You asked: “What to look for in a rebar pour” Concrete is a mix of cement (a powder that reacts with water and hardens into a glue), water, sand, and stone. Once it hardens, it resists compression — a squeezing load — extremely well. It is poor at tension — a pulling load. If you bend a plain concrete beam, the bottom stretches, tiny cracks form, and the beam can fail suddenly. Steel is the opposite in the way that matters here: it is excellent in tension. Rebar (reinforcing bar) is steel rolled with ribs so concrete can grip it. The partnership is a composite: two materials acting as one because they are bonded. The pour is the act of placing wet concrete around that steel so the bond can form as the mix hardens.

A beam is a member that spans between supports and carries load by bending. Under ordinary floor load, the bottom of a simple beam stretches (tension) and the top shortens (compression). A slab is a plate-like floor or roof doing a similar job in two directions. A cantilever (a member held at one end only, like a balcony) reverses this: tension is on top, near the support. If rebar is on the wrong face, it does almost no good. Bars must also run far enough past the stressed region that the concrete can grab them — that grab-length is development length. When two bars meet end-to-end, they usually lap splice: they overlap so tension can hand off from one to the other through the concrete.

Cover is the distance from the surface of a bar to the nearest outer face of the concrete. Too little cover, and two failures become likely: the bar cannot develop bond (the concrete around it is a thin shell that splits), and water plus air reach the steel, which then corrodes — rusts. Rust occupies more volume than the steel it came from, so it cracks the concrete from inside. Cover is held, before the pour, by chairs and dobies: small supports, plastic or concrete, that keep the cage from sagging onto the form. Tie wire is thin steel wire twisting bars at intersections so the cage does not rack when people walk on it or when concrete hits it. The ribs on rebar exist for bond: they turn a smooth rod, which would slide, into a bar the concrete can key against.

Fresh concrete is a thick fluid. If it is too stiff, it will not flow through a tight cage — that tightness is congestion. If it is too wet, the stone sinks and the water rises; that separation is segregation, and the result is weak, honeycombed concrete. Workers use a vibrator — a wand that shakes the mix — to release trapped air. Too little vibration leaves voids. Too much makes the stone settle. The mix must not knock the cage off its chairs; that is why ties and supports are not cosmetic. If a pour stops long enough that the first concrete starts to set, the joint between old and new may not bond; that is a cold joint. Weather matters because heat, wind, and cold all change how fast the mix sets and how much water it loses.

Start with the formwork — the mold. It must be the right size, tight enough that grout (the gluey part of the mix) does not leak, and braced so it will not blow out. Then read the steel as a map of tension: right bars on the right face, spacing matching the drawings, laps in the right places, not bundled so tightly that concrete cannot pass. Then height: chairs standing, cover blocks at edges, no bars sitting in the dirt or on the wood. Then surface: bars free of loose rust, mud, ice, and dried concrete, all of which kill bond. Then embeds — the bolts, sleeves, and blockouts that must end up in the right place because they cannot be moved later. Only then watch the pour: discharge close to the cage (not dropped from a height that segregates), vibration systematic, workers not kicking bars off chairs, a plan if the truck is late.