reaction occurs mainly on the surface of the clay–CCR clusters. The remolding of CCR stabilized clay breaks down the cementitious bonds between the CCR–clay clusters and the unreacted CCR and clay particles in the clusters are then free to interact with water. The research outcome reinforces the possibility of using the recycled CCR stabilized clay as fill and pavement materials. The strength and resistance to compressibility are slightly lower than those of the original CCR stabilized clay for the same CCR content while the unit weight of recycled CCR stabilized clay is much lower, which reduces the overburden on the foundation.