Abstract:
A polymer concrete system has been discovered which is useful in road overlay and repair. The binder for this aggregate-filled system consists of a liquid epoxy resin and triethyleneglycol diamine or tetraethylene glycol diamine curing agent. A piperazine accelerator ensures adequate strength development after short cure times at ambient temperatures. 
     The binder-aggregate system is relatively flexible, has excellent compression and flexural strength and adheres well to the substrate. The system is distinguished by its fast cure to a compression strength of 3000 psi which will support automotive traffic.

Description:
This is a division of application Ser. No. 07/079,384, filed July 30, 1987, now U.S. Pat. No. 4,828,879. 
    
    
     FIELD OF THE INVENTION 
     This invention is a method for repairing or resurfacing cementitious concrete roads. The method comprises the application of an epoxy resin binder-aggregate composition. 
     DESCRIPTION OF RELEVANT METHODS IN THE FIELD 
     Epoxy resins constitute a broad class of polymeric materials having a wide range of physical characteristics. The resins are characterized by epoxide groups which are cured by reaction with catalysts or curing agents to provide cured epoxy resin compositions with certain desirable properties. 
     U.S. Pat. No. 4,487,806 to K. B. Sellstrom and H. G. Waddill teaches a decorative epoxy resin aggregate binder composition. The composition comprises a vicinal polyepoxide, a stoichiometric amount of polyoxypropylene glycol diamine curative, nonylphenol and m-xylylene diamine. The composition is used to bind aggregate to cement surfaces such as patios and driveways of residential houses. The composition is a clear coating intended for outdoor use, which is noted for not yellowing with exposure to sunlight. U.S. Pat. No. 4,487,805 to K. B. Sellstrom teaches a decorative epoxy resin binder-aggregate composition. The composition comprises a vicinal polyepoxide, a stoichiometric amount of polyoxypropylene glycol diamine curative, nonylphenol, N-aminoethylpiperazine and a substituted benzotriazole ultraviolet light absorber. The composition is used to bind aggregate to large cement surfaces such as patios and driveways of residential houses. The composition is noted for not yellowing over time with exposure to sunlight. 
     U.S. Pat. No. 3,496,138 to R. F. Sellers and C. F. Pitt teaches curable epoxy resin compositions. These compositions include the reaction product of a diepoxide with a diamine such as the diamines of ethylene glycol, diethylene glycol, poly(ethylene glycol), propylene glycol, butylene glycol, etc. These compositions were used as adhesives and as coatings. 
     U.S. Pat. No. 3,236,895 to J. M. Lee and J. C. Winfrey and U.S. Pat. No. 3,462,393 to Legler are pioneer patents. They described a series of amine compounds which are solids or liquids and have utility particularly in curing epoxy resins. The amine compounds have the general formula: ##STR1## wherein R&#39;s are selectively defined as hydrogen, alkyl radicals and alkylene oxide radicals and x and m are defined integers. 
     U.S. Pat. No. 3,875,072 to H. G. Waddill teaches an accelerator for curing epoxy resins. The accelerator comprises piperazine and an alkanolamine in a weight ratio of 1:8 to 1:1. A number of alkanolamines are taught with triethanolamine preferred. U.S. Pat. No. 4,189,564 to H. G. Waddill teaches the accelerator comprising piperazine, N-aminoethylpiperazine and an alkanolamine. The accelerators are said to be synergistic for accelerating the curing of a polyglycidyl ether of a polyhydric phenol cured with a polyoxyalkylene polyamine at ambient or elevated temperatures. Such amines include polyoxypropylene diamines of the formula: 
     
