Ceramics-Silikáty 59 (2) 81-89 (2015)

CHARACTERISTICS AND DURABILITY OF ALKALI ACTIVATED SLAG-MICROSILICA PASTES SUBJECTED TO SULPHATE AND CHLORIDE IONS ATTACK

This research aims to produce cementless eco-friendly binding material using alkaline activation of blast-furnace slag (GBFS) and microsilica (MS). The preparation of cementless binding material was conducted with different GBFS-MS mass ratios (100:0; 98:2; 96:4; 92:8) with 0.75:0.50; Na₂O:SiO₂ mol kg^-1 of GBFS-MS. The characteristics and durability of alkali activated GBFS and MS mixes were studied. Chemically combined water, combined slag contents as well as compressive strength increase with MS up to 4 mass %, then decreases with MS up to 8 mass %. Increase of MS content up to 8 mass %, the compressive strength shows a lower values at early ages (3-14 days). But, at later age up to 28-90 days, the compressive strength values increase. SEM micrographs show the presence of C–S–H and (N,C)–A–S–H gel with low porosity. The alkali activated GBFS-MS pastes are more durable in 5 % MgSO4 or 5 % MgCl₂ solution than ordinary Portland cement (OPC) up to 180 days.

Keywords: Alkaline activation, Mechanical properties, Electrical conductivity, Thermogravimetric analysis (TGA), Electron microscopy (SEM)