Click for next page ( 43

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 42
42 (a) Pipewipe (b) DuralPrep A.C. (c) Transpo Sealate T-70 (d) Xypex Concentrate (e) DegaDeck Crack Sealer Plus Figure 3.50. Specimens coated in sealants. two-part substance comprised of liquid and powder hard- (2) DuralPrep A.C., (3) Pipewipe, (4) Transpo Sealate T-70, ener. It is recommended for horizontal surfaces only. How- and (5) Xypex Concentrate. ever, the team found that the product performed well on The top performing sealants retained for Stage II of the dura- vertical surfaces, such as girder webs, and did not flow off bility tests were DegaDeck Crack Sealer Plus, DuralPrep A.C., the exterior. DegaDeck Crack Sealer Plus was the best and Transpo Sealate T-70. performing sealant of the five tested. It also had a very easy workability and mixing procedure. However, when mixed, the chemical is highly volatile and produces harsh, poten- 3.4.3 Durability Test, Stage II tially dangerous fumes. It is also a skin and eye irritant. The For the second stage of the durability test, the team observed fumes, as well as the liquid, are flammable. how assorted sealers perform in preventing water from pen- etrating into concrete specimens exhibiting various sizes of Stage I Test Results cracks. The procedure was modified from two ASTM Stan- Tables 3.5 and 3.6 present a summary of the percent absorp- dards, G109-99a Standard Test Method for Determining the tion of each specimen at 24 h and 96 h, respectively. Also, these Effects of Chemical Admixtures on the Corrosion of Embedded tables provide the average, standard deviation, and variance Steel Reinforcement in Concrete Exposed to Chloride Environ- for the five sealants. ments, and D6489-99 Standard Test Method for Determining the The five sealants were rated from the analysis of the absorp- Water Absorption of Hardened Concrete Treated with a Water tion results at 24 h and 96 h and ease of application, and from Repellent Coating. (ASTM Standard D6489-99 is provided in the best to the worst were (1) DegaDeck Crack Sealer Plus, Appendix E.) Table 3.5. Summary of percent absorption of all sealants at 24 hours. Sealant Specimen Control DuralPrep Transpo Xypex DegaDeck Pipewipe Specimens A.C. Sealate T-70 Concentrate Plus 1 2.65% 1.58% 0.38% 2.52% 2.99% 0.62% 2 2.49% 1.31% 0.37% 2.45% 3.16% 0.52% 3 2.43% 1.71% 0.45% 2.59% 3.12% 0.44% 4 2.65% 1.41% 0.58% 2.23% 3.15% 0.29% 5 3.02% 1.38% 0.37% 2.13% 3.21% 0.27% 6 3.01% 1.39% 0.38% 2.29% 3.15% 0.68% 7 2.74% 1.50% 0.51% 2.59% 3.24% 0.23% 8 2.80% 1.55% 0.48% 2.53% 3.14% 0.16% 9 2.69% 1.46% 0.68% 2.05% 2.55% 0.18% 10 2.74% 1.54% 0.62% 2.71% 3.00% 0.15% Average 2.72% 1.48% 0.48% 2.41% 3.07% 0.35% Stand. Dev 0.190 0.118 0.112 0.219 0.199 0.195 Variance 0.036 0.014 0.012 0.048 0.040 0.038 Rating 3 2 4 5 1 (1 = best, 5 = worst)

