Concrete and Asphalt Sawing Methods
In concrete and asphalt cutting operations, the usual equipment used are 8, 11, 13, 20, 35, 65, 72 and 120 HP saws.
Asphalt cutting and the cutting of asphalt overlayed concrete should not be considered the same type operation from a blade recommendation standpoint. In the case of asphalt overlayments, the application involves cutting both asphalt and cured concrete which gives a different abrasive level than the cutting of asphalt alone.
Generally, the cutting of asphalt overlayed concrete is done at full depth with blades less than 18" in diameter as long as the asphalt is more than 1/3 the total depth of cut. Standard recommended specifications for asphalt overlayed concrete should be employed until the depth of the asphalt reaches 50% of the total cut. At this point, harder blades should be used which would increase the blade life.
The larger diameter blades, 18" and above, are used in a step cutting method at cutting depths of 2" and 3" in short travel distances of 15' to 20'. This allows the blade to remain in a free cutting condition and does not slow down the cutting operation. Asphalt cutting is primarily performed at full depth. However, if the aggregate used in asphalt is larger than .750 in diameter and/or is quartz or chert aggregate, the cutting operation may have to be modified to a step cutting operation.
Green Concrete Sawing Methods
Green concrete is cut to control cracking in large concrete pours. Usually saws from 8 HP to 65 HP are used for this purpose, depending on the size of the job. The initial sawing of the concrete is done within a 24 hour period at a depth of 1/3 to 1/4 of the total concrete thickness. Generally 12" and 14" blades are used with .125" or .150" widths.
After the initial cut has been made, the joint may require additional widening for the backing rod and/or sealant. This requires a blade diameter of 12" or 14" in widths up to .500".
Concrete-Deep Sawing Methods
Generally, deep sawing of cured concrete is done using high horsepower concrete saws and blades above 20" in diameter. 65 HP concrete saws are used in conjunction with 24", 30", and 36" diameter blades to obtain the desired depth of 8" to 14" (this is usually the standard thickness of concrete highways in North America). The blades are usually used at approximately 12,000 surface feet per minute (outside rim speed of the blade).
The use of these blades is usually dictated by the hardness of the aggregates contained in the concrete. A cutting rate of 4' to 6' per minute is the speed of cut most operators prefer. This cut rate is usually directly related to the depth of cut. In areas with hard aggregate, it is common to make multiple passes of 2" to 3" deep until desired full depth of cut is reached. Softer aggregates can be cut using deeper passes without sacrificing cutting speed.