Concrete, Masonry, and Structural Steel
Concrete
Strength is governed by the water-cementitious materials ratio - extra water for workability costs strength and increases shrinkage. Specified compressive strength is measured on 28-day cylinders; slump and air content are tested fresh. Air entrainment improves freeze-thaw resistance. Curing must maintain moisture and temperature, typically 7 days. Cold weather means protection from freezing (ACI defines cold weather around 40°F and falling); hot weather means placing and curing before flash set. Formwork removal depends on strength gain, not the calendar. Reinforcement needs specified cover (more in earth-contact or exposed conditions), correct lap lengths, and chairs to hold position. Inspect before placement: forms, ties, rebar, embedded items, cleanliness.
Masonry
Mortar types run M, S, N, O in descending strength; N is the general-purpose choice, S for higher flexural and lateral loads, M for severe exposure. Mortar bonds units; grout fills reinforced cores and must be consolidated. Control joints accommodate movement, flashing and weep holes drain the wall cavity, and wall ties connect veneer to backup. Brick expands; concrete masonry shrinks - joints and detailing must reflect that.
Structural steel
Erection follows AISC standards: shop drawings and erection drawings reviewed before fabrication; high-strength bolts (A325/A490) installed with turn-of-nut or tension-calibrated methods; welding performed under a qualified procedure by qualified welders to AWS D1.1, with visual and nondestructive testing as specified; temporary bracing and plumbness maintained; surfaces prepared and primed, with fireproofing applied to the specified rating.
Trap
Questions blame low strength on curing compound or weather when the mix actually carried too much water, or assume mortar type M is always 'best' regardless of exposure and flexibility needs.
Rule of thumb
You cannot inspect strength into hardened concrete - control the water and verify cover and consolidation before the pour.