What is Concrete Slurry?
Concrete slurry is a semi-liquid material produced when wet grinding, drilling, or cutting concrete. Each of these methods uses manufactured diamonds as abrasives. As the abrasive moves across or through a concrete slab, it removes part of the substrate. Slurry is the combination of concrete that’s removed, chemicals that have been absorbed in the concrete prior to the process, and water used to eliminate airborne dust while cooling the cutting diamonds.
Why Proper Slurry Management is Crucial
There are concerns when disposing of wet concrete slurry. The first is from the concrete particles that are suspended in the water. They can hold contaminants that must be kept and not allowed to seep from the slurry once disposed of. The contamination could consist of metals, semi-volatiles, or volatiles.
Concrete has a naturally high pH value. The value begins around 13 when the concrete is freshly placed. Under normal conditions, it will gradually drop down to 10.0-11.5. Carbonation and chemicals will lower the pH level. This drop in value happens in years and not days. When the slurry water mixes with the ground concrete particles, the pH of the water will increase to a value equal to that of the concrete. If this high pH value water seeps into the groundwater, it has the potential to contaminate streams, rivers, and the underground aquifer.
The EPA can impose severe penalties for the illegal dumping of concrete slurry. Here are fines that can be assessed.
- On-the-site fines:
- Up to $7,500.00 for individuals and up to $15,000.00 for corporations.
- Additional Fines:
- If waste is causing damage to waterways.
- Criminal Penalties:
- For knowing of violations, up to 6 years in prison and/or $100,000.00/day.
- Resource Conversation and Recovery Act (RCRA) penalties: Up to $50,000.00 per day of violation and/or up to 2 years in prison.
Concrete Slurry Waste Solutions
There are ways to avoid EPA fines. The first is to use a washout area to clean equipment and properly dispose of concrete slurry. A washout area is a dedicated zone where you can clean equipment and dispose of slurry waste without risking and damaging the environment. Whether you are cleaning equipment, or dumping the slurry, the area will hold any runoff liquids and combine solids for safe and easy disposal. To be able to dispose of the solids in the washout area, the water needs to evaporate completely, leaving the cake behind. This is the lowest cost method but depending on the temperatures, it can take time before the water has evaporated.
Recycling concrete and washout water is the most environmentally safe method and can be the least expensive overall. Using a flocculant in the washout area or slurry vault to separate the concrete solids from the water will reduce the disposal cost. As the water separates, the solids fall to the bottom. This makes it easy to remove the water. Once the water has been removed, the cake is the only thing brought to the landfill. This is the most effective way to recycle concrete washout water. Once the separation process has been completed, the water can be reused, and the remaining solids disposed of in an approved dump site.
Using super absorbent material as a solidifier in the washout area will absorb the free water while mixing with the solids. This powder material will absorb much more than its own weight in water and ready for disposal once the dry cake is produced. This method has the highest disposal cost. Not only are you disposing of the solids, but also the weight of the water. When disposing at a certified dump site, they charge by the pound so you will be charged for water disposal too.
How to Dispose of Concrete Slurry with Each Process
Before all processes
- Locate a dump site that will accept the final slurry cake.
- There might be regulations they follow. They should be able to supply them to you.
- What tests, if any, will they need to be performed on the dry slurry cake?
- There are landfill sites that require no testing at all.
Recycle water process before landfill disposal.
- Chemicals and equipment needed.
- DiamaPro® Slurry-Vault (washout container)
- DiamaPro® Slurry-Sifter (filter bag)
- DiamaPro® Slurry-Splitter (flocculant)
- DiamaPro® Slurry-Sponge (solidifier)
- DiamaPro® Slurry-Spout (transfer pump)
- Pressure washer – 3+ gallons per minute.
- Auto-scrubber
- Step 1
- Insert the filter bag into the vault.
- Attach the bag to all four corners of the washout container.
- Step 2
- Find the size of the auto-scrubber recovery tank.
- Add 4 oz. of flocculant into a gallon of potable water (hydrate) to treat every 20 gallons of concrete slurry recovery from the recovery tank.
- If the recovery tank is 40 gallons, hydrate 8 oz. of flocculant.
- Allow it to set for a minimum of 15 minutes while hydrating.
- Pour the hydrated flocculant solution into the recovery tank of the auto-scrubber and begin extracting the slurry from the floor until full.
