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This research evaluates the behavior corrosion of galvanized steel (GS) and AISI 1018 carbon steel (CS) embedded in conventional concrete (CC) made with 100% CPC 30R and two binary sustainable concretes (BSC1 and BSC2) made with sugar cane bagasse ash (SCBA) and silica fume (SF), respectively, after 300 days of exposure to 3.5 wt.% MgSO4 solution as aggressive medium. Electrochemical techniques were applied to monitor corrosion potential (Ecorr) according to ASTM C-876-15 and linear polarization resistance (LPR) according to ASTM G59 for determining corrosion current density (icorr). Ecorr and icorr results indicate after more than 300 days of exposure to the sulfate environment (3.5 wt.% MgSO4 solution), that the CS specimens embedded in BSC1 and BSC2 presented greater protection against corrosion in 3.5 wt.% MgSO4 than the specimens embedded in CC. It was also shown that this protection against sulfates is significantly increased when using GS reinforcements. The results indicate a higher resistance to corrosion by exposure to 3.5 wt.% magnesium sulfate two times greater for BSC1 and BSC2 specimens reinforced with GS than the specimens embedding CS. In summary, the combination of binary sustainable concrete with galvanized steel improves durability and lifetime in service, in addition to reducing the environmental impact of the civil engineering structures.

Depending on the morphology of the natural fibers, they can be used as reinforcement to improve flexural strength in cement-based composites or as aggregates to improve thermal conductivity properties. In this last aspect, hemp, coconut, flax, sunflower, and corn fibers have been used extensively, and further study is expected into different bioaggregates that allow diversifying of the raw materials. The objective of the research was to develop plant-based concretes with a matrix based on Portland cement and an aggregate of Agave salmiana (AS) leaves, obtained from the residues of the tequila industry that have no current purpose, as a total replacement for the calcareous aggregates commonly used in the manufacturing of mortars and whose extraction is associated with high levels of pollution, to improve their thermal properties and reduce the energy demand for air conditioning in homes. Characterization tests were carried out on the raw materials and the vegetal aggregate was processed to improve its compatibility with the cement paste through four different treatments: (a) freezing (T/C), (b) hornification (T/H), (c) sodium hydroxide (T/NaOH), and (d) solid paraffin (T/P). The effect of the treatments on the physical properties of the resulting composite was evaluated by studying the vegetal concrete under thermal conductivity, bulk density, and compressive strength tests with a volumetric ratio between the vegetal aggregate and the cement paste of 0.36 and a water/cement ratio of 0.35. The hornification treatment showed a 15.2% decrease in the water absorption capacity of the aggregate, resulting in a composite with a thermal conductivity of 0.49 W/mK and a compressive strength of 8.66 MPa, which allows its utilization as a construction material to produce prefabricated blocks.

This research evaluates four sustainable cementitious composites with sustainable plant fibers and bio-aggregates: (1) cementitious matrix composite with lechuguilla fibers (LFC) and (2) with flax fibers (FFC); and (3) cementitious matrix composite with wood shavings (WSC) and (4) with hemp shavings (HSC). The fibers are for reinforcement and the shavings act as bio-aggregates as a total replacement for limestone aggregates. The lechuguilla (LF) and flax (FF) fibers were treated; wood (WS) and hemp (HS) bio-aggregates were also processed. Nineteen mixtures were manufactured, and five were used as controls, and the hygrothermal, mechanical, and durability properties were evaluated. The results for LFC and FFC showed that fiber treatment negatively affected flexural–compressive strength; untreated LFC with accelerated deterioration had better mechanical behavior, higher density, and lower porosity than FFC. Strength and density decreased, but porosity increased with increasing fiber volume (Vf). Regarding WSC and HSC, the microstructure of WS and HS had a significant effect on the physical and mechanical properties. The high porosity influenced the results obtained, since it decreased compressive strength and bulk density; however, thermal conductivity, hygroscopicity, and vapor resistance showed better behavior in most cases than the control specimens, i.e., without bio-aggregates.