Q.: I am using a flat saw equipped with a diamond blade to cut joints in a reinforced-concrete slab. The blade is cutting very slowly, but is showing little wear. I am using plenty of cooling water. What can I do to increase cutting speed?

A.: Diamond blades don't actually cut concrete; they grind away the surface under the blade. The tiny diamond segments are held on the blade by a metal matrix or bond. After several thousand passes through the material being cut, the diamond segments begin to crack and break off. The matrix wears away, releasing the fractured diamonds and exposing new ones. This process continues until the blade is worn out.

An experienced saw operator or diamond blade supplier can look at a blade under a magnifying glass and tell you how the blade is working. If the blade is cutting slowly, its matrix probably is too hard and not wearing quickly enough to expose new diamonds. Try cutting back on the coolant water or switch to a blade with a softer matrix. If changing saws is an option, a saw with more horsepower can increase production.

Another cause of your problem could be too much reinforcing steel in the area being cut. The blade must always cut through concrete to be effective.