Alchatek Blog

Are You Smarter Than a Fifth Grader?

Jeff Foxworthy often asks if you are smarter than a fifth grader. Well if you're not, don't worry about it; you're probably still capable of estimating the amount of foam needed to raise a concrete slab. Through a combination of easy calculations, product information, and some site considerations, you should be able to estimate your slab lifting materials without too much trouble.

First of all you need to think about the basic volume calculation. How many square feet of slab are you jacking, how much do you need to lift it, and is it the whole slab being lifted or is it just one end of it? Calculate the volume (length x width x depth), adjust for the percentage of the slab being lifted, then compare it to the expansion properties of the injection foam in order to determine how much you need.

Beyond the geometry required to estimate lifting the slab, you must now take into account some job specific considerations. This is where it becomes critical to qualify the volume of material included in your proposal. And just as important, this is where you need to make sure you have included enough so you get the job done right and don't have to go back to the customer asking for more money. Sometimes that's unavoidable if you encounter surprises; but if you keep a few considerations in mind this can often be avoided.

Soil Compaction

Isaac Newton's third law of motion determined that for every action there is an equal and opposite reaction (or was that Wayne Newton, ha?). If you are trying to lift a slab, a porch, or a pool deck on ground with poor compaction or water issues, the foam will compact the soil until it is dense enough to support lifting the slab or deck. And the heavier the object, the more densely the ground will have to be compacted. Make sure to measure the soil conditions (using a penetrometer or probe) and adjust your material estimate accordingly.

Size / Shape of the Object Being Lifted

Extremely heavy objects can be lifted with polyurethane foam using a small amount of pressure and material. Often times the most difficult lifts are the smaller objects. Something with a small footprint, like some front steps or a stoop can be very dense and frustrating to lift. Injected material is going to seek the path of least resistance until it is contained enough to generate the lift. For a front stoop, the path of least resistance is usually going to be out the sides; meaning lost material and more cleanup. Proper injection techniques can contain the escaping material, but it is advisable not to underestimate your material on an innocent looking small job.

Voids

Sometimes the ground can be well compacted but due to erosion factors (usually misdirected water runoff) slabs and other foundation type settlement can occur. Although the object has only settled a few inches, sometimes a much deeper void can be hidden from view. In these cases it is advised to use a probe through a hole drilled in the slab in order to get an idea of the depth of the void. Personally I have seen voids that went down 20 feet, so do not ever assume anything. Most void depths are pretty easy to determine and you will get the optimum expansion out of your material when filling them. But once again, calculate the extra volume to fill it and spell it out in your proposal.

Typically for a lifting job with no other considerations aside from lifting volume, we recommend adding an additional 10-15% onto your material estimate to cover yourself. Just make sure you do a thorough evaluation of the conditions and possibilities so you don't underestimate the job and have to go back to the property owner with your hand out. 

If you haven't already, make sure you read this blog post on our custom Alchemy-Spetec material estimating app for your smartphone.

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Any successful slab lifting job begins with a thorough site evaluation. Some new jobs are like previous jobs, some are a little bit similar, and many are a completely new experience altogether. A site evaluation is not limited to, but should include Identifying the Cause of Slab Settlement, Gathering Information, Identifying Potential Hazards, and Visualizing the Mobilization.

Cause of Slab Settlement

Determining the cause of settlement is usually the first step in beginning your evaluation. The cause can be any number of things such as erosion, ground water, sink holes, poor compaction, and buried debris that breaks down over time. Correctly identifying the cause will help you determine if slab jacking alone will solve the problem or whether a combination of lifting, stabilizing, and / or void filling will provide the permanent solution.

Gathering Information

The next phase should include gathering information from multiple sources. This includes dimensional information such as length and width of the slab; but also, the amount it has dropped, to help determine the volume of structural foam needed to lift the slab back into place. Make sure to bring your camera, notepad, and tape measure. Gather information from the property owner; find out about any known irrigation, electrical, water, or drain lines. Specifically, find out from the owner about any areas or features that need protecting around the injection site, the location of your rig, and all points in between where your crew may be working.