- Step 3
- Connect the transfer pump to a pressure washer.
- Insert the pump into the recovery tank.
- Activate the pressure washer and pump the slurry into the washout container fitted with the felt-lined bag.
- Step 4
- The quantity of water within the slurry will depend on how fast the dewatering will take.
- If a large amount of slurry is generated, a second or even third washout container system could potentially be needed.
- As the water filters through the filter bag, pump it out.
- The filtered water can be reused in the auto-scrubber or disposed of.
- Step 5
- There will be residual water on the surface of the slurry cake after dewatering has taken place.
- Sprinkle the solidifier onto the cake.
- With a ½” drill and mixing paddle, mix the solidifier into the damp cake.
- Repeat if not all water has been absorbed.
- Step 6
- The cake is ready for disposal.
- With a forklift, remove the cake-filled filter bag.
- Repeat Step 1
Washout with Solidifier
- Chemicals and equipment needed.
- Washout container/area – must be watertight and not allow any fluids to absorb into the ground or flow away from the area.
- DiamaPro® Slurry-Sponge (solidifier)
- DiamaPro® Slurry-Spout (transfer pump)
- Pressure washer – 3+ gallons per minute.
- Auto-scrubber
- Step 1
- Extract the slurry from the floor with an auto-scrubber.
- Step 2
- Connect the transfer pump to a pressure washer.
- Insert the pump into the recovery tank.
- Activate the pressure washer and pump the slurry into the washout container/area.
- If possible, the auto-scrubber can be dumped directly into the washout container/area using the attached discharge hose.
- Step 3
- If a large amount of slurry is being generated, potentially a second or even third washout container/area might be needed.
- Step 4
- Sprinkle the solidifier onto the cake.
- With a ½” drill and mixing paddle or shovel mix the solidifier into the slurry
- Repeat if not all water has been absorbed.
- Step 5
- The cake is ready for disposal in a landfill.
- Repeat Step 1
Evaporation process
- Equipment needed.
- Exterior Washout container/area - must be watertight and not allow any fluids to absorb into the ground or flow away from the area.
- Pressure washer – 3+ gallons per minute.
- DiamaPro® Slurry-Spout
- Auto-scrubber
- Step 1
- Extract the slurry from the floor with an auto-scrubber.
- Step 2
- Connect the transfer pump to a pressure washer.
- Insert the pump into the recovery tank.
- Activate the pressure washer and pump the slurry into the washout container/area.
- If possible, the auto-scrubber can be dumped directly into the washout container/area using the attached discharge hose.
- Step 3
- If a large amount of slurry is generated, a second or even third washout container/area could potentially be needed.
- Allow the water to evaporate from the slurry.
- This can take a considerable amount of space and time to obtain a dry cake depending on environmental conditions.
Choosing the Right Slurry Waste Solutions
How does one select the right slurry solution for a project? There are factors that will affect the final decision.
Environment plays a big part in the choice. Where the project is within the building, is the building dried in (roof, walls, windows, doors installed), is there an area available to store a washout container/area, and will the washout container/area need to be outside in the elements all need to be considered.
If the building doesn’t have room for a washout area, it must be outside. If it is outside, having it tented is a way to keep rain from mixing with the slurry causing added dewatering. If the project is being conducted during freezing temperatures, the washout area needs to be heated or inside away from the elements.
If environmental concerns are important, the recycling process will be the process selected. It allows the reuse of water and reduces the cake weight which in turn reduces landfill disposal costs.
When working on small slurry-generating projects, using a solidifier can be most helpful. This can be done in a small, designated area inside or outside of the building. Building a dike using the solidifier on a watertight surface works well. If drilling, broadcasting a layer of solidifier in the immediate work area should hold the slurry.
Conclusion
Cement slurry management when wet grinding, drilling, or cutting concrete is the responsibility of the contractor generating the slurry or, if outlined in the contract, the General Contractor. Having the correct tools and chemicals allows for easy management. DiamaPro® Systems has developed systems to aid in safe slurry disposal.
DiamaPro® Systems has everything needed to bring slurry management within compliance. No matter what size, location, or environmental concerns, DiamaPro® can help you capture and dispose of slurry. Niagara Machine, DiamaPro Systems' primary distributor, has well-trained field representatives nationwide to call on for help. They have all been well-trained in proper concrete slurry management and will provide you with their experience while collaborating with you.