Concrete blocks and cement blocks are preformed, manufactured concrete structures that are ready for on-site installation. They are manufactured, cast, and cured in factories or other production facilities. Most concrete blocks and cement blocks are designed to meet specific requirements for dimensions, durability, and weather resistance. Concrete blocks and cement blocks are produced in several different ways. The traditional flat panel formation method uses a wet or semi-dry concrete mix. The mold method pours wet cement into a pre-formed mold. After compaction and drying, the finished product can be transported to the worksite for installation. To achieve the product standards require for more demanding applications, suppliers of concrete blocks and cement blocks may also use hot concrete, pre-tensioning, or hardening techniques.
Concrete blocks and cement blocks may be either hollow or porous. They also differ in terms of dimensional, thermal, mechanical, and physical specifications. Hollow blocks are supplied with an open internal bore. Porous blocks have a large degree of open or closed internal pores that provide a thermal barrier. Dimensional parameters for concrete blocks and cement blocks include length, width or outer diameter (OD), and thickness or wall thickness. Maximum use temperature is the most important thermal specification to consider. Mechanical and physical parameters include modulus of rupture (MOR), the maximum flexural stress a product can withstand before failure or fracture occurs. Crushing or compressive strength is also important to consider when selecting concrete blocks and cement blocks.
Cement type determines the bond or processing features for concrete blocks and cement blocks. Choices include calcium aluminate, carbon, Portland cement, phosphate, and slag cement bonds. Blocks with sulfate, sulfur and polymer bonds are also available. Portland cement may be modified with polymer additions to improve plasticity or water resistance, or to allow for use during cold weather conditions. Other cement types for concrete blocks and cement blocks include acrylate, epoxy, polyurethane, vinyl ester, and polyester.
Concrete blocks and cement blocks are used in a variety of applications. Some products are used as in-ground shelters. Others are used as distribution transformer pads. Many concrete blocks and cement blocks are designed for road construction and civil engineering applications. Examples include a highway barrier, bridge abutment system, bridge girder, and light pole. Building and construction products include masonry units, floors, beams, and columns. A pull box can be used in electrical applications. A chlorine tank can be used in industrial applications. Concrete blocks and cement blocks that are designed for agricultural applications include flood control products such as a catch basin and box culvert.
Concrete blocks and cement blocks meet standards published by organizations such as the American Concrete Institute (ACI) and the American Society for Testing and Materials (ASTM). The National Precast Concrete Association (NPCA) also provides voluntary factory certification programs. These programs are designed to improve quality control and ensure product consistency. Compared to other building materials, concrete blocks and cement blocks are both cost-effective and versatile in terms of colors, dimensions and finishes.