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What is Concrete Floor Grinding?

Concrete floor grinding is very popular in the construction industry; it is the process of smoothing the concrete and also making them glossier by using a series of diamond tools and sealers. There are big benefits of grinding the concrete floors, it can make the concrete floors with good looking, and also make cost-effective maintenance on concrete floors.

The benefits of doing concrete floor Grinding

Durability and low maintenance

Except for the concrete grinding, there are other flooring options, like the vinyl layer on unpolished concrete floors. However, the unpolished vinyl flooring are easily gotten damaged or worn along with the rate of use, or the changes of wear conditions. While the polished floors are very durable and have high wear resistance. Due to the durable nature, there is only minimal maintenance is needed. It may take up to 10 years before doing the restoring the concrete floors.

Affordability

Just by grinding and polishing, the concrete floor will get good looking, no need the purchase and installation additional materials. Also, the polished concrete floor only requires minimal maintenance. So it is really cost-effective to do concrete floor grinding.

Necessary preparations before grinding concrete floors.

1. Get the PPE ready

Always keep in mind that “safety is the priority”. Do remember to wear the PPE (Personal protective equipment), including the dust mask, ear protection, goggle, foot and hand protection devices.

2. Check the floor

3. Prepare the repair kits

If there are damages and cracks on the floor, then a repair kits is needed. a crack chaser blade and joint sealing material are necessary.

4. Choose Right Concrete Floor Grinder

Grinders are varies in different sizes, weight, power and direction of rotation, etc. according to the size of your floor as well as the concrete conditions to choose the most suitable grinder for your needs.

5. Choose Right Diamond Tooling

Diamond tools determine the efficiency of the grinding process; you need to choose the diamond tooling with right grit and metal bond hardness. Generally the 14 grit, 30 grit, 70 grit and 120 grit are the frequently used grit sizes on metal bond diamond tooling throughout the grinding process. When come to the bond types, it depends on the concrete hardness, if the floor is hard, the metal bond should be softer, in opposite the metal bond should be harder. After choosing the diamond tooling ,it is necessary to check diamond tooling after a pass or two to determine if the concrete is too soft causing excessive wear or if the concrete is too hard and it’s not grinding much at all

6. Hardening Agent

For starters, it is easier to achieve better polishing results with harder floors. Liquid hardeners are used to make concrete floors harder and denser. Hardening also helps to protect the floor from water penetration, staining and future damages.

The Steps Of Grinding Concrete Floor

1st Step:14 grit tooling and PCD tooling (Conditional)

If the concrete is extremely hard and there are heavy sealers on it, then the 14 grit tooling or PCD tooling is needed. However, before using the 14 grit, pls do to evaluate the concrete condition again, make sure to use the14 grit diamonds as the first step if it is absolutely necessary. Because it will take a lot of time to get the heavy scratches out left by the 14 grit diamonds or PCD tooling.

Do remember using concrete vacuum to clean the entire floor (mopping and wet vac pickup is an option for smaller floors). The key is to clean up all dust and diamond grit that drop from the diamond tooling. If you don’t clean up after each step, the subsequent grits will grind over top of residual bigger diamond grit, which will create scratches on the floor.

2nd Step: 30 grit diamond tooling

30 grit diamond tooling is the most used grit size; all of the primary grinding steps will be finished with 30# grit tooling. If you want to expose the aggregate, it must be completed by the end of this step. By running the grinder at a lower RPM, the grinding speed can be increased, then the diamonds will penetrate the floor without getting overheat.

If there is any patch or repair work is needed, then the repair work should be done after 30 grit grinding. Also, another 30 grit grinding is required after the repair work is completed.

Fix medium bond 30/40# metal bond tool to handheld grinder or walk behind grinder, Start at one side and grind from“west to east” across the entire concrete floor. Make sure to overlap the grinding pass as close as possible to the previous grinding pass.

After the grinding process is finished, clean up the floor with vacuum or scrubber.

Change the direction and go “north to south” pass after the “west to east”, still take care of the overlapping, make sure the grinding passes overlap one another as close as possible. Do the same cleaning job again.

It is better to use grind the floor in swing style, in this way, the grinding passes can be blended. Also, take care of your pace during grinding, it is great if the grinder leaves solid grinding pass. However, if there is swirl grinding passes on the floor that means you push the grinder too fast, you need to slow down. Also, there may be the occasion that the grinding speed becomes slow suddenly, it is possible that the soft top layer has been remove off, the harder concrete comes out, so you need to replace the medium hard tooling with a more softer bond. 

