T. H. McNEILLY
Mortar batching often follows Vitruvius’ rule, one part of cement and/or binder to three of sand, but poor practices too often result in weak mortar. The Australian mortar mixer’s capacity is three times the volume of a bag of cement or lime and accurate batching should result from a full bag in a full mixer.
However, the required cement could only fit if it filled all of the spaces in the sand. The author believed this to be so, but his experiment shows he is wrong. It also shows that the volume of mortar is not the sum of the volumes of its parts. The described measurements are not accurate enough to determine the actual mix volume, but indicate this as worth study to devise accurate site-batching.
Vitruvius’ three to one rule uses lime putty, but current practice uses powder, resulting in mortar containing more cement or binder than Vitruvius envisaged. Would mortar be adequate if its cement/binder content was based on paste?