Compressive strength of geopolymeric cubes produced from solid wastes of alum industry and drinking water treatment plants

Abstract

IN this work, geopolymer is produced from two by-products waste as an alternative environmentally green construction and building materials without using Ordinary Portland Cement (OPC). Water Treatment Sludge (WTS) from Marg Drinking Water Treatment Plants in Cairo and De-Aluminated Kaolin (DAK) from Egyptian Company for Aluminum Sulfate were used in this study. Sodium hydroxide (NaOH) solution was used as an alkaline activator. The effect of the various influential factors on compressive strengths of WTS/DAK geopolymer was investigated. These factors are mixing ingredient (WTS/DAK) ratios and amounts of NaOH of different normality. The mineralogical and chemical compositions of the WTS/DAK wastes were obtained using X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analyses. Results show that the optimum ingredients providing maximum strength are the Na2O/SiO2 ratio of 0.56 and WTS/DAK ratio of 30:70. The development of compressive strengths over curing time of WTS/ DAK geopolymer samples at optimum ingredients (30:70 WTS/DAK, 60 g NaOH 10 N and 70 oC for 72 hours). The compressive strength of WTS/DAK geopolymer gives 17 MPa after 7 days and increased to maximum strength of 22 MPa at 28 days. The compressive strengths obtained comply with the Egyptian Industrial Standards. Moreover, the WTS that traditionally disposed into landfills or drainage canals can be used sustainably in developing cement-free geopolymers with economical and environmental significance.