Concrete FAQ’s
Q. What is the difference between cement and concrete?
A.While the terms are sometimes used interchangeably, concrete and cement are not the same. Cement, a fine gray powder, is a key ingredient in concrete production. Cement typically comprises 10 to 12 percent of the entire mix. When cement is mixed with water, sand, and gravel, it turns into concrete—the rock-like substance associated with sidewalks, roadways, bridges, building foundations, and more.
Q. What are the main ingredients of concrete?
A. Concrete has four main ingredients:
- Portland Cement
- Water
- Sand (also known as Fine Aggregates)
- Stones (also known as Coarse Aggregates).
Additional materials or chemicals may be added to the concrete to help it achieve certain performance characteristics.
Q. How strong is concrete?
A. Concrete is very strong if you push on it, known as compression. Concrete is much less strong if you pull on it, known as tension. Concrete’s strength in tension is only about one-tenth of its strength in compression.
Q. What is reinforcement and why is it used?
A. As previously described, concrete is very strong in compression (pushing) but is relatively weak in tension (pulling). Because of this, reinforcement is used in any area of the concrete member where tension (pulling) exists. The bond between the concrete and the reinforcement allows the two materials to work as one unit. This is similar to your arm being composed of muscle and bones. They work together, with the bones in compression and the contracting muscle in tension, to raise your arm - acting as one unit.
Reinforcement may be made out of steel or fiber-reinforced polymers (FRP). The reinforcement is very strong in tension.
Reinforcement is comprised of bar (or “rebar”), wire, welded wire, strands, fibers, and thin sheets. The most common forms of reinforcement are reinforcing bar (“rebar”), wire, welded wire, and strand.Rebar is typically round and comes in diameters ranging from 3/8-in to over 1 in. Wire can be produced to any diameter ranging from 0.135-in to 5/8-in, and resembles a grid or mat when it is manufactured as welded wire reinforcement. Strand is six wires helically wound around a seventh center wire. These types of reinforcement are all typically placed inside of the concrete.
Other types of reinforcement are fibers as well as thin sheets. The fibers are dispersed throughout the inside of the concrete and may be constructed of steel, micro-synthetic, macro-synthetic, glass, or poly-vinyl alcohol (PVA). The FRP sheets are typically used to wrap around the outside of an existing piece of damaged concrete to repair it and make it stronger.
Q. Where is concrete used?
A. Concrete is the second most abundant material on earth. It is used in streets and highways, parking lots and garages, buildings, bridges, tunnels, dams, airport runways, pipes, transit facilities, the foundations for most every building in the modern world, wall assemblies for exterior and interior walls, and floors for manufacturing and warehousing,
Q. What makes concrete so durable?
A. Three of the primary ingredients of concrete (sand, stones, and cement) are mineral based. When mixed with water, the cement molecules chemically react with the water to create a crystalline matrix of high compressive strength. This matrix binds the sand and stones together, creating what is sometimes known as “liquid stone.” Unlike other construction materials, which can rust or rot, moisture is a necessary component in making concrete.
Q. How do concrete structures provide resilience?
A. Concrete’s combination of stiffness, strength, mass and non-combustible nature offer unmatchedlevel of safety and protection from fire; from natural disasters such as tornadoes, hurricanes, earthquakes and flooding; and from man-made disasters such as blasts. Communities rely on concrete structures to provide operational continuity for emergency responders, government and community services in the face of disaster.
Q. How does concrete effect the environment compared to wood and steel?
A. Concrete is one of the most inert building materials in use today. It does not rot, burn, or rust, providing durability that significantly outlasts many other building materials including wood and steel. The cement industry utilizes industrial byproducts like fly ash and consumes less energy than its competitors. According to the U.S. Department of Energy, U.S. cement production accounts for 0.33 percent of energy consumption—lower production levels than steel production at 1.8 percent and wood production at 0.5 percent. In addition, it places less stress on our environment to acquire the raw materials for concrete than steel or wood. This, concrete is an excellent choice for sustainable development.