Concrete Repair Posts

When do you need a professional for Concrete Crack Repair?

Posted by John Bors on Tue, Jun 19, 2012 @ 19:06 PM

concrete crack repairConcrete cracks. It’s a fact of life. Some cracks might not need attention while others could have serious structural consequences. How can you tell the difference?

 “It is important to accurately assess structural cracks to determine what is significant and what is not,” said John Duntemann, a principal at consulting engineering firm Wiss, Janney, Elstner Associates (WJE). “You have to properly identify the extent and cause of cracking before you can implement the right repair solution.” 

Cracks in concrete might be caused by a number of factors such as thermal expansion and contraction, sub-grade settlement, the loads being applied and even earthquakes. This all adds up to internal and external stress that manifests as large and small cracks.   

In many cases, however, there is uncertainty as to what to do about cracks.  Pete Barlow, a principal at Contech Services Inc., a company that repairs, strengthens and waterproofs concrete structures, said his company is constantly being contacted by anxious building managers and owners. “Many times a week, people send us photos of cracking at their facilities asking for advice,” said Barlow.  

Concrete Crack Classification

There are various methods of classifying cracks in concrete. One primary way is to split them into two groups: structural and non-structural. Structural cracking affects the integrity of the building. Cracking in support beams, columns and load bearing areas is of particular concern. 

Non-structural cracks, on the other hand, are not detrimental to building integrity, though they may need to be addressed due to cosmetic reasons, if there is water leakage or to take proactive steps to prevent those cracks from growing over time and eventually reaching the structural stage. Tiny fractures can also lead to other challenges. 

“Small cracks in below grade foundation walls can allow water to migrate into the structure,” said Barlow. 

Width, length and depth of the cracks are another consideration. Hairline cracks are generally not a problem, but it depends on where they are. A high frequency of them, though, could indicate an underlying stress issue that needs to be addressed.  But as the size of openings increases, so should the concern. As a rule of thumb, cracks larger than 0.015 inches or larger,” said Barlow, should be investigated. “The larger the width, the greater the likelihood you have lost aggregate interlock,’ said Barlow. “But repairs can be done on cracks down to 0.005 inches.” 

A third issue is location/orientation. Cracks in random directions are of lower priority than those in beams, columns or other load bearing areas. “If one side of the fracture is offset from the other, that is often a bad sign,” said Barlow. “Other warning signs are closely spaced cracks or repetition of cracking at the same locations on each floor.” 

Concrete Repair Epoxy

In many cases, epoxy injection is used as the optimum technique for concrete crack repair. Although there are many epoxy types and uses, high performance epoxies manufactured for structural concrete bonding and crack repair are the focus here. 

concrete crack repair aDuntemann gives the example of cracking that appeared in a cooling tower being constructed at a synthetic fuel plant. Cracking developed at the ends of pre-stressed concrete beams.  Demolishing the structure and starting over was not considered an option. Management brought in WJE to find an alternative. “The beams were injected with epoxy and load tested to verify their structural capacity,” said Duntemann.  

In another case, WJE was retained to investigate large cracks in the concrete caps that sat on top of concrete pile foundations. “We developed a method of reinforcing the pile caps and injected an epoxy into the cracks to reconnect the fragmented caps,” said Duntemann. 

Water, however, presented a further challenge – the epoxy had to deal with a saturated environment. WJE requested help from ChemCo Systems’ team of chemists. They formulated an epoxy that could fill three quarter inch cracks and cure in the presence of water. ChemCo specializes in making two component structural epoxies and application equipment designed for concrete structural repairs, including at industrial plants, bridges, stadiums and parking decks to name a few. 

“You often run into challenging environments such as cracks full of water, cold temperatures or exceedingly wide cracks that require a customized solution,” said Duntemann. “The ChemCo Systems staff is very knowledgeable about epoxy in general and their own products in particular, and the environment in which these products are applied. We typically identify potential products, and consult with the manufacturer like ChemCo Systems for advice on the product application.” 