         NH.sub.2 CH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2 
    
     wherein x ranges from 2 to 40. 
     Decorative Aggregate Studies I-IV (Texaco Chemical Company; TSB-1195, -1196, -1198, and -1199) describe the formulation of weatherable epoxy systems for binding decorative aggregate to concrete. 
     Gupta, Kar, and Mani, &#34;Effect of Binder Content and Coupling Agents on Mechanical Properties of Epoxy-Aggregate Composites&#34;, Journal of Reinforced Plastics and Composites, Vol. 1 (October, 1982), pp. 370-377, discusses the effect of binder:filler ratios and the use of silane coupling agents in an aggregate-filled epoxy system cured with a polyamide resin. 
     There is a need in the art for an epoxy resin formulation for repairing faults and for coating cementitious roads which is flexible and will cure to bear an 3000 psi traffic load in the shortest time, yet remain workable during application. 
     SUMMARY OF THE INVENTION 
     The invention is a method for repairing a fault in a cementitious road. The method comprises applying an aggregate and binder system to the fault. The binder comprises a vicinal polyepoxide having an average of at least 1.8 reactive 1,2-epoxy groups per molecule, a stoichiometric amount of a triethylene glycol diamine or tetraethyleneglycol diamine curative and an accelerator comprising an effective amount of piperazine and triethanolamine. 
     The method is distinguished by short cure time to reach a load bearing capacity of 3000 psi in order to support motor vehicle traffic. The method is also distinguished by its compatibility with an existing cementitious road. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Epoxy resin systems have been used to repair or resurface roadways because of their unique ability to bond well with Portland cement concrete. However, certain properties of the epoxy resin systems have limited their utility particularly in the repair of existing cementitious roads. These properties include slow cure rates, high coefficients of thermal expansion and high modulus of elasticity. We have invented an epoxy resin-aggregate system which overcomes these deficiencies. 
     The binder formulation of this invention is a low viscosity system which cures rapidly. High filler loadings are possible and compression and flexural strength develop quickly even at lower temperatures, e.g. 40° F. The coefficient of thermal expansion of a polymer concrete containing this binder system closely resembles that of Portland cement concrete up to about 120° F. Polymer concrete overlays containing this binder system resist delamination from a Portland cement concrete substrate during freeze-thaw cycling. 
     Nonylphenol may be used in this application because it improves flexibility. However, nonylphenol typically weakens the binder. There is also little need for the decorative, high gloss surface achieved with the addition of nonylphenol. Because of the high filler:binder ratios in this polymer concrete, there is very little of the binder system exposed on the surface of the overlay. 
     The invention is useful in preparing aggregate-filled systems for road and bridge repair, such as bridge deck overlays. The polymer concrete system of this invention has several properties that closely resemble properties of Portland cement concrete; these similarities offer improved durability of overlays and other types of repairs. 
     Generally the vicinal polyepoxide containing compositions which may be cured with the products of the invention are organic materials having an average of at least 1.8 reactive 1,2-epoxy groups per molecule. These polyepoxide materials can be monomeric or polymeric, saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic, and may be substituted if desired with other substituents besides the epoxy groups, e.g., hydroxyl groups, ether radicals, aromatic halogen atoms and the like. These vicinal polyepoxide containing compounds typically are of an epoxy equivalent weight of 150 to 250. Preferably the polyepoxide, which has an epoxide equivalent weight of from 175 to 195, is derived from condensing epichlorohydrin with 2,2-bis(p-hydroxyphenyl)propane to form 2,2-bis[(p-2,3 epoxy propoxy) phenyl] propane, a derivative of bisphenol A. 
