Inadequacy of Property Specifications in ASTM C 270

Abstract

Bond strength and water leakage were determined for Types M, S, and N mortars joined to six different brick types. The air content, water retention, and flow rate were varied for each mortar-brick combination. It was found that air content, water retention, and compressive strength were inadequate indices of bond strength and water leakage. Yet these are the only properties specified in ASTM Specification for Mortar for Unit Masonry (C 270-84). A plea is made to add a bond strength requirement to present property requirements. The initial rate of absorption (IRA) of brick was found to be significant in predicting water leakage. Low IRA brick provided the highest probability of zero leakage.

The Study of the Factors Effecting Bond Strength of Masonry

“…The mortar with a better workability can effectively improve the interface characters between units and mortars to enhance bond strength. It is hard to ensure uniform of mortar layers if water-cement ratios too lower, however, the mortar layer is too thin if it is too high [11] . Those two conditions can conduct a negative influence on bond strength.…”