ABSTRACT
The preplaced aggregate concrete (PAC) or TSC gets its name from the method used for placement. Formwork is constructed and the coarse aggregate is densely placed inside the formwork. The coarse aggregate is washed and screened just prior to placement to remove all fines. Grout is then injected through the forms to provide the matrix as shown in Figure 1. Grouting is begun at the bottom of the preplaced aggregate. The grout typically consists of sand, cement, pozzolan, and an admixture. The characteristics of the grout are affected by water content, sand grading, cement, pozzolan, and the types and amounts of admixtures. For each mixture there are optimum amounts of fillers and admixtures which produce the best pumpability or consistency. Proper proportioning of the structural grout mix components is necessary to produce the required strength and durability requirements of the finished preplaced-aggregate concrete. Mixture design tests are necessary for each job. TSC has been used for the resurfacing of lock walls and dams and for the repair of tunnel linings, piers, and spillways (King 1959) It may be used advantageously on repair jobs of heritage structures, and large concrete repair jobs:
• Where placement by conventional methods is difficult (e.g., massive reinforcing steel and embedded items are present or access to the area is difficult, such as the underpinning of the toe of a dam or apron).
