Evolution of alkaline activated ground blast furnace slag-ultrafine palm oil fuel ash based concrete

The two locally available pozzolanic solid wastes (PMs) - ultrafine palm oil fuel ash (UPOFA) and ground blast furnace slag (GBFS) - have been used as base materials to develop high alkaline activated strength concrete. The samples were prepared with combined aggregate modulus of 3.66 and at constant GBFS/PM that varied from 0 to 0.3. The combined alkaline activators (CAA) (Na2SiO3 and NaOH) to PMs ratios (CAA/PMs), temperature and curing durations also varied as 0.45-0.55, 25-90 degrees C, and 6-24 h, respectively. The findings revealed that the strength at 3-day and 28-day were 69.13 and 71.2 MPa, respectively and the respective optimum GBFS/PM, CAA/PM, temperature and curing duration are 0.2, 0.5, 60 degrees C and 24 h. GBFS was found to contribute to the soluble Ca, heterogeneity, and amorphousity of the product. This eventually facilitated the formation of suspected calcium-silicate-hydrate and the geopolymer products of Ca/Na-aluminosilicate-hydrate (C/NASH) that enhanced the compressive-strength results. (C) 2013 Elsevier Ltd. All rights reserved.