Materials selection for concrete overlays : the final report Page: 71
xviii, 192 p. : col. ill. ; 28 cm.View a full description of this report.
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Fifteen slabs were made using one mixture design with different types of reinforcement
(the layout is provided in Appendix B-3). The mixture design purposely utilized a w/c of 0.45 in
a 7-sack mix to promote crack development while staying within a reasonable range of typical
concrete pavement mixture designs. When high water to cementitious material ratio is used, the
water evaporation from concrete will increase and often causes cracking. The mixture design is
provided in Appendix B-3.
4.4.8 Surface Preparation
Two different methods were tried to prepare the surface of the existing slab for the
customized restrained shrinkage and bond tests: sandblasting (Figure 4.11) and shotblasting
(Figure 4.12). Sandblasting proved to be a more difficult process for two reasons. First, it was
very difficult to produce an even texture due to the fact that the discharge of sand particles was
excessively strong through the small nozzle opening. If the discharge nozzle was too close to the
surface, it left narrow and deep streaks. If the discharge nozzle was too far from the surface, it
left wide and shallow streaks. Thus, overall texture was very uneven. Second, the sandblasting
not only eroded the cement matrix but also the coarse aggregate due to its high power. Exposed
coarse aggregates are a key to proper bond between the concrete overlays and the existing slabs.
-Y S
- p ' "Si --- .
' ,, -i: , fa ' 4= /'. 'Figure 4.11. Sandblasting in progress
71
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Kim, Dong H.; Fowler, David W.; Ferron, Raissa P.; Trevino, Manuel M. & Whitney, David P. Materials selection for concrete overlays : the final report, report, July 2012; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth303706/m1/91/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.