Microstructure of 2 and 28-day cured Portland limestone cement pastes

In this study, microstructures of limestone cement pastes cured for 2 and 28 days are investigated. For this purpose, limestone and clinker are separately ground in a ball-mill until obtained a given constant 32 pm sieve residue. The gypsum is kept constant as 5% by weight of cement. Cement pastes with 0.5 water/binder ratios and 0, 6, 35% limestone/clinker ratios are prepared. After 2 and 28 days standard curing, ESEM investigations are carried out on these specimens. It is found that hydration products are accumulated around limestone particles. In 2 days, compared to the control specimen, pore percentages of cements containing 6% limestone are decreased whereas pore percentages of cement pastes containing 35% limestone are increased. The difference between porosities of the control paste and limestone cement paste is decreased at 28 days.