Identifying Potential Hazards

If the job is outside of a building, find out where the utilities are and have them professionally located. It's a lot harder to get paid when you have just drilled through the owner's power line or filled his landscape drains and fountains with foam. Additional information that may be available could include a soil engineering report, a structural engineering report, and reports from the builder of the structure. Don't forget a hammer drill, bits, and a penetrometer to determine soil compaction. Think about other issues that might create problems like slabs binding (concrete saw?), bent rebar from a settled slab, etc. Make sure you have considered all the tools you are going to need for the job and the cleanup.

Visualizing the Mobilization

After the data gathering is complete, it's time to visualize the job site as a whole and consider any challenges to mobilizing and physically reaching the areas that need lifting. Think about potential issues: How big is your rig? Is a trailer rig or a box truck rig going to face challenges getting into and out of the area? And once your rig is in place, do you have enough heated hose and pump power to get the required volume of material where it needs to go to do the lift?

Some of the above seem obvious but it's often the obvious things that get overlooked. Mistakes can drastically cut into your profitability and reputation. There's a reason pilots go through the same checklist prior to every flight. Sometimes you only get one chance to do the job.

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Understanding the causes of slab or structural settlement is key for the contractor to help identify potential opportunities for slab jacking with polyurethane.

Though there are many reasons for sunken slabs, we have identified the three main conditions that cause the settling issues we like to fix. These include erosion, poor compaction, and biological decay.

Erosion Often Leads to Concrete Slab Settlement

Erosion is the most common cause of settling and the most common reason for slab jacking. Poor drainage, improperly placed downspouts, leaking drain pipes, and broken water lines are common culprits. Water can either slowly erode soil over time, or very quickly erode away the soil beneath a concrete slab or structure causing it to settle.

Poor Compaction Can Cause Settlement & the Need for Raising Concrete

When backfilling on a jobsite, the site contractor is supposed to walk in backfill (drive over it with heavy equipment) and compact it in small lifts. However, this isn’t always done properly for one reason or another (inexperienced operators or people taking shortcuts). The result can be soil that will continue to compact itself and settle over time.

A great example of this is bridge approach slabs. These slabs are found on roads and highways all over the world. Bridges typically sit at a higher elevation than the roads that approach them. During construction, the final section of road (typically a concrete slab) is built on backfill to raise the elevation to meet the bridge. Over time, the slabs can settle due to poor or improper compaction. Compounding the problem is the fact that when a slab settles a little, the expansion joint opens up and allows water to get underneath the road, adding erosion to your compaction problem.

Biological Decay Can Result in Sinkholes and Sunken Concrete Slabs

Construction trash pits, buried trees, and other biodegradable materials all eventually break down. Sure enough, there always seems to be some corner of a building or a separate parking area or driveway that ends up right over it. These situations can range from slight settling to very severe.

Sometimes you have a combination of factors that cause settling. As we discussed in the bridge approach slab issue, poor compaction can lead to settling which will open a joint and allow water to compound the problem with erosion. Property owners and managers should not ignore these problems, or they will become more expensive to fix over time.

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Slab Jacking vs. Replacing Concrete

So, you're faced with a sunken concrete slab that could be repaired via complete replacement or being lifted back into place. How do you know which option to choose? Here are a few things to think about.

Raising Concrete is More Cost Efficient Than Replacing

If the slab is in good shape, and is of a reasonable enough size and thickness, it is usually going to be more cost effective to lift it back into place with structural polyurethane foam. Our PMC pumps can deliver the AP Lift series of foams as far as 400 feet away through heated hoses. And remember, wherever you deliver new concrete, you have to haul away old concrete.

More Environmentally Friendly with Polyurethane Concrete Lifting

Everybody wants to be green and take care of the environment these days, because it's the right thing to do. There is an environmental impact every time concrete is replaced. The cement manufacturing process is the second largest cause of greenhouse gas emissions in the world. Additionally, there is the issue of what happens to old concrete once it is removed. One would like to think it is recycled, but more often than not it ends up being dumped. Hopefully that would be in a landfill, but we've all seen piles of concrete rubble in places where it would be considered trash or pollution. It's worth considering. Meanwhile Alchemy-Spetec's AP Lift 430 and AP Lift 475 are so environmentally friendly they are NSF approved for contact with drinking water in their cured state.

