How much does the concrete weigh?

How much does concrete weigh?

Normal concrete weighs about 140 to 150 pounds per cubic foot; with steel reinforcement, engineers use 150 lb/ft³, as in ACI 318. Lightweight concrete made with expanded shale or clay runs about 90 to 115 lb/ft³. A cubic yard of normal concrete is about 3,900 to 4,050 pounds — roughly two tons.

How much does a concrete slab weigh?

Multiply length × width × thickness in feet to get cubic feet, then by the weight per cubic foot. A 10 × 10 ft slab 4 inches thick is 33.3 cubic feet; at 150 lb/ft³ it weighs 5,000 pounds — two and a half tons.

How much does a concrete post footing or column weigh?

A 12 inch round column 4 ft tall is π × 0.5² × 4 = 3.14 cubic feet, about 456 pounds of plain concrete. Pick Column on the piece and enter the diameter and height.

Why do I need the weight of concrete?

To plan removal — a dumpster or trailer has a weight limit well below its volume — to check that a truck or deck can carry it, and to size lifting gear for precast pieces. Broken-up concrete takes more space than the solid slab, but it weighs the same.

How do I plan hauling away an old slab?

Add up the weight of every slab and compare it with the weight limit of the dumpster or trailer — the hauler will tell you theirs. A 20 × 20 ft driveway slab 4 inches thick weighs about 10 tons, which often means more than one load.

How much does a cubic yard of concrete weigh?

At the reinforced-concrete value of 150 lb/ft³ a cubic yard (27 cubic feet) weighs 4,050 pounds, and at the plain-concrete value of 145 lb/ft³ it weighs 3,915 pounds. The same 150 lb/ft³ is 2,400 kg/m³ in metric units.

Should I weigh the concrete I order or the concrete in place?

The concrete in place: the volume you order includes extra for waste and uneven subgrade, so the delivered load is heavier than the finished slab. For a 12 × 16 ft slab 4 inches thick the reinforced weight is 9,600 pounds; ordering 10% extra delivers about 10,560 pounds.

How the weight is computed

Weight = volume × unit weight. The calculator finds the volume of each piece from its dimensions (slabs, walls, footings, columns and so on), then multiplies by a density. The three choices are plain normal-weight concrete, reinforced concrete (for which the building code uses 150 lb/ft³ in the self-weight of the structure) and lightweight concrete. The density of real concrete depends on the aggregate, the water and the air content, so any single figure is an estimate.

Worked example: a 12 by 16 ft slab, 4 inches thick

The volume is 12 × 16 × (4 ÷ 12) = 64.0 cubic feet, or 2.37 cubic yards. At 145 lb/ft³ the slab weighs 9,280 pounds, at 150 lb/ft³ (reinforced) 9,600 pounds, or 4.8 tons, and with a lightweight mix at 115 lb/ft³ 7,360 pounds. Spread over its 192 square feet, the reinforced slab loads the ground with 50 pounds per square foot, which is 12.5 pounds per square foot for each inch of thickness.

Common mistakes

Mixing units is the first: thickness in inches must be divided by 12 before multiplying by feet. The second is weighing the volume you order rather than the volume you pour; the ordered amount includes extra for waste. Third, demolished concrete weighs the same as the slab but takes up more space, and a hauler's weight limit may be reached long before the container is full. Finally, the weight of the concrete is not the load rating of a structure: a deck, a trailer or a floor carries a stated load that includes safety factors, so check it against the engineer's or manufacturer's figures.

Sources: ACI 318 (self-weight of reinforced concrete, 150 lb/ft³) and the Portland Cement Association's Design and Control of Concrete Mixtures for the ranges of normal-weight and lightweight concrete. Related: concrete calculator, cubic yard calculator, material weight calculator and rebar calculator.