Itis desirable that the workability of mortar be such that it spreadsand adheres well with the masonry unit. The water cement ratios andthe composition of the mortar mix are the chief factors thatinfluence the workability of the mortar.
Inthe initial state of a mortar, too much water than necessary thannecessary is present to fill the spaces in the loosely packed drymaterial. This can be noticed through simple observation of loosepacked bulk density of the dry material. The hygric properties ofmortar upon compaction is dependent on either the water content orthe void ratio.
Thevolume of mortar changes during application. When the solid skeletonis compacted, the diameter of pores decrease and consequently theliquid potential increases.
Thedynamics of the liquid in the porous material is determined by theabsorption, migration and desorption in the mortar. In theconstruction of a wall, the liquid is desorbed from the mortar andabsorbed by the brick (Azeredo, et al., 1468).
Theusual assumption of constant porosity of brick is not always true forthe zone of interface with mortar. The binder particles and finesfrom sand migrate into the brick. This causes a localized decrease inporosity.
Fromthe experimental results, an increase in the amount of water causesan increase in the dragging force of water. The outcome is anincrease in the displacement of mortar. This implies that the flow ofmortar increases correspondingly to its water content. The higher thewater content of mortar the more easily it can flow. In other words,it is more workable and ca adhere more readily to masonry units.
Theability to absorb water is affected by the composition of the mortar.
Azeredo,G., Morel, J., and Lamarque, C. (2008). Applicability of Rheometersto characterizing Earth Mortar Behavior. Part i: experimental deviceand validation. Materials and structures, 41:1465–1472.