     Preferred polyepoxides are those of glycidyl ethers prepared by epoxidizing the corresponding allyl ethers or reacting, by known procedures, a molar excess of epichlorohydrin and an aromatic polyhydroxy compound, i.e. isopropylidene bisphenol, novolac, resorcinol, etc. The epoxy derivatives of methylene or isopropylidene bisphenols are especially preferred. 
     A widely used class of polyepoxides which are useful according to the instant invention includes the resinous epoxy polyethers obtained by reacting an epihalohydrin, such as epichlorohydrin, and the like, with either a polyhydric phenol or a polyhydric alcohol. Typically the epoxy resins have an average of at least 1.8 reactive, 1,2-epoxy groups per molecule. An illustrative, but by no means exhaustive, listing of suitable dihydric phenols includes 4,4&#39;-isopropylidene bisphenol, 2,4&#39;-dihydroxydiphenylethylmethane, 3,3&#39;-dihydroxydiphenyldiethylmethane, 3,4&#39;-dihydroxydiphenylmethylpropylmethane. 2,3&#39;-dihydroxydiphenylethylphenylmethane, 4,4&#39;-dihydroxydiphenylpropylphenylmethane, 4,4&#39;-dihydroxydiphenylbutylphenylmethane, 2,2&#39;-dihydroxydiphenylditolylmethane, 4,4&#39;-dihydroxydiphenyltolylmethylmethane and the like. Other polyhydric phenols which may also be co-reacted with an epihalohydrin to provide these epoxy polyethers are such compounds as resorcinol, hydroquinone, substituted hydroquinones, e.g., methylhydroquinone, and the like. 
     Among the polyhydric alcohols which can be coreacted with an epihalohydrin to provide these resinous epoxy polyethers are such compounds as ethylene glycol, propylene glycols, butylene glycols, pentane diols, bis(4-hydroxycyclohexy)dimethylmethane, 1,4-dimethylolbenzene, glycerol, 1,2,6-hexanetriol, trimethylolpropane, mannitol, sorbitol, erythritol, pentaerythritol, their dimers, trimers and higher polymers, e.g. polyethylene glycols, polypropylene glycols, triglycerol, dipentaerythritol and the like, polyallyl alcohol, polyhydric thioethers, such as 2,2&#39;,3,3&#39;-tetrahydroxydipropylsulfide and the like, mercapto alcohols such as monothioglycerol, dithioglycerol and the like, polyhydric alcohol partial esters, such as monostearin, pentaerythritol monoacetate and the like, and halogenated polyhydric alcohols such as the monochlorohydrins of glycerol, sorbitol, pentaerythritol and the like. 
     Another class of polymeric polyepoxides which can be cured to form the polymer concrete of the present invention includes the epoxy novolac resins obtained by reacting, preferably in the presence of a basic catalyst, e.g. sodium or potassium hydroxide, an epihalohydrin, such as epichlorohydrin, with the resinous condensate of an aldehyde, e.g. formaldehyde, and either a monohydric phenol, e.g., phenol itself, or a polyhydric phenol. Further details concerning the nature and preparation of these epoxy novolac resins can be obtained in Lee, H. and Neville, K., Handbook of Epoxy Resins, McGraw Hill Book Co., New York, 1967. 
     Because of the relative cost, it is desirable to minimize the amount of binder in any composition. To achieve this end, while maintaining a product of acceptable quality, the aggregate combination must be chosen to yields the smallest void volume. The aggregate formulation used in the Example is based on the results of the publication Optimization of Polymer Concrete for Flame Spread Specimens, by Troy Madeley, Technical Memorandum No. 2, University of Texas, Austin, Tex., July 1984. This publication reports that a combination of 60 wt % coarse gravel, 30 wt % coarse sand and 10 wt % fine material produced a low void volume. As a result, the aggregate used in the present work was 60 wt % of 3/8 inch gravel, 30 wt % sand and 10 wt % fly ash. 
     The aggregate-binder ratio was adjusted to yield the most workable system. Ratios of 7:1 to 12:1 were tried. It was found that for an aggregate based on 3/8 inch gravel, that the optimal weight ratio of aggregate-binder was 11:1. For an aggregate comprising pea gravel, a ratio of 8.5:1 was determined to be most workable. Compositions comprising more aggregate, i.e. greater than 12:1, were judged to be unworkable. Compositions comprising less aggregate than 7:1 ratio were judged not to be cost effective. 
    
