SECTION 03361

SHOTCRETE

PART 1 GENERAL

SECTION INCLUDES

Preparation of substrate form surfaces[.] [and placing reinforcement.]

Pneumatically applied concrete.

PRODUCTS INSTALLED BUT NOT FURNISHED UNDER THIS SECTION

Section [_____-__________]: Supply of accessories for placement by this Section.

RELATED SECTIONS

Section 02222 - Excavation: Forming earth to achieve contours and surfaces required.

Section 03100 - Concrete Formwork: Prepared forms to achieve contours and surfaces required.

Section 03200 - Concrete Reinforcement.

REFERENCES

ACI 506.2 - Specification for Materials, Proportioning, and Application of Shotcrete.

ASTM C150 - Portland Cement.

ASTM C330 - Lightweight Aggregates for Structural Concrete.

ASTM C332 - Lightweight Aggregates for Insulating Concrete.

SUBMITTALS

Submit under provisions of Section [01300.] [01340.]

Shop Drawings: Indicate [formwork] [shaped earthwork] dimensions and contours, reinforcement, accessories[,][.] [and] [_______________.]

Submit shop drawings sealed by the Structural Design Engineer identified in Article 1.07 - QUALIFICATIONS.

QUALITY ASSURANCE

Perform Work in accordance with ACI 506.2.

Maintain [one] [_____] copy of [each] document on site.

QUALIFICATIONS

Design Work of this Section under direct supervision of a Professional Structural Engineer experienced in design of this work and licensed [at the place where the Project is located.] [in the State of [_________________].]

Applicator: Company specializing in performing the work of this Section [with minimum [__________] years [documented] experience.] [approved by manufacturer.]

ENVIRONMENTAL REQUIREMENTS

Ensure materials and surrounding air temperature are a minimum [50] [___] degrees F ([10] [___] degrees C) prior to, during, and 7 days after completion of work.

During freezing or near freezing weather, provide equipment and cover to maintain minimum [50] [___] degrees F ([10] [___] degrees C) and to protect work completed or work in progress.

Suspend shotcrete operations during high winds, rainy weather, or near freezing temperatures when work cannot be protected.

FIELD MEASUREMENTS

Verify that field measurements are as [shown on [Drawings] [shop drawings].] [instructed by the manufacturer.]

PART 2 PRODUCTS

MATERIALS

Cement: ASTM C150, Type [Normal] [Sulphate-resistant], [white.] [grey.]

Aggregate and Water: Proportioned to achieve mix design.

Additives: [____________________.]

Lightweight Aggregate: ASTM C330.

Insulating Aggregate: ASTM 332.

Curing Compound: [_______________], and not detrimental to application of subsequent surface finish materials.

SHOTCRETE MIX

Conform to following requirements:

Compressive Strength	[3000] [____] psi

(28 day minimum)	([20.7] [____] mPa)

Aggregate Size (maximum)	[3/8] [____] inch

([9] [____] mm)

Air Entrainment	[____] percent/cu yd

([____] percent/cu m)

Chemical Admixture	[____] percent/cu yd

([____] percent/cu m)

Pozzolanic Mineral	[____] percent/cu yd

Admixture	([____] percent/cu m)

Slump	[1] [____] inch

(plus or minus 1/2 inch)	([25] [____] mm)

Thoroughly mix shotcrete. Use mix within 45 minutes.

Develop mix design to give good compaction and low percentage of rebound, but stiff enough not to sag.

Maintain quality control records during production of shotcrete. Make records available to Architect/Engineer.

EQUIPMENT

Mixing Equipment: Capable of thoroughly mixing aggregate, cement, and water in sufficient quantity to maintain continuous placement.

Air Supply: Clean, dry air adequate for maintaining sufficient nozzle velocity, uniformly steady for work while simultaneously operating blow pipe for cleaning away rebound.

Delivery Equipment: Capable of discharging aggregate-cement-water mixture accurately, uniformly, and continuously.

****** [OR] ******

C.	Mixing Equipment: Capable of thoroughly mixing aggregates and cement in sufficient quantity to maintain continuous placement.

Air Supply: Clean, dry air adequate for maintaining sufficient nozzle velocity, uniformly steady for work while simultaneously operating blow pipe for cleaning away rebound.

