Effect of aggregate properties on the mechanical and absorption characteristics of geopolymer mortar

Various amounts of natural resources are consumed to manufacture ordinary Portland cement which causes considerable environmental problems for its production. A new technological process called geopolymerization provides an innovative solution in this issue. In addition to potentially reducing carbon emissions, geopolymers can be synthesized with many industrial waste products or natural pozzolans such as fly ash, ground granulated blast furnace slag, metakaolin, etc. In the present study, the experimental study was executed to establish the relation between aggregate features and some engineering properties of fly ash based geopolymer mortar. To achieve this goal, two types of sand and four grading of each type of aggregate were used. The geopolymer binder is mixture of alkaline liquids and fly ash. Compressive strength values were in the range of 47.83-40.25 MPa, 44.93-38.09 MPa, and 39.37-28.25 MPa, for crushed limestone, combined sand, and natural sand respectively. In addition, the absorption of geopolymer mortar, made of these mixes, was also studied, using water absorption test and water sorptivity test. The test results indicated that absorption of fly ash based geopolymer mortar was improved by using combined sand aggregate (50% crushed limestone and 50% natural sand) compared to the ones with single aggregate type.