MATURITY FUNCTION TO PREDICT STRENGTH DEVELOPMENT OF MORTARS CONTAINING GROUND GRANULATED BLAST FURNAGE SLAG (GGBS) CURED AT DIFFERENT TEMPERATURES
Abstract
The accuracy of concrete strength prediction in structural element is very important. It can enable engineers to take a decision for accelerating schedule of constructions. The existing maturity functions were validated only to concrete with Portland cement only, while the use of ground granulated blast furnace slag (ggbs) in concrete construction is increasing. The strength development of equivalent mortars of C45, which had target mean strength of 55 N/mm2 were investigated. The mortars contained ground granulated blast furnace slag with varying levels of replacement (0, 20, 35, 50 and 70%), where 0% ggbs means mortar with Portland cement only. The mortars cast into 50 mm cube moulds, wrapped and cured them at different temperature i.e. at 10, 20, 30, 40, 50 0C and adiabatic curing temperature. The results of all mortars show that mortars at higher curing temperatures gain strength more rapidly at early age, however they have a lower calculated strength ultimate. Three cubes represented each mix and curing temperature was tested at age 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256 and 365 days. Apparent activation energies were calculated referring to ASTM C1074 and were seemed likely linearly to with ggbs level and water binder ratios have little even no effect on the apparent activation energy. The maturity of each mortar at different curing temperature was calculated to obtain the equivalent age at reference curing temperature (20 0C) with the same maturity. The predicted strengths development at other curing temperatures was determined using maturity function and compared them to the experimental results. The results showed that the existing maturity function i.e. Nurse-Saul and Freiesleben Hansen and Pedersen methods gave good prediction at early age only but it lead to wrong prediction at later ages.