Permanent Strain of Unsaturated Unbound Granular Materials from Construction and Demolition Waste

Abstract

This paper presents a new equation for estimating the permanent strain of different combinations of recycled clay masonry and recycled concrete aggregate using the concept of matric suction. The aim of this paper was to develop a new equation with a single set of constants for all the materials. The unbound granular material (UGM) was prepared at moisture contents ranging between 70 and 90% of optimum moisture content (OMC) and tested in a repeated-load triaxial test (RLTT) apparatus under a single-stress state. 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 order to obtain the wet end of the SWCC, further samples were conditioned on a tension plate at suctions controlled by the hanging water column method. Permanent strain was influenced by moisture content or suction and was found to provide a better correlation with suction than with moisture content. Permanent deformation under a single-stress state was able to be estimated successfully using an equation developed on the basis of number of load repetitions, initial matric suction, dry density ratio, weighted plasticity index, and masonry content in the blend. Sets of material constants were found for all UGMs. It is shown that the equation can be used with a single set of constants to provide satisfactory predictions of permanent strain (