Investigation of the use of ground raw vermiculite as a supplementary cement materials in self-compacting mortars: Comparison with class C fly ash

Abstract

A significant part of the global CO2 emission comes from the production of Ordinary Portland Cement (OPC). Supplementary cement materials (fly ash, silica fume, blast furnace slag, natural pozzolans, etc.) have been used in concrete and mortar production for decades. Due to the limited resources of these supplementary cementitious materials, there was no significant reduction in CO2 emissions. Therefore, the search for new materials and methods continues. In recent years, the use of clay types such as kaolin, metakaolin and bentonite in mortar has become widespread. However, no information has been found in the literature regarding the use of finely ground raw vermiculite as a supplementary cement material. In this study, the effects of ground raw vermiculite (RV) replaced for cement on self-compacting mortar (SCM) were investigated. In this context, 5%, 10%, 15% and 20% ground RV was used in SCM mixtures. SCM mixes was tested for fresh concrete such as slump-flowing and V-funnel times. The pozzolanic activity of fly ash and ground raw vermiculite have been using the strength activity index test. Prism specimens of 40 × 40 × 160 mm3 were produced in order to determine their mechanical properties. These samples were subjected to the flexural strength test at the end of 7, 28 and 90 days and the compressive strength test was performed on the parts obtained from the flexural test. In addition, the durability properties of SCM mixes such as capillary water absorption, sorptivity and porosity were determined. The fresh concrete, mechanical and durability results of RV replacement mortars were compared with Class C fly ash (FA), which is commonly used in SCM mixtures. The results showed that the presence of 5% RV gives the highest compressive strength value at all ages. The presence of 5% and 10% RV improved the 90 days compressive strength value by 3.68% and 2.91%, respectively, compared to the FA substituted series at the same rate. The lowest sorptivity coefficient of 90 days was calculated in the RV5 series with 0.037 mm/min1/2. The results showed that the presence of ground RV in the range of 10–15% in SCM mixtures did not adversely affect the mechanical and durability properties of the mixtures. However, 20% RV use negatively affected the properties of SCM.