Modified lime binder with gypsum and metakaolin

Lime is used as a building material for thousands of years. Nowadays, due to its low mechanical strength and low resistance to weather conditions it is reduced or even discontinued its use in the construction industry. This natural building material has a positive effect on the microclimate inside buildings, and through alkaline nature, prevents the formation of mold. The use of lime as a replacement for traditional materials, like cement will bring not only environmental but also economic benefits.
This paper describes the own study of basic physical and mechanical properties of modified lime binder. In order to improve the unfavorable performance of lime binder it was modified by variable quantity of gypsum in an amount of 10%, 15%, 20% by mass, and different water content by ratio water/binder 0.65, 0.7, 0.75 for a mixture which contains 15% of gypsum. In all formulations a constant amount of metakaolinite equal to 10% by weight of the binder was used. In the studies, after 7 days of maturation, a flexural and compressive strength test were performed. Also the density, porosity and water absorption of binder were examined. With an increase in the content of gypsum was an increase of strength parameters and a decrease in water absorption with minor changes in porosity. Much bigger differences were observed after the modification of water/binder ratio – with its decline the strength increased and the water absorption and porosity decreased.