Blocks

Blocks

Concrete Masonry Unit (CMU) , also called concrete block, cement block, and foundation block – is a large rectangular brick used in construction.

Concrete blocks are made from cast concrete, i.e. Portland cement and aggregate, usually sandand fine gravel for high-density blocks. 

Lower density blocks may use industrial wastes as an aggregate. 

Blocks can be laid more quickly than bricks because they are larger than bricks. However, the larger sizes also means that less versatility in laying especially when building up ends or corners and also laying to curves.

Uses of Blocks

When built in tandem with concrete columns and tie beams and reinforced with rebar, block is a very common building material for the load-bearing walls of buildings, in what is termed "concrete block structure" (CBS) construction. 

American suburban houses typically employ a concrete foundation and slab with a concrete block wall on the perimeter. Large buildings typically use copious amounts of concrete block; for even larger buildings, concrete block supplements steel I-beams. Tilt-wall construction, however, is replacing CBS for some large structures. 

Sizes and Structures

Concrete blocks may be produced with hollow centres to reduce weight or improve insulation. The use of blockwork allows structures to be built in the traditional masonry style with layers (or courses) of staggered blocks. 

Blocks come in many sizes. 

In the US, with an R-Value of 1.11 the most common nominal size is 16×8×8 in (410×200×200 mm); the actual size is usually about ³⁄₈ in (9.5 mm) smaller to allow for mortar joints. 

In Ireland and the UK, blocks are usually 440×215×100 mm (17×8.5×3.9 in) excluding mortar joints. 

In New Zealand, blocks are usually 390×190×190 mm (15×7.5×7.5 in) excluding mortar joints.