After the “north to south” pass completed, have a short break, check the entire floor carefully. If the exposed aggregate doesn’t meet your expectation, then go back and repeat the grinding process until get the exposed aggregate as you want.

3rd   Step: 70 grit diamond tooling

Replace the medium hard 30/40# tool with Medium hard 60/70#, grind the perimeter of the floor as you did in step 2. After the grinding is done, do the clean job again.

4th   Step: Repeat 70 grit diamond tooling

Still use the 60/70# tooling, repeat the grinding process.

The initial scratches left by the 30/40# should be removed in this step, if you still can see the significant scratches, do the grinding until all the big scratches are gone.

Remember to vacuum the entire floor area before moving to next step.

5th   Step: 120 grit diamond tooling

Change to the 120/140# diamond tooling and repeat the grinding process. Vacuum the entire floor area carefully and check your grinding job so far. Do extra grinding job if needed.

6th   Step: Use the resin polishing pucks to do transition

Use the 50 grit or 100 grit resin polishing pucks to do transition grinding, to make preparations for the polishing job in the following steps.

When we buy diamond saw blade, we hope it can last as long as possible, but the blade life varies depending on a number of variables. Of course, the most key factor is the quality. The blade quality should be superior, and then we can talk about its lifespan.

Before we know how to use the saw blade as long as possible, we should know the factors that affect the longevity. Basically, these factors can be classified into 3 categories.

cutting green concrete

I) Blade Itself

  1. The diamond concentration

How can we define the diamond concentration? There is standard in diamond tool industry. The diamond concentration will be 100%, if there is 4.4 karat diamond in one cubic centimeter of segment, if there is 3.3karat diamond, the concentration is 75%.

Except for the weight concentration, there is volume concentration as well. The diamond concentration will be 100% if the diamond volume occupies 1/4 of the total volume of segment. So, increase the diamond concentration, the blade life can be lengthened.

30/40 to 60/80, this is the popular grit size range for diamond saw blade. The blade will have longer life with fine diamond grit. However, we have to consider the material hardness before choosing the grit size. If the blade is to cut granite, it is better to choose 40/50 or 60/70, while if the material is concrete, 30/40 is better.

The bond is composed of several different metal powders; it is used to wrap the diamond grit. The harder bond, the better resistance to wear. To improve the hardness of the bond, cobalt or tungsten carbide is usually added to the bond.

II) The materials

Cutting a hard material such as concrete requires a different blade than one used to cut a soft, abrasive material such as asphalt. The harder material requires diamonds to be exposed more quickly, and a softer bond to hold the diamonds to the segment.

If the material is hard stone, then choose the fine diamond grit.

III) Cutting Parameters during operation

  1. The Linear Speed

In practice, the linear speed of blade is confined by the equipments, blade quality and cutting materials. In consideration of the blade lifespan and cutting efficiency, the cutting linear speed should be different according to different material. To cut granite, the optimum linear speed is between 25 to 35 m/s. For high quartz content and difficult cutting granite, remove the blade speed limit is appropriate.  cubic boron nitride tiles in the production, the use of smaller diameter diamond saw blade, the line speed can reach 35m / s.

2.  Cutting Depth: 

Diamond cutting depth is the key parameter in relation to diamond wearing, cutting performance and cutting material. Normally, the cutting depth should be set smaller if the blade linear speed is high. According to the current technology, the cutting depth of the diamond is between 1mm ~ 10mm. Usually with a large diameter saw blade cutting granite blocks, the cutting depth can be controlled within 1mm ~ 2mm between the feed rate should be reduced at the same time. When the linear speed is high, a large cutting depth should be selected.

3.  Feeding speed: 

    The feeding speed affects the cutting efficiency, impact force on blade and the cooling of cutting area. A suitable feeding speed should be set based on the nature of the cutting material. Generally, to cut the soft material, the marble for example, in order to get big cutting depth, the feeding speed can be slower. While, if the material is granite, the feeding speed should be higher, otherwise the diamond grit will be worn out easily. The feeding speed on cutting granite is 9-12m/min.

Tips for longer life
Given these variables, there are still some things we can do to maximize the lifespan of diamond saw blade.

