Concrete is one of the most adaptable and versatile materials used in the construction industry. It can be custom-mixed to the desired compressive strength or for color application, it can be placed in almost any shape or form using a variety of methods, and it can be finished to resemble a variety of surfaces such as wood, masonry or stone. Concrete is durable and virtually maintenance-free. It is also fairly easy to work with and installs relatively quickly. For these and many other reasons, concrete is one of the most widely used materials in construction projects.
To be accurate, the estimator should carefully check all the plans and specifications for the project. Concrete often appears on drawings other than structural drawings, such as the need for equipment pads in the mechanical and electrical drawings, or curbs and sidewalks in the civil drawings.
When estimating structural concrete, pay particular attention to requirements for concrete additives, curing methods and surface treatments. Special consideration for climate conditions such as humidity as well as hot or cold weather conditions must be included in your estimate. Also include requirements for concrete placing and finishing methods and equipment.
For accurate concrete estimating, the estimator must consider each of the following major components individually: formwork, reinforcing steel, ready-mix concrete, placement of the concrete mix, finishing of the surface, and curing.
Formwork is normally taken off in square feet (generally in square feet of area in contact with the concrete, as opposed to the actual area of forms used).
Reinforcing is normally taken off in tons of rebar, hundreds of square feet (CSF) of welded wire fabric, or pounds of pre-stressing strands.
Ready-mix concrete is normally taken off in cubic feet, but then converted to cubic yards, as this is the unit of measure that suppliers charge for.
Placing of ready-mix concrete is normally taken off in cubic yards for each of the placing methods (direct chute, conveyor, pump truck, and crane & bucket).
Finishing the concrete surface is normally taken off in square feet and can include the top surface of flatwork as well as vertical walls and horizontal structure faces that will be exposed.
Curing is normally taken off in hundreds of square feet (CSF) for each of the curing methods (water curing, chemical compound membrane, and sheet membrane).
Each of these major components will be explored further in future articles.