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2017SummerShotcreteEMag

| SHOTCRETE CORNER 3. Chemically bonded waterproofing relies on an adhesive activated by heat and minimal contact pressure. This type of system does not rely on confining pressure and stops water from traveling laterally along the wall face to a crack, creating a leak. 4. Integral crystalline waterproofing admixtures are added to ready mixed concrete. Once the concrete has cured, cracking occurs and leads to water infiltration; the crystalline cracks and voids to seal off the passageways for potential 5. Post-groutable fabric membrane is a newly developed waterproofing system that takes full advantage of the unique properties offered by the structural shotcrete process. A fabric with an attached woven geo-like grid is attached to the shoring substrate. After the reinforcing bar is installed, grout tubes are connected to the fabric grid and project slightly past the final wall face. Later, these tubes are used to inject grout to fill the curtain wall fabric to completely seal the blindside of the basement wall. This injection grouting is done after much of the concrete shrinkage has occurred, with an elastomeric, hydrophilic adhesive, two-part grout. SHOTCRETE THE BLINDSIDE SOLUTION The use of structural shotcrete for blindside walls is rapidly expanding and is becoming a common solution on tight urban sites, with fast-track schedules that require a watertight projects fully understand the similarities and differences of Fig. 4: In-place crack control inducer (two pipes for thicker walls) is only possible with structural shotcrete. Concrete placement in form-and pour would wash pipes away 50 waterproofing grows internally to fill in non-moving water leaks. below-grade structure. Once all the players of these form-and-pour and structural shotcrete, and get past the misconceptions, they can benefit from these advantages to create a better blindside waterproofing assembly: • Speeds up the concrete placement schedule because little or no formwork is needed, thus freeing up the workforce and crane time, and requiring less on-site formwork storage. • Steel trowel final finish on the exposed surfaces, requiring far less touchup than form-and-pour. • The ability to place concrete for blindside walls around obstructions such as shoring struts and rakers while still addressing tall, complex wall configurations. • The unique ability to shoot around properly spaced in-place control joint inducers, which helps to meet ACI requirements to reduce wall thickness by 20 to 25% at control joints (refer to Fig. 4). • Shotcrete delivers concrete to the bottom of the wall without the segregation of concrete dropping through the reinforcement and with no formwork in the way, enabling complete consolidation at the bottom of the wall and creating a better construction joint for the blindside waterproofing. • Shotcrete can achieve better concrete consolidation in walls with dense reinforcement because greater access is available with no formwork in the way, making it easier to create a denser surface for the blindside waterproofing integrity. • With much lower concrete pressure and no impact dropping concrete from the top of a form, shotcrete inherently has far less risk of damaging the waterproofing system. Shotcrete | Summer 2017 www.shotcrete.org


2017SummerShotcreteEMag
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