    
     This invention is shown by way of Example. 
     EXAMPLE I 
     
         ______________________________________A. Binder Formulation, pbw                6109-5______________________________________Liquid epoxy resin (EEW-188)                100Triethyleneglycol diamine                 20Sand:binder ratio (wt.)                7:1Compressive strength, psi                8500after 24 hours at ambienttemperaturesModulus of elasticity, psi                3,171,000after 24 hours at ambienttemperatures______________________________________ 
    
     This concrete system offered excellent compressive strength after curing 24 hours at ambient temperatures. Portland cement concrete has an ultimate compressive strength of about 4000 psi after a much longer cure time. 
     
         ______________________________________B. Binder formulation, pbw (6109)                -6A       -6B______________________________________Liquid epoxy resin (EEW 188)                100       100Triethyleneglycol diamine                 20        20Accelerator 399       10        15Sand:Binder ratio (wt.)                7:1       7:1Compressive strength, psi                6700      7700after 2 hours at ambienttemperatures______________________________________ 
    
     Addition of an accelerator to the epoxy concrete system cured with triethyleneglycol diamine resulted in improved compressive strength with time. Excellent compressive strength values were obtained within two hours of molding. 
     
         ______________________________________C. Binder formulation, pbw (6109)                  -7B    -7C______________________________________Liquid epoxy resin (EEW 188)                  100    100Triethyleneglycol diamine                  20     --Tetraethyleneglycol diamine                  --     28Accelerator 399        15     20______________________________________ 
    
     A three component aggregate blend (3/8-inch aggregate, sand, fly ash) was used in this example. 
     
         ______________________________________Filler:binder ratio (wt.)              11:1       11:1Compressive strength, psi              10000      3500after 3 hrs at ambient temp.after 6 hrs at ambient temp.              11200      8500after 9 hrs at ambient temp.              13000      10600after 12 hrs at ambient temp.              13300      10900after 24 hours at ambient temp.              13500      11300Modulus of elasticity, psi              5,093,000  4,018,000after 24 hrs at ambient temp.______________________________________ 
    
     Exceptional compressive strength was obtained after short cure times with the epoxy concrete system cured with triethyleneglycol diamine. Ultimate strength properties of systems cured with the two amines (triethyleneglycol diamine and tetraethyleneglycol diamine) are similar. 
     Accelerator 399 is a mixture of 10 to 20% piperazine and 5 to 10% N-aminoethylpiperazine in triethanolamine. Described in U.S. Pat. No. 4,189,564 to H. G. Waddill. 
     EXAMPLE II 
     
         ______________________________________A.1 Formulations and Properties for Modified Binder SystemFormulation, pbwLiquid epoxy resin (EEW 188)            100     100     100   100Triethyleneglycol diamine             20      20      20    20Nonylphenol       10      20      30    40Exotherm DataBrookfield viscosity, cps            900     1050    1550  2040(25° C.)Gel time, min. (200 g mass)            23.2    17.8    15.3  13.6Peak exothermic temp., °C.            235.5   215.6   201.8 186.9Time to peak temp., min.            26.4    21.2    18.0  19.7Properties of cured 1/8-inchCastings Cured 14 days @25° C.Shore D hardness, 0-10 sec            73-70   71-68   71-67 70-66Elongation, %    4.3     3.3     3.7   5.5HDT, °C., 264 psi/66 psi load            49/50   45/48   46/48 42/42Izod impact strength, ft-lb/in            0.10    0.16    0.09  0.07Tensile strength, psi            9800    9500    8500  7700Tensile modulus, psi            430000  400000  390000                                  350000Flexural strength, psi            15600   15900   15600 13500Flexural modulus, psi            470000  473000  438000                                  384000% wt. gain, 24-hr water boil            3.4     2.7     2.0   1.03-hour acetone boil            11.3    14.4    13.3  (1)Compressive strength, psi            23000   27400   22000 27000(1) Samples destroyed.Adhesion PropertiesTensile shear adhesion, psi            1000    920     990   860T-peel strength, pli            3.1     2.3     1.6   2.2A.2 Formulation, pbwLiquid epoxy resin (EEW 188)            100     100     100   100Tetraethyleneglycol diamine             28      28      28    28Nonylphenol       10      20      30    40Properties of Cured 1/8-inchCastings Cured 14 days 25° C.Shore D hardness, 0-10 sec            76-73   74-70   73-68 68-61Elongation, %    3.0     4.3     5.4   60HDT, °C.,264 psi/66 psi            47/49   42/45   41/43 28/34Izod impact strength, ft-lb/in            0.11    0.11    0.10  0.09Tensile strength, psi            8800    8500    7000  3300Tensile modulus, psi            420000  420000  350000                                  230000Flexural strength, psi            14200   13600   11300 5300Flexural modulus, psi            440000  423000  350000                                  185000% wt. gain, 24-hr water boil            5.3     4.2     3.4   2.13-hr acetone boil            13.7    16.3    17.0  (1)Compressive strength, psi            32000   31000   34000 45000(1) Samples destroyed.Adhesion PropertiesTensile shear adhesion, psi            1500    1460    2300  2400T-peel strength, pli            4.5     2.2     1.6   1.8______________________________________ 
    
     The two sets (A.1 and A.2) of formulations and cured epoxy properties indicated that addition of nonylphenol to epoxy systems cured with these amines caused little change in strength properties of the neat systems. There is a maximum amount of nonylphenol that is useful. If more than that amount is added to a system, properties are damaged. Note the decrease in strength in the system cured with tetraethyleneglycol diamine when 40 phr of nonylphenol was added. 
     
