Evaluating the use of mucilage from opuntia ficus-indica as a bio-additive in production of sustainable concrete

Abstract

The global demand for a sustainable and environmentally responsible economy, has called for incorporation of aspects of sustainability into infrastructure materials. Being the most globally consumed primary construction material, concrete’s strength and durability enhancement using green approaches is pivotal to sustainability of the built environment. Production of chemical admixtures is high energy consuming and environmentally taxing, thus the need for bio-available sustainable substitutes and/or supplements. This paper presents findings of an experimental and environmental impact evaluation, conducted on Normal Strength Concrete (NSC) mixtures dosed with Opuntia ficus-indica mucilage (Ofim) by mass-replacement of the mixing water. ASTM compliant tests for consistency, strength, and durability performance were conducted at standard time intervals up to 56 days, while the Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were employed for concrete micro-characterization. The study explored the interaction between the natural bio-additive and synthetic commercial admixture. A comparative Environmental Life Cycle Assessment (E-LCA) was also conducted to assess resource use efficiency and quantify the environmental impacts of Ofim-modified concrete relative to conventional concrete. Test results showed that the use of Ofim led to slight increase in the compressive strength and elastic modulus, in addition to a pronounced impact on durability of concrete, resulting in reduced fluid ingress by up to 39%, a lowered decrease in K-values by 14%, and an increase in the freeze–thaw resistance with high retention of Relative Dynamic Modulus of Elasticity (RDME) in the Ofim-modified mix relative to the control mix. A 15% mixing-water mass-replacement resulted in an average reduction in greenhouse gas (GHG) emissions of 9.6%. Hence, even if the improvement in the mechanical performance is not substantial, a reduction in GHG emissions scales up as the concrete industry is huge and tremendously contributes to climate change through embodied carbon.