RICHARD BRADY & ASSOCIATES, INC-A-2020-064

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1192 R. c, xENMIR lmtr.AW4VA joints should be bonded to waterstops in the wall. It is good practice to use both wa- terstops and joint sealant in floor joints, particularly in deep reservoirs, as illustrated in Fig. 12 and 13. Poly - sulfide and polyurethane materials are widely used for this purpose. Poly- urethane appears to have better bond- ing characteristics than polysulfide and appears to be superior in other respects. In hydraulic structures, where there may be only very slight movements at the joints, a firm sealant with a shore hardness of 30 to 40 should be used to prevent the possibility of extrusion of the sealant through a honeycombed area in the concrete. joint sealant used Apply Bondbreaker, �64n. PVC Wate stap steel continuous Across Ja Fig. 10. Typical Roof Slab Joint for Buried Concrete Reservoir in the roofs of concrete reservoirs ex- posed to the weather should be softer, with a shore hardness of 10 to 20. Where sealant and waterstops are used in the floor joints, the sealant groove should be carried along the joint as far as the horizontal waterstop in the wall footing and bonded to ,the waterstop, as illustrated in Fig. 14. If this is not done, the margin of safety against leakage provided by the sealant is greatly reduced. Floor joints in many shallow reser- voirs and other hydraulic structures have been successfully sealed with joint sealant alone without the use of water - stops. This is standard practice where reservoirs are lined with unreinforced concrete. The strips used for forming the seal- ant grooves should be left in place un- tit the structure is complete and all debris has been removed. Any grout overlays on the side of the sealant groove originating from the second concrete pour should be removed; next, the joint grooves should be sand- blasted, blown out, and primed before the sealant is placed. Although some sealant manufacturers claim their seal- ants do not require groove surfaces to be primed, the author believes that priming is inexpensive insurance against an ineffective sealing job. It is of utmost importance that great care be used in thoroughly mixing all two -component sealants with electric stirring devices. Incompletely mixed two -component sealant will not set up 6-In. PVC Weterstop Apply Bandhreaker tight Wire Ties ® 18-in. 3:! . Stop Alt Nodz. Bars at Jolnt Fig. 11, Typical, Wall Joint for Buried Concrete Reservoir and is difficult and expensive to re- move. Entrainment of air in the seal- ant as it is placed is less likely to occur if the sealant is pumped and dis- charged through a nozzle kept sub- merged in the sealant groove. 5. Concrete quality. Good concrete quality cannot be over -emphasized if a reservoir is to be watertight and maintenance -free. Although this ar- ticle mentions some of the more impor- tant factors in producing good quality concrete, more detailed information can be found in authoritative publi- cations', As the usual design compressive strength of 3,000 psi at age of 28 days is easy to obtain, concrete strength is a lesser problem in producing good RICHARD BRADY & ASSOCIATES, INC. F-61