Corrosion Behavior of Steel-Reinforced Green Concrete Containing Recycled Coarse Aggregate Additions in Sulfate Media

Analysis of the Mechanical Properties of a Stabilized Subgrade Type Soil under a Sustainable Approach for Construction

This article presents an experimental study to analyze the mechanical properties of a soil stabilized with ordinary Portland cement (OPC) under a sustainable approach consisting of a significant substitution of OPC for sugarcane bagasse ash (SCBA) to reduce the quantity of cement used in the stabilization, reaching the necessary mechanical requirements for its use as a subgrade layer. Soil specimens were elaborated with 3%, 5%, and 7% OPC as a stabilizing agent by weight of the soil. These mixtures were then partially substituted with 25%, 50%, and 75% SCBA, with these percentages being by weight of the stabilizer (OPC). Compaction, compressive strength, and California bearing ratio (CBR) tests were performed to evaluate the mechanical properties of the specimens. The results indicate that a 25% substitution of OPC by SCBA shows a similar performance to the mixture with only Portland cement, so a reduction in OPC use can be made. Further, with a substitution of 100% OPC by SCBA, the CBR of natural soil without stabilizers is improved.

Effect of the Addition of Agribusiness and Industrial Wastes as a Partial Substitution of Portland Cement for the Carbonation of Mortars

The present research work shows the effect on the carbonation of Portland cement-based mortars (PC) with the addition of green materials, specifically residues from two groups: agricultural and industrial wastes, and minerals and fibres. These materials have the purpose of helping with the waste disposal, recycling, and improving the durability of concrete structures. The specimens used for the research were elaborated with CPC 30R RS, according to the Mexican standard NMX-C-414, which is equivalent to the international ASTM C150. The aggregates were taken from the rivers Lerma and Huajumbaro, in the State of Michoacan, Mexico, and the water/cement relation was 1:1 in weight. The carbonation analyses were performed with cylinder specimens in an accelerated carbonation test chamber with conditions of 65 +/− 5% of humidity and 25 +/− 2 °C temperature. The results showed that depending on the PC substitutions, the carbonation front advance of the specimens can increase or decrease. It is highlighted that the charcoal ashes, blast-furnace slags, and natural perlite helped to reduce the carbonation advance compared to the control samples, consequently, they contributed to the durability of concrete structures. Conversely, the sugarcane bagasse ash, brick manufacturing ash, bottom ash, coal, expanded perlite, metakaolin, and opuntia ficus-indica dehydrated fibres additions increased the velocity of carbonation front, helping with the sequestration of greenhouse gases, such as CO₂, and reducing environmental pollution.

Physical, Mechanical and Durability Properties of Ecofriendly Ternary Concrete Made with Sugar Cane Bagasse Ash and Silica Fume

In the present investigation, the physical, mechanical and durability properties of six concrete mixtures were evaluated, one of conventional concrete (CC) with 100% Portland cement (PC) and five mixtures of Ecofriendly Ternary Concrete (ETC) made with partial replacement of Portland Cement by combinations of sugar cane bagasse ash (SCBA) and silica fume (SF) at percentages of 10, 20, 30, 40 and 50%. The physical properties of slump, temperature, and unit weight were determined, as well as compressive strength, rebound number, and electrical resistivity as a durability parameter. All tests were carried out according to the ASTM and ONNCCE standards. The obtained results show that the physical properties of ETC concretes are very similar to those of conventional concrete, complying with the corresponding regulations. Compressive strength results of all ETC mixtures showed favorable performances, increasing with aging, presenting values similar to CC at 90 days and greater values at 180 days in the ETC-20 and ETC-30 mixtures. Electrical resistivity results indicated that the five ETC mixtures performed better than conventional concrete throughout the entire monitoring period, increasing in durability almost proportionally to the percentage of substitution of Portland cement by the SCBA–SF combination; the ETC mixture made with 40% replacement had the highest resistivity value, which represents the longest durability. The present electrical resistivity indicates that the durability of the five ETC concretes was greater than conventional concrete. The results show that it is feasible to use ETC, because it meets the standards of quality, mechanical resistance and durability, and offers a very significant and beneficial contribution to the environment due to the use of agro-industrial and industrial waste as partial substitutes up to 50% of CPC, which contributes to reduction in CO2 emissions due to the production of Portland cement, responsible for 8% of total emissions worldwide.

Experimental Study of the Resistance to Influence of Aggressive Liquids on Lightweight Concrete

In light of the scientific research, the corrosion of concrete structures is one of the main problems that may reduce their durability due to the negative impact of the natural environment. The paper analyzes the influence of the type of component on the selected properties of lightweight concrete subjected to the influence of aggressive liquids. Four concrete mixes were prepared with a granular aggregate made of foamed glass (GEGA) and aggregate made of sintered fly ash (GAA) with the use of a mineral additive: silica fly ash. The prepared lightweight concrete after one year was exposed for 60 days to the following environments: strong acid—HCl, 1% and 2% concentration, weak acid—CH₃COOH, 1% and 2% concentration, and an aqueous salt solution of Na₂SO₄, 1% and 2% concentration. Then, the compressive strength was tested, and the microstructure analysis of the ready-made lightweight concrete (LWC) was performed. The degree of penetration of aggressive solutions into the cracks of the samples was assessed by means of applying 1% phenolphthalein solution. Changes in the weight of lightweight concrete samples after the test period were estimated. The obtained test results indicate that the decrease in the durability of lightweight concrete can be classified as a long-term process. Concrete with GEGA and GAA showed high resistance to aggressive environments. Moreover, the environment containing chlorides turned out to be the most aggressive, while the environment containing sulfates proved to be the least aggressive. The higher the concentration of the destructive factor was, the faster the corrosion process went. This has been proven by measuring the pH using phenolphthalein and carrying out microscopic examination. Concretes containing aggregates made of foamed glass and sintered fly ash are suitable for use both in traditional construction and in facilities exposed to an aggressive environment (e.g., in the chemical industry and at gas stations).

Electrochemical Corrosion of Galvanized Steel in Binary Sustainable Concrete Made with Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF) Exposed to Sulfates

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.