Type S Portland Cement-Lime Mortar as a Low-Lift Grout

Abstract

Abstract Specification for Grout for Masonry, ASTM C 476, allows grouts to be specified by a proportion method using the cementitious materials of portland cement, blended cement, hydrated or putty lime (with a 1/10 by volume limit), and aggregate. There is no limitation on slump values in ASTM but industry standards recommend a slump of 8 to 11 in. (203 to 279 mm). A second method of specifying grout is by its properties with a minimum 28-day compressive strength value of 2000 psi (13 790 kPa). It is not an uncommon practice, however, for masonry contractors to use portland cement-lime mortars in low-lift (less than 5 ft [1.52 m] height) applications at a consistency of bedding mortar or a pourable consistency. According to ASTM C 476, this application would neither meet the proportion specification because of too much lime nor the property specification because of too low a slump. This study, investigating the comparative compressive strength properties and reinforcement pull-out strength of Type S and Type N ASTM C 270 proportioned cement-lime mortars, ASTM C 476 grout, and grout with comparable hydrated lime proportions to a Type S mortar, supports the following conclusions: • Type S portland cement-lime mortar at a bedding mortar consistency will perform as grout in specific low-lift grouting applications. • Type S portland cement-lime mortar at a pourable consistency will perform as grout in specific low-lift grouting applications. • Type M portland cement-lime mortar at a bedding mortar consistency or pourable consistency could also be used as grout in specific low-lift grouting applications.