Characterisation and mix specification of commonly used masonry mortars

The proper selection and execution of mortar are imperative processes in the masonry construction. While there are different mortar designations available in standards; except their compressive strengths, the detail characteristics are seldom stated. The standards mainly outline mortar mix in volume proportion without any specification on consistency limits and water to cement ratio (w/c). This leads to inconsistency in mortar mix preparation and properties in real practice. Thus an extensive experimental investigation was carried out to identify suitable consistency and w/c limits of five commonly used masonry mortars to detail the mortar mix specification. The research was divided into three phases. The properties of mortar constitutive materials were characterised in the first phase of the research. In the second phase, the fresh properties such as bulk density, air content, and consistency were measured for those mortars with possible two different w/c ratios. Then dry density, water absorption, sorptivity, porosity, compressive strength, flexural strength and shrinkage were determined for hardened mortars. Further the mortars were casted in non-absorbent and absorbent moulds to compare the influence of casting conditions on the hardened properties. Thereafter the third phase of experimental testing was carried out to determine the suitable consistency and w/c ratio thresholds for those masonry mortars. Finally from the results, detail specification of those masonry mortars in terms of w/c, consistency and target compressive strength is recommended.