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25 incredible tips for concrete repair with epoxy


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Epoxies are structural repair polymers offering permanent repair of concrete. This brief discussion focuses on tips for success with epoxies including handling, safety, applying, mixing, surface preparation, environmental factors and other considerations for successful repair. It is oriented towards the professional concrete repair specialist contractor.

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25 incredible tips for concrete repair with epoxy

  1. 1. 25 INCREDIBLE TIPSFOR CONCRETE REPAIR WITH EPOXY Leaders in Construction Polymers ChemCo Systems
  2. 2. 1. Surface prep is vitalAs in many other construction activities, taking proper stepsto properly clean and prepare surfaces prior to the use ofrepair materials is critical to the time efficiency and long termsuccess of your repair. Surface preparation methods include(from gentle to aggressive) detergent scrubbing, acid etching,grinding, abrasive blasting, steel shotblasting, scarifying, needlescaling, high pressure water blast, scabbling, flame blasting,bush hammering and milling/ rotomilling.Note that some abrasive methods may leave a thin film ofdust on the surface which should be flushed with a highpressure water blast. For protective coatings, often a shotblast is the best first step with the goals of removing all contaminants, opening pores and light cracks and providing a roughened surface profile resembling 40 grit sand paper (such as ICRI CSP 3). For spalls and crack repair, it is essential to remove all concrete laitance, surface contaminants and traces of form or release oils and curing compounds using some form of abrasive removal. If you are considering pressure washing, 5000 psi has been From Concrete Intl, v 84, No. 6, 2012 determined as the minimum pressure to provide acceptable levels ofcleaning of concrete surfaces. In cases where the cementitious surface was overworkedwhen placed or excess water was used, it is highly recommended that the paste layer bepartially or completely removed for the optimum performance of the repair. Applicablespecifications include: ACI 503R, ASTM 4263, ASTM 4260, ICRI 03732 and ICRI 310.2.2. Elcometer tab pullsEven with the best surface preparation (and a smallmock-up), unexpected issues can interfere with goodsurface bonding. For a small investment, you can test thebond of any repair material or coating in suspect areasrelatively quickly using small circular metal tabs. Thewhole process is explained in ASTM D4541, a testhandled by an Elcometer 106 portable pull tester.Consider that this test has been known to havereproducibility issues, so use plenty of dollies in your evaluation. You can also make a Leaders in Construction Polymers
  3. 3. home-built version that uses 2” diameter pipe caps (ground flat) and an Enerpac®hydraulic cylinder (if you elect this option, have a third party check the calibration).3. Provide a mockup when feasibleThis preconstruction step demonstrates that you are willing to take the extra care toensure a quality project. This tactic is especially useful if you are planning to use a newmaterial. Disagreements should be minimal when the actual appearance is presentedbefore the project starts. Sometimes, you can be compensated for your time andmaterials. 4. Save $ with local aggregates For polymer repair mortar or grouts, many (if not most) manufacturers package their aggregate filled systems in a 3 package system which includes bags or pails of graded sands. Unfortunately, shipping a low cost and dense product such as sand around the country or overseas is very costly and we don’t think that it is necessary. So call us when you develop a requirement for this type of a system and we’ll provide recommendations to locally source a gap graded aggregate system that can provide significant savings for you and your customer. Use only dried sand (less than 0.2% moisture) in polymer mixes.5. Estimate with a waste factor marginFor most of the repair jobs (not counting coatings) where epoxies and other polymericproducts are used, the material cost is typically within a range of 5-10% of the total jobcosts which include other materials, equipment, mobilization and labor. So if youestimate conservatively and your guys run short, there may be several negativeconsequences.First, the guys might shortcut the application rate which might undermine theperformance of the areas that were short. Second, they might run out and call you onlate Friday afternoon looking for a very costly delivery by air on Saturday, or your crewmight have to re-mobilize because the owner needs the area back in service whileawaiting the replacement material. There isn’t much cost risk in buying a little extra asepoxies are very long-lived materials so you can use them on future projects or returnthem in unused condition (we charge a 15% return fee). Plus, if you elect to buy a littleextra material, you likely just saved a lot more on your most expensive cost item whichis labor. Finally, if your guys discover a bit of extra work not originally noticed, you havean option for a change order without excessive costs.6. Operate safelyMaintain copies of all MSDS (now called SDS in the new globalharmonized system) to be easily accessible on site. Don’t Leaders in Construction Polymers
