Effect of free lime content on properties of cement-fly ash mixtures

► The free lime particles have irregular shape and are distributed outside the fly ash particles. ► Higher free lime in fly ash leads to early setting and higher compressive strength especially at early age. ► The autoclave expansion and the expansion due to alkali-aggregate reaction increases as free lime in fly ash increases. ► Carbonation depth, chloride and sulfate resistances are only slightly affected by the content of free lime in fly ash. ► It is possible to utilize the tested fly ash with free lime content up to 4.51% as mineral admixture in concrete.