Choose the right blade for the job. There are concrete blades/asphalt blades/granite blades/green concrete blades/ring saw blades, etc. These blades are specially designed for different applications, while general-purpose blades can cover a wide variety of cutting tasks, application-specific blades are engineered with a specific bond to meet the needs of a certain application. They do the best job and will last longer.

So, before choosing the saw blade, it is better to ask yourself the following questions

Follow the instruction on blade. if the blade shows “wet,” then use this blade when wet, it is the common mistake to use wet blade dry. If a wet blade is used in dry condition, it is high possibility that the blade segment will burn up without taking long. But every dry blade can be used wet, in fact the lifespan of dry blade will be longer if water was added during cutting. Also, water will eliminate heat and dust.

Don't bury the blade. Another common mistake is burying the blade all the way to the flange, or forcing the blade through the material being cut.

Forcing the blade through material will damage the saw by increasing the amperage, burning up the motor and overheating the blade, which causes premature wear and damage, Metal in the diamond rim can get so hot that it actually covers the diamonds. Glazing over diamonds on the rim can cause blades to dull and stop cutting, even though there's a lot of life left on the diamond rim of the blade

Don't push too hard. There is operating limit on both equipments and saw blades. Equipment and blade will fail if push too hard. Just follow the recommended rpm.

Install the blade properly. Pay attention to the directional arrows labeled on the blade to ensure the blade is installed properly and spins in the intended direction. The blade will wear out quickly if it is spinning the wrong way.

The pinhole behind the center arbor is also very important on walk behind saw blades, the pinhole on the flange steadies the blade and prevents wobbling.

Be careful in the turns. If you are going to change directions, do remember to switch off the saw machine and lift up the blade. The blade easily get bend and break if the saw machine change directions while the blade is still in the cut.

When we say a diamond saw blade is good or bad, normally we consider the cutting efficiency and life of the blade. The blade segment is composed of diamond and metal bond. As the main function of metal bond is to hold the diamond. So, the diamond grit size and concentration ratio affect the cutting performance.

There is a saying “the higher diamond concentration, the longer life and the slower cutting speed.” However, this saying is not right.

The blade life relies on the diamond quantity, the more diamond the longer life. Of course, there is also a limit. If the diamond concentration is too low, every diamond will receive bigger impact, easy to get cracked and drop out. While, if the diamond concentration is too high, the diamond will not get edged properly, the cutting speed will slow down.

Before you are looking to buy a diamond blade, it is necessary for you to take some time to reserch various options, as choosing the wrong one could result in decreased efficiency, increased cost and project downtime.

Choosing the right blade will make the process of cutting material smoother and safer as well as provide a seamless cut. Here are some advices for your reference

Please be clear about the material you are going to cut.

If you choose the wrong type of diamond blade for the materials that you need to cut, it could have disastrous consequences. You may end up wasting expensive material as the diamond blade does not give you a clean cut, and it can also cause safety issues due to the blade skipping and not effectively being able to cut the material.

Choosing the right blade will ensure that the process is quick and easy. When you are cutting materials such as concrete and asphalt, you should be aware of exactly what the mixture is made up of. Finding out what aggregate was used is the best way to match up a specific blade to your materials. If you deal with a professional diamond blade supplier, they will be able to help narrow down your shortlist when you provide the details of the material you need to cut.

What equipment will you be using?

Whether you are using a saw or a power cutter, you need to know the speed and power specs of the specific tool. This will determine what size blade you need as well as help determine what type of surface you need on the blade. The choice between a dry blade and a wet blade is determined by the capabilities of the tool.

Is the material you will be cutting wet or dry?

This is an important factor to consider when choosing a diamond blade. Dry blades are only to be used when cutting shallow material or making step cuts. This is due to the fact that dry blades need substantial air flow around them to prevent excessive heat from building up. Wet diamond blades need to be used with water in order to cool it down and prevent it from overheating. It will also decrease the amount of dust that is generated. You need to ensure that there is a continuous water supply on the wet blade or else you will be putting yourself and fellow workers at

The “age”, or length of curing time, greatly affects how the diamond saw blade performs on cutting concrete. Before choose the right diamond blades, it is important to know something about the curing of concrete. The “state” of concrete from initial pouring to a period of 72 hours and over can be divided into 3 types, temperature, weather, moisture, aggregate, time of year, admixtures and composition also influenced the concrete state.

