ACI 303R-12 Guide to Cast-in-Place Architectural Concrete Practice.
All rustication strips or other inserts should be installed continuously tight to the form contact surface. Back- screwing the strip so it can be released before stripping may help obtain a tight seal. Nailing the strips to the form face for some architectural treatments may be acceptable but will not attain a tight seal. Insufficient nailing of the form strip will usually result in leakage and leave the reveal void ragged and discolored. Rustication strips should be uniform in dimensions, nonabsorbent, and of suficient stiffness to maintain align- ment during concrete placement operations. In areas of possible deflection of the sheathing, a method of treatment to prevent mortar leakage should be used. Metal chamfer or rustication strips and other materials of similar stiffness should have a minimum width of 3/4 in. (20 mm). Widths of wooden rustication strips should be at least equal to their depths. Joints smaller than recommended above can be attained with special form detailing using steel insert strips installed between the forms. Intersections of chamfer or rustication strips should be mitered or coped to fit snugly. Chamfer, rustication, or isola- tion strips may be placed so as to cover form joints. Soffits- A drip should be installed in soffits near vertical surfaces where there is a potential for downward movement of rainwater on the vertical concrete face (Fig. The drip molds should be placed as near to the external vertical face as practicable, but not closer than 1 in. (25 mm) from the finished concrete surface. Note that the drip in Fig. is interrupted at either end of the under- side horizontal surface to to help facilitate downward move- ment of water before it reaches the inside vertical face.
3.2.3 Combination with precast concrete– Cast-in-place architectural concrete and precast elements may be success- fully combined using one of two site options: 1. On-site- Color and texture may be reasonably matched by on-site precasting at the same time cast-in-place work is done, using the same concrete mixture, materials, formwork techniques, and curing for both types of concrete; or 2. Off-site- Contrasting colors and textures in the design between off-site precast concrete and cast-in-place archi- tectural elements are provided. In some cases, color and texture can be closely matched using dissimilar materials. A mockup panel can be used to demonstrate the match for approval by the architect. Trying to achieve an exact match of cast-in-place concrete with precast units cast off- site is extremely difficult and may not be achievable. Nevertheless, both on-site and off site combina- tions with precast concrete require detailed effort on the parts of the owner, architect, contractor, and inspector (Fig. 3.2.3).ACI 303R pdf download.