— David Wagner 2007/08/07 16:07

#8 (1” diameter), 60 ksi.

Concrete formwork must be safe, economical, and produce the desired shape and surface texture.

1. Slump tests and tests for air and cement content are checked on site, along with concrete temperature, if needed.
2. A rapid strength test (estimate) may be done by establishing a relationship between 28-day strength and water/cement ratio, then measuring water and cement contents in the field to predict the ultimate strength.

The single greatest cost of concrete construction is usually the cost of the formwork.

Though they often cost more to construct, prestressed, precast members can be made more uniformly, to tighter tolerances, and in overall smaller dimensions than equivalent cast-in-place members. In addition, special transportation may be needed for large precast members and so increase costs dramatically. However, these increase costs may be offset somewhat by quicker construction time and some erections require strengths only prestressed, precast members can achieve.

4

1. Interior columns are isolated from floor slabs to permit differential movement caused by concrete shrinkage, temperature and moisture changes, and foundation settlement.
2. Interior columns are usually isolated from floor slabs either by providing a breakout in the floor slab or by forming a pinwheel isolation joint.

Wales are used in concrete wall forms to maintain the shape of the form; they help keep the walls parallel.

1. Use drop chutes or elephant trunks to avoid segregation.
2. Limit free-fall distance to 5' or less.
3. Allow the vibrator to penetrate 1-8” into the previously placed layer of concrete.

[Programming Problem]