Eleni Aggelakopoulou

The effects of limestone characteristics and calcination temperature to the reactivity of the quicklime

Abstract This study has examined the effects of limestone characteristics (microstructure and texture) and calcination temperature on the reactivity of the produced quicklime. Two types of limestone have been calcined at four selected temperatures (900°C, 1000°C, 1100°C, 1200°C), and the produced quicklime was slaked. Chemical, physical, and mineralogical analyses have been performed in limestone, quicklime, and slaked lime samples with the intention of studying the quicklime reactivity. Test results indicate that the lower the limestone calcination temperature, the more reactive the produced quicklime. The optimum calcination temperature is ∼900°C, which was the temperature performed in traditional limekilns. Concerning the quicklime, the reactivity is related to its microstructure, which is, in turn, related to microstructural characteristics of the limestone (texture, grain size, porosity). The most reliable factors for the estimation of quicklime reactivity are the specific surface area of the quicklime and the rate of temperature increase during the slaking process.

Compatible Mortars for the Sustainable Conservation of Stone in Masonries

Incompatible restoration mortars used extensively in recent years have inferred irreversible damage to the original building stones of masonries. Recent research has led to the development of compatibility criteria for the restoration mortars in relation to historical materials, through the reverse engineering approach. In the restoration of historical stone masonries, apart from the issue of compatibility which is mainly of a physicochemical nature linked to ensuring breathability and avoiding preferential percolation of salt solutions to the original building stones, the issue of restoration mortars’ mechanical performance is of equal importance to achieve sustainability. An integrated methodological approach is presented aiming to the selection of the optimum compatible and performing restoration mortar for conservation/restoration interventions. The Kaisariani Monastery and the bridge of Plaka in Greece, as well as the Holy Aedicule in Jerusalem, serve as case studies in order to illustrate the methodological approach.

Design and evaluation of restoration mortars for historic masonry using traditional materials and production techniques

Cement based mortars used for historic restoration presented unsatisfactory results, due to their chemical and physico-mechanical incompatibility to original buildings. In the present research, several syntheses of restoration mortars are produced using traditional techniques and materials such as binders (aerial and natural hydraulic lime), pozzolanic additives (natural and artificial pozzolanas) and aggregates (sand and crushed brick). The technical characteristics of the mortars were determined using mechanical tests (compressive and flexural) and mercury intrusion porosimetry measurements at the time of 1, 3, 9, 15 months of curing. Water absorption measurements were performed at the time of 9 and 15 months and the total percentage of absorbed water. The aerial lime – artificial pozzolana mortar presented the best mechanical and microstructural performance. Hydraulic mortars acquired the maximum of the mechanical strength in 1 month, lime-pozzolana mortars in 3 months while aerial lime mortars continue to gain mechanical strength even in 15 months curing. Furthermore, the use of ceramic aggregates produces lightweight and elastic mortars, compatible to historic ones.