Setting time is important in paving activities because it influences the interval of time before finishing and joint sawing activities can be carried out. The cements obtained by mixing clinker, gypsum and fly ash present more important extension of setting time than the cement containing only limestone or the joint addition of fly ash and limestone.

The delay in the time of setting can be attributed to the dilution effects resulting from clinker replacement, or to the change of the paste rheology, which can be affected by the existence of elementary carbon. (I. Elkhadiria. et al). Batch intergrinding cement with 0, 3, 5.5, and 8% limestone to constant specific surface showed little effect on setting time, while grinding the cement to constant residue on a 325-mesh resulted in a reduction of setting time (Hawkins, 2003).


The setting time is much influenced by the degree of fineness of additions which is appeared to be advantageous for the decrease of both initial and final setting time of blended mixtures. It can be noted that the setting time increases with higher dosages of slag and limestone amounts, this can be explained by the low activity of additions, as the increase in surface area (3500, 5000 and 11000 cm²/g) influences positively the time of setting so the amount of water used increases to obtain a cement with normal consistence (Z. Leila et. al).

            Both initial and final setting time of Portland limestone cement pastes were decreased with an increasing of limestone content at the same fineness.  At the same level replacement, the cement pastes using small-sized limestone show lower setting time than those using large-sized limestone (P. Thongsanitgarn1. et. al).

            A study on the potential of using bottom ash as pozzolanic material was done. The quality was improved by grinding until the particle size retained on sieve 325 mm was less than 5% by weight. The results showed that pastes of cement with replacement by original or ground bottom ash, between 10-30% resulted in longer initial setting time, depending on the fineness of the ashes, compared to setting time of the cement paste. Original bottom ash mortar had higher water requirement than that of the cement mortar and ground bottom ash mortar had lesser water requirement than that of the cement mortar. Bottom ash could be used as a pozzolanic material if it was ground having retention on 325-micron sieve less than 5%, (P. Aggarwal et. al).

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