Kearney Concrete Co. offers this section to inform contractors, homeowners and purchasers on the basic vocabulary of our industry. The following terms and definitions are widely used in our industry and are provided to assist you when you call to order concrete, acquire information on your next project, or have questions about optimizing your concrete mix.
Concrete
We specialize in producing high quality concrete. We will work to ensure the concrete mix design meets the strength, performance, and durability you desire for your project. We strictly adhere to all ACI guidelines and with our chemical admixtures, have the ability to produce high-quality concrete that will meet and exceed your expectations. In general, the basic materials required to produce concrete are cement, aggregate, water, and chemical admixtures.
Aggregate
Broadfoot Sand and Gravel Company supplies us with our 3/8 nominal fine aggregate (Commonly recognized as 47B Fine Aggregate). Depending on your job, different types of fine aggregates are available. In central Nebraska, our concrete gravel is unique because of our specific location along the North Platte River.
Limestone in the form of ¾ nominal White Rock (Commonly recognized as 47B Course Aggregate)is our most popular course aggregate. We do have the ability to attain any type of course aggregate to any project’s unique specifications. Adding ¾ nominal White Rock to your concrete mix design increases the overall durability and performance of your concrete. The use of 47B course aggregate in exterior concrete is recommended for our location.
Water
Water affects the concrete’s consistency and workability. In general, the more water added to your concrete mix design, the concrete’s viscosity increases. However, the downside of adding a lot of water to your concrete mix design increases the water/cement ratio, which affects the concrete’s overall performance. If your project requires the use of high slump concrete (6-8 inch slump), this can be achieved while maintaining specified water/cement ratios.
Water/Cement Ratio
It is the ratio of the weight of water to the weight of cement used in a concrete mix and has an important influence on the quality of concrete produced. A lower water-cement ratio leads to higher strength and durability, but may make the mix more difficult to place. Placement difficulties can be resolved by using plasticizers or super-plasticizers.
Slump
Slump is a measure of concrete consistency or fluidity. For given proportions of cement and aggregates (without admixtures), the higher the slump, the wetter the mix. Four-inch (4”) slump is very common with normal weight concrete and is a good average slump. Above-average slump—due to the addition of water—considerably reduces the strength, durability and permeability of concrete and can cause segregation. When possible, admixtures should be used instead of water to achieve higher slump.
Compressive Strength
Is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g. many concrete structures have compressive strengths in excess of 7200 PSI, whereas a material such as soft sandstone may have a compressive strength as low as 725 to 1450 PSI. Compressive strength is often measured on a universal testing machine. Measurements of compressive strength are affected by the specific test method and conditions of measurement. Compressive strengths are usually reported in relationship to a specific technical standard. The standard compressive strength test for concrete is: ASTM C39 / C39M – 11a Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. More information can be found at http://www.astm.org/Standards/C39.htm.