HIGH-PERFORMANCE CONCRETE FOR PRODUCTION OF BOARDS TO REPAIR UNDERWATER STRUCTURES

The field of repair of submerged hydraulic structures (dams, stilling basins, lock chambers, and so forth) is becoming more and more importa nt given the economic worth of such structures. Damage caused by abras ion can make it difficult to maintain such structures in service. The purpose of the study described in this paper was to develop durable hi gh-performance concretes that can be used for manufacture of board for repair of abrasion-damaged surfaces. The board might also be placed o n surfaces already repaired with colloidal concrete poured underwater. Two types of cement (Type 30 and Type 10) and two high-performance co arse aggregates (granite and dolomitic limestone) were used. The eight concrete mixes developed included a variety of additives and admixtur es such as silica fume, steel fibre, latex, and superplasticizer, For precise characterization of the mixes, hydraulic abrasion tests, compr essive strength tests, and freeze-thaw cycle resistance tests were per formed. In addition, shrinkage, thermal expansion coefficient, and per meability of the concretes were measured; in some cases, the board mig ht be subject to freeze-thaw cycles in structures partially emptied fo r repair or maintenance. Results show that high-performance concretes with very low water : cement ratio, good workability, and improved fre eze-thaw cycle resistance can be manufactured. Concretes made with Typ e-30 cement, silica fume, and granite or limestone aggregate offer exc ellent hydraulic abrasion resistance (depth of erosion on the order of 1 mm after 72 h), compressive strength greater than 115 MPa after 91 days, and a freeze-thaw durability factor of more than 100%.