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2015SpringShotcreteEMag

Goin’ Underground brick, egg-shaped combined sewer in late 2013 to the installation of the wire. The installed welded in Muncie, IN, for the Muncie Sanitary District wire reinforcement consisted of 2 x 2 in. (50 x (MSD). The project was advertised as a cured- 50 mm), 12/12 gauge galvanized wire conforming in­place pipe (CIPP), modified polymer liner, or to ASTM A185 (Fig. 2). The wire was placed shotcrete rehabilitation job. When the bid results 1 in. (25 mm) from the existing brick substrate were announced, shotcrete was by far the most with 1/4 x 3 in. (6 x 75 mm) hook anchor bolts economically sound option. The sewer is spaced 24 in. (0.6 m) in each direction (Fig. 3). 100 years old (Fig. 1) and the 6500 ft (2000 m) Coastal Gunite opted to use dry-mix shotcrete section that was rehabilitated ranged in size from batched on-site. The compressive strength 48 to 56 x 92 in. (1.2 to 1.4 x 2.3 m). There were requirement was 5000 psi (35 MPa) at 28 days, a few 24 x 36 in. (0.6 x 0.9 m) sections that were and was easily accomplished with the site- subcontracted to Insituform Technologies (a CIPP batched mixture. Once the reinforcement was contractor). The project was designed by GRW installed, the shotcrete was placed in two lifts Engineers, located in Indianapolis, IN. (Fig. 4). To ensure that the required shotcrete This particular sewer rehabilitation project thickness was achieved, measuring pins were consisted of installing a 3 in. (75 mm) thick placed at 5 ft (1.5 m) centers in each direction welded wire fabric reinforced shotcrete lining (Fig. 5). The final finish of the shotcrete was a around the entire circumference of the sewer line. brush finish parallel to the direction of the flow The sewer was fairly clean of debris, but some in the sewer (Fig. 6). Coastal Gunite mobilized root and loose brick removal was required prior in June 2013 and all shotcrete lining was Fig. 3: Close-up of wire reinforcement lap and brick Fig. 5: Measuring pin installed to ensure correct thickness substrate of shotcrete Fig. 4: First lift of dry-mix shotcrete Fig. 6: Brush finish parallel to the direction of the flow Shotcrete • Spring 2015 41


2015SpringShotcreteEMag
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