A minimum compressive strength of at least 4500 psi, after 180 days of curing (aging) time, is specified for the concrete used in a bridge project. It is further specified that a water-cement ratio of 0.5, a slump of 1.5 inch, and an air entrainment of 4% be used. To provide a curing protocol that will produce the required compression strength, the concrete should be moist-cured and then cured: A. In air after 3 days B. In air after 7 days C. In air after 14 days D. A compressive strength of at least 4500 psi cannot be attained

Afoot bridge is made as a simple deck, 4 m long, with a cross section 2 m (wide) and 20 cm thick, and made of wood. the deck is supported at the two ends. the maximum load allowable on the bridge is 10 tons, provided it is uniformly distributed on the deck. to sense this load, a strain gauge is placed at the center of the bridge and its resistance is monitored. if the sensor has a nominal resistance of 350 s2 and a gauge factor of 3.6, what is the reading of the strain gauge at maximum load? the modulus of elasticity for the wood used in the construction is 10 gpa.