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I have used ASA’s Position Statements from the Pool and Recreational Committee and find them very useful. Are there any design guides or books on shotcrete pool design that are available? I am a structural engineer and tend to design pools as retaining walls, but I believe some of my designs could be “value engineered” to reduce rebar in the case of walls with a vertical curve (base of the wall is curved and not straight) and possibly the use of a bond beam at the top.

The current International Swimming Pool and Spa Code (ISPSC) has [...]

By |2023-06-07T16:35:16+00:00June 7th, 2023||
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A new gunite pool of ours was sprayed in an irregular fashion by a non-certified worker in the Bahamas. For the most part, the pool looks good, but one wall was measured at 3 in. The rest of the pool is 6 in. The rebar in the thin area was encapsulated which was good, but a couple of linear cracks in the wall formed even after ample wetting during the initial cure period. Six months have gone by. Our plan now is to pressure wash the cracked areas and add an additional 6 to 8 in. of gunite thickness which may not look too bad since the pool is a natural lagoon style pool. Staples with gunite over the top would be the other option. What is your opinion?

Properly prepared surfaces along with proper shotcrete materials, equipment and [...]

By |2023-06-07T16:33:47+00:00June 7th, 2023||
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ACI 318-14 (Building Code Requirements for Structural Concrete) requires post-installed expansion anchors to meet the testing criteria of ACI 355.2-07 (Qualification of Post-installed Mechanical Anchors in Concrete). ACI 355.2 specifies certain anchor testing and evaluation requirements to verify suitable anchor performance and to determine other aspects (such as failure mode) to use in conjunction with Chapter 17 of ACI 318 when designing the post-installed expansion anchors. Anchor testing is required largely to be performed by an independent agency and normally is conducted in normal weight and/or light weight concrete that meet pertinent ACI, ASTM and other requirements. Some post-installed expansion anchor manufacturers (like Hilti) have not had their anchors tested per ACI 355.2 in shotcrete type concrete, only tested in normal weight and light weight concrete. As such, these anchor manufacturers typically do not publish/offer any permitted load ratings, installation torques or other design and installation requirements for their expansion bolts when used in shotcrete. Instead, they recommend site testing to determine anchor performance or that the responsible design engineer can make an engineering judgment on anchor acceptability, as appropriate, if site testing is not performed. Do you have knowledge of any expansion bolt manufacturers that have tested their products is typical shotcrete? If yes to #1 above, do you know if the testing was done per ACI 355.2 requirements?

Shotcrete is a placement method for concrete. With proper equipment [...]

By |2023-06-07T16:32:55+00:00June 7th, 2023||
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We have a wet-mix shotcrete steel fiber overhead application progressing in our state. The question is about the use of a steel trowel finish, as opposed to say a magnesium or wood float finish. In the ASA Shotcrete Inspector seminar, it was stated that a steel trowel is less durable, reduces freeze-thaw resistance and shows cracking more proximately. As this particular application is overhead and, in a tunnel, there is not as much of a concern with water infiltration and the associated freeze-thaw exposure. We usually don’t allow steel trowels for flat work, due to deicing salts, but that concern wouldn’t apply here. My superintendent has asked me to reach out to you to see if you might have any further detailed advice on this type of application. Construction is wanting a smooth finish and looks do matter here as it is a high-profile project. If the DOT were to allow the steel trowel for finishing, what would be your concerns or suggestions to this approach?

Freeze-thaw deterioration is dependent on the concrete being saturated in [...]

By |2023-06-07T16:31:59+00:00June 7th, 2023||
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I have a question regarding shotcrete pools. Does the ASA have a position on how to detail reinforcement at bulky elements that are shot interior to the main pool shell? This would typically involve stairs or large stoops. I notice a lot of contractors shoot these as unreinforced bulk elements, but this practice appears to promote cracking at the face of the pool shell. I’m only asking because I saw a few of these this past summer.

Shotcrete is a placement method for concrete. Thus, any concrete [...]

By |2023-06-07T16:31:15+00:00June 7th, 2023||
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I was taught in engineering courses that conventional concrete should not be counted on to carry tensile stress. For steel reinforced concrete, the reinforcing bar is designed to carry all tensile loads. Although concrete obviously has some tensile strength, it is too low and prone to cracking failure to consider it in design. In fact, I believe you can assume it is cracked from the shrinkage during curing. Is gunite treated the same way? I have a pool that is developing a crack through an elevated wall/beam and down into the plaster to the bottom floor at the sun shelf. I witnessed the plumbers cutting some rebar in the beam to allow for PVC plumbing to water sheer (up at top of beam, just under the tile topping) and I worry this is the root cause along with settlement that put the top of the beam in tension. The rebar down low should be intact and I hope the crack width may stay minor down in the plaster. On top of the tiles beam where the maximum tensile stress would have been, the crack is fairly wide. The crack movement opened up a gap in the grout line between tiles of about 0.08 to 0.10 in. (2-2.5 mm). I think it was a real sin for them to have cut the rebar. If it is necessary to reinforce the tensile side to halt future movement, I would think cutting a slot or two in the gunite across the crack (say 12 in. [300 mm] each side. Up high just under the water sheer) and epoxy a rebar in the slots.

Shotcrete, both dry-mix (gunite) and wet-mix are a placement method [...]

By |2023-06-07T16:30:31+00:00June 7th, 2023||
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We are reinforcing an exterior pool wall with shotcrete, and wanted to know what preparations need to take place for the shotcrete to adhere correctly, and what the minimum thickness needs to be? We also need to level out the floor up to 5 in. (125 mm) that will gradually go to zero to meet other side. Can shotcrete be used in this application?

When shooting onto existing concrete sections the surface must be [...]

By |2023-06-06T23:45:29+00:00June 6th, 2023||
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I am a TBM Tunnel Engineer from India, and I was looking for information on the applicable compressed air pressure range required for a wet-mix shotcrete application (small shotcrete pump-capacity 7 CU.M/Hr) hand spraying with a 30m hose for a better-compacted mix. I would kindly request you to please send me information on the pressure range to be expected for good quality shotcrete placement of the concrete mix on the rock substrate in NATM Tunneling.

Wet-mix shotcrete depends on air flow at the nozzle to [...]

By |2023-06-06T23:44:11+00:00June 6th, 2023||
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