Polyurethane Slab Jacking Requires Less Downtime

Last but not least, how long can a property owner or manager afford to have that area out of service? Consider a busy warehouse, an airport taxi way, or a bridge approach on a highway. There is an economic impact when those are out of service for replacement. It can be a couple days before new concrete is traffic ready. Wouldn't it be better to have it lifted in a few hours, and then back in service 15 minutes after the slab jacking is done? I know what I would want.

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A home or commercial building is only as good as the foundation it’s built on. And regardless of how well-constructed a structure may be, most foundations settle. That’s just a fact of life. Shifting soil compaction and many other environmental conditions that tend to cause settling, however, should ideally be stabilized before significant structural damage is done.

One or two minor hairline or shrinkage cracks shouldn’t necessarily send off any warning bells – though both merit monitoring. But multiple or widening cracks indicate more serious problems and may lead to additional damage. For the property owner, this can disrupt business, displace occupancy, and cause a domino-effect of infrastructure woes serious enough to break the bank. Or worse. Litigation can result if preventative action isn’t taken before loss or injuries occur.

These factors alone make acting sooner rather than later imperative. Stabilization and lifting are key solutions to consider in cases of foundation or slab distress. How can you know for sure if slab lifting or soil stabilization is needed? Watch for these five warning signs:

Bulging or Cracked Floors

It’s estimated that 60 percent of homes built on expansive soils result in shifting and heaving in all or even just part of the foundation. One can’t-miss sign of distress caused by wobbly soil compaction is buckling and bulging wood floors or evidence of cracking concrete in other types of flooring.

Cracked Walls

When soil moisture levels are all over the map, you can be sure that problems will ensue. Poor drainage, soil decomposition, naturally occurring conditions, nearby sewer line damage, underground aquifers – all can play a role in fluctuating soil moisture levels that lead to foundational settling. Cracked sheetrock or concrete walls are a warning sign that trouble is brewing underneath the surface.

Sticking Doors

When doors suddenly start sticking or won’t easily open or close, it’s a sign that either moisture levels are causing the door to swell or something in the structural frame has shifted. And that something might very well be the foundation.

Displaced Moldings

Look up toward the ceiling or down at the floor for moldings that may have gone wonky, jutting this way or that.

Leaning Trees, Fence Posts, Etc.

It’s hard not to notice a tree, fencepost, mailbox, or flagpole that is leaning like the Tower of Pisa. If you don't associate this abnormality with foundational distress, you should. It can be a sign of sinkholes – the kind that gape and maw without warning. If the site you're evaluating is in what is known as karst terrain, which about one-fifth of the nation is, it's susceptible to sinkholes. Likewise if there are abandoned coal or other mines, sewer construction or groundwater pumping nearby. All are signs that further investigation may be needed, pronto.

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Welcome to the 3rd and final part of my blog post series “Sealing Leaks on Remote Job Sites”. In Part 1 and Part 2 of this series, I described a remote leak seal job I assisted a customer with and the unique preparations it required. So to pick up the story where I left off - there we were, in the jungle, about a mile from our trucks. Of course we were doing our best to deal with the August heat and humidity. At least we had poison ivy, ticks, and yellow jackets to keep us company as we tackled these pipe penetration leaks on the aerial manholes.

As I mentioned, we removed as much of the old mortar from the pipe penetrations as we could. We also drilled our port holes at this time, about 5 inches apart and all the way around the pipe penetration. The port holes were drilled at a 45º angle, and located so that the injected resin would hit the pipe about midway through the penetration. Then we flushed out the areas and port holes with clean water.

Now it was time to seal it. We soaked oakum in the polyurethane and then gave it a quick dip in a bucket of water to get it activated. Then we packed it into the pipe penetration as deep as we could get and all the way around the pipe completely to form a back seal. Then we did it again forming another seal all the way around the pipe penetration but this time towards the outside wall of the manhole. Finally we injected the urethane into the ports working our way from the bottom to the top, completely around the pipe penetration.

