Section 1908

Shotcrete is mortar or concrete that is pneumatically projected at high velocity onto a surface. Except as specified in this section, shotcrete shall conform to the requirements of this chapter for reinforced concrete,

[OSHPD 1R, 2 & 5] and the provisions of ACI 506R. The specified compressive strength of shotcrete shall not be less than 3,000 psi (20.69 MPa).

[OSHPD 1R, 2 & 5] Concrete or masonry to receive shot- crete shall have the entire surface thoroughly cleaned and roughened by a method acceptable to the enforcement agency, and just prior to receiving shotcrete shall be thor- oughly cleaned of all debris, dirt and dust. Concrete and masonry shall be wetted before shotcrete is deposited, but not so wet as to overcome suction.

Shotcrete proportions shall be selected that allow suitable placement procedures using the delivery equipment selected and shall result in finished in-place hardened shotcrete meeting the strength requirements of this code.

Coarse aggregate, if used, shall not exceed ³ /4 inch (19.1 mm).

[OSHPD 1R, 2 & 5] For structural walls, when total rebar in any direction is more than 0.31 in ² /ft. or rebar size is larger

Copyright © 2019 ICC. ALL RIGHTS RESERVED. Accessed by Kevin Day (kevin.day@dgs.ca.gov), (California Building Standards Commission) Order Number #100735044 on Jul 24, 2019 03:54 PM (PDT) pursuant to License Agreement with ICC. No further reproduction or distribution authorized. Single user only, copying and networking prohibited. ANY UNAUTHORIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT, AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.

100735044

CONCRETE

Except where permitted herein, unfinished work shall not be allowed to stand for more than 30 minutes unless edges are sloped to a thin edge. For structural elements that will be under compression and for construction joints shown on the approved construction documents, square joints are permitted. Before placing additional material adjacent to previously applied work, sloping and square edges shall be cleaned and wetted.

[OSHPD 1R, 2 & 5] The film of laitance which forms on the surface of the shotcrete shall be removed within approxi- mately 2 hours after application by brushing with a stiff broom. If this film is not removed within 2 hours, it shall be removed by thorough wire brushing or sand blasting. Con- struction joints over 8 hours old shall be thoroughly cleaned with air and water prior to receiving shotcrete.

In-place shotcrete that exhibits sags, sloughs, segregation, honeycombing, sand pockets or other obvious defects shall be removed and replaced. Shotcrete above sags and sloughs shall be removed and replaced while still plastic.

During the curing periods specified herein, shotcrete shall be maintained above 40°F (4°C) and in moist condition. [OSHPD 1R, 2 & 5] Maintain above 50°F (10°C) and in moist condition.

1908.9.1 Initial curing. Shotcrete shall be kept continuously moist for 24 hours after shotcreting is complete or shall be sealed with an approved curing compound.

1908.9.2 Final curing. Final curing shall continue for seven days after shotcreting, or for three days if highearly-strength cement is used, or until the specified strength is obtained. Final curing shall consist of the initial curing process or the shotcrete shall be covered with an approved moisture-retaining cover.

1908.9.3 Natural curing. Natural curing shall not be used in lieu of that specified in this section unless the relative humidity remains at or above 85 percent, and is authorized by the registered design professional and approved by the building official.

Strength tests for shotcrete shall be made by an approved agency on specimens that are representative of the work and that have been water soaked for not fewer than 24 hours prior to testing. Where the maximumsize aggregate is larger than ³ /8 inch (9.5 mm), specimens shall consist of not less than three 3-inch-diameter (76 mm) cores or 3-inch (76 mm) cubes. Where the maximum-size aggregate is ³ /8 inch (9.5 mm) or smaller, specimens shall consist of not less than 2-inch-diameter (51 mm) cores or 2inch (51 mm) cubes.

1908.10.1 Sampling. Specimens shall be taken from the in-place work or from test panels, and shall be taken not less than once each shift, but not less than one for each 50 cubic yards (38.2 m ³ ) of shotcrete.

1908.10.2 Panel criteria. Where the maximum-size aggregate is larger than ³ /8 inch (9.5 mm), the test panels shall have minimum dimensions of 18 inches by 18

inches (457 mm by 457 mm). Where the maximum-size aggregate is ³ /8 inch (9.5 mm) or smaller, the test panels shall have minimum dimensions of 12 inches by 12 inches (305 mm by 305 mm). Panels shall be shot in the same position as the work, during the course of the work and by the nozzlemen doing the work. The conditions under which the panels are cured shall be the same as the work. [OSHPD 1R, 2 & 5] Approval from the enforce- ment agency shall be obtained prior to performing the test panel method.

1908.10.3 Acceptance criteria. The average compressive strength of three cores from the in-place work or a single test panel shall equal or exceed 0.85 f ′ c with no single core less than 0.75 f ′ c . The average compressive strength of three cubes taken from the in-place work or a single test panel shall equal or exceed f ′ c with no individual cube less than 0.88 f ′ c . To check accuracy, locations represented by erratic core or cube strengths shall be retested.

1R, 2 & 5] Forms for shotcrete shall be substantial and rigid. Forms shall be built and placed so as to permit the escape of air and rebound.

Adequate ground wires, which are to be used as screeds, shall be placed to establish the thickness, surface planes and form of the shotcrete work. All surfaces shall be rodded to these wires.

[OSHPD 1R, 2 & 5] Shotcrete shall be placed in accordance with ACI 506R.