How to Pour Transit Mix Concrete

Order the concrete from the supplier, stating the name and address for delivery. Specify use for the concrete, the required compressive strength, and slump -- workability -- expressed in inches. State the maximum aggregate size, or any special requirements, such as color pigments or lightweight aggregate.

Tell the supplier about site accessibility for the truck chute, time of delivery and interval between truckloads. State the quantity of concrete needed, expressed in yards. Add 10 percent to the quantity, and round the figure up.

Clear routes around the site to ensure the transit mix trucks have access. Plan the sequencing of the pour, and how the concrete will be placed. Allow space for trucks, wheelbarrow ramps, and room for equipment. Check that all labor and tools are available, and preparation of the site is completed before delivery of the concrete.

Add air-entraining, water-reducing or set-retarding admixtures to the concrete as required according to weather or time-of-travel conditions, when the truck arrives. Let the supplier advise if the admixtures are necessary, and let the supplier adjust the mix.

Check that the mixing speed of the truck complies with 70 revolutions per minute, or five minutes mixing time. Pour as close to the final position as possible, from the chute. Pour from the chute to the wheelbarrow where the chute can't reach.

Start the pour at the corners of the formwork, or the lowest point of a sloping site. Pour vertically, at a distance of not more than five feet. Advise the operator if more or less time is needed between truck loads than initially ordered.