Carborundum Blades

Low cost, abrasive blades are now widely used to cut green concrete made with soft aggregates, such as limestone, dolomite, coral, or slag. These blades are made from a mixture of silicon carbide grains and a resin bond. This mixture is pressed and baked. In many cases, some of the medium hard aggregates can be cut by the step cutting method. This method uses two or more saws to cut the same joint, each cutting only a part of the total depth. This principle is also used on the longitudinal saw, which has two individually adjustable cutting heads. When a total depth of 2 1/2 inches is to be cut, the leading blade cuts the first inch and the trailing blade, which is slightly narrower, cuts the remaining depth.

Abrasive blades come in 14 and 18 inch diameters. They are made in various thicknesses to cut joints from 1/4 inch to 1/2 inch wide.

When to Use

When is the best time to saw green concrete? In the case of abrasive blades, there is only one answer; as soon as the concrete can support the equipment and the joint can be cut with a minimum of chipping. In the case of diamond blades, there are two factors to consider. In the interest of blade life, sawing should be delayed, but control of random cracking requires sawing at the transverse joints as early as possible. Where transverse joints are closely spaced and on large projects, cut every second or third joint initially and the rest later.

Saw joints as soon as the concrete is hard enough not to be torn or damaged by the blade, but before random cracks can form in the concrete slab. With wet cut saws, this condition usually occurs from 4 to 12 hours after finishing is complete, although sawing as late as 24 hours may be successful under some conditions.

For proper operation and maintenance of the concrete saw, follow the manufacturer’s manual.