Cement-free mortar using ground granulated blast-furnace slag with different alkali-activators

Abstract

The present study concerns a development of cement-free concrete using ground granulated blast-furnace slag(GGBS) with alkali-activators such as KOH, NaOH, and Ca(OH)2. To find out the development among three different activators, the concentration of hydroxyl ion was kept 0.5%, 1.0%, 1.5%, 2.0% and 3.0% by weight of binder irrespective of cations.The setting time was measured by penetration resistance immediately after casting of mortar. The development of compressive strength was measured at 7, 14, 28, and 91 days. The pore structure of cement-free mortar was examined by the mercury intrusion porosimetry(MIP) and rapid chloride penetration test(RCPT). Simultaneously, grew sample was used to microscopically observe at the XRD. For strength of cement-free mortar, mixed with KOH or NaOH was as high as OPC at 3.0% by weight of binder. However, the compressive strength of cement-free concrete mixed with 3.0% Ca(OH)2by weight of binder had just half strength of OPC mortar. Cement-free concrete activated with NaOH and Ca(OH)2hadhigher total pore volume, however, it had lower ionic penetrability due to the pore type which mostly consist of gel pores. For pore structure of cement-free mortar mixed with KOH, the total volume had similarity to that of OPC mortar, however, it had lower penetrability. Therefore, it may have higher resistance to chloride transport than that of OPC mortar. © (2014) Trans Tech Publications, Switzerland.