concrete without coarse aggregate
concrete without coarse aggregate
(OP)
Is it possible to justify that a proper mixture of sand, water and cement (concrete witout coarse aggregate) with strenght of +3000psi, placed pnewmatically (shotcrete) is still concrete and can thus be designed by ACI requirements.





RE: concrete without coarse aggregate
Dry mix shotcrete (gunite) does not include coarse aggregate. It's mixed at the jobsite and water is added immediately just before discharge from nozzle. It can easily meet f'c of 3000 psi. 1 part cement to between 4 to 4-1/2 parts sand is very common.
When it's ready mixed, its referred to as wet mix shotcrete; essentially a low slump(2 inches) pea gravel (3/8 inch MSA) concete mix is typically used on commercial projects. Some public works projects specify 3/4 MSA.
Regarding maximum aggregate size, here is what IBC Sec 1914.3 states. "Coarse aggregate IF used, shall not exceed 3/4 inch. So I guess this permits a fine aggregate wet or dry shotcrete mix.
Shotcrete can be designed as concrete using ACI 318 but check relevant sections in ACI 506 Guide to Shotcrete (explains what design code to use) like Sec 5.4.2 and IBC Sec 1914.4 for splice requirements...contact lap splices are not permitted. Check the FAQ page at http://www.shotcrete.org/ASAfaqs.htm question 38 is a good one.
RE: concrete without coarse aggregate
RE: concrete without coarse aggregate
RE: concrete without coarse aggregate
FYI, there are 3 companion documents for ACI 506...namely: 506R, 506.2 and 506.4R
An internet search indicates ACI 506R-90 (5.4.1) states reinforcement for shotcrete shall be designed per ACI 318.
Further Evidence:
In the last version of the UBC(97) according to Sec 1900.4.2 Shotcrete...it states" In addition to the requirements of Division II, design and construction of shotcrete structures shall meet the requirements of Division IV". Division II of the 97 UBC was essentially ACI 318-85 and Div IV is similar to IBC Sec 1914 and both are based on ACI 506.
Fast forward to the present. In the IBC-03, Sections 1901.2 and 1914.1 are the references stipulating ACI 318 be used for design...but as mentioned in previous post, amongst other things, IBC Sec 1914, modifies reinforcement requirements of ACI 318.
RE: concrete without coarse aggregate
RE: concrete without coarse aggregate
RE: concrete without coarse aggregate
Check paragraph 5 of the response to question 44 http://www.shotcrete.org/ASAfaqs.htm it indicates a typical slump for air-entrained concrete in Canada. Now check Corp of Engrs Standard Practice for Shotcrete Sec 3.7 (e) Wet Mix proportioning http://w
Perhaps what you have in mind is a pea gravel (3/8 in/ 10mm MSA) mix that has a high range water reducer...a mix which is commonly used for situations where the reinforcement is congested..no?
RE: concrete without coarse aggregate
RE: concrete without coarse aggregate
1. The adjectives 'Wet-mix' and 'dry-mix' as used in this thread are construed to be part of shotcrete terminology consistnet with ACI 506.
2. Wet-mix shotcrete has a much stiffer consistency than the 5- 10mm mix you describe. The mix you describe has a much wetter consistency and is typical of small aggregate concrete with a super-plasticizing admixture, in fact very similar to masonry grout; it will not be used for shotcrete.
3. Positive dispacement piston type sytems and pneumatic pumping systems are used for both wet-mix shotcrete and regular concrete(including the super-plasticized small aggregate concrete mix you describe).
4. The pneumatic type of pumping system used for regular concrete is similar in certain operational aspects to the one used for shotcrete. However, in addition to the differences in operating air pressures there are other major differences.
5. Shotcrete is delivered at a much higher velocity (for effective impact so it adheres to surface it impinges on)..just look at the wet-mix shotcrete nozzle in Fig 4-9 and how it fits into the system in Figures 4-6 and 4-7 http://w
RE: concrete without coarse aggregate
While submiting design calculations as per ACI 318, city official told me that this was not possible and that ACI 318 does not cover this type of construction.
Henri2 your answer was right on the money. Found .pdfs of both ACI 506 and IBC and I have corroborated your post.
Thanks Again