1. If most slab spans are small, the load is limited, and the calculated reinforcement amount of most slab spans does not reach the minimum reinforcement ratio (pmin=0.2%, 45ft/fy double control), it is worthwhile to use the first-class reinforcement (PRB235), because the cold-rolled ribbed reinforcement needs as much as the first-class reinforcement to meet the minimum reinforcement ratio, but
2. If the span of the slab is large or the load is large, most slabs are controlled by calculating the reinforcement amount, and cold-rolled ribbed steel bars (generally CRB550 grade) are worth using because of their high tensile strength.
Cold rolling of ribbed steel bars is not prohibited. Because it is cold-drawn by PRB235, the ductility will naturally be worse, but it can still be used in cast-in-place slab. Even if the earthquake comes, it will not be the cast-in-place slab that collapses (the bearing capacity of the cast-in-place slab is quite amazing, and the actual load exceeding several times the design value in the experiment cannot completely collapse it). However, in recent years, there are more and more manufacturers processing cold-rolled ribbed steel bars, and it is difficult to distinguish good from bad. In addition, the small-diameter third-grade steel bar (HRB400) is more and more popular, so the cold-rolled ribbed steel bar is less and less used in engineering.