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Epoxy Resins for Civil Engineering Applications

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Presentation on theme: "Epoxy Resins for Civil Engineering Applications"— Presentation transcript:

1 Epoxy Resins for Civil Engineering Applications

2 What is Civil Engineering ????
Concrete Protection and Repair Floorings Self-leveling Trowelable Decorative Floorings [ Stone Carpets ] Concrete Repair Mortars / Grouting Bonding Systems Crack Injection With “Civil Engineering” applications we mean the use of epoxy resins in order to protect or repair mineral substrates; CONCRETE!!! Floorings (in the case of protecting the concrete underneath) as well as the repair of the concrete structures ( concrete adhesives, tunnel repair etc.). CE applications are room temperature curing epoxy binder systems. No need for heat (oven) or similar like in many other applications. This means also that we talk about chemical products which are reactive at room temperature. Once this reaction has started we cannot stop it anymore and a significant amount of heat is released (we say that the reaction is exothermic). One coffee cup of mixture of standard epoxy resin with amine curing agent (about 100 g) can reach a temperature of well over 200 °C. We will see that we use liquid epoxy products, which in principle do not contain solvents. The reason for this is that our binder systems are used in thick layers and that therefore solvents would not be able to evaporate from the bottom part of a flooring /coating.

3 Why Protect and Repair Concrete ?
pH of concrete decreases due to acid attack (CO2 , SO2 , acid rain etc.) } pH decrease Corrosion of steel rebars Chloride salts (e.g. de-icing) Water absorption of concrete Frost Now WHY do we need to protect the concrete ? Concrete is so strong ! The concrete is typically very alkaline, up to pH = 14. This pH is or can be decreased due to environmental influences such as for instance acid rains. This decrease of pH in combination with any ionic chlorides (salts) will make the steel reinforcement rust (volume expansion) and thus brake / degrade the concrete. Also any water absorbed can freeze and thus expand in the winter; physically cracking / breaking down the concrete. A common example of this would be for instance the terraces made outside where the tiles get loose after a while (some years). Besides this we might want to think of making the concrete, which is porous, impervious to chemicals (spillage areas etc). Or avoid the contact of food-stuffs with the “dirty” concrete ( concrete wine-storage tanks, slaughter houses etc.). As you can see many, many, applications. Degradation of Concrete

4 Desired properties Protection and repair of concrete
ambient cure application window easy to apply workable pot-life quick dry to enable to walk on it after 1 day impact strength flexural strength resistance against mechanical stresses crack bridging properties ground water protection chemical resistance self-leveling and seamless flooring systems Now civil engineering applications are protection and repair of concrete. Besides the protection part there are however many more needs and requirements to the binder systems performance. To consider are items such as for instance that we want to be able to “easily” apply a flooring system at ambient temperatures. This means that in summertime we should have enough time to be able to apply the flooring before it gels (gets solid) and that in wintertime the system should cure quickly enough to allow access onto the floor the following day(s). A finished flooring system as commercially on the market is a careful balance of some of these requirements. There is no “ideal system” doing everything at the same time. Again it is the formulators’ expertise which allows them to satisfy both applicator’s and end-users’ requirements. Naturally there are some areas where a raw material supplier such as Dow can be of help to our formulators, there where resin properties are concerned. Moreover, we also have a broad expertise on the best resin choice for a certain requirement. One need to understand however that the epoxy resin component is “only” ONE component of a multi-component system as we will see later.

5 Features of Epoxy resins for CE
adjustable curing speed at RT low sensitivity to moisture during curing very good adhesion on concrete and “green-concrete” very low linear shrinkage and corresponding tension very good chemical resistance very high durability BUT limited weatherability (UV-light) What are the major advantages of epoxy (EP) binder systems and also what can be a problem, the following items needs highlighting: * The curing rate of an EP binder system can be adjusted by the proper selection of resin type and curing agent type from very slow to very quick, * unlike many other binders systems, EP binder systems have a very low sensitivity to moisture during the curing process. Some epoxy formulations are on the market which can be even used for under-water painting, * EP binder systems have a very good adhesion to many different kinds of difficult substrates (poor surface preparation: surface tolerant coating systems) * EP systems have a very low shrinkage and can easily be formulated as larger surface coverings without incorporation of reinforcements such as (fiber-mats etc) * the chemical resistance can be tailored to meet many severe environments. Again the smart selection of the combination of epoxy resin and corresponding curing agent is of extreme importance. This is were our formulators build their competitive advantages. * EP system have a very high abrasion resistance versus other polymeric materials. On of the major issues which need to be considered, especially for decorative applications, is the limited weatherability. The aromatic back-bone of the epoxy resin degrades under influence of UV-radiation and yellows/chalkes. This is why sometimes PU top-coats are used for EP flooring systems.

