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A group of 25 tests on a given type of concrete had a mean strength of 4,600 psi and a standard deviation of 400 psi. Does this concrete satisfy the strength requirement for 3,500 psi concrete?

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

A lower water/cement ratio reduces the porosity of the hardened concrete and thus increases the number of interlocking solids.

Bond cracks are microcracks that occur along the interface between paste and aggregate.

Which of the following is not a common durability problem in a concrete structure.

Fly ash may not even dramatically affect the final strength of concrete but can improve the _______.

There are no standards governing the quality of water for use in mixing concrete. In most cases, drinking water is suitable.

A group of 20 tests on a given type of concrete had a mean strength of 4,000 psi and a standard deviation of 800 psi. Does this concrete satisfy the strength requirement for 5,000 psi concrete?

Would you expect a ready-mix concrete plant to produce concrete with a higher or lower coefficient of variability compared to a standard mix-on-site concrete?

A wall footing has the following conditions. Determine the required cross-sectional area of shrinkage and temperature reinforcement. Assume the footing is 4 ft wide, the pressure that acts on the bottom of the footing is 6,100 psf, and the reinforcement is a #9 bar spaced every 12 inches.The bottom of the footing is at a depth of 2 ft below grade.The service dead load is 11 kips/ft, and the service live load is 7 kips/ft.The wall is 10 in. thick.The footing is 11 in. thick.The allowable soil pressure, qa, is 5,100 psf.The soil has a density of 130 lb/ft3.The concrete has a density of 150 lb/ft3.The concrete cover has a thickness of 3 in.f’c = 3,600 psi and fy = 60,000 psi.