Controlled low-strength materials for pavement foundations in road tunnels: feasibility study and recommendations

This paper presents the results obtained during a laboratory and field investigation which focused on the assessment of the feasibility of using controlled low strength materials (CLSMs) in pavement foundations of road tunnels. The CLSM considered in the study, which contained a significant amount of recycled asphalt pavement, was designed by optimizing its flowability and by considering its sensitivity to changes in cement dosage. For comparative purposes, a standard low-strength Portland cement concrete mixture was also included in the investigation. Both mixtures were produced in a Portland cement concrete batching plant and were thereafter subjected to laboratory tests for the evaluation of flowability, consistency, compressive strength, California bearing ratio and resilient modulus. Furthermore, full-scale slabs constructed with the two mixtures were subjected to plate loading tests and to the transit of a fully-loaded heavy vehicle. Obtained results indicated that both mixtures are suitable for the formation of pavement foundations since they exhibit a short-term mechanical behavior which is comparable to that of standard granular sub-base materials. However, the CLSM proved to be superior in terms of its improved flowability, easier long-term excavatability, lower production cost and enhanced sustainability. Finally, recommendations for future applications of cement-bound materials in pavement foundations were provided in the form of preliminary performance-based acceptance criteria.