Use of Waste Gypsum, Reclaimed Asphalt Filler, and GGBS as a Full Replacement of Cement in Road Base

Abstract

Laboratory experiments were used to determine the suitability of raw industrial by-products obtained within the United Kingdom that are being taken to landfill sites and develop a hydraulically bound cementitious material for applications in road (base), foundation, and subgrade in pavement construction. The by-products were predominantly sourced locally. Tests were carried out to determine the mechanical stability of the by-product binders and performance determined in strength development by time. High-pressure permeability tests were performed to determine the permeability of the materials, and frost susceptibility tests were conducted to determine the freeze–thaw resistance of the materials. Compressive strength tests were conducted at 7, 14, 28, 90, and 180 days of age. Strength development on the hydraulic paste was slow during the early stages of hydration for mixtures containing 40%–60% ground granulated blast furnace slag (GGBS). After 28 days and up to 90 days when the ultimate strength of the hydraulic paste was achieved, strength increased with the presence of GGBS of up to 60%. Ternary mixtures with proportions of 20% plasterboard waste gypsum (PWG); 20% reclaimed asphalt filler (RAF), 60% GGBS, and 10% vitamin B5 gypsum (V-B5G); 30% RAF; and 60% GGBS attained the highest compressive strengths of 41 and 40 MPa, respectively, at 90 days. One of the dominant factors that influenced the strength was the presence of calcium sulfate, CaSO4 (CaO+SO3), in the PWG and V-B5G materials; calcium silicate, CaSiO3 (CaO+SiO2), in the GGBS; and pozzolanic activity (SiO2+Fe2O3+Al2O3) in the RAF. The results suggest most of the mixes in the groups are suitable for use as road (base) and foundation materials.