Matric Suction in Recycled Unbound Granular Materials

Abstract

The matric suction within unbound granular materials (UGMs) can be small when compared with cohesive soil, however suction can influence the engineering behavior of UGMs. Unfortunately, there are few studies on the potential matric suction in UGMs. This paper presents matric suctions for seven recycled products and one virgin aggregate. The products were recycled concrete aggregate (RCA) and recycled clay masonry blended with RCA. The percentage of masonry in the blended materials varied between 10% and 30% by mass. Soil water characteristic curves (SWCC) were established for each material by preparing samples at various moisture contents and measuring matric suction with filter papers in contact with the soil. In order to define the wet end of the SWCC, further samples were conditioned on a tension plate using a hanging water column. The recycled products had suctions higher than the virgin aggregate at an equivalent moisture state. Air entry values and residual suctions were determined for each material. Three published models were applied to fit SWCCs to the experimental data. Generally these models provided good fits to the data for each UGM. The influence of matric suction on both resilient modulus and permanent strain of the recycled materials are presented.

Resilient modulus for unbound granular materials and subgrade soils in Egypt

“…They observed that water content had little impact on the resilient modulus of base materials compared to the subgrade soils. Studies conducted by [23,24,17], found that the matric suction has been appeared to be a vastly improved predictor of engineering behavior than moisture content.…”

“…Numerous studies stated that the Mr of UGMs and subgrade soils fundamentally depends on moisture content or matric suction in both laboratory and in-situ condition [14,17].…”