In construction industry every project involves nearly some form of cutting concrete or core boring. Hand-held saws are used in the construction project to cut or shape paving slabs, stones or other concrete products.

Cutting concrete may seem to be simple but on practical ground there are several safety measures to keep in mind to have a safe and successful concrete cutting or boring project.

Safety and concern becomes an issue with concrete cutting because the concrete dust generated by the cutting action contains high respirable crystalline silica content. Breathing in this dust can lead to the development of respiratory ill health affecting your lung tissue resulting in serious breathing difficulties depending on the extent of exposure

Therefore, dust control becomes an important consideration when cutting concrete either with a saw or a drill or core boring bit.

The two most dust Control methods are:

1. 1. Wet Cutting System:

In wet cutting the dust is collected in the cooling water and pneumatic devices that pulls the dust away in an air stream. Wet systems are preferably used on saws powered by combustion engines or compressed air. Wet dust suppression should not be used on saws that are electrically operated.

Wet cutting systems spray water onto the rotating cutting disk to reduce dust emissions. There are two sources by which water may be supplied.

(a) Portable Pressurised Tank System
This pressurized tank system consists of a polypropylene bottle containing approximately eight litres of water. The bottle is connected by narrow plastic tubing to two spray heads or jets normally attached to opposite sides of the guard. An on-off valve is fitted to control the water supply. An in-line filter is often fitted to prevent the heads becoming blocked. The spray heads/jets can be made from polypropylene but brass is considered a more resilient material. Water flow is produced by pressurizing the tank by hand.

(b) Mains Water System
This system is essentially the same as the tank, except the water source is from mains supply through a hose to the two water jets. Studies have shown that a minimum flow rate of about 0.5 litres per minute is required to optimise dust suppression. Low flow rates  will reduce performance. Very much higher flow rates do not improve dust suppression, they only increase the need to refill the portable tank more often.

Difference between Portable and Main Water System

The portable tank needs to be regularly pressurised to maintain the flow rate.

The mains water system does not have this limitation but portability is restricted by the need to cut near a mains supply. The portable tank is more flexible as it can be easily transported around the site but it still requires a water source for refill.

For cutting a paving slab with a diamond tip blade normally requires a single pressurization stroke with portable system whereas tank sytem require re-pressurising during the cut if adequate control is to be maintained.

Precautions:

Diamond cutting blade or other abrasive disk cutting device such as concrete saw, uses water to  lubricate and cool the cutting tools. The spillage of cooling water on to the surface during  cutting should be managed by providing a  drainage or a vacuum system like a wet vacuum which can be used to control the spillage of cooling water.

When using electric powered tools, adequate grounding, insulation and appropriate ground fault protection must be provided. If proper safety measures are not taken by the operator while operating electric toll and standing in a puddle of water can be fatal .

Core drilling machine requires an additional precaution as most of the machines depend on suction to keep the base in place during the drilling operation. The friction of the base suctioned against the floor provides the resistance to rotation while drilling depending on wether the floor is slicker or rough. The rough floor may provide more friction and will not allow a strong vacuum seal against the floor. In either case the vacuum seal is not completely reliable and may fail during the drilling operation. The operator must be aware about this and should keep his body out of the possible rotation path of the machine base during   core drilling operation.

A reliable and secure method to work with core drilling  machine is to have a concrete anchor through the base in addition to the vacuum seal. Most machines have a provision for such an anchor and the small hole required for the anchor is easily repaired in the concrete floor.

What lies beneath the concrete should be an important consideration even for a straight line cut with a concrete saw or making a round hole with a core drill. Concrete imaging and scanning is the technique used for relocating the presence of rebar,pipes, conduits, steel wire mesh,sinkholes, plumbing holes or even electrical conduits often buried in or under the concrete.

Concrete cutting equipments require sharp tools, a good supply of cooling water and a skilled operator to handle these machines. Operating concrete cutting equipment can be simple and safe, but the operator must be familiar with the potential hazards and should be well skilled in his concrete cutting profession.

1. 2. Local Exhaust Ventilation:

The method of local exhaust ventilation used on hand held concrete cutting saws uses the saw’s guard as a type of high velocity hood. The guard is connected to an industrial vacuum cleaner which provides sufficient exhaust ventilation to capture the majority of dust emitted during the cutting operation. Guards with adjustable inner sleeves are preferable. These maximize enclosure and can be adjusted to accommodate different depths of cut. This system does not produce the wet slurry associated with wet dust suppression.

Common Problems and Solutions with Control Systems:

(a)Wet Systems
• Chalk is used to mark the line of cut which can easily wash off by water supply generated in wet system. Wax crayons or a carbon brush (from old electric motors) are better options to be used instead of chalk.
• Operators require waterproof PPE as both pressurized portable system and mains water system make use of water.

(b)Local Exhaust Ventilation
• Abrasive wheels wear during cutting activities. A system with an adjustable inner sleeve does not automatically compensate for abrasive wheel wear. Diamond wheels wear less quickly and are recommended for this system.
• A generator is required for both vacuum cleaner and saw. Small portable generators can be moved around the site on a wheel barrow.
• Operators should be aware of correct posture as local exhaust uses 9 inch diameter wheels which require operators to bend a little lower during cutting operation.

Personal Protective Equipment
• Concrete cutting operator should be provided with suitable RPE as concrete cutting products contain high silica.
• Dust mask is required while emptying the vacuum cleaner.

Concrete slab sawing is the latest technique that is used in cutting and breaking very think concrete structures. Literally, the process of Concrete slab sawing and flat sawing is a path breaking method for architectural implementations. Currently there are several agencies that are particularly located for slab sawing in DC, in MD and in VA. But the flat sawing and slab sawing processes are spreading worldwide with all its updated tools and machineries. Nowadays, this process of building has become so popular that there are special training given to those who are willing to work in the challenging projects of concrete sawing and flat sawing.

As the recent global concern is the minimization of pollution, it is by means of concrete slab sawing and flat sawing that we get a much dust free way to break and cut the thick concrete slabs and bars. In today’s world, there are large constructions that are made in scanty space. Therefore, the traditional process of jack-hammer method is of no use since it is too time consuming and makes the whole of the surroundings too dusty. As an effective replacement, there is this concrete slab sawing method that is eco friendly and cost effective. The slab sawing in VA, MD and many other places employ highly skilled professionals in their projects. Side by side there are grooming sessions for flat sawing in DC, MD, VA and many other places to make the new comers well versed in concrete slab sawing jobs.

There are many latest electrical and completely automated tools that are used for concrete slab sawing. But the most commonly used tool is the concrete slab sawing saw. In the projects where it is needed to work with thick concrete slabs, diamond blade fitted tools are used that has diameter of about 30 inches or more. With the help of this advanced tool, a doorway penetrating a think wall of about 24 inches can be easily cut out. The blades move very fast and can be operated by means of electricity. Moreover, the cutting that is done by such a concrete slab sawing process is so précised that it leaves least amount of dust particles after the job done. The complete project of flat sawing and concrete slab sawing is very fast and with least amount of risk.

The state authority of DC, VA, MD and other neighboring places are very much particular about the safety and health factors of the employees that are employed in this type of projects. Although the tools and equipments are wholly automated and there are least possible chances of any kind of accidents, still the agencies of flat sawing in MD, VA and other areas are allowed to work in concrete cutting job after a valid license. Also, health and safety certificate is provided to each of the employees that are engaged in flat sawing in VA, DC and MD. Concrete slab sawing is rapidly used in some of the top valued projects like excavation, bridge building and mining.