Contech Services, too, has worked with ChemCo Systems for almost two decades. All field personnel have been thoroughly trained in the use and application of ChemCo Systems epoxy resins and equipment for structural repair. 

“Their chemists understand the physical properties of the various resins and how to blend them to ensure the job is done right,” said Barlow. “We prefer ChemCo Systems as it acts as a single source of equipment, material and expertise for a broad line of resins. Most major manufacturers have two or three resins at best. ChemCo Systems has about a dozen so when you run into something unique, they know which one or which mixture is best suited.”  

Summary

Building owners noticing cracks, then, are advised to contact a structural engineer to assess the extent of the damage. They can help determine whether or not it is a significant issue. 

“As building owners are typically not engineers, they are advised to retain a licensed structural engineer who can evaluate concrete cracking,” said Barlow. He also advises against a do-it-yourself approach for all but the most minor problems. In his view, there are too many factors involved in the engineering and chemical formulation side to leave anything to chance. 

“When a problem is identified, it is important to retain professionals with experience solving these problems,” said Duntemann. “The correct solution to a problem requires a good understanding of the cause of that problem.” 

For more information, call (800)-757-6773 or fax (650)-261-3799. E-mail is email@chemcosystems.com or visit www.chemcosystems.com. For more details about epoxy injection, visit: http://chemcosystems.com/pdfs/crack_injection_for_concrete_crack_repair.pdf

Tags: concrete crack repair, concrete repair epoxy, epoxy injection

Consider Lifecycle Costs for Concrete Restoration or Replacement

Posted by John Bors on Fri, Jun 15, 2012 @ 11:06 AM

It seems obvious on the surface that repair or restoration of cracked or spalled structural concrete in a stadium, parking deck, bridge, tunnel, dam, dock or runway will reduce ownership costs. But if the underlying damage is severe, it may be more cost effective to tear down and rebuild.

A critical element in this evaluation is an assessment of overall lifecycle costs. This is the time-honored method to determine the best course of action with regard to structural concrete repairs. By considering all aspects of the financial equation, an owner can achieve a fuller understanding of available options. Spending a little more today to fix an immediate problem correctly may considerably reduce the total cost of the structure over its lifespan.

“Life cycle costs (LCC) are cradle to grave costs summarized as an economic model of evaluating alternatives for equipment and projects,” said H. Paul Barringer, P.E. of Barringer & Associates. Inc. “The objective of LCC analysis is to choose the most cost effective approach from a series of alternatives to achieve the lowest long-term cost of ownership.”

Concrete Condition Survey epoxy plus steel for seismic upgrade

Identifying unseen conditions and the extent of damage is a key element in any LCC evaluation. Non Destructive Testing (NDT) is often used by engineers to obtain detailed structural information. NDT techniques include sounding, galvanic pulse testing, ground penetrating radar and in-situ load tests. When more upfront condition detail is available, the engineer can prepare a more accurate remedial cost estimate and it is less likely the owner will face costly change order surprises should he elect a repair option.

A huge repair bill may tilt the balance towards replacement as is the case with some older hospitals in California where state regulations require emergency buildings to meet current more stringent earthquake codes. A major healthcare provider in Los Angeles, for example, recently demolished two large buildings erected around 30 years ago and is rebuilding. The high cost of improving the structural elements of these facilities to meet current seismic standards was one of several factors which led management to select the replacement path.

In some cases, replacement may prove to be the better option for an older structure with only a few years left before the design life ends. In all instances, it is prudent to hire an engineer for a structural lifecycle evaluation and condition survey. If the damage is not disruptive to the entire structure, often the best option is to repair.concrete spall repair testing

Take the case of San Francisco Airport, which has taxiway lights embedded in concrete structures. When the concrete collars for these lights began to fail, the airport tried a quick setting cementitious repair material which failed to eliminate the problem. Faced with a live heavily used aircraft taxi lane, it considered all options for further repair or complete replacement. In this case, it chose a proven solution capable of being injected in harsh loading conditions: a customized epoxy formulated specifically to cope with the difficult working conditions and without compromising concrete integrity. “The ChemCo epoxy stabilized our taxiway lights and eliminated further deterioration,” said Charlie Freas, a civil engineer at San Francisco International Airport. “This proved to be the right decision in the long term, both financially and structurally.”