         ______________________________________B. Epoxy Concrete System/Formulations and Properties______________________________________Binder Formulation, pbwLiquid epoxy resin (EEW 188)                100Triethyleneglycol diamine                20Nonylphenol          40Accelerator 399       5Aggregate Blend, pbw3/8-inch aggregate   60Coarse sand          30Fly ash              10______________________________________ 
    
     An 11:1 (wt.) aggregate:binder ratio was used in preparing samples for testing. The table below lists compressive and flexural strength values at varying cure times. 
     
         ______________________________________     Compressive Strength,                     Flexural StrengthCure Time psi             psi______________________________________3 hours   5000            --4 hours   --              21006 hours   8100            260012 hours  9000            260024 hours  9800            27007 days    9500            --28 days   10200           2600______________________________________ 
    
     Although compressive strength may develop faster in systems containing larger amounts of the accelerator and no nonylphenol, those systems did not offer the enhanced flexibility these modified systems offer. 
     EXAMPLE III - (Comparative) 
     
         ______________________________________A. Binder Formulation, pbw (6109)               -3A        -3B______________________________________Liquid epoxy resin (EEW 188)               100        100JEFFAMINE D-230      32        --JEFFAMINE D-400     --          55Sand:Binder Ratio (wt.)               7:1        7:1Compressive strength, psi               11077      5970after elevated temperature cureModulus of elasticity, psi               2,806,000  810,000after elevated temperature cureCompressive strength, psi               8700       3900after ambient temperature curefor 3 days______________________________________ 
    
     Compressive strength and modulus values obtained after elevated temperature curing were about as high as they can be for these formulations because a complete cure was reached. 
     Compressive strength values obtained after a three-day cure at approximately 77° F. are somewhat lower than those listed earlier. Systems cured at ambient temperatures require longer cure times although they offer excellent properties even before a complete cure was reached. 
     JEFFAMINE® D-230 and D-400 are represented by the structure: 
     
         H.sub.2 NCH(CH.sub.3)CH.sub.2 --[OCH.sub.2 CH(CH.sub.3)].sub.x --NH.sub.2 
    
     wherein: 
     for D-230, x averages 2.6 and 
     for D-400, x averages 5.6. 
     
         ______________________________________B. Binder formulation, pbw             6109-4______________________________________Liquid epoxy resin (EEW 188)             100JEFFAMINE D-230    32Accelerator 399    20Sand:binder ratio (wt.)             7:1______________________________________Cure Time atAmbient Temperature, hrs            Compressive Strength, psi______________________________________3.5               2125                15427                427924               6939______________________________________ 
    
     Although compressive strength developed slowly during early curing, large increases in compressive strength were seen between 3.5 and 5 hours cure time and between 5 and 7 hours cure time. A more gradual increase was seen between 7 and 24 hours. 
     
         ______________________________________C. Binder formulation, pbw                6109-7A______________________________________Liquid epoxy resin (EEW 188)                100JEFFAMINE ® D-230                 32Accelerator 399       20______________________________________ 
    
     An aggregate blend containing 3/8-inch aggregate, sand, and fly ash was used in this example. 
     
         ______________________________________Filler:Binder Ratio (wt.)                   11:1Compressive strength, psi                   12,209after 24 hoursModulus of Elasticity, psi                   4,041,000after 24 hours______________________________________ 
    
     Use of a three-component aggregate blend resulted in higher compressive strength and modulus because of improved packing. Also binder content of this system was lower than when only one aggregate was used; this would reduce the cost of the system. 
     EXAMPLE IV 
     Accelerator 399 in Binder Formulation 
     
         ______________________________________A. Binder A______________________________________Liquid epoxy resin (EEW 188)              100 pbwJEFFAMINE D-230     32 pbwAccelerator 399    As specified______________________________________Accelerator Concentration,             Compression Strength,phr               psi______________________________________ 0                Not cured at 24 hours 5                Not cured at 24 hours10                7780 psi at 24 hours15                7850 psi at 24 hours20                8700 psi at 24 huurs25                6550 psi at 24 hours30                Not workable______________________________________ 
    
     Twenty (20) phr Accelerator 399 was determined to be the optimum amount of this accelerator to use for maximum compression strength after a 24-hour cure time. 
     
