Physical and mechanical characterization of bio concrete produced with Coffea arabica coffee husk

Abstract

This research aimed at the chemical and physical characterization of Coffea arabica coffee husks, and its use as an aggregate for the development of lightweight bio concrete, evaluating its physical and mechanical properties and thermal conductivity. The bio aggregate was characterized by chemical composition and basic density. Infrared spectroscopy with Fourier transform (FTIR) was also performed. The residue was submitted to a pre-treatment in hot water at 80ºC, followed by immersion in calcium hydroxide solution, this process was used to avoid delay in cement hydration. The bio concrete production, used Portland Cement CPV-ARI, metakaolin, and fly ash, with a water/cementitious material ratio of 0.35 and 3% of calcium chloride about the cement mass, and 45% of the coffee husk in volume. 180% compensation water was added. The coffee husk has an extractive content of 47% and 23.47% of lignin, featuring a high content compared to some woods. Its presents 0.41 g/cm³ of apparent density and is considered a low-density material. The uniaxial compressive strength test obtained values for 7 and 28 days of 1.23 MPa and 1.16 MPa, respectively. Bio concretes can be classified as lightweight with a density of 1.19 g/cm³ and a good thermal conductivity of 0.32 W/mK. The composites produced showed potential for application in the civil construction industry.