Assessing and Reinforcing Properties of Greywater-made Green Concrete Using Pozzolanic Materials

Abstract

Considering the increasing need for optimal use of water resources, using types of waste water instead of part of the water for making concrete and also reducing the use of potable water in concrete is particularly important, especially in developing countries. Accordingly, this study aimed to investigate and reinforce using greywater as a potential alternative to mixing water in concrete. The specimens’ fresh, hardened, and durable properties from 14 concrete mix designs containing six mixing water types, three natural zeolite levels (0, 10, and 20%), and two silica fume levels (0 and 8%) were tested to achieve that. Mixing waters in this study consisted of distilled water, raw greywater, diluted greywater (50% greywater, 50% distilled water), simulations of greywater’s salt and organic pollutants, and synthetic greywater. The results showed that raw greywater reduced average compressive strength by 8%, while diluted greywater caused a 1.5% increase instead. Mixing water standards requirements were satisfied on both raw and diluted greywater cases. The results also showed that the impact of greywater on the durability properties of concrete was non-critical in most cases, while diluted greywater, even slightly (4%), improved bulk electrical resistance (RCPT). The test results of synthetic waters showed that reducing chemically active salts and/or organic pollution in greywater can effectively increase the performance of the produced concrete. Using 8% silica fume as cement replacement improved the compressive strength of greywater-made concrete by up to 16% and reduced the cracks and porosity of the specimens based on SEM images. On the other hand, using 20% natural zeolite as cement replacement increased surface (using Wenner probes) and bulk chloride ion penetration by 36 and 78%, respectively. Based on these results, silica fume and natural zeolite replacement are impressive tools to reinforce greywater-made green concrete so that it can properly rival and even replace regular concrete even when using more polluted greywater. Furthermore, these replacements can be great potential alternatives to wastewater dilution or treatments.