compatibility of ultra high performance concrete as repair material

UHPC is a cost-effective solution if the service life is taken into consideration, as shownby Denarié et al. (2005) in his economic analysis of the rehabilitation of bridge over LaMorge River in which the cost of the rehabilitation by using UHPC was compared to thatthat would have cost by a traditional solution composed of mortar and waterproofingmembrane. They stated that the UHPC solution is only 12% more expensive that the“traditional” alternative. If factors such as the longer service-life of UHPC and shortdown time are into consideration, it would be expected that the use of UHPC is cheaperfrom a life-cycle perspective. Furthermore, the UHPC alternative would be even cheaperif it starts to become a common practice among engineers.Denarié et al. (2009b) developed new UHPC recipes in which the 50% of the amount ofcement from the optimize formulation (CEMTECmultiscale ® ) was replaced by locallimestone filler, reducing considerably the cost and environmental impact. Fidjestol et al.(2012) also succeeded in developing a UHPC made up with local sand, cement, fly ashand admixtures. The author emphasized the reduction of the logistics cost if locallyavailable materials are used.2.3 Factors that affecting the Bond StrengthThe bond strength between two different concrete materials is influenced by manyfactors, such as substrate surface (wetting conditions, roughness, presence ofmicrocracks, cleanliness), compaction method, curing process, concrete substrate(strength and aggregate gradation), use of bonding agents, age of the bond, and overlaymaterial (strength and thickness), (Beushausen 2010; Momayez et al. 2005; Silfwerbrand1990). There is a broad consensus among researchers that substrate surface preparationmethods influence the bond. For example, hydrodemolition followed by power washinghas been shown to be the best unsound concrete removal and surface preparationtechnique. Impact methods (scabbling, milling, scarifying) present the advantage of beingthe most economical treatment to remove the damaged concrete, but one majorshortcoming is that they fracture the remaining concrete surface, causing a low fracturetensile strength. Substrate surfaces prepared by these methods usually achieve half of thebond strength of that prepared by hydrodemolition method (Hindo 1990; International26