Saws for cutting concrete flatwork vary in size, blade type, operating speeds, cooling systems, and power source. Questions such as "When will the concrete be cut?" and "What type of aggregate and rebar does the concrete contain?" and "How deep does the material need to be cut?" are just a few of the matters to be considered before slicing into concrete flatwork. The choice of saw and blade depends on factors other than personal preference. In determining the correct cutting equipment for a job, first assess the material being cut. The saw and blade used to cut green concrete differ from those used on hardened concrete. Green concrete is soft and usually more abrasive than cured concrete. The type of aggregate contained in concrete also influences a blade's performance and length of life. When cutting concrete with heavy rebar or hard aggregates, use blades with soft metal segment bonds. Concrete with soft aggregates will not dull diamonds as quickly. Therefore, blades with harder metal segment bonds are needed to hold the diamonds in place long enough to use their full potential. Other factors in tool selection are horsepower and speed. Saws must be matched with blades that operate within their power and speed range. A blade used on a saw that cannot power it will stop cutting and will be damaged. Manufacturers always list the blade shaft rpm of the saw. This number must be matched with recommended operating speed for the blade for successful sawing.