Compressive And Flexural Strength of Non- Hydraulic Lime Mortar with Metakaolin Pozzolan

Mortar for masonry is important because it provides the linkage between masonry units so enabling the composite to behave as a single material. The type of mortar used determines the flexural and compressive strength of the masonry. Nowadays most mortars used in construction are cement based. However, due to the heavy energy-intensive processes that are involved in its production the cement industry is responsible for up to 10% of global CO2 emissions; therefore, there are serious environmental implications with the usage and application of cement mortars. A sustainable alternative are lime mortars which have 30% less embodied CO2. Lime mortars confer benefits in comparison to cement based mortars such as accommodating a greater degree of wall movement and improved damp resistance. The main disadvantage with lime mortars is the longer setting time which can take up to 91 days in addition to the low strength. A way to overcome this is to add cement replacements e.g pozzolans. This paper investigates the properties of non-hydraulic (lime putty) lime mortar containing metakaolin (MK). Findings show a minimal amount of MK addition of 2% increases the mortar strength to 2 MPa within 28 days with an eventual strength of over 17 MPa achieved with 10% MK. Strengths satisfying minimum requirements for all four mortar designations were achieved with between 2-8% MK addition, mostly within 28 days ageing. Therefore, non-hydraulic lime mortars with MK offer a more sustainable alternative to cement based mortars without compromising setting time or strength whilst offering improved flexibility and breathability.