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There is a permanent reduction in strength when concrete is exposed to sustained high loads.

Concrete subjected to a temporary axial load greater than the critical load will eventually fail under loads less than the critical load.

A wall footing has the following conditions. Determine the critical one-way shear, Vu, at a distance of d from the face of the wall. Assume the footing is 5 ft wide, the pressure that acts on the bottom of the footing is 5,680 psf, and the reinforcement is a #7 bar spaced every 12 inches.The bottom of the footing is at a depth of 2 ft below grade.The service dead load is 13 kips/ft, and the service live load is 8 kips/ft.The wall is 10 in. thick.The footing is 12 in. thick.The allowable soil pressure, qa, is 4,900 psf.The soil has a density of 120 lb/ft3.The concrete has a density of 150 lb/ft3.The concrete cover has a thickness of 3 in.f’c = 4,000 psi and fy = 60,000 psi.

A wall footing has the following conditions. Determine the shear capacity, φVn, of the footing. Assume the footing is 4 ft wide, the pressure that acts on the bottom of the footing is 5,500 psf, and the reinforcement is a #6 bar spaced every 12 inches.The bottom of the footing is at a depth of 2 ft below grade.The service dead load is 9 kips/ft, and the service live load is 7 kips/ft.The wall is 16 in. thick.The footing is 15 in. thick.The allowable soil pressure, qa, is 4,400 psf.The soil has a density of 115 lb/ft3.The concrete has a density of 150 lb/ft3.The concrete cover has a thickness of 3 in.f’c = 4,000 psi and fy = 60,000 psi.

A group of 30 tests on a given type of concrete had a mean strength of 4,000 psi and a standard deviation of 600 psi. Does this concrete satisfy the strength requirement for 3,000 psi concrete?

A concrete block will eventually break if a constant load is applied at 75% to 80% of its ultimate compressive strength due to _______.

The concrete in the core of a spiral column is subjected to a uniform confining stress σ3 of 220 psi. What will the compressive strength σ1 be? The unconfined uniaxial compressive strength is 4,700 psi.

The increase in the volume of concrete during hardening and drying under constant temperature is called shrinkage.

Other strength parameters are expressed relative to the compressive strength.

Concrete near the top of deep members tends to be weaker than the concrete lower down.