Materials and Material Behavior
Concrete, steel, wood, and masonry
Material questions test how each material behaves and how its properties enter design. For concrete, know mixture proportioning, water-cement ratio, admixtures, curing, compressive strength f'c, tensile weakness, modulus Ec, creep, and shrinkage. For steel, know grades, the stress-strain curve with a yield plateau and strain hardening, ductility, toughness, and weldability. For wood, know species and grades, moisture content, and grain direction. For masonry, know units, mortar, and grout. Corrosion and fire resistance are also fair game.
Traps
Do not use f'c where fc is intended. Concrete tensile strength is normally neglected in flexure. Watch psi versus ksi and the difference between nominal and specified strengths. Steel is not linear to failure. Wood strength and stiffness depend strongly on moisture and load duration. Concrete gains strength with curing, so 7-day and 28-day values differ.
Worked example: Normal-weight concrete modulus is approximately Ec = 57,000√f'c psi. For f'c = 4,000 psi, √4000 ≈ 63.2, so Ec ≈ 3,600,000 psi = 3,600 ksi. A common trap is to use 4,000 directly without taking the square root.
Rule of thumb: Normal-weight concrete weighs about 145–150 lb/ft³; steel E = 29,000 ksi.