         ______________________________________B. Binder B______________________________________Liquid epoxy resin (EEW 188)              100 pbwTriethyleneglycol diamine               20 pbwAccelerator 399    As specified______________________________________Accelerator Concentration,             Compression Strength,phr               psi______________________________________ 0                Not cured at 3.5 hours 5                Not cured at 2 hours10                4650 psi at 1.5 hours15                5200 psi at 1.5 hours20                Not Workable______________________________________ 
    
     Fifteen (15) phr Accelerator 399 was the optimum amount of this accelerator to use for maximum compression strength in the shortest amount of time. 
     
         ______________________________________C. Binder C______________________________________Liquid epoxy resin (EEW 188)              100 pbwTetraethyleneglycol diamine               28 pbwAccelerator 399    As specified in table______________________________________Accelerator Concentration,             Compression Strength,phr               psi______________________________________ 0                Not cured at 3 hours 5                Not cured at 2.5 hours10                Not cured at 2.5 hours15                3400 psi at 2.5 hours20                3500 psi at 2.5 hours25                Not Workable______________________________________ 
    
     Twenty (20) phr Accelerator 399 was the optimum amount of this accelerator to use for maximum compression strength in the shortest amount of time. 
     Binder A cures quite slowly, even with large amounts of Accelerator 399 added to the system. Binders B and C both cured rapidly. However, for the repair-type applications in which this invention is useful, it is necessary to obtain the highest compression strength in the least amount of time. It is also desirable to keep accelerator levels as low as possible. For these reasons, Binder B is the preferred formulation. 
     EXAMPLE V 
     Compression Strength Development at Three Temperatures 
     PC-A (Polymer Concrete A) contains 11 pbw of the 3-component aggregate mix described earlier for each 1 pbw of Binder A of Example I. 
     PC-B (Polymer Concrete B) contains 11 pbw of the 3-component aggregate mix described earlier for each 1 pbw of Binder B of Example I. 
     PC-C (Polymer Concrete C) contains 11 pbw of the 3-component aggregate mix described earlier for each 1 pbw of the Binder C of Example I. 
     
         ______________________________________Compression Strength Development at 40° F.for Three Polymer Concrete SystemsTime Required to Reach SpecifiedCompression Strength.Compressionstrength, psi        PC-A       PC-B     PC-C______________________________________2000         &gt;24 hr.    5 hr.     6.5 hr.3000         &gt;24        5.25      84000         &gt;24        5.5       9.55000         &gt;24        5.75     116000         &gt;24        6        12.5______________________________________Compression Strength Development at 70° F.For Three Polymer Concrete Systems.Time Required to Reach SpecifiedCompression Strength.Compressionstrength, psi        PC-A       PC-B     PC-C______________________________________2000         6.25 hr.   &lt;0.5 hr. 1.25 hr.3000         7.25                1.754000         8           1       2.255000         9                   36000         9.5         1.5     3.5______________________________________Compression Strength Development at 110° F.for Three Polymer Concrete Systems.Time Required to Reach SpecifiedCompression Strength.Compressionstrength, psi        PC-A       PC-B     PC-C______________________________________2000         1 hr.      &lt;0.5 hr.  0.75 hr.3000         1.5                  1.254000         2           0.5      2.255000         2.5                  66000         3           0.75    10.25______________________________________ 
    
     PC-A, the polymer concrete containing JEFFAMINE D-230 curing agent, did not cure at 40° F. and cured slowly at 70° F. PC-C, which contained tetraethyleneglycol diamine, cured slowly at 40° F. PC-B was the preferred formulation; this system cured quite rapidly at 70° F. Even at 40° F., this concrete system developed compression strength much more quickly than the other two systems. 
     EXAMPLE VI 
     
         ______________________________________Flexural Strength Development at 40° F.for Three Polymer Concrete Systems.Time Required to Reach SpecifiedFlexural Strength.Flexuralstrength, psi     PC-A       PC-B        PC-C______________________________________ 500      &gt;24 hr.    2 hr.       5.25 hr.1000      &gt;24        3.5         71500      &gt;24        6.25        7.752000      &gt;24        18          8.752500      &gt;24        22          17.75______________________________________Flexural Strength Development at 70° F.for Three Polymer Concrete Systems.Time Required to Reach SpecifiedFlexural Strength.Flexuralstrength, psi     PC-A       PC-B        PC-C______________________________________ 500      6.5 hr.    1.5 hr.     2.25 hr.1000      7.5        2.25        2.751500      8.25       2.5         3.252000      9.5        2.75        4.52500      11         3           6.5______________________________________Flexural Strength Development at 110° F.for Three Polymer Concrete Systems.Time Required to Reach SpecifiedFlexural Strength.Flexuralstrength, psi     PC-A       PC-B        PC-C______________________________________ 500      1 hr.      &lt;0.25 hr.   1 hr.1000      2          0.5         1.751500      2.75       1           2.752000      3.25       1.25        4.252500      5.5        2           6.25______________________________________ 
    
