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Increasing the water/cement ratio of concrete might make it _______ but also _______.

A group of 30 tests on a given type of concrete had a mean strength of 4,200 psi and a standard deviation of 500 psi. Does this concrete satisfy the strength requirement for 3,000 psi concrete?

For _______ to occur, there must be a source of oxygen and moisture, both of which diffuse through the concrete.

At very slow loading rates, the strength of concrete decreases.

A wall footing has the following conditions. Determine the moment capacity, Mn, of the footing. Assume the footing is 5 ft wide, the pressure that acts on the bottom of the footing is 5,200 psf, and the reinforcement is a #4 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 8 kips/ft.The wall is 12 in. thick.The footing is 12 in. thick.The allowable soil pressure, qa, is 4,200 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.

Σ(Ti + 10)ti is the equation for concrete _______.

A wall footing has the following conditions. Determine the required cross-sectional area of shrinkage and temperature reinforcement. Assume the footing is 5 ft wide, the pressure that acts on the bottom of the footing is 5,040 psf, and the reinforcement is a #7 bar spaced every 12 inches.The bottom of the footing is at a depth of 3 ft below grade.The service dead load is 13 kips/ft, and the service live load is 6 kips/ft.The wall is 16 in. thick.The footing is 16 in. thick.The allowable soil pressure, qa, is 4,500 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 = 3,900 psi and fy = 60,000 psi.

A concrete cube is subjected to biaxial loading. Estimate the compressive strength σ1 if σ2 = 0.2 times the compressive strength, in compression.

Drying shrinkage occurs without the loss of moisture due to hydration reactions inside the cement matrix.

The concrete containing Type I cement in a structure is cured for 4 days at 75°F, followed by 2 days at 60°F. Use the maturity concept to estimate its strength as a percentage of the 28-day strength under standard curing. Maturity is defined as M = Σ(Ti + 50)(ti) where Ti is in degrees F and ti is in days.