Delivery Equipment: Capable of discharging aggregate-cement mixture into delivery hose under close control, and maintaining continuous stream of uniformly mixed material at required velocity to discharge nozzle. Equip discharge nozzle with manually operated water injection system (water ring) for directing even distribution of water to aggregate-cement mixture.

Water Supply: Uniform water pressure at discharge nozzle sufficiently greater than operating air pressure to ensure intimate mixing with aggregate-cement mix. Provide water pump to system if line water pressure is inadequate.

PART 3 EXECUTION

APPLICATORS

[__________________________________________.]

[__________________________________________.]

[__________________________________________.]

EXAMINATION

Verify that field conditions are acceptable and are ready to receive work.

Verify field measurements are as [shown on [Drawings] [shop drawings].] [instructed by the manufacturer.]

Verify fabricated forms are true to line and dimension, adequately braced against vibration, and constructed to permit escape of air and rebound during gunning operations.

Ensure correct placement of reinforcement. Ensure sufficient clearance around reinforcement to permit complete encasement.

Ensure easy access to shotcrete surfaces for screeding and finishing, to permit uninterrupted application.

Beginning of installation means installer accepts existing conditions.

PREPARATION

[Remove [existing unsound concrete] [_______________] from substrate surfaces by chipping.]

[Minimize abrupt changes in thickness of repair.] Remove square external corners from substrate by radiusing the edge.

[Sandblast] [Clean] surfaces to receive shotcrete.

Determine operating procedures for placement in close quarters, extended distances, or around unusual obstructions where placement velocities and mix consistency must be adjusted.

Clean and wet cementitious surfaces prior to receiving shotcrete. Keep porous surfaces damp for several hours prior to shotcreting.

ALIGNMENT CONTROL

Provide alignment wires to establish thickness and plane of required surfaces.

Install alignment wires at corners and offsets not established by forms.

Tighten alignment wires true to line. Position adjustment devices to permit additional tightening.

APPLICATION

Do not place shotcrete on any surfaces that is frozen, spongy, or where there is free water.

Applied shotcrete not to sag.

Direct nozzle perpendicular to surface to ensure maximum compaction with minimum rebound.

Build up thickness by layers, in multiple passes of the nozzle over the work area. Cover reinforcement with the first layer.

Allow each layer to take initial set before applying succeeding layers.

After initial set of final layer, remove excess material outside of forms and alignment lines.

[Sandblast to remove laitance.	Clean with air-water jet.]

Sound work with hammer for voids. Expose voids and replace with new shotcrete.

Remove trapped rebound at construction and expansion joints.

Remove rebound material which does not fall clear of work. Discard rebound.

Finish surface of final layer with [wood float] [rubber float] [steel trowel] [wet cementitious/sand spray] [__________] finish.

Maintain surfaces wet for minimum of [7] [___] days.

****** [OR] ******

Apply curing compound to exposed surfaces[.] [to manufacturer's instructions.]

FIELD QUALITY CONTROL

Field [inspection and] testing will be performed under provisions of Section [01400.] [01410.]

Prior to start of work, testing [and inspection] firm will verify mix proportions, gradation, and quality of aggregate.

Test Panels: Provide [three] [_____] test panels fabricated by placing shotcrete onto plywood for each mix design being considered, for each shooting position to be encountered, and for each [___] sq ft ([___] sq m) of placed shotcrete. Panels: Identical thickness, reinforcement, and reinforcement placement as required for Work.

Testing firm will drill 3 inch (75 mm) diameter core samples from test panels. Core samples will be tested for strength, water absorption, drying and shrinkage, freeze and thaw resistance, and [____________________.]

Provide additional test panels during the course of the Work as may be requested by the testing [and inspection] firm.

PROTECTION OF FINISHED WORK

Protect finished installation under provisions of Section [01500.] [01535.]

Immediately after placement, protect shotcrete from premature drying, excessively hot or cold temperatures, and mechanical injury.

Maintain shotcrete with minimal moisture loss at relatively constant temperature for period necessary for hydration of cement and hardening of shotcrete.

SCHEDULES

Swimming Pool Shell: 5 inch (125 mm) thick shotcrete, reinforced, wood float finish, to receive ceramic tile finish.

Wading Pool Shell: 3 inch (75 mm) thick shotcrete, unreinforced, steel trowel finish, to receive glazed coating.

END OF SECTION