  4. 4. assume that because you’ve worked in the industry for 30 years that the content of theMSDS is the same as in 1982—they are frequently updated and the contents are subjectto change. For example, in the case of accidental ingestion, syrup of ipecac is no longerroutinely suggested.Make sure that your guys wear the proper PPE even in hot/humid weather. Theminimum level of protection for handling chemical polymers for concrete repair typicallyincludes long sleeves, long pants, rubber gloves and safety glasses (with side shields).Other levels of PPE can include face shields, goggles, Tyvex® or other synthetic outerclothing, dust and organic vapor masks and hearing protection. PPE training shouldensure the technician knows how to remove it without contaminating himself so a tripto the washroom or food trailer doesn’t mean more exposure. In some individuals,certain chemicals can cause an allergic sensitivity that can be triggered over repeatedexposures and make working in the field impossible. Encourage your employees to cleantheir work clothing regularly rather than allowing contaminants to build up. Finally, don’tassume your guys will think about drinking sufficient water on the hottest days—you willhave to keep reminding them.7. Soap and water vs. solvents For cleaning epoxies and other polymers from tools, many fieldtechs use acetone or MEK. If there are only minor amounts ofproduct to be cleaned and the bulk material is uncured, you cansquirt a bead of liquid dishwashing soap right on the tool surfaceand rinse off the blade or surface with hot running water. Many ofthe polymers will emulsify and rinse off if you use a little extraconcentrated soap which is far less costly (and never flammable) than solvents. Thesame technique works on cleaning any exposed skin—liquid detergent is better for yourskin than acetone. Some contractors swear by film forming liquid skin protectant creamsfor the times when the gloves are off.8. Save cardboardInstead of disposing of large cardboard shipping cartons, have your warehouse guy savethem and cut them into 12”x12” (or some other favorite size) squares to use as mixingplatforms for small quantities of 2 component polymers or for making small paste mixes.When the project is over, you can toss the cardboard as the epoxy scraps should be inthe hardened form of a cured plastic. 9. Always take pictures Your project site pictures could have a value far in excess of 1000 words. It should be an absolute requirement that your foreman takes shots before and after every job. These can help in many ways: establish baseline conditions, provide visual backing for changeorder situations, assist in accident investigations, provide evidence of quality work andproject completion, are valuable for marketing and establishing credibility and to helpeducate new employees. Leaders in Construction Polymers
  5. 5. 10. Timing an industrial floor or concrete deck Plan your projects so the prepatory steps take place in the morning. Avoid placing impermeable coatings (includes most high solids epoxies and polyurethanes) during periods of rapidly rising temperatures which is usually morning to early afternoon (especially in situations without climate controlled environments). In most areas, the daily temperature cycle has reached its maximum around 3-4 pm (15-1600 hours) so this is a great time tostart the coating. This late day timing minimizes the potential for high rates of vaportransmission to interfere with the success of the coating. If the building has a functionalheating/cooling system, the air conditioner should be run for at least 2 days prior to thecoating to minimize the same issues.11. Don’t wait 30 daysWe offer several primer solutions for bonding, repairing or coating green concreteincluding QuikPrime which even works underwater. You can generally use CCS Coating,QuikPrime 24 hours after concrete placement.12. Hammer your concrete Don’t attempt to fix delaminated concrete withoutconfirming the extent of the problem. Bring a soundinghammer and test the area to be repaired. A heavy steelchain can also be used. Cracks and spalls will sometimesbe caused by poorly bonded topping slabs or old repairswhich have disbonded or never bonded over the originaldamaged substrate. Concrete can debond from steel inelevated slab on pan installations. If the concrete isdelaminated in areas, fixing the cracks without repairingthe underlying delamination is a waste of time. Beprepared to consider the cause(s) and offer a fix for thedelamination as first steps in the repair.13. Heat is speedierMost ambient temperature cure epoxies exhibit reaction rates that increase or decreaseby a factor of 2 for every 18°F or 10°C change in temperature. So if your epoxy repairmaterial is curing too slowly, gently add heat to speed cure times. There are manytechniques for heating which include: heat guns, warming blankets, pre-heating the cansof epoxy before use, warming the substrate with local baseboard heaters contained withtemporary walls of plastic sheeting, etc. It’s best to use temperatures below 300°F(150°C) for speed curing (this includes heat guns). Also since epoxies react by giving offheat (in an exothermic reaction), the thicker you apply an epoxy, generally, the faster itcures. Conversely, if your summer temperatures are very hot, the amount of useful lifeof epoxy mixes may be too short for practical use. In this case, cooling the separatecomponents before use in an ice bath or air conditioned area will help extend the mixedlife. Leaders in Construction Polymers
  6. 6. 14. Get thinner with heatIf your epoxy is too thick, preheat the components before mixing. Store them overnightin a closet with a portable heater or put them in the cab of the truck with the heaterturned up when it’s cold outside. Some field technicians mount a light bulb inside theirepoxy injection pump to warm the epoxy in the reservoirs. An epoxy with a viscosity of1000 cPs at 50°F might have a viscosity of only 150 cPs at 80°F. Don’t forget that useful(mixed) lives and cure times are also affected by temperature.15. Polymers shrinkEpoxies and other polymers have a secret property that is rarely discussed. When A +B components are mixed in proper proportions, most polymers exhibit both linear andvolume shrinkage upon cure. This is because the newly formed cross linked polymertakes up less space than the separate unreacted components. Shrinkage is factor thatmust be considered when the use of repair polymers might involve a thick cross-sectionof cured material.So, how thick is too thick before you will develop a problem such as internal stresses inthe repair? The answer is that it depends on the specifics. There are some tactics whichinclude the use of installing multiple lifts, low exotherm and/or low modulus resins andaggregate filled systems which help alleviate problems when thicker cross-sections ofrepair materials are needed. Please call us for advice.16. Polymers move moreIn addition to shrinkage, remember that most concrete repair polymers includingepoxies have a thermal coefficient of expansion that is greater than that of othersubstrates such as concrete or steel. How much different varies with the polymer but itwould be fair to say that the polymers expand or contract with heat about 5-10 timesmore than concrete or steel over the same temperature change. This is another factorto consider when placing large cross-sections of polymer repair materials. Call us forspecific advice. 