Date: January 1, 2010

News - How to Order Ready Mixed Concrete

Here are some basic requirements to keep in mind when placing a concrete order:
  • When specifying aggregate size, remember that the aggregates should be smaller than the narrowest dimension through which concrete should flow. Usually the maximum size of coarse aggregate is ¾ or 1 inch.  
  • Be sure to indicate your desired slump. Slump is a measure of the consistency of the concrete. A 3 to 5 inch slump (the measure of the distance a wet concrete cone will fall) is typical. If you want more slump, it is always safest for the concrete to adjust slump at the plant. Adjusting slump at the job site will damage the concrete. Adding just 1 gallon of water per cubic yard can decrease compressive strength 150 to 200 psi, waste cement and increase shrinkage by 10%. This is especially a problem for concrete that might be exposed to freezing and thawing conditions.
  • Air entrained concrete should always be used if the concrete will ever be exposed to freezing temperatures, so it is usually the default option—this means that if non air-entrained concrete is needed it should be clearly stated at the time of the order. A typical range is 4 to 6 percent. 
  • To ensure that you order enough concrete, order 4 to 10 percent more concrete than is estimated from the plan dimensions: this will make up for over-excavation, loss of entrained air during placement, waste or spillage, or spreading of forms. Reevaluate the needs during placement and tell the supplier about any changes.
  • Strength is most commonly measured by the designed compressive strength in pounds per square inch (psi) of a hardened cylinder of concrete. Any slab exposed to freeze-thaw conditions should be a minimum of 4,000 psi.
  • 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 888-244-0411.
  • Concrete Washout - You will need to provide a washout area for the truck after it is finished pouring the concrete. This should be a contained area that would not allow liquids to seep into surrounding areas. A wheelbarrow or other container is often the easiest to supply.

Other news articles from January 2010