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40 3.4 Durability Testing 3.4.1 Introduction To prevent chloride penetration into end zone cracks, espe- cially for coastal regions and areas where deicing chemicals are used in winter, waterproofing sealants can be used. However, since the cracks tend to open and close with the loading of the girder, the sealant must be able to withstand this movement while spanning the gap created by the crack. The objectives of the durability testing were to investigate the following issues: 1. If repair is required, what sealant material should be used? 2. Is it required that end zone cracks be filled with a patching material before a surface sealant is applied? (a) Before Testing 3.4.2 Durability Test, Stage I The research team devised an experiment to gauge the effec- tiveness of commonly used sealants in order to select charac- teristics that can be recommended to the public for use in crack repair. This test also observed and recorded the properties of each sealant as well as the method and ease of application. Stage I Test Procedure The test slightly modified the test from ASTM D6489-99, Standard Test Method for Determining the Water Absorption of Hardened Concrete Treated with a Water Repellant Coating. (ASTM Standard D6489-99 is provided in Appendix E.) Concrete cylinders were used as test specimens in the proce- dure. Sixty specimens were produced at Concrete Industries' precast plant in Lincoln, Nebraska, from a self-consolidating (b) At Failure concrete production line. After the cylinders were received at the structures laboratory, they were washed and cleared of debris and then heated in a draft oven for 24 hours to remove any moisture. They were then coated with the sealants, which were mixed, prepared, and applied according to the manufac- turers' specifications, taking care not to leave any uncovered spots. A control group was designated, which received no sealant coating. All of the specimens were then immersed completely in water and left to soak, as shown in Figure 3.49. At 24 h, and again at 96 h the specimens were towel dried and weighed. By taking the weight of the specimens before and after submersion the percent absorption was calculated and aver- aged for each sealant type. Five different sealants were tested for effectiveness in pro- tecting against water and chloride penetration as follow: 1. Pipewipe, 2. DuralPrep A.C., (c) At Failure 3. Transpo Sealate T-70, Figure 3.48. Specimen S2R (UNL end zone reinforcement 4. Xypex Concentrate, and unrepaired specimen). 5. DegaDeck Crack Sealer Plus.

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41 Table 3.4. Test results of the five specimens. Girder Specimen Specimen #1 Specimen #2 (Without Special End (With Special End Reinforcement) Reinforcement) Test Specimen S1L S1R S1MS S2L S2R Location of the Specimen Left End Right End Midspan Left Right Nominal Cracking Load 23.1 25.5 25.0 (kip) Nominal Ultimate Load 77.3 175.6 153.2 (kip) Test Results Cracking Load (kip) --- --- --- --- --- Failure Load (kip) 56 109 103 103 154 Midspan Deflection (in.) --- 0.236 0.251 0.260 0.246 Appendix D provides technical information on the sealants. be used as a coating for steel reinforcement. The mixture Figure 3.50 shows the cylinders after being sealed with the five requires the blending of three separate chemicals. The mix- sealants. ture is non-volatile and does not give off any harmful fumes. The product is very viscous, making it difficult to apply a Pipewipe is a cement-based product designed to produce thin coating. Once dry, the product is rough and cement- a "sack rubbed" finish to the concrete. It fills in any voids or like in texture, giving the impression of being porous. cracks to create a smooth, uniform coating. Its primary pur- Transpo Sealate T-70 is a high molecular weight methacry- pose is to be a cosmetic repair product. Pipewipe contains late resin system. It is designed to fill and seal concrete cracks. a polymer-bonding agent along with very fine aggregates. It has a very low viscosity that is designated to penetrate deep It expands and contracts at the same rate as normal con- into cracks of small widths. Due to this low viscosity, the crete, therefore preventing cracking at extreme tempera- product works best on horizontal surfaces where it cannot ture changes. As a liquid, the product is thick and easy to flow away. It is a three-part substance that, when its chemi- apply by hand. However when dry, the coating could eas- cal components are combined, may produce skin irrita- ily be rubbed away and was also water absorbent. Due to its tion and will give off harsh, volatile fumes. However, the cement base, Pipewipe is not intended to be a waterproof- seal that is produced appears glassy and has water-resistant ing sealant. Therefore, the research team decided not to con- characteristics. The team believes that the product itself is water resistant, but the method of application and orienta- sider Pipewipe for further testing. tion of the cylinders prevented a solid coating around the DuralPrep A.C. is a water-based epoxy modified Portland specimens. Due to the ultra low viscosity of the product, it cement bonding agent and anti-corrosion coating. It con- easily flowed off the surface before setting up. This shows tains a migratory corrosion inhibitor and claims that it can that the product is satisfactory for the water and chloride prevention requirement, but may not be effective for ver- tical application on the webs of precast girders. Xypex Concentrate is designed to waterproof and repair concrete. When exposed to water, this product causes a catalytic reaction that produces a non-soluble crystalline formation within the pores and capillary tracts of concrete and cement-based materials. It is mixed with water and can be made into different consistencies to match the applica- tion method. The results for this sealant may be confus- ing due to initial saturated surface and the moist curing procedure. It may be that the Xypex layer absorbs a limited amount of water, yet would not allow any to leak through. The Xypex-coated specimens absorbed more water than the uncoated control specimens. DegaDeck is a reactive methacrylate resin designed to pen- etrate and seal cracks in concrete. It produces a hard, clear, matte, water repellant surface. The product has a low enough Figure 3.49. Specimens submerged in water. viscosity to flow easily into small cracks. DegaDeck is