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2013WinShotcreteEMag

2012 Honorable Mention Fort mott State Park— rehabilitation Phase i By Warren Cruz Fduring the post-Civil War modernization concrete to be removed. No. 5 (No. 16M) epoxy-(100 to 500 mm) deep (refer to Fig. 1 and 2). Therepair specification called for all deterioratedort Mott was part of a three-fort defensesystem designed for the Delaware River period, situated on the Delaware River in coated steel reinforcing bars 18 in. (450 mm) long Pennsville, NJ. Troops were regularly stationed were doweled 2 ft (0.6 m) on center to anchor the there from 1897 to 1922. Construction started in new No. 5 (No. 16M) reinforcing bar cage with 1872 and stopped in 1876 with only two gun bars 18 in. (450 mm) on center (refer to Fig. 3 emplacements and two magazines in the mortar and 4). The repair method originally called for a battery completed. Plans were originally for 11 “form-and-pour” repair approach. Cruz Concrete gun emplacements with 20 guns and a mortar and Guniting Repair, Inc., proposed a dry-mix battery with six emplacements, but construction shotcrete approach instead and was accepted by never reached that point. the New Jersey State Parks Department. Four to Shortly after World War I, Fort Mott and this 18 in. (100 to 450 mm) of shotcrete was placed three-fort system became obsolete as newly over everything and restored back to the original constructed Fort Saulsbury in Delaware became lines, while recreating the original finish. Cruz the principal defense on the Delaware River. Concrete was contracted to place the dry-mix The federal government maintained a caretaking shotcrete on 3520 ft2 (327 m2) of vertical detachment at the fort from 1922 through 1943. walls, sloped walls, and columns. The shotcrete New Jersey acquired this reservation as a historic portion of the project lasted 3 weeks (refer to site and State Park in 1947. It was then opened to Fig. 5 and 6). the public in June of 1951 and remains open As a historic site, a major challenge on this today for guided tours and walking tours. project was providing 3000 psi (21 MPa) concrete Fort Mott held massive cannons to protect to match the existing concrete. With all the common the mouth of the Delaware River from invaders. concrete technology of today using admixtures and It was no wonder that the fort was originally additives, it was an accomplishment to match this constructed of solid, 20 ft (6 m) thick concrete lower strength level of the past and match the walls and buried on one side of a huge earth berm. existing walls. Many mockup test panels were made The interior walls were severely spalled and with using different colors and textures. Finally, one was deteriorated concrete ranging from 4 to 20 in. chosen and Cruz Concrete was able to proceed. Fig 1: Cannon pit before Fig. 2: Exterior Fort Mott before 40 Shotcrete • Winter 2013


2013WinShotcreteEMag
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