At high loading rates, the strength of concrete increases.

Microcracks that occur along the interface between paste and aggregate are called _______ cracks.

Exceptional shrinkage can occur when concrete is _______.

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 pressure that acts on the bottom of the footing. Assume the footing is 4 ft wide.The bottom of the footing is at a depth of 2 ft below grade.The service dead load is 9.7 kips/ft, and the service live load is 6.9 kips/ft.The wall is 12 in. thick.The footing is 12 in. thick.The allowable soil pressure, qa, is 4,900 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 = 3,200 psi and fy = 60,000 psi.

A well-graded aggregate mix helps reduce the shrinkage in a concrete structure.

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.

The strength of concrete under biaxial compression is less than the uniaxial compressive strength.

A group of 20 tests on a given type of concrete had a mean strength of 4,800 psi and a standard deviation of 400 psi. Does this concrete satisfy the strength requirement for 4,500 psi concrete?

The standard compressive strength acceptance test is performed on concrete cylinders that are how old?