Chiang Mai Journal of Science

 This research studies the interfacial transition zones (ITZ) of pervious geopolymer concrete and pervious cement concrete containing recycled coarse aggregate from crushed broken clay brick (RCB). Geopolymer and cement pastes were used as binder. Geopolymer was synthesized using fly ash, sodium hydroxide solution and sodium silicate. Physical observation, optical microscope (OM) and SEM, EDS techniques were used to characterize ITZ of both pervious concretes. XRD technique also used to characterize the crystalline phases of geopolymer pastes and cement paste. In addition, the compressive strength of geopolymer pastes, cement paste, pervious geopolymer concrete, and cement pervious concrete were also determined at the age of 7 days. The results showed that the ITZ of pervious geopolymer concrete and pervious cement concrete were totally different in shape. The ITZ of pervious cement concrete was wider than those of geopolymer system. It was also found that geopolymerization reaction occurred rapidly when fly ash was mixed with alkali activated solutions and it might not contribute to the network in ITZ while hydration reaction from cement paste and water had Ca(OH)₂ which had an opportunity to coat around the aggregates. Although cement paste presented the highest compressive strength as a binder, the compressive strength of cement pervious concrete was lower than those of geopolymer pervious concrete.