For this application, AP Seal 500 was the right choice. It reacts when contacted by water, it's flexible, and it bonds tenaciously to concrete. Plus, its low viscosity allows it to get into tight cracks and voids to seal off leaks. If there is water present in the cracks, it can be injected straight. We actually injected it with water using a two chambered cartridge and static mixer. One chamber held the resin and the other was filled with water just prior to injecting. The reason we did this was because we were working during the middle of the day when sewer flow was the lowest. There was no leaking water present in the penetrations so we had to provide our own. Injecting with the water provided the “kick” to make the urethane foam expand and form an excellent seal between the front and back oakum gaskets we created.

Although it was not in the contract, we couldn't ignore the other small leaks through the manhole walls. Plus we wanted to help the county in return for their clearing the footpath to the manholes. These particular leaks were below the pipe penetrations and were constantly seeping sewage water. There were literally hundreds of yellow jackets swarming on the wet manhole face but they didn't bother us. To repair these leaks we drilled port holes that would intersect the cracks at an angle. As always, we flushed out the holes with clean water. As an experiment, we only put in a couple ports and then started injecting the same polyurethane; this time without additional water as there was already water present in the cracks. Sure enough, the low viscosity resin traveled throughout the cracks as it was injected and sealed off the areas where water was working its way through.

When we were finished, the manholes were completely dried out and there was no longer sewage leaking into the sandy soils beside the creek. It always feels good to get a job done when there's the added benefit of doing something to protect the environment. It also feels good when a project goes smoothly because you took the extra time to visualize it, plan the work, and work the plan.

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In Part 1 of this series, I laid out the challenges my customer's crew faced repairing pipe penetrations on aerial manholes in a very remote area. The repairs aren't that hard, but when you have to carry all of your materials and gear across creeks and down gullies, you have to work smart.

Previously, I indicated how we took the time to do a thorough site evaluation. Then we created a plan and a master list of what we would need; knowing we would have to carry everything in and out. We decided to repair the penetrations with a combination of polyurethane soaked oakum as a packing material and a low viscosity hydrophilic polyurethane that we would inject.

These particular pipe penetrations had originally been sealed with mortar and the manholes were of brick construction. Since they were also quite old, the leaks were not very hard to find. In fact there were gaps up to one inch in width between some of the pipes and the penetration holes. The mortar had just crumbled away. In addition to the penetration leaks, there were also several leaks through the walls of the manholes. A skim coat of mortar had been applied to the outside surface, covering the bricks. But now waste water and sewage was finding its way through the many brick seams and joints, and the crumbling mortar too.

I'll spare you some of the things we used that are common to all of our jobs; items such as buckets, mechanical ports, drill bits, gloves, safety glasses, etc. Items of note that did come in handy on this remote project were as follows:

1. Plastic sheeting to cover our gear when it rained and ponchos for ourselves.
2. A hand powered, 2-component cartridge gun. We were prepared to use a small CO² tank to power our pneumatic gun but it turns out we did not need much pressure to inject the resin.
3. Battery powered Ridgid brand hammer drill with 3 extra batteries. It took one battery to drill port holes 360º around each 22” diameter penetration. During lunch we would take the batteries to the truck and recharge them with our generator.
4. We brought a light weight plastic chemical sprayer. We were able to fill it with water from the creek and it generated enough pressure to flush our drill holes and the areas around the penetrations where we dug out the old mortar.
5. Light weight dry oakum. This was great for sealing the large gaps. Dry oakum can be soaked in polyurethane, packed into joints and cracks, and activated with water. It will swell up and become like a flexible gasket.
6. Bug spray and a sense of humor.

In my next and final installment on this subject, I'll go into detail about how we actually completed the repair and saved the planet. To wrap up this one, I would just say that it pays to think things through and be creative. There are usually several ways to get the job done; in our case we had to get the job done without exhausting ourselves getting there and back. We brought lightweight cartridges and oakum, battery powered hammer drills, and simple plastic sheeting to protect from the elements. These things took the place of pumps, compressors, electrical power, and shelter.

