Scientists use compression and flexural mechanical strength tests to determine the strength of concrete. The strength of concrete depends to a large degree on the water-cement ratio, and the quality of the aggregates and paste in the cement.
Basic Concrete FAQs
- How is the strength of concrete measured?
- Are there quality standards for concrete?
Yes. Concrete must comply with local building codes, ACI, and ASTM.
- What is the difference between cement and concrete?
It’s simple. Concrete is used for the finished products, such as sidewalks, foundations, and the surface of many roads. Concrete contains sand, gravel and cement. Cement is the special hardening ingredient (the gray powder) that makes concrete harden. Cement is usually made of 60% lime (limestone), 25% silica, 5% alumina, and 10% other materials, such as gypsum and iron oxide.
- How is concrete measured?
Concrete is measured by the cubic yard – measuring three feet by three feet by three feet, or 27 cubic feet. One cubic yard of normal concrete will weigh about 4,000 pounds
- Does concrete gain strength by drying out?
No. Concrete is made by mixing cement, aggregates and water together. When the water comes in contact with the cement a chemical reaction starts to take place. This chemical reaction is called hydration. Hydration is the reaction between the chemicals in water and the chemicals in cement. This reaction forms new compounds and crystals interlocking themselves and the aggregates together. A majority of this reaction takes place over the first month after placing the concrete. Small amounts of additional reaction and strength gains could take place for years as long as moisture is still present to cause more hydration. Actually, when the concrete does finally dry out, it stops gaining strength.