Click for next page ( 35


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 34
34 TABLE 2 POLYMERIC BINDER SYSTEMS FOR TPOs Property Epoxy Polyester Methacrylate Test Method Viscosity, Poise 725 15 1113 ASTM D2393 Gel Time, Minutes 1545 1025 1545 AASHTO T237 Tensile Strength (Binder) MPa @ 7 days 13.834.4 13.834.4 3.48.3 ASTM D638 (2,0005,000 psi) (2,0005,000 psi) (5001,200 psi) Tensile Elongation (Binder) % @ 7 days 3080 3080 100200 ASTM D638 PC Compressive Strength, MPa @ 3 h Min. 6.9 Min. 6.9 Min. 6.9 ASTM C579 (1,000 psi) (1,000 psi) (1,000 psi) PC Compressive Strength, MPa @ 24 h Min. 34.4 Min. 34.4 Min. 34.4 ASTM C579 (5,000 psi) (5,000 psi) (5,000 psi) PC Tensile Bond Strength, MPa @ 24 h Min. 1.7 Min. 1.7 Min. 1.7 ASTM 1583 (250 psi) (250 psi) (250 psi) PC Cure Time @ 32C (90F), ha 2 2 2 ASTM C109 PC Cure Time @ 24C (75F), ha 3 3 3 ASTM C109 PC Cure Time @ 16C (60F), ha 68 56 4 ASTM C109 aTime required to obtain compressive strength = 6.9 MPa (1000 psi). Source: Sprinkel (15). help reduce the resin content. Topping aggregate, like the TABLE 3 aggregates in the multiple-layer systems, however, must be TYPICAL AGGREGATE GRADINGS FOR TPOs angular, hard, and tough for long-term performance. (Percentage Passing Sieve) Sieve Size Multiple-Layer Slurries: Slurries: Premix Slurry Aggregates Overlays Sand Fine Fillers Overlays 0.13 100 Similar to the premixed system, aggregates must be small 0.10 83100 and well graded. Additionally, a finely graded silica flour or No. 4 100 6282 other filler is introduced to help build the apparent viscosity or to add rheology and support the larger aggregates in the No. 8 3075 4564 matrix. No. 16 05 100 2750 No. 20 90100 Table 3 lists common gradings for some of the aggregate No. 30 01 6080 1235 systems used for TPOs. No. 40 515 No. 50 05 620 The durability and the skid resistance of TPOs are greatly affected by the relative volumes and distribution of the aggre- No. 100 07 gates into the binder system. Also, some of the materials rely No. 140 100 on a primer to ensure the best bond to the concrete substrate No. 200 98100 03 over time, and MMA slurry systems typically require a seal No. 270 96100 coat for better retention of the exposed friction aggregate No. 375 9399 course. Application rates for TPOs are listed in Table 4. Source: Sprinkel (15). QUALIFICATION OF SUBSTRATE yd3) be marked for removal. The concrete substrate should have a minimum tensile rupture strength of 1.0 MPa (150 Evaluation of Substrate psi) based on ACI 503R (13) or ASTM C1583 (14); other- wise, the concrete must be removed and replaced. The deck is to be sounded for delamination, and the areas from which concrete is to be removed need to be clearly Repair marked. The area needs to be evaluated for corrosion activ- ity using the copper sulfate electrode method in accordance Concrete needs to be removed in areas determined by the with ASTM C876 (26 ). It is important that the concrete in evaluation of the substrate. It is important that vertical saw areas where the chloride content exceeds 0.77 kg/m3 (1.3 lb/ be made to a minimum depth of 25 mm (1 in.) with care taken

OCR for page 34
35 TABLE 4 APPLICATION RATES FOR TPO COMPONENTS Overlay Multiple-Layer Epoxy Epoxy Slurry Methacrylate Slurry Premixed Polyester Thickness, mm (in.) 6.4 (1/4) 7.5 (5/16) 7.6 (5/16) 19.1 (3/4) Prime Coat, kg/m2 (lb/yd2) None 1.1 0.14 0.41 0.14/-0 0.41 0.14/-0 1.2 (2.0 0.3) (0.8 0.3) (0.8 0.3) Layer 1 Resin, kg/m2 (lb/yd2) 1.1 0.14 6.0 0.4 2.7 0.27 5.29 0.41 (2.0 0.3) (9.8 0.8) (5.0 0.5) (9.8 0.8) Layer 1 Aggregate, kg/m2 (lb/yd2) 5.4 0.54 6.5 0.5 6.5 0.54 38.6 0.54 (10.0 1.0) (12.0 1.0) (12.0 1.0) (71.0 1.0) Layer 2 Resin, kg/m2 (lb/yd2) 2.2 0.14 None None None (4.1 0.3) Layer 2 Aggregate, kg/m2 (lb/yd2) 7.6 0.54 None 7.6 2.7 None (14.0 1.0) (14.0 0.5) Seal Coat Resin, kg/m2 (lb/yd2) None None 0.68 0.14/-0 None (1.3 0.3) Approx. Resin Content, % 25 25 24 13 Source: Sprinkel (15). not to cut reinforcing steel. Concrete needs to be removed in such a manner as to not weaken or crack the surrounding sound concrete. Chipping hammers heavier than 15 lb are not to be used. It is important that concrete be removed beneath the steel to a depth of 12 mm (0.5 in.) or three times the diameter of the largest size aggregate, whichever is greater, in areas where the steel is corroded or the chloride content exceeds 0.77 kg/m3 (1.3 lb/yd3) at the level of the steel. Final cleaning could be by shot blasting or grit blasting; shot blast- ing cannot be used for deep patches. The steel is be cleaned from corrosion scale and other contaminants. Materials for repair are to be low shrinkage and applied in accordance with the manufacturer's instructions. The repair material is to be compatible with the resins used in the TPO. If a hydraulic cement repair material is used, it needs to dry FIGURE 15 Fiber fabric applied previous to overlay over for a minimum of 28 days before placing the TPO unless bridge joint. bond tests show that earlier application is acceptable. Latex- modified concrete repair materials need to be wet cured for Surface Preparation 2 to 3 days before beginning the drying process. Grinding might be considered to remove rough or unlevel areas. The deck surface must be cleaned prior to placement of the TPO to remove all contaminants, including oil, grease, Cracks wider than 1 mm (0.04 in.) need to be filled with dirt, asphalt, paint, carbonation, weak surface mortar, cur- a gravity-fill resin that is compatible with the overlay primer ing compounds, and laitance. The surface is to be shot or resin. It has been noted that an application of high-molec- blasted the day of the placement, preferably just before ular-weight methacrylate for crack repair before installation overlay placement. A reasonable texture can be achieved of an epoxy TPO resulted in delamination of the (epoxy) by meeting the ICRI CSP 7 profile. Oil-free and moisture- overlay, and the reason was believed to be the incompat- free compressed air can be used to remove dust or debris ibility of the materials (3). ACI 548.8 (2) cautions against just before application of the resin. The surface should be placing TPOs "over crack-fill materials that will affect the dry as determined by ASTM D4263 (46 ) modified to keep bonding or the curing of the overlay." the plastic sheet in place a minimum of 2 hours. Some parts of the deck, including low areas and other areas that drain Moving cracks in the substrate will likely cause reflective slowly, such as gutters, dry more slowly and need to be cracking through the TPO. Synthetic fiber fabrics have been tested to be certain that the surface is sufficiently dry to used over joints in segmental bridges, shown in Figure 15. receive the TPO.