The airport has since used similar epoxy formulations to repair cracking in parking structures, service tunnels below groundwater level, and the airport’s light rail system, as well as for concrete spalling on taxiway aprons and ramps.

With regards to pavement concrete spall repair, the airport is constantly inspecting its runways, aprons, and the surrounding concrete infrastructure for any signs of degradation in order to avoid flying object damage (FOD) which can cause catastrophic damage to jet engines. “As concrete spalling can be substantial at times and the consequences so significant, we would rather replace an entire concrete section than be faced with the possibility of having to buy a new airplane engine,” said Freas. “However, we have confidence that effective epoxy spall repairs provide the flexibility and strength to support our planes without further spalling.”

Factors to Consider for Concrete Restoration

Freas pointed out that lifecycle costs may not be the only factor to take into account when it comes to the repair versus replace question. In some instances, the airport needs to realign a runway or change the grade, at which point all associated concrete areas may be completely removed and replaced.

concrete crack repairSimilarly, the Port of Oakland in California has to look beyond the subject of lifecycle costs for certain structures. One tenant, for instance, utilized an 80-year-old wharf complex for container crane operations. While the wharf clearly needed to be rebuilt, the port had no temporary site available. Repair was the only possibility.

Another time a tenant dropped a 60-ton piston from a height of 100 feet onto a wharf resulting in severe damage. In this case, lifecycle costs favored repair. The port harnessed epoxy injection for concrete crack repair of the wharf deck and soffit (underside). “I’ve inspected the wharf below sea level and the ChemCo Systems customized epoxy prevented any corrosion of the rebar, returned the structure to its original strength and extended its lifespan,” said Bill Morrison, Manager of Harbor Facilities for the Port of Oakland. “After many years, these wharves are still operating as designed.”

Repurpose for Changing Times

A recent fast-growing trend is to find and adapt new uses for vacant buildings or structures that have remaining useful life. Governments world-wide are passing new regulations and may offer monetary incentives to recycle or adaptively reuse existing buildings rather than choosing demolition. This is already happening widely in the U.S. where the practice is often referred to as brownfield redevelopment. In China’s large cities, owners are rewarded with financial incentives if they agree to convert an old hotel into condos or an aging office structure into a warehouse. Several former parking decks have been transformed into computer server farms in Beijing after exterior shells were revamped.

This repurposing trend for existing buildings is a high growth element of the sustainable construction movement and is beginning to eclipse new construction in urban areas of North America due to architectural preservation, environmental and waste disposal concerns.

 Whether you elect to repair, restore or replace concrete, do it right, select the correct materials and consult an engineer who can help you evaluate your options from a lifecycle perspective. Call or email us at ChemCo Systems if you need help with concrete restoration, repair or protection.

Tags: cracked concrete repair, concrete restoration, runway epoxy, concrete spall repair

Baby carrots, F-16's and flexible epoxy

Posted by John Bors on Wed, Jun 13, 2012 @ 12:06 PM

What do F-16’s, F-18’s and baby carrots have in common? They have all landed on CCS Binder Patch, Nosing, Slurry (PNS) which is our low modulus (flexible) epoxy.F 18 lands on flexible epoxy

PNS is our most popular binder for use in repairing control joint nosings and spalls, often located in very tough applications like Navy and Air Force runways, municipal refuse handling facility floors, large vehicle repair shops, machine shops and even food processing grinding wheels.

These days, it is very popular to reuse old concrete floors in some buildings that have been repurposed from industrial use to retail or commercial. The control joints in the old floor often need repair or rebuilding. To accomplish the joint repair, a horizontal section is cut out on each side of the joint and a plastic piece is placed in the old opening as a block out, then a PNS-based grout or polymer concrete extended with aggregates is poured or troweled into the new slots on both sides of the joint.

