Improvement in Field CBR Values of Subgrade Soil Using Construction-Demolition Materials

Many countries suffer from the stacks of construction and demolition (CD) materials as they cause environmental and health problems in society. The city of Mosul in Iraq suffers from a huge amount of demolition materials resulting from destruction of most of the infrastructure. In the present study, attempts have been made to assess the influence of three types of CD materials (dragged asphalt, DA; crushed brick, CB; and crushed concrete, CC) on the response of a low-plasticity clay (CL) for use as a road subgrade layer. An intensive series of both experimental and numerical studies on the CL with 10% CD materials was carried out using field California bearing ratio (CBR) tests performed in a large-scale model box. The results showed significant improvement in the CBR values upon the addition of CD materials to the CL soil. The CBR values increased by 12.4, 13.7, and 49.7% with the addition of DA, CB, and CC, respectively. The CBR values improved between 1.1 and 1.7 times, corresponding to an increase in the layer thickness from 50 to 100 cm. Further increases in CBR values range from 1.5 to 1.8 times attendant with increasing the thickness of layer from 50 cm to 150 cm. The addition of CC is more active and gives higher CBR values. A good match was observed between the CBR values obtained from the experimental results and the numerical analysis using the PLAXIS 2D package.

Automated summary

The study found that adding CD materials to clay soil can significantly improve the bearing capacity of road subgrade layers, different materials have different effects on the increase in bearing capacity, and increasing the layer thickness also affects the enhancement of bearing capacity.