Evaluating the Use of Mucilage from Opuntia ficus-indica as a Bio-additive in Production of Sustainable Concrete

Abstract

In a bid by the construction industry to meet global demand for a sustainable and environmentally responsible economy, attention has recently been drawn to incorporating aspects of sustainability into infrastructure materials. With concrete being the most consumed primary construction material globally, enhancement of its strength and durability performance using green approaches is pivotal to sustainability of the Built Environment Ecosystems. Production of chemical admixtures that have over time been used to enhance plastic and hardened-state properties of concrete is high energy consuming and environmentally taxing, thus the need for bio-available sustainable substitutes and/or supplements. This study sought to investigate performance enhancement of Normal Strength Concrete using Opuntia ficus-indica mucilage (Ofim), by mass replacement of mixing water. In the first phase of the study, plastic and hardened-state properties of bio-additive and chemical admixture modified concrete mixes, with varying additive proportions, were investigated relative to the control mix. Tests were performed at standard time intervals up to 56 days, including concrete compressive strength, split tensile strength, Youngs modulus of elasticity, standard flexural strength, and rate of water absorption. Based on the results of the first phase, the study explored additional experimental variables in a second phase, followed by durability tests and an investigation of interaction of the bio-additive and chemical plasticizer. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FT-IR) Spectroscopy were employed for concrete micro-characterization. A comparative Environmental Life Cycle Assessment (E-LCA) was conducted to assess resource use efficiency and quantify the environmental impact of Ofim-modified concrete relative to conventional concrete. Much as Ofim modification enhanced the strength performance of concrete, such enhancement was considered insignificant, for the concrete mix used in the study. Ofim exhibited pronounced impact on durability performance of concrete, that is; reduced fluid ingress by up to 39%, lower K-values by 14% and increased freeze-thaw resistance with low Relative Dynamic Modulus of Elasticity (RDME) deterioration in Ofim-modified mixes relative to the control mix. A 15% mixing-water mass replacement resulted to a 10% average reduction in GHG emission, moreover, reduction in K-values would result into low energy consumption, and further reduction in emission over time, during operation of Ofim-modified concrete infrastructure.