Most of the time, PNS is extended with 4-5 volumes of gap graded aggregates to provide a durable (5000 psi) surface that is highly resistant to chipping, impacts, point loads and large temperature swings. When used as an extended binder, it has a useful working life of up to 45 minutes at 72°F, so there is time to properly place the entire batch you just mixed. It should be noted that a mortar mixer is the best way to obtain the shear needed for optimum blending of aggregates although some contractors use a rotary 5 gal pail mixer with a scraper blade. If the aggregate extension is not extreme and the application is small, a Jiffy mixer can be used in a pinch. Just don’t use a cement mixer—it does not generate sufficient shear to properly wet out the aggregates.

PNS is a very good substrate wetting binder and will bond to damp and even completely saturated concrete. It will also adhere to steel, wood, FRP and many elastomers and is ideal for bonding flexible materials to concrete. For best results, ensure that the substrate surface has no contaminants and preferably is roughened to the texture of 40 mesh sandpaper.

flexible epoxy polymer concreteWhat is the role of the aggregates? Depending on the size distribution, shape, hardness and quantity used, they can dramatically affect the placement properties, strength, wear, impact resistance and thermal behavior of the grout. Because the material is flexible and is extended, it will tolerate deeper placements than more rigid epoxy polymer concretes. It’s possible to achieve workable mixes that are only ~10% epoxy with excellent trowelable properties or you can use a slightly lower quantity of aggregates and obtain self leveling. Unlike cementitious patches, there’s rarely a bonding problem and in most cases, priming isn’t necessary. Note that it is critical that the aggregates are dry and should have less than 0.2% moisture. Please call us if you need some advice on locating the best aggregates locally—it is far more cost effective if you buy the aggregate this way rather than shipping a low cost heavy material around the country.

So what’s the deal about baby carrots? Well, we can’t reveal secrets of our best customers. We can tell you that baby carrots are formed from larger carrots that have been cut and ground. The longest-lived grinding wheels are made with a high mod epoxy and a low mod epoxy in a special combination. Similar wheels handle even harder tasks like pistachio nut hulls.

Tags: spall repair, low mod epoxy, low modulus epoxy, flexible polymer concrete, concrete overlay, concrete patch, flexible epoxy

Injection Ports for Concrete Crack Repair

Posted by John Bors on Fri, Jun 8, 2012 @ 16:06 PM

 

Do you always consider alternative porting methods as you prepare to execute an epoxy crack injection repair project? 

Maybe not. Yet the method selected by your field technician may make a significant difference in the quality, linear footage productivity and job profitability. Many crack injection specifications intentionally leave this option to the practical experience and judgment of the concrete repair contractor.

With a goal of filling a crack with epoxy quickly, neatly, and completely, several factors to consider are:

 surface_port_epoxy_crack_injection

  • Crack width and substrate thickness
  • Application temperature and moisture
  • Orientation (ceiling, wall or floor)
  • Gross linear footage
  • Access limitations
  • Surface appearance after repair
  • Average time duration on port
  • Choice of surface seal material (epoxy vs other)

 Many of our concrete restoration contractors use a combination of several porting methods:

     Taped surface ports 

Stripseal-removable-seal-for-epoxy-injectionLow cost ports are established as gaps in the surface seal with quarter inch masking tape applied at the proper interval prior to the surface seal. The tape is pulled before the seal hardens completely. With hand pressure, the injection mix head directly contacts the open gaps left by the tape though a compressible rubber grommet or rubber tip such as our part # B07 which is available in two sizes (see last image below). After the port is filled, soap or wax is manually rubbed over the crack to seal the port. Some of the long time specialty concrete repair contractors insist that this method is the most efficient practice for most crack injection projects. This method is illustrated in the top image for use on an industrial floor and in the second image (to the left) in conjunction with our peelable surface seal StripSEAL.

     Rubber tips, pins, wire, (finishing) nails, straws, golf tees and toothpicks 

These alternatives to tape often require no drilling. Sometimes they are used in combination. For example, rubber tips (such are our part # B07-3 or B07-12) can be located along the crack with toothpicks, (or pins or nails) prior to the seal application. To inject, the toothpicks are withdrawn and the mix head nozzle is inserted into the tip. Conical shaped golf tees work better than standard tees (because of their thicker shaft) but are hard to find.

