Effects of natural zeolite on mechanical properties and durability indexes of concrete

Abstract

This study evaluated the effects of a locally available natural zeolite (NZ), on properties of concrete. To the best knowledge of the authors, this paper is the first study wherein NZ concrete has been evaluated using durability index methods. The NZ studied is presently not used as pozzolan in the local cement industry, hence its potential use in concrete would be new. In the investigation, concrete mixtures of 0.50 and 0.70 water/cementitious ratios were prepared using CEM I 52.5R cement type blended with 0, 10, 20 and 30% NZ. Performance characteristics of NZ were compared with those of 20% or 30% fly ash (FA), which is a conventional pozzolan. The mechanical properties measured were strength development, workability and setting time. Durability properties including carbonation and a consortium of indexes comprising oxygen permeability index, water sorptivity index and chloride conductivity index were also tested. Interestingly, NZ concretes exhibited good or excellent durability index values and lower carbonation results, relative to those of the corresponding FA concretes. In fact, adding 20% NZ into concrete mixtures gave optimal performance, including significant reduction of carbonation, which is a unique beneficial effect as pozzolans typically increase carbonation.