Pages F-74 through F-75.pdf

F-74 DIVISION 550

566.09 Curing Shotcrete. Cure the surface according to Subsection 552.15 and Chapter 19 Curing and Protection of ACI 506.5, Guide for Specifying Underground Shotcrete. For intermediate shotcrete surfaces, or if a finished final surface is required, cure the shotcrete according to Subsection 552.15(b). If a finished surface is not required, apply curing compound to the final exposed shotcrete surface according to Subsection 552.15(c). Maintain shotcrete at a temperature above 40 °F (5 °C) until shotcrete has achieved a minimum compressive strength of 1500 pounds per square inch (10.3 megapascals).

Revised by Amendment A002

Special Contract Requirements Project: OR DOT CRGNSA 100(4), Historic Columbia River Highway State Trail, Mitchell Point Crossing

(d) Shotcrete application. Using only the approved Nozzlemen who have created acceptable test panels, apply shotcrete in accordance with the following:

(1) Apply shotcrete within 45 minutes of adding cement to the mixture unless an approved hydration stabilizer is used. If a hydration stabilizer is approved, deliver and place the shotcrete within the approved design discharge time limit not to exceed 3½ hours.

(2) If shotcrete accelerator is used, strictly follow and document the approved application methods.

(3) Apply shotcrete at an orientation as near as possible to perpendicular to the surface to receive shotcrete.

(4) Apply shotcrete with a steady nozzle motion, commencing with application at the bottom of the surface to receive shotcrete and working to the top.

(5) Limit the layer thickness of each shotcrete application such that no sloughing or sagging occurs. If additional thickness is required, broom or scarify the previously applied layer to receive additional shotcrete. Allow the previously applied layer to harden and provide a saturated, surface dry condition before applying additional shotcrete.

(6) Taper construction joints to a thin edge over a distance of at least 12 inches (300 millimeters). Provide a saturated surface dry condition at the joint surface before applying additional shotcrete.

(7) Taper transitions in shotcrete thicknesses, due to different ground support types, over a distance of at least 12 inches (300 millimeters).

(8) Promptly remove rebound shotcrete from the work area.

(9) Cut out pockets, sags or other defects to a minimum surface area extent of 12 inches (300 millimeters) by 12 inches (300 millimeters) and reapply shotcrete.

(10) Finish shotcrete as shot without troweling, as directed by the CO.

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F-75 DIVISION 550

566.10 Production Report. Prepare and submit a written report within 24 hours of shotcrete production and application for each shift. Include the following information:

566.11 Acceptance. See Table 566-2 for sampling, testing and acceptance requirements as well as the quality characteristic category.

Material for shotcrete will be evaluated under Subsections 106.02 and 106.03. Submit a production certification with each shipment of hydraulic cement.

The shotcrete mixture’s air content, density, boiling absorption and permeable void volume will be evaluated under Subsections 106.2 and 106.4. Compressive strength, flexural toughness and residual flexural strength will be evaluated under Subsection 106.05. See Table 566-1 for sampling and testing requirements.

The shotcrete placement system will be evaluated under Subsections 106.2 106.02 and 106.4 106.04.

566.12 Contingency Shotcrete. Following completion of production shotcrete placement, provide access to the CO for inspection of the tunnel to assess the extents and aesthetics of shotcrete and exposed rock below springline (based on the distribution of ground support types, as indicated in the Plans). If the CO assess that locations of exposed rock should be covered with shotcrete, place shotcrete to fill zones of exposed rock to a minimum thickness consistent with the shotcrete thickness above springline.

Measurement

566.13 Measure the Section 566 pay items listed in the bid schedule according to Subsection 109.02.

When measuring shotcrete by the square yard (square meter), measure on the surface on which it is shot.

Revised by Amendment A002

Special Contract Requirements Project: OR DOT CRGNSA 100(4), Historic Columbia River Highway State Trail, Mitchell Point Crossing

(a) Quantity and location of shotcrete applied including photos of areas where shotcrete was placed;

(b) Observations of success or problems of equipment operation, application, final product condition, and other relevant issues during production and application;

(c) Batch numbers (if applicable);

(d) Name of Nozzleman; and

(e) Name(s) and signature(s) of person(s) performing observation.

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