There's one last thing I recommend looking in to: Even though this was a job that could only be accomplished on foot, the owner of the pipeline was the county and they have to maintain a path so they can walk the line, make repairs, and cut up trees that fall across the pipes connecting the manholes. For this job we worked hand in hand with the county, walked the line with them, and got them to send in their crew to clear out the path anew for us. Our repairs repaid them for their free help.

Want in-depth info on leak seal procedures and products?

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Hopefully these tips on overcoming obstacles on remote job sites will be of assistance on your next out-of-the-way project. At one point I had the opportunity to advise a customer who was repairing pipe penetrations of aerial manholes along a drainage basin in SW Atlanta. Aerial manholes are typically found in low spots next to creeks and rivers. They are usually connected by steel or ductile iron sewer pipes that are above ground and thus, so are the penetrations.

The conditions of the job site were unique as there was no access to the individual manholes except by foot. This particular project covered a winding 1-1/2 miles through ravines and involved several crossings of the stream. The goal was to seal the 18” and 22” pipe penetrations that were leaking raw sewage down the faces of the manholes located along the creek. In this report I will let you know how we got started in preparation for the unique set of challenges this project presented.

First of all, a thorough evaluation of a remote job site must be undertaken. This should be done prior to submitting a bid, but it should also be done again with an extra set of eyes prior to commencing the work. Then create a plan and a master list of what you will need:

1. Consider all of the possibilities of how to mobilize; where can you set up the nearest base camp for your trucks and supplies.
2. What tools or alternative tools can be used to get the job done; realize there are certain conveniences you're not going to have, like generators and air compressors, and find alternative methods.
3. Select the right Leak Seal materials to get the job done such as AP Seal 500, AP Fill 700 and activated oakum.
4. Prepare a good safety plan. We experienced rugged terrain, snakes, bees, ticks, extreme heat, downpours, and lightning. Think about how to protect your people, your materials, and your gear. Make sure to have first aid and hydration available on site and at the base camp.
5. Have a communication plan – make sure you have reception between the job site and the base camp. If cell phones don't work then bring walkie talkies. Have someone at the base camp to watch gear, to get supplies when necessary, and to be available for help in case of an emergency.
6. Be prepared to clean up your job site with respect for the environment. If you haul it in, be ready to haul it out.
7. Last of all, choose the right people for your crew. Think carefully, because these kinds of jobs are not for timid or easily discouraged personality types.

In my next post I will go into detail on the procedures and tools we used to stop the leaks through a combination of polyurethane injection and activated oakum.

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Water leaking through concrete can lead to structural failures, sinkholes, and other costly types of property damage. For property owners, it is important to be aware of potential problem areas in your facility, factory, or residence. For concrete restoration and waterproofing contractors, it is important for your business to know where to look for leak sealing opportunities.

So where are the areas that contractors and property owners need to be looking? Here we have broken it down into two broad categories: Commercial / Industrial / Municipal and then of course, Residential.

Commercial / Industrial / Municipal

• Tanks: Water and Wastewater Treatment Plants, Aquariums
• Infrastructure: Concrete Pipe, Manholes, Pipe Penetrations, Lift Stations, Pumps Stations, Utility Vaults
• Industrial Plants: Machinery Pits, Containment Structures, Retaining Walls, Slab Joints
• Tunnels: Tunnel Segments, Retaining Walls, Headwalls and Wing Walls
• Commercial: Floors, Parking Structures, Elevator Pits, Basements
• Specialized arenas for sealing leaks in Mines, Dams, and Power Plants.

Residential

• Single Family: Basements, Foundation Walls, Swimming Pools, Fountains, Seawalls, Retaining Walls
• Multi Family: Elevator Pits, Parking Garages, Seawalls, Pools, Basements
• Farms: Silos and Tanks, Earthen Dams, Manmade Ponds

Alchemy-Spetec manufactures an effective range of polyurethanes designed to seal leaks for all of the above issues. We also strive to continually educate the market. 

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