6 Typical Flooring Composition
2 Pack system [ or 3 pack ] Component A Component B Epoxy Resin Curing Agent Pigments Pigments Quartz sand Additives Additives mix prior to use, pot-life of 30 minutes to 2 hours Ambient Cure Civil engineering systems, are ALWAYS TWO COMPONENTS systems (or even 3 components). The A component is in general the epoxy resin part pre-mixed with sand, pigments and other additives. Component B is in general the curing agent part sometimes also with the addition of pigments and additives. Just before the application both components are mixed in the correct ratio and then the material is applied as quickly as possible, since as soon as you mix the 2 components a chemical reaction starts which cannot be stopped. Typically you have about hours to apply your material. After about hours at °C the first careful steps can be made on the new floor and after around 7 days the new flooring is completely cured. Many things are to be consider when using these types of materials and these systems are in general laid by special companies with dedicated, trained personnel and equipment.

7 Surface must be clean and sound.
Surface Preparation Surface must be clean and sound. All dirt, laitance, grease, curing compounds and other foreign matter must be removed by sandblasting, abrasion, or acid etching. Water and dust must be removed from all surfaces immediately prior to application. The success of a good epoxy flooring system is to a very high degree depending on the adhesion of the primer/coating to the concrete. In order for the primer to be able to nicely penetrate the concrete and attach itself to it, the surface must be clean and free of all kinds of disturbing compounds. Many techniques have been developed to clean concrete surfaces. Sand blasting, mechanical abrasion and hot-water jetting are currently the most frequently used. Enjoying enhanced popularity in recent days is also the ultra-high pressure water-jetting. Care has to be taken however that for normal epoxy binder systems a moisture content of maximum 4% is specified. Typically when UHP water-jetting is employed special primer systems are used which have a higher water tolerance or are even water-based and dilutable.

8 Crack Bridging Self-leveling Flooring System Typical three layer (3 days operation) build-up
Concrete Inspection and Preparation Finishing Layer 2700 g/mm2 to 2 mm thickness viscosity below 2000 mPa.s 4 mm Functional Layer 2700 g/m2 to 2 mm thickness viscosity below 2000 mPa.s Concrete Substrate Now let’s come back to an the epoxy floor. On this slide a typical example of an epoxy flooring build-up will be depicted. The epoxy layer, the functional layer, has to be applied to the substrate, the concrete, in such a manner that maximum adhesion is aimed. This is achieved by means of a very good concrete surface preparation and by the use of a priming layer. The primer ensures, due to its low viscosity, excellent wetting of the substrate and thus adhesion between the functional layer and the substrate. The primer serves as an adhesion layer to “glue” the functional layer onto the concrete. This means that the primer has to have an exceptional good adhesion to the substrate: this is why the primer is typically of very low viscosity, to ensure good penetration into the concrete. However, the surface of the substrate has to be of such a quality that the primer CAN adhere well to the concrete, thus the importance of the surface preparation. Just after the application of the primer, the floor is covered with sand: after the cure the excess of sand is taken off and we have created an “artificial” rough surface profile again to enhance the adhesion between the concrete primer layer and the functional layer. The functional layer is the coating compound that gives the required mechanical properties, whether this is the chemical resistance requirement or whether this is the abrasion requirement. Potentially a finishing layer (top-coat) is applied over the functional layer. The reasons for applying the top-coat can be many; for example, the top-coat can serve as a wear-indicator, if different colors are used between the top-coat and the functional layer. Or the top-coat can be used to protect the functional layer from break-down as a result of UV radiation, thus helping to enhance the resistance against yellowing and chalking. One of the shortcomings of epoxy binder systems is often seen as the limited resistance against sunlight exposure. The double bounds of the epoxy molecules are destroyed by the UV rays from sunlight, which results in a shift in color (yellowing), but also in the pigment particles lying loosely on the surface of pigmented systems, being the binder destroyed. Rubbing with a cloth or finger results in pigment deposits on the fingers (chalking). Impregnation g/m2 viscosity below 500 mPa.s cover with 1000 g/m2 Quartz-sand mm

9 Dow Epoxy resins for Civil Engineering
D.E.R.™ 331™ / D.E.R. 336 Epoxy Resin Liquid Bisphenol-A based Epoxy Resin D.E.R. 354 Epoxy Resin Liquid Bisphenol-F based Epoxy Resin D.E.R. 352 / D.E.R. 356 Epoxy Resin Liquid Bisphenol-A/F Epoxy Resin { to prevent crystallization } Reactive Diluent Blends { reduced viscosity } D.E.R. 321 / D.E.R. 324 Epoxy Resin Bisphenol-A type D.E.R. 353 / D.E.R. 358 Epoxy Resin Bisphenol-A/F type The major category of epoxy resins being used, the so-called work-horses, are the standard liquid Bisphenol-A epoxy resins. The second category are the standard liquid Bisphenol-F epoxy resins. These resins which are chemically slightly different offer a lower viscosity and a better reactivity / chemical resistance. Unfortunately raw material and production costs of these type of resins are high. Also Bisphenol-F epoxy resins have a tendency to crystallize. A performance and cost compromise as well as a solution to potential crystallization problems is offered by our third category, our Bisphenol-A/F epoxy resin blends, physical mixtures. In order to reduce the viscosity further, diluents can and are being used. Dow offers several pre-mixed epoxy resins with Reactive diluents blends. Besides a reduction in viscosity these materials also alter the performance properties. Dow does not sell the neat reactive diluents, however, such materials can be obtained from UPPC (Polypox R-products). Further remains to be mentioned some solid-solutions which can be use as priming materials. Thin coatings allowing solvent evaporation. As you will understand this is only a (small) selection of our product range. You will find many more products and information on our web-site as well as that Algol will be able to help you with any specific product selections. D.E.R. 671-X75 and 684-EK40 Epoxy Resin Solutions Primer - Surface Impregnation ™ Trademark of The Dow Chemical Company

