Blending Plastics Waste with Highly Available Jordanian Kaolin for Preparation of Alkali-Activated Mortars

Abstract

Due to their lower energy demand, alkali-activated materials or geopolymers (GPs) are strong candidates to replace ordinary Portland cement binders in some applications. The present article attempts to investigate the possibility of incorporating plastics waste in place of silica sand filler in the GP mortars. The compressive strength, density, FTIR, XRD, BET and SEM of the prepared mortars were evaluated. Satisfactory compressive strength was achieved for metakaolin (MK)-based GP mortars containing plastic fillers (polyvinylchloride (PV), polystyrene (PS), polypropylene (PP) and polyethylene (PE)) which was dependent on the nature of plastic incorporated in the GP matrix: MKPV (30.3 MPa) > MKPS (15.8 MPa)~MKPP (15.9 MPa) > MKPE (9.1 MPa). The 28-day compressive strength of GP containing polyvinyl chloride was almost equivalent to that containing silica sand. Much lower values were obtained for the corresponding kaolin-based GPs (2.5, 2.8, 1.8 and 2.2 MPa, respectively). As reflected by FTIR absorption bands at 1447 and 1400 cm−1, the addition of plastic filler reduces absorption of CO2 from the atmosphere which enhanced dissolution of Al species from metakaolin. The morphology of GPs containing plastic fillers exhibited amorphous tissue-like structure compared to crystalline structure in the case of GP containing silica sand. However, both types of GPs exhibited lower porosity than previously prepared metakaolin-based GPs. Remarkably, poor adhesion of plastic filler to the GP binder was observed due to the inertness of plastic fillers toward alkali activators.