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Masonry grout is a cementitious mixture used to fill
cores or cavities in masonry construction. While usually added for
structural reasons, grout can also increase: fire ratings, security,
acoustical performance, termite resistance, blast resistance, thermal
storage capacity and anchorage capabilities. Grout is composed of cement,
aggregate, lime (optional) and sufficient water to allow ease of placement
and ensure complete filling of the grout space. With approval, admixtures
may be added to the grout mix. The high initial water content of typical
grout mixes compensates for water absorption by the masonry during and
after grout placement. The final water-to-cement ratio is significantly
reduced, thus grout develops high compressive strength despite its
apparent high initial water to cement ratio.
Generally, grout is used to structurally bond wall
elements into a wall system. The most common example is in reinforced
construction, where grout bonds the steel reinforcing bars to the masonry,
allowing them to act as one system in resisting loads. Composite walls
consist of two wythes of masonry with a solidly grouted collar joint with
or without reinforcing steel.
Grouted cores also increase the net cross-sectional
area of concrete masonry and permit walls to carry higher compressive,
shear loads and lateral loads. Masonry cantilever retaining walls are
often solidly grouted to increase the wall’s weight, and hence resistance
to overturning. Grouted masonry construction is not required to be
reinforced, but typically is for design economy. Reinforced masonry
construction, however, requires grout to be placed around the
reinforcement.
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