Caracterización mecánica de un hormigón sostenible con sustitución parcial de cemento por arcillas calcinadas y reforzados con fibras naturales Amazónicas

Abstract

The research presented herein constitutes the master’s degree Project in Civil Engineering, with a specialization in Sanitation and Construction, at the Escuela Superior Politécnica del Litoral (ESPOL). Concrete remains the most widely utilized material in contemporary construction; however, its production is associated with a considerable carbon footprint. This circumstance necessitates the exploration of alternative materials with reduced environmental impact. Accordingly, this study aims to characterize the mechanical behavior of a sustainable concrete wherein cement is partially replaced by calcined clays and reinforced with natural fibers sourced from the Amazon, thereby supporting the anticipated reduction in CO₂ emissions and promoting the sustainable use of national resources. The local clay used in this investigation was procured from Puyo city, in Pastaza province. These clays were analyzed by X-ray Diffraction (XRD) both before and after calcination, and the material exhibiting superior characteristics was selected for further study. The concrete mixture was designed in accordance with American Concrete Institute (ACI) standards, targeting an expected compressive strength of 21 MPa. The mixture’s fresh properties—specifically workability and setting time—were assessed, and, upon hardening, specimens were subjected to compressive strength testing in accordance with ASTM C39 (cylinders) and flexural strength testing per ASTM C293 (beams). Results from several mix proportions indicated that mixtures with calcined clay reached 80% of the compressive strength of conventional concrete at 28 days, suggesting the potential for later strength gain. Regarding the flexural strength results, the sample with a calcined clay mixture showed a higher relative index compared to the compressive strength at the same age, reaching up to 59%. It is confirmed that the design of concrete with a fractional substitution of cement by calcined clay, at an optimal and moderate substitution level, constitutes a viable approach toward the production of sustainable concrete with a lower carbon footprint and efficient mechanical performance. Keywords: Sustainable concrete, calcined clays, natural fibers, long-term mechanical strength, relative performance index.