Type 1 – 0 to 8 hours


normally, this is the “green concrete” we always talk about. The concrete is considered in its “green“state 0 to 8 hours after the pour, meaning it has set but has not hardened completely. With green concrete, the sand in the mixture has not bonded to the mortar blend firmly and will cause extreme abrasive action once the physics of sawing begins. Further, the slurry generated by green concrete is equally as abrasive and will require special undercutting protection for the steel core of the diamond blade, the Soff-cut blades are specially designed blade for green concrete cutting, with the special designed skid plate, it can effectively prevent the chipping during cutting. Typically, sawing control joints of highways, industrial flooring, driveways, runways and similar projects is performed during this state.

Type 2 – 8 to 24 hours


the concrete is considered as cured 8 to 24 hours after the pour. The sand is held firmly adhered to the overall mixture. Generally, control joints established in State 1 are widened during this time.

Type 3 – 24 to 72 hours

The concrete is considered as cured 24 to 72 hours after the pour. The sand is held firmly in the mortar mixture, and the overall abrasive actions and properties of the concrete are greatly diminished. Now, consideration of the aggregates, compression strength and steel content of the concrete become important factors in determining proper diamond-blade selection.

Useful guide on how to grind concrete floor more efficiently

Preparatory work for grinding

  1. Always keep in mind that “safety is the priority”. Do remember to wear the PPE (Personal protective equipment), including the dust mask, ear protection, goggle, foot and hand protection devices.
  2. Measure the size of the floor and choose the right equipment to do the job, is the satellite grinder, cub floor grinder or hand grinder is needed? Anyway, choose the right tool will yield twice the result with half the effort.
  3. Check the floor condition, to check if the floor is damaged too much or wear out too much. If so, patching or crack chasing will be needed before grinding.
  4. Measure the hardness of the floor to decide which type of metal bond diamonds should be used. The hardness of the concrete floor is normally classified by Mohs’ hardness, generally, the hardness of concrete floor ranges from 3 to 5. On the site, we can find some substitution to the durometer, the keys or iron nail for instance. If we can make scratches on concrete floor by keys or iron nails, then the hardness is below 5, otherwise it is higher than. Make sure to check several areas on the floor, because the hardness is different from slab to slab.
  5. If the walk behind floor grinder is needed to do the job, then take care to keep the grinder flat. Because the gouges will be generated if you hold the floor grinder on an edge. It is difficult to remove the gouges.
  6. Prepare the diamond grinding tools to be used in the whole grinding process. Generally below are the frequently used diamond tools: Diamond grinding cup wheels, grinding diamonds, polishing pads, grinding plates, PCD diamond tools

Equipment and tools to be used

Steps of Grinding

Step 1.

Connect the handheld grinder or walk behind grinder with the dust extraction system. Start the grinder machine and carefully grind around the perimeter of the working area. This is the testing process, on one hand, to check if the grinder machine is running well, on the other hand, we can check if the concrete is too soft causing excessive wear or the concrete is too hard and it is not grinding much at all.

Step 2.

Fix medium bond 30/40# metal bond tool to handheld grinder or walk behind grinder, Start at one side and grind from“west to east” across the entire concrete floor. Make sure to overlap the grinding pass as close as possible to the previous grinding pass.

Clean up the floor with vacuum or scrubber, this cleaning step is to clear up all the dust and residual diamond grit come off the tools, if the cleaning job is not done, the residual diamond grit will leave scratches on the floor.

Tips #1: 30/40# tool is for standard concrete grinding, usually the concrete is medium hard and there isn’t heavy sealer on the floor. However, if the concrete is extremely hard and there is sealer on it, pls choose the 14/16# to start this step

Tips #2: Running the grinder at a lower RPM, almost half the speed of the grinder. Because the main object is to expose the aggregate, lower the grinder speed can allow the diamonds to penetrate the floor without overheating too early. The sign of the optimum RPM is that there is a lot dust generated during grinding process.

Step 3

Change the direction and go “north to south” pass, still take care of the overlapping, make sure the grinding passes overlap one another as close as possible.

Do the same cleaning job as you did in step 2 after the “north to south” pass completed.