     Surface ports  plastic-injection-surface-ports-for-crack-injection

Injection molded of PE plastic or nylon, surface ports for crack injection have become very popular in the last 10 years. These consist of a flat base flange perpendicular to a small diameter tube for easy connection to the injection equipment using a 1/8” NPT press-to-fit connection. Although more costly from a disposable parts cost standpoint, field technicians appreciate the benefit of not having to manually hold the injection head against the port, particularly on ceilings or when time on port will be high.

     Packers, Zerk fittings and grease fittings

These port options for epoxy injection are popular when high pressures are used and are standards for use with chemical grouting, a term usually affiliated with polyurethane (PU) injection. PU is a material option for waterproofing and leakproofing but is not considered for structural repairs. Almost always these types of port connections are a most expensive cost option and are used with a drilled hole (see below). These connectors are often self-sealing with a spring loaded ball so the field technician doesn’t have to worry about material leaking from an uncapped port.

     Drilled Injection Ports

Port connections for drilled holes can be made by the contractor at low cost by cutting sections from 1/4 or 3/8” polypropylene supply hose (same as used for the water supply line for an icemaker), purchased as pre-molded units or supplied as a tapered Semko® tip. This method is one of the first choices when injection flows are obstructed by the type of crack, surface obstructions, plugging, or  for accessing voids under a sound surface (such as a de-bonded topping slab). If the crack is narrow, a water-flushed core bit is far superior to an impact bit as it is less likely to pack the crack around the hole with drill fines (leading to more obstruction).

rubber-tips-for-surface-port-epoxy-injection

Tags: plastic crack injection ports, concrete crack repair epoxy, concrete restoration epoxy

Why your concrete repair epoxy is out of stock

Posted by John Bors on Fri, Jun 1, 2012 @ 18:06 PM

 

To our industry friends,structural epoxy mortar

On behalf of ChemCo Systems, we hope that your summer is off to a great start!

We are hearing a number of sad stories from concrete repair contractors across North America. They are telling us that getting epoxy and other concrete adhesives, restoration and repair materials on a timely basis has been a frustrating challenge especially this year.

Why are manufacturers and distributors keeping such small inventories? What is taking so long to fill back orders? 

The answer is that the construction chemical business (which includes epoxy adhesives, bonders, grouts and coatings for concrete repair, maintenance and restoration) is notorious for being impossible to forecast. So the manufacturers of the finished polymer based products don’t know how much raw material to inventory especially since the economy has been in the doldrums for so long. Nor can the manufacturers can’t rely on previous year’s results to help with estimating their needs. Another issue has been that the raw material producers have reduced their inventories and discontinued some very useful specialty additives that are hard to replace in formulations (with little or no notice). Finally, because pricing battles between major brand names for the few large orders have reduced profit margins, the corporate bosses have mandated lower inventory levels.

The net result is that even popular epoxy concrete restoration products are frequently out of stock and sometimes unavailable for a month or longer. 

One contractor recently needed to precisely schedule delivery of materials because his customer was setting a narrow time window for a manufacturing shutdown for a concrete resoration project to repair surfaces in some material storage bins. So he contacted the specified product’s manufacturer a month in advance to place his order for two epoxy repair bonders. With less than a week to go, he recontacted the manufacturer to learn that his material had not been made and would not be available for another month. At the last minute, he called ChemCo to see if we could help.

We were able to schedule, package and ship his order in 2 days.

We can act fast because we don’t report to any big bosses. And in the last year we have increased our raw material inventory levels so we can respond to contractors in last minute panic situations including Friday afternoon at 3 pm. Please give us a call any time you need epoxies for concrete repair in a hurry. You won't be disappointed!

ChemCo Systems epoxies for concrete repair

Tags: concrete restoration, out of stock epoxy, concrete repair epoxy, concrete restoration epoxy