A comparative study of two methods to produce geopolymer composites from volcanic scoria and the role of structural water contained in the volcanic scoria on its reactivity

Volcanic scoria (Z(G), Z(K)) and kaolin (MY38) were applied for producing geopolymer mortars using two methods such as fusion and conventional methods. Kaolin was transformed (700 degrees C, 1 degrees/min, 4 h) into metakaolin and used to consume the excess alkali needed for the fusion and also to increase the amount of amorphous phase in volcanic scoria. In order to investigate the effect of structural water contained in volcanic scoria on their reactivity, only volcanic scoria were used to produce geopolymer pastes using conventional method. X-ray pattern of volcanic scoria Z(G) shows the presence of muscovite and TG curves indicate that Z(G) and Z(K) content approximately 6 wt% and 0 wt% of water respectively. Geopolymer pastes from Z(K) (Z(K)G) obtained only with volcanic scoria were handled easily after 7 days at ambient temperature. Whereas geopolymer pastes from Z(G) (Z(G)G) at the same curing condition were handled after 24 h. The compressive strength of GZ(K) (geopolymer mortars from Z(K) using conventional method), GfZ(K) (geopolymer mortars from Z(K) using fusion method), (G)Z(G) (geopolymer mortars from Z(G) using conventional method), GfZ(G) (geopolymer mortars from Z(G) using fusion method), Z(G)G and Z(K)G are 25, 15, 39, 17, 33 and 10 MPa respectively. It can be concluded that the conventional method is a good process to synthesize geopolymers using volcanic scoria. The structural water from muscovite (clayey mineral) influences positively the properties of volcanic scoria based-geopolymers. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.