It is better to use grind the floor in swing style, in this way, the grinding passes can be blended. Also, take care of your pace during grinding, it is great if the grinder leaves solid grinding pass. However, if there is swirl grinding passes on the floor that means you push the grinder too fast, you need to slow down. Also, there may be the occasion that the grinding speed becomes slow suddenly, it is possible that the soft top layer has been remove off, the harder concrete comes out, so you need to replace the medium hard tooling with a more softer bond.

The Step 2 and Step 3 determine if the concrete floor has a good finished “looking”. So, after the “north to south” pass completed, have a short break, check the entire floor carefully. If the exposed aggregate doesn’t meet your expectation, then go back and repeat step 2 and step 3 until get the exposed aggregate as you want.

Step 4 (optional)

Patch or repair work can be done in this step. Also, if the floor needs crack chasing or filling, then arrange it in this step.

Step 5

Replace the medium hard 30/40# tool with Medium hard 60/70#, grind the perimeter of the floor as you did in step 1.

Step 6

Still use the 60/70# tooling, repeat step 2 and step 3, grind “east to west” first, and then go for “north to south”

The initial scratches left by the 30/40# should be removed in this step, if you still can see the significant scratches, then pls repeat step 5 until all the big scratches are gone.

Remember to vacuum the entire floor area before moving to next step.

Step 7

Change to the 120/140# diamond tooling, and then repeat step 2 and step 3. Vacuum the entire floor area carefully and check your grinding job so far. Do extra grinding job if needed.

During the process of using diamond saw blade, there are always some problems will occur, some are the defect of the blades, some are caused by the improper use. Below are 9 normal problems caused by the improper use of blade, but not the responsibility of the diamond blade manufacturer.

1.SEGMENT LOSS

CAUSE: Blade burnd due to insufficient water, usually evident by dark blue steaks on the core beneath the segment, or heat(burn) marks on the segments, also by extreme side pressure, i.e., machine abor bent or operator neglect.

SOLUTION: Segment can be replaced. Normally blade doesn’t need to be re-blanked.

2.BLADE STOPPED CUTTING (LIFE STILL REMAINS)

CAUSE: blade too hard for application

SOLUTION: can be dressed on softer material, such as haydite block or silica brick.

CAUTION: Glazing will usually continue, unless softer material is intermittently cut or softer bonded blade is used.

3.VERTICAL HAIRLINE CRACKS APPEAR IN SEGMENTS

CAUSE: Normally, blade too hard for application, RPM too high.

SOLUTION: softer bond must be used if determined this is the problem occurs most often in concrete cutting where much harder & more abrasive-resistant metal bonds are used.

4. VERTICAL HAIRLINE CRACKS APPEAR IN CORE

CAUSE: possibly bond too hard for application, or due to unforseen circumstances blade does not have proper tension for r.p.m required.

SOLUTION: softer bond, if it’s determined the bond is too hard. Otherwise customer must review all circumstances,i.e.,r.p.m, machine, and material to be cut. Check holes can be drilled at base of crackes, depending on life remaining blade size, and steel core fatigue factors.

5. HORIZONTAL HAIRLINE CRACKS APPEAR IN CORE

CAUSE: blade doesn’t have proper tension for machine r.p.m and is wobbling, bond could be too hard, machine not tracking parallel to blade, etc.

SOLUTION: Blade must be reblanked

6. ARBOR HOLE OUT OF ROUND

CAUSE: Material excessively abrasive.

SOLUTION: Blade should be removed before segment loss and reblanked. If cutting is to be extensive in the same material and under the same conditions, then a special wear guard core is recommended.

7. UNDERCUTTING OF CORE BENEATH SEGMENT

CAUSE: Material excessively abrasive.

SOLUTION: Blade should be removed before segment loss and reblanked. If cutting is to be extensive in the same material and under the same conditions, then a special wear guard core is recommended.

8. CORE DISHED- BLADE LOST TENSIONING

CAUSE: Possibly bond too hard, r.p.m not proper for blade diameter, blade flanges not parallel or other machine problems.

SOLUTION: Blade can be retensioned depending upon the extent of damage.

9. MORE SEGMENT REMAINS ON ONE SIDE OF THE BLADE THAN ON THE OTHER

CAUSE: Insufficient water on worn side.

SOLUTION: check water ports to ascertain if water is flowing freely on both sides of blade. Remember, water around the blade does not mean it is being properly utilized.

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