17. Moisture vapor can drive you crazy Standard practice for concrete floor construction today is to install a vapor barrier between the structural slab and underlying compacted earth or engineered fill. This practice is relatively new, so what can be done with older concrete floors which don’t have a vapor barrier? Today, if your moisture test shows 3 lbs/1000 sq. ft/24 hrs or more (ASTM F18690), don’t even think about installing animpermeable coating or flooring material without first using an epoxy vapor barrier.We make a great product for this purpose called MVR Coating. When properly used, itwill reduce the vapor drive to a safe level and can be recoated in about 12 hours. Leaders in Construction Polymers
  7. 7. 18. Width matters Before embarking on an epoxy crack injection repair, get a good idea of the average width and depth of the cracks. How? You can start with using a plastic crack card and graduate to a lighted portable crack scope. Remember that for smaller projects, you will consume more epoxy by flushing the gun and cleaning that probably will be used in the cracks. So on smaller projects, your waste factor can be over 50%. Don’t be caught short on materials.19. Roll your portsSurface ports have become a popular tool to use with epoxyinjection. Yet, they can also lead to poor performance onthese projects if they are plugged or fall off in use. Whenplacing ports with a paste adhesive, it is critical that theadhesive doesn’t plug the barrel of the port over the crack.Some contractors have found that mixing their paste adhesiveon a piece of cardboard and then rolling the flange of the portthrough the adhesive (rather than using a trowel to applypaste) works best. Others insert a cocktail straw ortoothpick into the port to hold it in place and ensurecontinuity into the crack.20. Epoxies last longerWhen your project is complete, don’t automatically react off your leftover A and Bcomponents to dispose of partial containers of epoxy. Most epoxy products arerelatively stable and can be used for extended periods if kept within a reasonabletemperature range and sealed. We say that most of our epoxy products can be safelyused within 3 years of manufacture. There may be some settling (particularly forcoatings) but the products will still perform if the separate components are mixed wellbefore use. Caution: moisture sensitive materials such as polyureas or polyurethaneshave a much shorter shelf life.21. Cosmetic surgery for concreteSay you have a sound substrate with a myriad of different tones or slight cracks or chipsthat disturb the smooth face. What can be done? Consider sacking, a repair techniquethat involves pre-wetting the substrate and then hitting the surface a burlap sackcontaining fine aggregate of the same color as the concrete along with some Portlandcement. A fine wet cement based slurry can also be applied by heavy brush. This trickcan also rid the substrate of the dark crack “shadow” following epoxy crack injection onarchitecturally sensitive surfaces such as light precast panels—call us for moreinformation. Leaders in Construction Polymers
  8. 8. 22. Bulk loaders work for epoxy too Contractors who specialize in caulking and waterproofing may use bulk loaders to shoot single component elastomeric caulks. For delivering both liquid and paste viscosity epoxies, bulk loaders come in a wide variety of gun types and applicator tips including battery and pneumatic operated. They can be used with twocomponent epoxies as long as the mixed material has an extended potlife. The biggestreasons to consider a bulk loader are time and material savings—they can easily loadedfrom a bulk mix in a 5 gallon bucket, placed just where needed and products sold in bulkare less costly. For larger projects, air-driven two-way bulk loaders might offeradditional efficiency. Albion Engineering is a great place to look for a wide selection.23. Use a scale On all of our data sheets, we include the separate weights ofparts A and B. Why? We have noticed many othermanufacturers require that all of the materials in multiplecontainers be used to make a mix. Yet, we know that notevery project needs all of the materials in our containers andwe hate wasting good materials. Of course, you can also judgeproper quantities by filling clear plastic measuring cups or pails,but the safest way to reproducibly get accuracy is to pre-weighboth components since the weight is not affected if thecontainer becomes too dirty or colored to read the volumes on the sides. Justremember that a material which is 2:1 by volume is not likely to have the same ratio byweight.24. Join upACI and ICRI are international members-drivenorganizations where you can meet in local chapters orattend regional or national conventions twice a year tolearn more about concrete and its repair. Many of the attendee members have beenperforming the same specialized concrete repair specialities and are happy to sharesuccess stories. 25. Come to our class We organize free training sessions in structural concrete repair and epoxy injection at least two or three times a year—they take a day and a half. Call or email us if you’re interested. Leaders in Construction Polymers