A concrete cube is subjected to biaxial loading. Estimate the compressive strength σ2 if σ1 = 0.8 times the tensile strength, in tension.

A wall footing has the following conditions. Determine the required development length, ld, for the reinforcement. Assume the footing is 3 ft wide, the pressure that acts on the bottom of the footing is 6,933 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 8 kips/ft, and the service live load is 7 kips/ft.The wall is 14 in. thick.The footing is 15 in. thick.The allowable soil pressure, qa, is 5,500 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 = 3,200 psi and fy = 60,000 psi.

A wall footing has the following conditions. Determine the distance to the neutral axis, c, measured from the top of the footing. Assume the footing is 6 ft wide, the pressure that acts on the bottom of the footing is 4,866 psf, and the reinforcement is a #8 bar spaced every 12 inches.The bottom of the footing is at a depth of 5 ft below grade.The service dead load is 15 kips/ft, and the service live load is 7 kips/ft.The wall is 16 in. thick.The footing is 13 in. thick.The allowable soil pressure, qa, is 4,500 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.

Exceptional shrinkage can occur when concrete is _______.

A wall footing has the following conditions. Determine the depth, d, of the reinforcement. Assume the footing is 4 ft wide, the pressure that acts on the bottom of the footing is 5,300 psf, and the reinforcement is a #8 bar spaced every 12 inches.The bottom of the footing is at a depth of 5 ft below grade.The service dead load is 7 kips/ft, and the service live load is 8 kips/ft.The wall is 14 in. thick.The footing is 14 in. thick.The allowable soil pressure, qa, is 5,500 psf.The soil has a density of 125 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.

The concrete containing Type I cement in a structure is cured for 3 days at 40°F, followed by 5 days at 71°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.

The concrete containing Type I cement in a structure is cured for 4 days at 53°F, followed by 4 days at 52°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.

Although concrete is made up of essentially elastic, brittle materials, its stress-strain curve is nonlinear and it appears to be somewhat _______.

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

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