Measurements are not always exact, so we highly recommend ordering a little extra. A good rule of thumb is take your calculation and add 4% to 10% to the total to account for waste, spillage, over-excavation, settlement, loss of entrained air or other changes in volume. Remember, you can order concrete in 1/2 yard increments.
Slump is a measurement of the consistency of the concrete. A 4″ slump is typical. Keep in mind adding one gallon of water per cubic yard can decrease compressive strength 150-200psi, waste cement and increase shrinkage by 10%. This can be a problem for concrete that is exposed to freeze-thaw conditions.
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 4000psi.
Entrained air is little bubbles of air primarily to increase the durability of the hardened concrete to freeze-thaw conditions. Any exterior slab in our climate should have air entrainment.
You will need to provide a contained area for the truck to washout. This area would not allow liquids to seep into surrounding areas. A wheelbarrow or other container is often used. We also have portable washout boxes available for an additional cost. Please inquire with dispatcher.