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Sustainability (a) Fig. 2: (a) The corner of this photo was the starting point for shotcreting; and (b) one of the biggest challenges faced was the wall reinforcing steel moving out 4 in. (100 mm) by Fig. 3: Mockup with waterproofing—one of many reinforcing bar and the weight of the shotcrete waterproofing configurations Coastal faced. The blowpipe operation was key to keeping the rebound, overspray, and water out of the wall sections (b) for the day and commenced later. Another pre- construction test examined how much water could be sprayed on the waterproofing before it would activate. The mockups also allowed the owners to see what their foundation would look like after it was shot and finished. One would think having most of the designers present in the weekly project meetings would have made getting the shotcrete submittals approved on a timely basis easy. Unfortunately, this wasn’t the case, and approvals often took longer than expected. When the submittals were finally approved, Coastal shot and finished the preconstruction panels. The shotcrete crew had to wait to install the grade wires, check the tight- ness of the reinforcing bars, and set up the equip- ment while drain tile was installed under the new wall reinforcing steel. To make it even more difficult, the bentonite waterproofing could not be installed until the day of shooting wet-mix shotcrete. Wetting down the reinforcing bars was The project’s testing firm retained Consultant challenging because too much water would acti- Ray Schallom to train their inspectors on the vate the bentonite waterproofing material. proper application of wet-mix shotcrete. Several There were hiccups along the way with con- meetings were required to establish and identify crete quality control (QC) issues including tem- which ASTM test documents were to be used and porary shutdown of the shooting operation, much who was paying for the tests specified by the to the displeasure of Hensel Phelps’ Superinten- structural engineer. Two different mockups were dent. The ready mix concrete supplier’s QC built with different wall layouts to evaluate shot- personnel, Hensel Phelps’ Project Engineer, crete placement on lagging waterproofing. The Coastal’s Superintendent, and both inspectors mockups were set up to show the performance drove to the concrete plant to try and determine of waterproofing strips when shooting stopped what had gone wrong with the concrete. As it Shotcrete • Summer 2015 37


2015SummerShotcreteEMag
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