Opuntia ficus-indica mucilage: A sustainable bio-additive for cementitious materials

With the growth of bioconstruction, new technologies have emerged to optimize natural construction processes, from the most traditional to the most alternative. Besides, the production of chemical admixtures consumes significant energy and exacts a toll on the environment. Therefore, there is a pressing demand for sustainable, bio-available substitutes or supplements. Utilizing biomass presents a significant environmental challenge amidst conservation efforts and the ongoing depletion of fossil fuel reserves. Opuntia ficus-indica, a cactus species, is a typical vegetable waste from which mucilage in gel form can be extracted. Thus, this study explored mucilage from Opuntia ficus-indica as a natural additive in cementitious materials. Extracted in water at a ratio of 1:3 with 0.45 % solids, it replaced 0-100 % of the mixing water. The effects on microconcrete consistency, strength, and water absorption were tested, while cement pastes were analyzed by porosimetry, X-ray diffraction, infrared spectroscopy, and thermogravimetric methods. The additive samples showed an increase in consistency in the fresh state. After 28 days, there were no significant changes in the porosity of the hardened samples. However, the added microconcretes had a strength gain of up to 17 % compared to the reference. After 180 days, no harmful effects of the additive were observed, with a dosage of 10 % of the mixing water resulting in a 9 % increase in compressive strength. Therefore, the evaluated bio-additive can be regarded as an eco-friendly and cost-effective natural alternative, capable of fostering the development of sustainable cement composites with properties comparable to those of traditional cementitious materials.