10 Self-leveling Flooring System Typical formulation:
Binder [ % ] 40 D.E.R.™324 Liquid Epoxy Resin 25.2 Quartz-sand [ mm ] 35.2 Quartz-powder [ < 0.06 mm ] 22.5 Titanium-dioxide [ Color ] 1.7 Air-release agent 0.4 e.g. BYK A-525 Amine - Epoxy Adduct Curing Agent 15.1 (e.g. Polypox H 043 ex. UPPC ) {Concrete} Compressive Strength = 50 N/mm2 { 40 } Flexural Strength = 60 N/mm2 { 4 } Tensile Strength = 43 N/mm2 { 2 } The following formulation is a formulation of a self-leveling epoxy flooring. Notice that the epoxy resin part is of the type of diluent modified Bisphenol-A epoxy resin (D.E.R. 324). Further sand, quartz powder and Titanium Dioxide are the pigments/fillers. An (air-release) additive is used as well as an amine epoxy adduct curing agent. The mechanical properties mentioned at the bottom demonstrate that when fully cured this flooring system is stronger than concrete: by nearly a factor of 15 in flexural (bending) and tensile direction. Note that a defined mixing ratio between the curing agent and the epoxy resin component exists. Pigments and fillers should be mixed in such a ratio that the holes and pores around each particle are a small as possible. This will result in a smaller quantity of binder system used and thus in a cheaper formulation. STRONGER THAN CONCRETE !!! ™ Trademark of The Dow Chemical Company

11 D.E.R.™ 324 Liquid Epoxy Resin

12 ground water protection
Regulatory Trends ground water protection secondary containment VOC reduction and regulation elimination of aromatic amines use of safer reactive diluents Regulatory The secondary containment market is a direct, positive result of governmental regulations requiring that companies line concrete containment systems to make them impervious to the chemicals involved. VOC regulations will almost certainly impact Civil Engineering markets. Most epoxy system are generally considered 100% solids. For thin coatings aqueous systems can be used, because the application can be done on "wet" concrete. For floorings such systems show a very good adhesion to old epoxy coating. Aromatic amines, which have been used in most chemically resistant applications, are being eliminated from formulations because MDA is considered a carcinogen. There is growing concern about the toxicity (potential for skin sensitization, carcinogenicity and neurotoxicity) of any of the reactive diluents. Similarly there is growing concern about the corrosivity and severe sensitization potential of many of the amine hardeners. Dow has been a driving force within the European plastics committee, APME, in selecting safer reactive diluents. A study has shown that two reactive diluents (long alkyl chain GE and HDDGE) looked favorable compared to other reactive diluents such as for instance butylglycidylether.

13 Technology Trends lower temperature cure
curing down to, below, 0 °C mainly driven by curing agent lower viscosity { Bisphenol-A/F and RD blends } °C aqueous systems coatings on concrete polymer concrete Epoxy Cement Concrete flexible epoxy resins % Elongation crack-bridging concrete non crystallizing Resins stable on filler addition winter time outside storage stable Lower temperature cure is requested by applicators needing systems which cure at 5 °C or even below. Some formulators offer systems claiming "winter cure", which cure close to 0 C. These systems are often based on LER and special hardeners. Lower viscosity is required for easy formulation handling at lower temperatures and good self leveling properties. Lowest resin component we currently offer has around 500 mPa.s Aqueous systems have a role for use in ambient cure applications. There is a large range of functional performance requirements. These systems can be applied onto wet concrete and show very good adhesion to "old" epoxy flooring for repair. An interesting application for WB epoxy binders in CEG is in epoxy cement concrete (ECC) systems. This technology is thought to certainly grow because it is an excellent way of improving mechanical and especially chemical properties of standard cement based concrete. A wide variety of flexibilizer technologies are being developed to meet the need with epoxies. The need for flexible systems is driven by adhesives, crack bridging, park deck ramps etc. NON Crystallizing

14 End of the Civil Engineering Part !!!
Further Technical as well as Product Stewardship related information can be found on e.g. Dow Epoxy Products Portfolio incl. Corresponding technical datasheets, Dow Liquid Epoxy Resin Brochure Dow Epoxy Novolac Brochure Dow Epoxy Resin Product Stewardship Manual Dow Epoxy Curing Agents Product Stewardship Manual


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