Concrete Repair Posts

10 Things Not to do with Concrete Repair Epoxy

Posted by John Bors on Thu, Aug 2, 2012 @ 13:08 PM

 

1.      Leave Large Quantities of Mixed Epoxy in Bulk

concrete repair epoxyEpoxies that cure at room temperature generally give off heat (are exothermic) when the two components react. Most products if mixed in quantites as small as a pint will heat up to as much as 450°F (this includes hardware store products). So, if you need a large quantity of epoxy adhesive or coating, mix only what you can use within the potlife and plan to place it on the substrate as soon as possible.

 

If the epoxy in bulk is not used quickly, the generated heat can be enough to boil the epoxy and some products will generate smoke and possibly ignite as well as melt a plastic pail. Should this occur, you can add dirt or sand to the hot epoxy to cool it down and prevent additional smoke—be careful!

 

2.      Use wet aggregate

If you want to add aggregate (or sand) to epoxy to make a mortar or grout, use aggregate that contains less than 0.2% moisture. Don’t use sand that was stored in a loose pile that could contain excess moisture or the strength and properties of the mixed grout can be negatively impacted.

 

3.      Mix with a stick

Two component epoxies require adequate sheer in order to properly react. With some lower viscosity products, a rotary paint mixing blade on a drill is fine. For higher viscosity epoxy coatings or pastes, a “Jiffy” type mixer is strongly recommended as it will provide shear without adding excessive air to the mixture.

 

4.      Use wrong proportions

Most epoxies can tolerate off-ratio proportions to 5% and some epoxies will cure with higher off-ratio mixes. To be safe, stay within 5%. Most professionals who mix epoxies by hand will purchase either disposal plastic measuring cups to ensure proper proportions or on critical projects will weigh each component separately. If you elect to weigh the components, check the proper amount of A and B as the weight ratio is often much different from the volume ratio.

 

5.      Apply epoxies wearing a t-shirt, shorts and sandals

The minimum proper personal protection equipment (OSHA term is PPE) for mixing epoxies generally includes eye protection (safety glasses, face shield or goggles), skin protection (rubber gloves, long sleeves and pants). In most jurisdictions, there is also a requirement to have an eyewash station available within less than a minute from the location of the work.

 

6.      Apply epoxies to dirty or contaminated substrate

Most professionals know that taking a shortcut on surface preparation can ruin a project. Attempting to adhere to concrete, wood or steel that has oil contamination is foolhardy and the bond will likely fail in use. Discuss the issue of contamination with your supplier and he will provide the best way to prepare for the application. In most cases, a slight removal of the surface with a grinder or shotblast with some roughening (similar to 40 mesh sandpaper) is a preferred approach.

 

7.      Apply epoxy over a moving crack or joint

When repair epoxies or protective epoxy coatings are used on concrete (particularly in exterior applications), the concrete will expand and contract linearly in relationship with temperature. This means that cracks or cold joints will become smaller as the concrete temperature increases and larger when the concrete temperature decreases. In some climates, the daily temperature cycle is as much as 40°F or more. In these locations, the crack will move a considerable amount each day and the repair material will crack almost immediately.

 

8.      Store epoxy overnight in pickup truck or outside in cold weather

If the nighttime temperature is expected to fall below 40°F, the epoxy stored in the truck will be cold. It will cure very slowly and also be much thicker and difficult to mix properly. In cooler seasons, store epoxy as close to 73°F as possible prior to use. In some cases, professionals will intentionally “condition” their epoxy by storing it at an elevated temperature so that it will cure faster and be easier to mix especially in cold weather applications.

 

9.      Place neat epoxy in large voids

For the same reasons as stated in item #1, epoxies in large masses can become very hot to the point where the epoxy is damaged. If it is necessary to repair a large void, consult your manufacturer for his recommendations. One solution to prevent damage from epoxy exotherm is to mix aggregate with the epoxy which lessens the exotherm effect as most of the mass is in the aggregate. We offer several low exotherm products (a low viscosity liquid epoxy and a paste epoxy) which are especially designed for this use.

 10.  Purchase the exact quantity

With the high costs of delays, manpower, shipping and mobilization, most professionals purchase excess materials for their project. For coatings, often a 15% safety factor is used and for other concrete repairs or restorations with epoxy, the factor can be 5-10%. We offer a great estimator tool and you can preset the safety factor to account for accidental losses and unforseen quantity needs (exact measurements on construction projects are never exact which is why they are often called estimates).

Please call or write us at ChemCo Systems if you need more information on concrete repair epoxy or epoxy protective coatings.

Tags: epoxy repair tips, concrete repair epoxy, epoxy coatings

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

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