Evaluation of degradation and mechanical parameters and sustainability indicators of zeolite concretes

Abstract

The continued need of reducing greenhouse gas emissions is the main motivator for the research related to the design of new cement-based composite materials. A sustainability indicator used in this study is a suitable tool to compare a group of concrete mixes based on their mechanical and degradation properties, together with information on the production and environmental value of each raw material. The study shows the results of the analysis of two groups of concretes with the replacement of the aggregate by zeolite. Experimental data were taken from a published study and numerical evaluations were made. The two groups differ in the value of the water-cement ratio, 0.44 and 0.40 respectively. The other additional cementitious materials (SCMs) used were volcanic pumice, ground granulated blast furnace slag grades 100 and 120, silica fume and metakaolin. The results of six and sixteen concrete mixes incorporating reference concrete made of Portland cement are compared. Compressive strength and diffusion coefficient results were obtained at 28, 56, and 91 days after concreting. The values of the sustainability indicator are determined in these times and ultimately allow the sorting of all the analyzed mixes. The results show that the use of zeolite alone in concrete is not always advantageous but rather depends on the specific w/c. Among many other interesting results, one of the most important is the sustainability index value (1.99) for concrete combining 15% of zeolite and 35% ground granulated blast furnace slag of grade 120, so almost twice as good as the reference concrete. Among concretes with only zeolite as SCM, 35% of the replacement is the most suitable choice. Furthermore, the combination with other SCMs can produce a significant positive effect in terms of sustainability.