Novel low emissions supersulfated cements of pumice in concrete; mechanical and electrochemical characterization

Novel low emissions supersulfated cements based on volcanic pumice were evaluated in reinforced concretes; the mechanical, microstructural and electrochemical properties were studied for 180 days. The volcanic pumice was chemically activated with anhydrite or hemihydrate and an alkaline activator of quicklime and Portland cement. The binder consumption in the concretes was of 720 kg/m(3), of which only 72-144 kg/m(3) were of Portland cement; a reference concrete based on the latter was also prepared with 415 kg/m(3). The specimens were cured at 25 degrees C or for 22 h at 60 degrees C then at 25 degrees C; these were exposed to laboratory conditions or to immersion in 3.5%NaCl at 25 degrees C to induce accelerated corrosion. Compared to the reference concrete, the supersulfated cement based concretes had 65-82% less Portland cement and at least 49% lower CO2 emissions, were up to 26% cheaper and showed similar 28-day and better 180-day compressive strength, reaching up to 44 MPa. Compared to green concretes from the literature, similar or better strengths and up to 24% less CO2 emissions were noted. The penetration of chlorides and electrochemical tests showed that the activation with 10%CaO promoted adequate protection to the embedded steel, in some instances better than the reference concrete. The novel supersulfated cements appear to be a promising alternative to produce sustainable and durable concretes for regions on the world with access to volcanic materials. (C) 2020 Elsevier Ltd. All rights reserved.