October 1992 Table of Contents

Features Bigger aggregate reduces curling

We supply concrete for two large flatwork contractors who each place several hundred thousand square feet of concrete floors per year. One experiences curling on some jobs but the other doesn't. Both use 4000-psi concrete and do a good job of curing. There's one difference between the contractors. One uses concrete with 11_4-inch-maximum size rock for all floors 5 inches thick or greater. He doesn't get any curling. The other uses 3_4-inch-rock concrete regardless of floor thickness. His floors sometimes curl. An engineer told me he thinks the large-rock concrete doesn't curl as much because of better aggregate interlock. Is that correct? Or are there other factors involved? Read more

Features Thinking Metric
Problem Clinic Preventing Trowel Burns on White Floors

We're building a floor that calls for a white dry-shake to make it light-reflective. The specs also call for a hard troweled finish. We're concerned about burning the white surface. Is a stainless steel or plastic trowel better than an ordinary steel trow Read more

Problem Clinic Effect of Fly Ash on Setting Time

The sands in our area are mainly river sands that are deficient in very fine particles (material that passes the No. 50 sieve). Concrete made with these sands is hard to finish, especially when a steel trowel is required. Our ready mixed concrete supplier Read more

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