OCR for page 42
43 Table 3.6. Summary of percent absorption of all sealants at 96 hours. Sealant Specimen Control DuralPrep Transpo Xypex DegaDeck Pipewipe Specimens A.C. Sealate T-70 Concentrate Plus 1 2.76% 1.67% 0.66% 2.92% 3.23% 0.82% 2 2.60% 1.39% 0.63% 2.81% 3.40% 0.67% 3 2.54% 1.80% 0.65% 2.98% 3.35% 0.58% 4 2.77% 1.48% 0.83% 2.60% 3.40% 0.47% 5 3.14% 1.45% 0.63% 2.55% 3.46% 0.42% 6 3.15% 1.47% 0.60% 2.70% 3.44% 1.05% 7 2.86% 1.59% 0.74% 2.99% 3.52% 0.34% 8 2.92% 1.61% 0.81% 2.89% 3.36% 0.87% 9 2.81% 1.55% 1.04% 2.36% 2.74% 0.27% 10 2.87% 1.63% 1.11% 3.07% 3.27% 0.26% Average 2.84% 1.56% 0.77% 2.79% 3.32% 0.58% Stand. 0.199 0.122 0.177 0.226 0.219 0.273 Dev. Variance 0.040 0.015 0.031 0.051 0.048 0.074 Rating 3 2 4 5 1 (1 = best, 5 = worst) The sealants chosen for this experimentation are the three 800, rubbed into the cracks by hand, and then sealed with the best-performing sealants from the first durability test (Dega- same sealant as the first set. An additional set was made as Deck Crack Sealer Plus, DuralPrep A.C., and Transpo the control, where the specimens were not repaired with any Sealate T-70) along with SilACT, which was recommended sealant at all and did not contain any artificial cracks. Table 3.7 by Central Pre-Mix Prestress Co. of Washington State. The shows the test plan. specimens were made from the same concrete mix design, The specimens were placed on their sides and the selected with a concrete strength of about 5,000 psi. Although this con- sealants and REM 800 were applied to their specific sets. This crete mix is relatively more porous than the concrete normally orientation mimics the orientation of the cracks on the webs used in precast girders, it was used to amplify the amount of of production girders. Care was exercised not to leave any con- water absorbed if the sealers failed. crete surface uncovered or to allow any air bubbles to form. The REM 800 was rubbed into the cracks by hand but the Stage II Test Procedure sealants were applied with a roller. Once all of the specimens dried, they were turned upright The concrete specimens were made in the structures labora- and a 3-in.-tall rectangular plastic dam was built on the top tory of the University of Nebraska, in the form of 3 3 12-in. rectangular prisms. Artificial cracks were formed with metal and plastic shims, penetrating down 2.25 in. from the top sur- face of the specimens and measuring 9 in. in length, as shown in Figure 3.51. These shims were placed in the concrete while it was still wet and removed when it began to set. The artifi- cial cracks were produced in a variety of widths, ranging from 0.007 to 0.054 in. After all specimens were fabricated, they were placed in a draft oven for 24 h to remove any moisture. When cooled, their weight was recorded as WA, and then the sealants were used to cover the four sides and bottom face of each specimen, leaving only the top surface containing the crack uncoated. These sides were covered to prevent moisture from either entering or escaping the areas not being tested. There were two sets of specimens for each sealant, with each set containing prisms with cracks of each available size. The first set was sealed only with the specified sealant. The second set had a Hilti Brand hydraulic cementitious material, REM Figure 3.51. Specimens with metal shims.

OCR for page 42
44 Table 3.7. Plan for the durability tests, Stage II. Transpo DuralPrep DegaDeck SilACT Crack Sealate A.C. Control Width With Without With Without With Without With Without Batch (in.) REM REM REM REM REM REM REM REM 800 800 800 800 800 800 800 800 Number of Specimens, Stage II (Total = 46 Specimens) 0.000 1 0.007 1 1 1 1 1 1 1 1 1 0.012 1 1 1 1 1 1 1 1 1 0.016 1 1 1 1 1 1 1 1 1 0.033 1 1 1 1 1 1 1 1 1 0.054 1 1 1 1 1 1 1 1 1 Total 6 5 5 5 5 5 5 5 5 surface of each specimen around the artificial crack so that Stage II Test Results water could pond on the repaired surface. Waterproof caulk- The test results show that packing larger cracks with a thick, ing material was used to secure the plastic walls in place, as cementitious material (REM 800) allowed the cracks to be shown in Figure 3.52. With the dam in place, the specimens closed, while repair with a sealant alone failed in most cases were weighed, recording the data as W1. with large cracks. Typically, the specimens with REM 800 were The specimens were all placed face up in an area where able to keep the water out better than the specimens without they would not be disturbed. Each dam was then filled to the REM 800. The material packed into the crack created a bridge, top with water. The specimens were given the opportunity to over which the less viscous water-resistant sealants were allowed absorb water for 24 h. Every effort was made to ensure that to lay, forming an unbroken seal across the entire surface. the dam remained filled with water at all times. At 24 h, the Without REM 800, the sealants with a water-like consistency water in each dam was emptied. Then, the specimens were (DegaDeck, Transpo Sealate, and SilACT) were not able to towel dried. The weight of each sample was measured and adequately fill the large-sized cracks when applied on a ver- recorded as W2. The percent of water absorption by each tical surface. Table 3.8 gives a summary of the 24-h percent sample can be found using the following equation: absorption of the specimens. 100 i (W2 - W1 ) This experiment was designed to exaggerate actual bridge Percent Absorption = (Equation 1) conditions to which end zone cracks would be exposed. In WA service, the crack surface would not be continuously under Where WA is the weight of the concrete specimen after dry- water, as the specimens were, but the exposure to wet envi- ing, but before exposure to the sealant and before dam place- ronmental conditions would extend for a much longer period ment, W2 is the weight of the sealed specimen after soaking, of time. and W1 is the weight of the sealed specimen before soaking. DegaDeck Crack Sealer Plus was effective when coupled with REM 800, but without the hydraulic cementitious material enough water penetrated into the crack for it to be con- sidered ineffective. About half of these DegaDeck specimens remained relatively water resistant while the remaining seals failed. The sealant was not thick enough to be able to bridge the gap created by the crack on its own, as shown in Figure 3.53. Transpo Sealate was not considered effective with or with- out REM 800. Except for a few outliers, the specimens contain- ing REM 800 collectively had a much lower percent absorption of water than the specimens without REM 800. The ineffective- ness of Transpo Sealate may be attributed to the thin, water- like consistency of the product. When applied to the vertical surface, most of this sealant flowed off of the sample. There- fore, the layer that remained was not thick enough to prevent water infiltration. The product is recommended for horizon- tal application and the experiment confirms that this is where it would be most useful. Figure 3.54 shows the specimens Figure 3.52. Specimens with water dams. sealed with Transpo Sealate.

