Novel green concrete (GC) admixtures containing 50% and 100% recycled coarse aggregate (RCA) were manufactured according to the ACI 211.1 standard. The GC samples were reinforced with AISI 1080 carbon steel and AISI 304 stainless steel. Concrete samples were exposed to 3.5 wt.% Na2SO4 and control (DI-water) solutions. Electrochemical testing was assessed by corrosion potential (Ecorr) according to the ASTM C-876-15 standard and a linear polarization resistance (LPR) technique following ASTM G59-14. The compressive strength of the fully substituted GC decreased 51.5% compared to the control sample. Improved corrosion behavior was found for the specimens reinforced with AISI 304 SS; the corrosion current density (icorr) values of the fully substituted GC were found to be 0.01894 µA/cm2 after Day 364, a value associated with negligible corrosion. The 50% RCA specimen shows good corrosion behavior as well as a reduction in environmental impact. Although having lower mechanical properties, a less dense concrete matrix and high permeability, RCA green concrete presents an improved corrosion behavior thus being a promising approach to the higher pollutant conventional aggregates.

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.

This research evaluates of the electrochemical behavior of steel bars of the AISI 316 and AISI 1018 embedded in sustainable concrete with partial replacement of CPC 30R by Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF). The electrochemical techniques used to evaluate the corrosion were half-cell potential or Ecorr -ASTM C-876-15- and the Linear Polarization Resistance Technique (LPR) - ASTM G59-. Ecorr and Icorr results indicate after more than 300 days of exposure to the marine environment (3.5% NaCl solution), a high resistance of AISI 316 steel, with Ecorr values lower than -200 mV indicating a 10% probability of corrosion, and a level of negligible corrosion, with values less than 0.1 µA/cm2 in the three mixtures, with sustainable concrete values slightly lower. The results indicate a resistance of more of almost 100 times greater than AISI 316 steel compared to the results obtained in AISI 1018 steel.

RESUMENEn la presente investigación se estudiaron 8 muestras de suelo, con adiciones de 5 y 7 % de adición de CBCA, CPC y combinaciones de estos en diferentes proporciones. Se realizó la caracterización y clasificación del suelo de estudio, determinándose la Humedad Natural, Curva Granulométrica, Límites de Consistencia, clasificación de suelos de acuerdo con el SUCS, Equivalente de arena, Desgaste de los Ángeles, Partículas alargadas y lajeadas, compactación AASHTO, CBR y Expansión. Los resultados muestran que es viable el uso de la CBCA para mejorar significativamente las propiedades físicas y mecánicas del suelo granular tipo base hidráulica, con incrementos de más del 100% del CBR en los suelos con adición del 7% de la combinación de CBCA-CPC. Palabras clave: CBCA; Base Hidráulica; Mejoramiento de suelos. ABSTRACTIn the present investigation 8 soil samples were studied, with additions of 5 and 7% of addition of CBCA, CPC and combinations of these in different proportions. The characterization and classification of the study soil was carried out, determining the Natural Humidity, Granulometric Curve, Consistency Limits, soil classification according to the SUCS, Sand Equivalent, Los Angeles Wear, Elongated and Layered Particles, AASHTO compaction, CBR and Expansion. The results show that the use of the CBCA is viable to significantly improve the physical and mechanical properties of the granular soil type hydraulic base, with increases of more than 100% of the CBR in the soils with addition of 7% of the combination of CBCA-CPC.

This research evaluates of the electrochemical behavior of steel bars of the AISI 316 and AISI 1018 embedded in sustainable concrete with partial replacement of CPC 30R by Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF). The electrochemical techniques used to evaluate the corrosion were half-cell potential or Ecorr -ASTM C-876-15- and the Linear Polarization Resistance Technique (LPR) - ASTM G59-. Ecorr and Icorr results indicate after more than 300 days of exposure to the marine environment (3.5% NaCl solution), a high resistance of AISI 316 steel, with Ecorr values lower than -200 mV indicating a 10% probability of corrosion, and a level of negligible corrosion, with values less than 0.1 µA/cm2 in the three mixtures, with sustainable concrete values slightly lower. The results indicate a resistance of more of almost 100 times greater than AISI 316 steel compared to the results obtained in AISI 1018 steel.