Concrete block construction has gained importance and has become a valid alternative to fired clay bricks. The essential ingredients of concrete are cement, aggregate (sand, gravel) and water. Concrete blocks are produced in a large variety of shapes and sizes. They can be produced manually or with the help of machines.
Ever wondered why there is a hole in concrete blocks?
There are two categories of concrete blocks:
-The solid and
-The Hollow
Solid blocks have no cavities, or- according to US standards- have no voids amounting to not more than 25% of the gross cross-sectional area. The Hollow blocks are the most common type of concrete blocks, having one or more holes that are open at both sides. The total void area can amount to 50% of the gross cross-sectional area.
The openings in a block are called “cells”.
The one reason they are there is to make the blocks lighter and easier for a mason to handle. Also the primary purpose of the cells is that they align from top to bottom of the wall when laid, and enable a builder to fill some cells with grout/concrete in order to strengthen the wall. This is often done at sides of a larger window, door openings, and vertical steel reinforcing bars are added. This detail is especially important in storm and hurricane-prone areas of South Florida that are designated by the Florida Building Code (FBC) as within the High Velocity Hurricane Zone (HVHZ).
There are different types and sizes of concrete blocks. Here are some of their specifications:
Six-inch Blocks
A 6 x 8 x 8-inch sash block has a single rectangular core measuring 35/8 inches wide by 4 7/8 inches. The corners of a 6 x 8 x 8-inch sash block are rounded at a 5/8-inch radius. A 6 x 8 x 14-inch concrete pier block has two cores, both measuring 3 5/8 inches wide by 5 5/16 inches long. The two hollow cores on a 6 x 8 x 16-inch pier block are 7 5/16 inches long and identical in width to the cores on a 6 x 8 x 14-inch block.
Eight-inch Blocks
An 8 x 4 x 16-inch double stretcher block has two hollow cores measuring 5 1/8 inches wide by 5 9/16 inches long. The two large hollow cores on an 8 x 4 inch x 16-inch split pier block both measure 5 1/8 inches wide by 5 3/8 inches long. The 8-inch pier blocks also have a small central core measuring 5 1/8 inches long by 3/8 inches wide. An 8-inch square sash block has a single, slightly offset hollow core measuring 4 3/8 x 5 1/8-inch long; 8 x 8 x 12-inch hollow blocks have two cores measuring 4 1/16 inch wide by 5 1//8 inches long.
Ten-inch Blocks
A 10 x 8 x 16-inch pier block has two equal cores measuring 6 1/16 inches wide by 7 1/8 inches long. The two cores in a 10 x 8 x 16-inch “L” corner block measure 5 1/8 inches wide by 5 11/16 long. A 10 x 8 x 16-inch sash block has three total cores. The small central core measures 38 inches wide by 7 1/8 inch long while the two larger outer cores measure 4 5/8 inches wide by 7 1/8 inches long.
Twelve-inch Blocks
A 12 x 12 x 8-inch sash block has a single, slightly offset core measuring 4 4/16 inches wide by 8 5/8 inches long. In addition to the hollow core, a 12-inch sash block also has a 3/4 inch square notch running up the entire height of a long-sided face. The notch is located 7 7/16 inches from the left side of the block. A 12 x 8 x 12-inch pier block has two equal hollow cores measuring 7 3/4 inches wide by 8 5/8 inches long.
All Concrete block, when built with integral steel reinforcing or in tandem with concrete columns and tie beams and reinforced with rebar, 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. Other common uses for concrete block wall is interior fire-rated partition walls, and exterior backup wall for attachment of building envelope systems and façades.
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