Reinforced Concrete Slurry walls are designed and constructed to carry structural loading. These slurry walls are backfilled with steel reinforcing and concrete, and used as temporary and permanent retaining walls and/or load bearing elements especially when groundwater presents a construction problem. There are at least two kinds of structural walls; diaphragm (or cast-in-place) walls and precast walls. The appearance of the completed wall is a direct reflection of the soils encountered throughout the excavation. In some cases, the surface of the wall can be covered with paint or shotcrete for a better visual effect
Diaphragm walls are the most common concrete slurry walls. They are usually excavated under bentonite slurry in alternating panels, called primary and secondary panels. The length of the panels depend on site conditions and dimensions of the excavating tool, typically a slurry clam bucket. The panels are concreted through tremie pipes to prevent segregation of the wet concrete. After the set of the primary panels, the secondary panels are excavated and concreted to complete the wall. Different systems are used to insure the integrity of the joints between primary and secondary panels. Sometimes steel beams (soldier piles) are used in lieu of rebar cages and for the connection between primary and secondary panels. This is referred to as the “soldier pile tremie concrete”, (SPTC), method.
Stringent quality control measures are required to ensure the quality of diaphragm walls, including:
• Control of the alignment of the wall prior to its excavation.
• Control of verticality during the excavation process.
• Prior to concreting a panel, the slurry must be “desanded” to remove excess sand suspended in the slurry. This will insure the quality of the concrete as well as the integrity of the joints between panels.
• Thorough inspection of the rebar cages to insure that they conform to the design and that the blockouts and other reservations will be at the proper locations.
• Testing of the concrete
• Making sure that the tremie pipes are always embedded in the concrete during the concreting operation.
Precast concrete slurry walls are built utilizing precast concrete panels, either reinforced or prestressed, which are inserted into C-B slurry-filled trenches. When the C-B slurry is set, it seals the joints and secures the panel to the ground. One of the advantages of the precast walls is the architectural appearance of the completed wall.