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2013WinShotcreteEMag

the ASTM C662 freeze-thaw resistance test, and concluding remarks ASTM C672 surface scaling test were important The rehabilitation project of the reservoir indicators for success. spillway was successfully done with surface Two cores were cut into 2 in. (50 mm) thick preparation using hydrodemolition and then specimens and tested for rapid chloride permea- application of high-performance shotcrete with bility at 28 days after shotcrete placement. The careful consideration of the material specifica- results showed 934 and 906 coulombs, which rate tions, the importance of curing, and efficient as a “very low” permeability according to the ASTM C1202 guide. The freeze-thaw resistance test of Type A was performed up to 300 cycles. The relative dynamic moduli were measured every 30 cycles. The final durability index after 300 cycles was 91, indicating very good freeze-thaw resistance. The repetitive cycles of freezing and thawing will cause the concrete surface to scale if it does not possess adequate strength or the required volume of entrained air. Deicing chemicals used for snow and ice removal exacerbate the buildup of internal stresses in concrete and thereby con- tribute to the tendency to scale. The scaling resistance qualitatively determined by a visual arbitrary rating resulted in “0,” which indicates no scaling. Figure 6 compares the specimen sur- face before and after 50 cycles of the surface scaling test. Fig. 5: Mockup panel test Shotcrete • Winter 2013 51


2013WinShotcreteEMag
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