Abstract
The present investigation is directed to determine if a natural/botanical addition, from Opuntia ficus-indica (OFI) cactus, increases durability for cement-based materials exposed to CO2-laden environments (urban and industrial). The use of this botanical addition in cement-based material applications has shown good performance when these materials are exposed to chloride-laden environments, but no investigations to date have shown the performance of this addition in urban/industrial environments. Therefore, the aim of this investigation is to complement OFI mucilage performance in the most hazardous environments where most of these construction materials are naturally exposed: marine, urban, and industrial. Steel-reinforced mortar prisms, containing OFI mucilage at different addition levels (0%, 1.5%, 4%, 8%, 42%, and 95%, by water mass replacement concentration), were exposed for 14 years (5110 days) in a natural CO2-laden environment. Linear polarization resistance measurements were performed in a wet–dry cycle (between 5020 and 5110 days of age, after mortar fabrication) to determine the possible corrosion-inhibiting effect of OFI mucilage additions. Little corrosion-induced cracking was observed in carbonated mortars with OFI mucilage additions, compared with the carbonated control mortar that showed high corrosion-induced cracking. The electrochemical results showed corrosion-inhibiting efficiencies for steel in carbonated mortar with OFI mucilage additions of 40–70% for low OFI mucilage concentrations (1.5% and 4%), and 70–90% for medium and high OFI mucilage concentrations (8%, 42%, and 95%). Experimental findings suggest that adding OFI mucilage might be useful as a corrosion inhibitor for steel in carbonated cement-based materials (i.e., mortar) because corrosion rates and cracking initiation/propagation were decreased.
Highlights
Opuntia ficus-indica (OFI, a cactus named Nopal in Mexico) grows in semi-arid and arid environments forming thickets, regularly the size of a bush and, in some cases, as large as a 6 m tall tree
Experimental findings suggest that adding OFI mucilage might be useful as a corrosion inhibitor for steel in carbonated cement-based materials because corrosion rates and cracking initiation/propagation were decreased
Average half-cell potentials (HCPs) and average linear polarization resistance (LPR) measurements were performed during the time period: two dry cycle measurements and one wet cycle measurement
Summary
Opuntia ficus-indica (OFI, a cactus named Nopal in Mexico) grows in semi-arid and arid environments forming thickets, regularly the size of a bush and, in some cases, as large as a 6 m tall tree. Cactus mucilage from OFI has been used as an addition in lime mortars for restoration work on historic lime and/or adobe buildings in Latin America [3,4] Their use in hydraulic concrete has shown flow improvement, retarded setting times, increased workability, and increased mechanical strength at a later age [2,4,5]. A further chemical composition of OFI mucilage, specialized biopolymer, can be found elsewhere [3,4] These mineral contents, especially calcium, mean that OFI mucilage remains stable in highly alkaline media over long time periods, and long-term degradation of this botanical product in cement-based materials should be not possible
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