ABSTRACT
Over the years, the construction industry consumes large amount of materials and produces waste in large quanties, this practice depletes natural resources like aggregates and causes problem of waste accumulation. In order to attain sustainability, emphasis is made on circular pattern of consumption as against the linear pattern of consumption. Recycled Concrete Aggregate (RCA) is an example of waste produced from construction and demolition activities. Efforts have been made to eliminate the problem associated with cement usage and its production by fully replacing cement with an environmentally friendly binder known as geopolymer. Many researchers utilized natural aggregates in the production of geopolymer concrete but few researches have been carried out producing geopolymer concrete using RCA. This research evaluates the properties of metakaolin based Geopolymer Concrete (GPC) containing RCA. Metakaolin and alkaline solution (sodium hydroxide and sodium silicate) is the binder used for concrete production in this research. A total of 336 specimens of 100mm x 100mm x 100mm cubes were cast with each sample containing 0%, 20%, 30% and 40% RCA. A total of 192 concrete specimens were tested for compressive and tensile strength, for absorption capacity and abrasion resistance, 96 concrete specimens was used while 48 concrete specimens were tested for its resistance to magnesium sulphate (MgSO4) attack. GPC was produced and cured at 60oC in the oven for 24hrs, after which they were cooled at room temperature in the laboratory and their properties evaluated after 7, 14, 28 and 56days of curing periods. The Portland Cement Concrete (PCC) was also tested after curing in water at the same curing ages. The average compressive strength obtained at 28 days of curing for PCC specimens with 0%, 20%, 30% and 40% RCA are 24.23N/mm2, 21.09N/mm2, 19.81N/mm2 and 19.37N/mm2, xvi while for GPC specimen with same replacement of RCA are 31.54N/mm2, 31.17N/mm2, 28.55/mm2, 26.40N/mm2 respectively. The result obtained showed that GPC specimen have better compressive strengths when compared to PCC. This is concluded herein that hardened GPC specimens with various replacement of RCA showed higher compressive strength than PCC specimens. This research recommends that metakaolin based geopolymer concete containing RCA up to 40% RCA could be used for structural concrete.