For example, an 8-by-16-inch (200 mm × 410 mm) block may be scored in the middle to simulate 8-by-8-inch (200 mm × 200 mm) masonry, with the grooves filled with mortar and struck to match the true joints. Blocks may be scored by grooves the width of a mortar joint to simulate different block modules. Special textures may be produced by splitting a ribbed or solid two-block unit such factory-produced units are called "split-rib" or "split-face" blocks. Ĭoncrete masonry units may be formulated with special aggregates to produce specific colors or textures for finish use. A wide variety of decorative profiles also exist. Other features, such as radiused corners known as " bullnoses" may be incorporated. Blocks with grooved ends permit the construction of control joints, allowing a filler material to be anchored between the un-mortared block ends. Blocks with a channel on the end, known as "jamb blocks", allow doors to be secured to wall assemblies. U-shaped blocks or knockout blocks with notches to allow the construction of bond beams or lintel assemblies, using horizontal reinforcing grouted into place in the cavity. Ī variety of specialized shapes exist to allow special construction features. Reinforcement is primarily used to impart greater tensile strength to the assembly, improving its ability to resist lateral forces such as wind load and seismic forces. To hold the reinforcement in proper position and to bond the block to the reinforcement, the cores must be filled with grout (concrete). A core also allows for the insertion of steel reinforcement, tying individual blocks together in the assembly, with the goal of greatly increased strength. Most CMU's have two cores, but three- and four-core units are also produced. In Australia, New Zealand and Canada, blocks are usually 390 mm × 190 mm × 190 mm (15.4 in × 7.5 in × 7.5 in) excluding mortar joints.īlock cores are typically tapered so that the top surface of the block (as laid) has a greater surface on which to spread a mortar bed and for easier handling. In the US, the most common nominal size is 16 in × 8 in × 8 in (410 mm × 200 mm × 200 mm) the block measures a ⅜ in shorter, allowing for mortar joints. The use of blockwork allows structures to be built in the traditional masonry style with layers (or courses) of staggered blocks. Lightweight blocks can also be produced using autoclaved aerated concrete.Ĭoncrete blocks may be produced with hollow centers (cores) to reduce weight or improve insulation. Lower density blocks may use industrial wastes, such as fly ash or bottom ash, as an aggregate. Portland cement and aggregate, usually sand and fine gravel, for high-density blocks). A wheelbarrow or other container is often the easiest to supply.Concrete blocks are made from cast concrete (e.g. This should be a contained area that would not allow liquids to seep into surrounding areas. Concrete Washout – You will need to provide a washout area for the truck after it is finished pouring the concrete.
Other Supplies – Do you need aggregate (stone or gravel) for the project? Do you have the concrete tools that you need? Our professional customer service representatives and our Concrete Store Representatives can help you make sure you are prepared, just call 70.Any exterior slab in our climate should have air entrainment. Entrained Air – Entrained air is little bubbles of air primarily to increase the durability of the hardened concrete to freeze-thaw conditions.Any slab exposed to freeze-thaw conditions should be a minimum of 4,000 psi. Strength – Strength is most commonly measured by the designed compressive strength in pounds per square inch (psi) of a hardened cylinder of concrete.This is especially a problem for concrete that might be exposed to freezing and thawing conditions. Adding just 1 gallon of water per cubic yard can decrease compressive strength 150 to 200 psi, waste cement and increase shrinkage by 10%. Adjusting slump at the job site will damage the concrete. If you want more slump, it is always safest for the concrete to adjust slump at the plant. A 4 inch slump (the measure of the distance a wet concrete cone will fall) is typical. Slump – Slump is a measure of the consistency of the concrete.Concrete can be ordered in ½ yard increments. A good rule of thumb is take your calculation and add 4% to 10% to the total to account for waste, spillage, over-excavation, settlement, spreading of forms, loss of entrained air or any other changes in volume. Quantity – Measurements can frequently be a little off, so we highly recommend ordering a little extra, because coming up short can be a disaster.