Faculty: Rashmin Damle

Impact of mortar/plaster material on the indoor hygrothermal environment of test spaces.

Before the 20th century, lime mortar and lime plaster were widely used in old and historical buildings. In addition to the soothing appearance, it imparts to the building lime plaster has excellent moisture buffering properties. The usage of lime saw a decline when Portland cement was introduced in the 19th century. However, lime has numerous advantages as a binder and finish material. Lime is capable of self-healing by the autogenous process due to evaporation of penetrated water. This is especially needed in the case of old and historic buildings. Previous experimental work with lime and cement cells showed lower temperature and relative humidity in the lime cell. The surface area of mortar in a brick wall is around 20 % in a wall of 1 m2. Also, the mass of mortar is significantly higher for the cement cell. To study the isolated effect of heat gains/losses through cement and lime plaster/mortar, the current work proposes to develop two cells (1m x 1m x1m). Of the six surfaces of the resulting cube, five surfaces will be made-up of insulation sheets only. The sixth surface will made similar to a brick wall with cement and lime mortar but with the difference that the bricks will be replaced by insulation material. Additionally, this surface will be internally finished with lime and cement plaster of 10-15 mm. Thus, we have an insulated box with one face where the main path of transmission of heat and moisture will be through the mortar layers. Environmental variables such as temperature of air, relative humidity and surface temperatures will be measured in the cells. The outdoor conditions will also be monitored. Several tests will be carried out by changing the air change rate and moisture sources in the cells. The difference observed in the thermal environments can then be attributed to the type of mortar and plaster employed.