CONCRETE CRACK REPAIR EQUIPMENT

All equipment employed in the concrete crack repair operation must be inspected before, during, and after the repair project to ensure proper operation of the equipment, safety of the personnel involved in the project, and potential damage to the pavement due to equipment problems. Proper safety procedures in accordance with OSHA guidelines and common sense practices must be followed for the protection of all project personnel. Hand tools should always be available for working in areas where machinery is not practical or allowed. All sealant equipment must be equipped with nozzles designed to fill the concrete cracks from the bottom up. The equipment must be inspected daily prior to application of the sealant and during the operation to ensure safe operation and that the sealant is being applied properly. If a

Two-component sealant is used, the metering ratio must be checked daily.

Random Crack Saw

Sawing is the preferred method for preparing concrete cracks for sealing. This device is essentially a concrete saw but has a smaller rear-mounted blade approximately 5 inches (130 millimetres) in diameter. These saws are generally self-propelled machines with caster wheels that allow more freedom of movement than an ordinary concrete saw for following the path of cracks. Diamond blades are typically employed and should be thick enough to saw the crack to the desired width and prevent warping of the blade during operation.

Vertical Spindle Router

Cracks may be routed out if a saw is not available. The vertical spindle router has a vertically mounted router bit and is constructed such that the device can caster and easily follow the contours of a crack . The bit must be the proper size for the sealant reservoir and be belt-driven for safety considerations arising from jamming of the bit ifthe router are forced along the crack. The bits must yield the proper shape for the sealant reservoir and not cause spalling or ravelling along the crack path.

Sandblasting Equipment

The necessary sandblasting equipment includes an air compressor, air hose, and a 1/4-inch- (6-millimeter-) diameter venturi-type nozzle. The compressor must be capable of delivering 150-cubic feet/minute (4.25-cubic meters/minute) at 90 pounds/square inch (620 kPa) and be equipped with operating in-line traps to keep the air hoses and the sandblasted surface free of oil and water. This device must be capable of removing all sawed slurry, dirt, and old sealant that may be present in cracks that are being resealed. Ceramic and tungsten carbide nozzles are available for sandblasting, but the tungsten nozzles last longer. A guide that keeps the nozzle a constant height from the pavement surface promotes consistency to the sandblasting technique and reduces operator fatigue. The nozzle should have an adjustable guide that will hold the nozzle aligned with the joint approximately 1 inch (2.5 centimetres) above the pavement surface. Safety must always be a primary concern. Sandblasting operators are required to follow OSHA guidelines. A helmet with separate air source and air purification equipment reduces the possibility of inhalation of silica dust. Protective clothing may also be required.

Compressed Air Equipment

Compressed air can be employed for the final cleaning phase of the project. The air source must produce sufficient pressure and contain no oil that may foul the surface prior to sealing. Some compressors have in-line sources for the constant lubrication of air tools. These devices must be removed along with the oil-coated pressure hoses, and in-line oil and water traps must be installed to provide a clean air source for the airblasting operation.

Hot-Air Lance

A hot-air lance is sometimes employed to dry the surface of the pavement immediately prior to sealing. Strict safety precautions that must be employed to reduce operator hazard may include protective clothing as well as eye and ear protection. The operator must take special precaution not to overheat the pavement which may cause cracks and chalking of the concrete surface. Direct flame devices must not be used.

Water blasting Equipment

Waterblasting is an excellent technique for cleaning joint faces. This technique is sometimes employed as an alternative to sandblasting due to local air regulations or where the sand and debris might create additional problems. Waterblasting equipment should consist of a trailer-mounted water tank, pumps, high-pressure hoses, an auxiliary water supply, a wand with a safety cut off if the operator should lose control, and a proper size nozzle for the crack width. After water blasting is completed, the entire joint must be dried.

Power Broom

A vacuum-type power broom should be present to remove debris from the pavement surface and reduce the potential for .

Backer Rod Installation Equipment

Backer rod may be placed by hand and many contractors have constructed their own hand-held equipment for this operation. However, there are manufacturers of installation equipment. These devices place the rod at a consistent depth without undue stretching or tearing of the backer materials

Hot-Applied Sealant Equipment

There are two basic types of hot-applied sealant equipment: one for heating sealants that are solids or liquids at room temperature and one for sealants that are liquids only. The former devices are much more prevalent. Both types must be capable of holding a sufficient amount of sealant and be able to heat the material to the proper controlled application temperature (usually between 325 degrees Fahrenheit (163 degrees Celsius) and 480 degrees Fahrenheit (249 degrees Celsius)) without overheating.

1. Solid. The equipment necessary for application of room-temperature solid sealants must consist of a double-wall-type kettle that is heated by a fluid between the walls of the chamber anda mechanical agitator to prevent localized overheating at the walls. Calibrated thermometers must be easily visible to allow constant monitoring of the sealant temperature to prevent the possibility of overheating. The sealant must be circulated through the delivery hose and back to the heating chamber when not being applied.

2. Liquid. The equipment employed to apply sealants that are liquids at room temperature

does not maintain the sealant reservoir at the application temperature. The sealant is heated just

prior to application by pumping through transfer lines immersed in an oil bath.

Cold-Applied Sealant Equipment

The necessary equipment for application of cold-applied sealants depends on whether the sealant is a single-component or a two-component mix and whether the material is hand-mixed or machine-mixed. Two-component machine mixers consist of an extrusion pump, air compressor, and the associated hoses to dispense the components through separate nozzles and mixed in a 50:50 ratio with less than ±5 percent error just prior to discharge from the nozzle. Hand-mixing equipment for two-component sealants is generally a slow-speed electric drill with a paddle mixer or an air-powered mixer. Single component sealants should be mixed to overcome any segregation before they are applied to the pavement. Small hand-held caulking guns can also be employed for small jobs.