OCR for page 42
45 Table 3.8. Summary of 24-hour percent absorption for the durability test, Stage II. Crack Width Control DegaDeck Transpo Sealate DuralPrep A.C. SilACT (in.) With Without With Without With Without With Without 0.000 4.28 REM REM REM REM REM REM REM REM 800 800 800 800 800 800 800 800 0.007 1.81 0.22 4.10 2.06 4.63 0.42 0.66 0.09 2.17 0.012 1.49 0.11 1.44 2.96 0.87 0.51 2.78 0.13 0.46 0.016 2.59 0.36 0.69 2.82 1.03 1.07 3.25 0.19 1.45 0.033 4.19 0.35 0.37 2.29 4.04 0.33 1.46 0.17 1.94 0.054 1.69 0.08 3.81 1.34 4.03 0.72 0.54 0.15 2.43 (a) With REM 800 (a) With REM 800 (b) Without REM 800 (b) Without REM 800 Figure 3.53. Specimens coated with DegaDeck. Figure 3.54. Specimens coated with Transpo Sealate.

OCR for page 42
46 DuralPrep A.C. was moderately effective with an under- hard, water-resistant outer shell that covers the specimen, as coating of REM 800, but was not effective without it. The is the case with the other sealants. Instead, the water-resistant sealant was mixed by combining a powder with two liquid layer is actually within the concrete. Without the hard, outer chemicals. This created a thick, slurry-like liquid that was able layer, there is nothing to bridge the crack gap. The strength of to bridge the space created by the cracks, even without REM SilACT comes from being able to be soaked into the concrete. 800 and with the largest 0.54-in. crack. DuralPrep A.C. was This is why it performed well after soaking into the REM 800 the only sealant of the four tested that did not gap when applied layer. Without the patching material, the crack was left open over the crack, especially when voids appeared at the crack and SilACT was not able to soak all of the way into the crack location. However, the product performed well when the when the opening was located on a vertical surface. If the sur- specimen was batched with REM 800. Figure 3.55 shows face had been horizontal and the product had been allowed the specimens sealed with DuralPrep A.C. to soak all the way into the crack, the results would have been SilACT was effective at preventing water penetration with more effective, but this would not be representative of the REM 800, but was ineffective without the cementitious pack- actual end zone crack position. Figure 3.56 shows the spec- ing material. The manufacturer states that SilACT chemically imens sealed with SilACT. bonds with the substrate and creates a water-resistant layer just In comparison to what the study team expected, the data below the concrete surface that repels water but allows gasses had quite a few inconsistent results. It seemed that whether the to flow through. Therefore, SilACT has a different method sealant was effective or not depended largely on how well the of water resistance than the other sealants tested. There is no application was executed. Specimens (such as the 0.016-in. (a) With REM 800 (a) With REM 800 (b) Without REM 800 (b) Without REM 800 Figure 3.55. Specimens coated with DuralPrep. Figure 3.56. Specimens coated with SilACT.