     Portland cement concrete has about 500 psi flexural strength. It is important that the polymer concrete exceed 500 psi in a short time. Both PC-A and PC-C cure slowly in comparison with PC-B. Even at 40° F., PC-B reached the 500 psi flexural strength within two hours. 
     EXAMPLE VII 
     
         ______________________________________Coefficient of Thermal Expansion at Varying Temperaturesfor Three Polymer Concrete Systems      Coefficient of Thermal Expansion,      in/in/°F. × 10.sup.-6Temperature, °F.        PC-A        PC-B    PC-C______________________________________ 0           0.00        4.20    1.03 40          3.97        4.20    5.83 80          8.26        4.20    10.58120          13.1        16.4    15.4158          17.6        16.4    20.0______________________________________ 
    
     The coefficient of thermal expansion for Portland cement concrete is 5.5×10 -6  in/in/°F. It is important that a polymer concrete system used in conjunction with normal concrete (such as a polymer concrete overlay on Portland cement concrete) have a coefficient of thermal expansion similar to that of concrete. If an overlay expands and contracts to a much greater degree than the material it covers every time the temperature changes, it will break loose from the substrate (or delaminate) and will not provide the protection it was designed to provide. 
     PC-B has a coefficient of thermal expansion that is constant up to greater than 80° F.; this thermal expansion is similar to that of Portland cement concrete. Above 120° F., the coefficient for PC-B is higher, but is still constant and is ultimately lower than the coefficients for either of the other polymer concrete systems. 
     EXAMPLE VIII 
     
         ______________________________________Comparison of Three Epoxy Polymer Concretes withPortland Cement Concrete (PCC)Typical Properties of Portland Cement Concrete andPolymer Concrete After 28 Days Cure at AmbientTemperatures        PCC    PC-A    PC-B     PC-C______________________________________Compression strength, psi          3000-    14000   15000  13000          5000Compression modulus,          3-4      3.9     4.2    3.9psi × 10.sup.6Flexural strength, psi          410-     2900    2800   3000          530______________________________________ 
    
     All three of the polymer concrete systems were considerably stronger than Portland cement concrete after a standard 28-day cure time. Modulus values are similar for the three polymer concrete systems and the Portland cement concrete; this similarity indicated that these epoxy systems are no more rigid than Portland cement concrete. 
     
         ______________________________________Table of Test Methods______________________________________Gel Time (minutes)    ASTM D-2471-71Shore D-Hardness 0-10 seconds                 ASTM D-2240Elongation at Break (%)                 ASTM D-638Heat Deflection Temperature (HDT)                 ASTM D-648(°C., 264 psi/66 psi)Izod Impact Strength (ft lbs/in)                 ASTM D-256Tensile Strength (psi)                 ASTM D-638Tensile Modulus (psi) ASTM D-638Flexural Strength (psi)                 ASTM D-790Flexural Modulus (psi)                 ASTM D-790Compression Strength (psi)                 ASTM D-695T-peel Strength (pli) ASTM D-1876Tensile Shear Strength (psi)                 ASTM D-1002Modulus of Elasticity-Concrete (psi)                 ASTM C-469-83Brookfield Viscosity (cps @ 25° C.)                 ASTM D-1824Compression Modulus-Concrete (psi)                 ASTM C-469-83Compression Strength-Concrete (psi)                 ASTM C-3983bFlexural Strength-Concrete (psi)                 ASTM C-78-75______________________________________ 
    
     While particular embodiments of the invention have been described, it is well understood that the invention is not limited thereto since modifications may be made. For example, the amount of accelerator may be adjusted with ambient temperature to ensure adequate strength development after short cure times. Nonylphenol may be added to improve flexibility if the decrease in strength is acceptable. It is therefore contemplated to cover by the appended claims any such modifications as fall within the spirit and scope of the claims.