Traditional methods of mortar preparation: The hot lime mix method

This paper studies the effect of maturation on mortars prepared according to a traditional method of slaking quicklime mixed with sand and kept wet until used (hot lime mix). Two lime/aggregate weight proportions were considered, a rich one (1:5) and a normal one (1:13). The quicklime was used as pieces of crushed calcined limestone and as micronized quicklime, both from industrial production. The mortars prepared with hot lime were kept wet for periods of 1, 7, 45 and 90 days, before moulding, while those prepared with micronized quicklime were matured for 7, 45 and 90 days. After the specimens were moulded, their mechanical and water-related behaviour was studied at 28, 90 and 360 days. Mercury intrusion porosimetry and SEM observations were performed for some of the mortars to follow the microstructure changes. The aim was to understand the advantages and drawbacks of this traditional process and of a similar process with industrial quicklime. It was concluded that the maturation time has a very positive influence on flexural and compressive strength, cracking susceptibility and water absorption by capillarity. However, the process has also disadvantages, such as time consuming preparation and need of extreme care.