In this work, the effects of raw algal biomass on the hydration kinetics of portland cement are reported. Specifically, direct addition of 0.3%, 0.5%, 1.0%, and 3.0% photosynthetic Chlorella algal biomass to cement paste substantially delayed cement hydration, as indicated by 16.5%, 29.4%, 82.4%, and 812% delays in the main peak of heat evolution measured by isothermal calorimetry. Retardation was confirmed via FTIR to be mechanistically caused by the existence of −COOH and −OH functional groups in raw algae. We substantiated the observation that elimination of −COOH and −OH functional groups in the algae through heat treatment coincided with the disappearance in the retardation effect, while enhancement of these functional groups through H 2 O 2 treatment induced further retardation. In addition, the effects of untreated and treated algae on the morphology, mineralogy, and compressive strength of cement pastes containing 0.5% Chlorella were found to be negligible. An addition of 0.5% algal biomass is estimated to cost approximately USD $1.6−2.6/m 3 of concrete, suggesting that raw algae could be used as a renewable, cost-competitive, CO 2 -storing set-retarding admixture for portland cement-based materials.
Portland cement concrete, the most used manufactured material in the world, is a significant contributor to anthropogenic carbon dioxide (CO2) emissions. While strategies such as point-source CO2 capture, renewable fuels, alternative cements, and supplementary cementitious materials can yield substantial reductions in cement-related CO2 emissions, emerging biocement technologies based on the mechanisms of microbial biomineralization have the potential to radically transform the industry. In this work, we present a review and meta-analysis of the field of biomineralized building materials and their potential to improve the sustainability and durability of civil infrastructure. First, we review the mechanisms of microbial biomineralization, which underpin our discussion of current and emerging biomineralized material technologies and their applications within the construction industry. We conclude by highlighting the technical, economic, and environmental challenges that must be addressed before new, innovative biomineralized material technologies can scale beyond the laboratory.
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