Physical and mechanical properties of volcanic tuff based alkali-activated binders

In recent 50 years, CO2 amount releasing to atmosphere have remarkably increased by the development of technology and industrialization. Emissions caused by the production of indispensable materials for construction sector suc as cement, brick, tile and ceramic have an important role on this increment. For instance, cement production is responsable for the 8% CO2 emissions of the world. Therefore, researchers have tried to develop new binding materials similar with the Portland cement which are environmental-friendly, cost effective and with lower CO2 emission by using alkali-activation method. In this study, grinded tuffs with different properties from Bayburt region were mixed with NaOH+Na2SiO3 and Ca(OH)2+Na2SiO3 separately in specific ratios, and alkali-activated pastes were prepared. Moreover, grinded marble waste was added to some mixes in order to enhance compressive strength. Initially and final setting time tests according to the TS EN 196-3, flow table test according to the ASTM C230 and relative consistency measurement were performed on fresh pastes. Compressive strength tests according to ASTM C109 and water absorbtion test at the age of 2nd, 28th and 90th days were performed on hardened alkali-activated pastes as well. In addition to these, SEM+EDS and XRD analysis were applied on hardened pastes at the age of 90th day. As a result of the study, solution/dust ratio, NaOH/Na2SiO3 ratio, solution temperature and NaOH molarity effect to the tests results significantly. Compressive strengths of some pastes decreased between 2nd and 28th days. Compressive strengths of most alkali-activated pastes are measured between 10 MPa to 38 MPa at the age of 90th day. Maximum compressive strength was measured 37,8 MPa on a group of paste which contained 100% Bayburt green tuff and NaOH+Na2SiO3 activator at the age of 90th day. Maximum compressive strength was measured 19,7 MPa on a group of paste which produced with 100% Bayburt white tuff and Ca(OH)2+Na2SiO3 activator at the age of 90th day.