Quote:

What is the maximum allowed air temperature for concreting works?

Temperature of the the concrete is important. Maximum ambient air temperature is not specified, nor should it be. There is more to the definition of "hot weather" than just air temperature.
Concerns about "hot weather" may start becoming important at about 80^o F.

See this article: "Hot Weather Concrete Placement"

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I suppose it is the maximum concrete temperature at the point of delivery you should be asking.

Typical values are between 80° and 95° F as measured by ASTM C 1064-86. UK CIRIA publications generally suggest 32° C which lies in between the above.

I think it is the maximum green concrete temperature one must adhere to as well as the maximum differential temperature within the pour. They are 70° C and 20° C respectively. Concrete is liable to be damaged if the above is breached.

High air temperature generally means hot aggregate and high concrete temperature at the point of delivery making thermal problems in green concrete difficult to control. Many of our sites have to use ice for to batch concrete.

There is a whole ACI standard for hot-weather concreting (305R-10). You need to deliver concrete to the site at a prescribed maximum temperature - I see above 32degC; specs I have seen is 30degC (in Asia). But with the high ambient air temp, you should also be considering shading (tent or tarp of other means) for both minimizing the temperature AND for damaging wind effects on the setting up of the concrete - and also misting - you want to keep the surface of the concrete from drying out - if it dries out too fast, you can get plastic shrinkage cracks. And, in my view, I don't like curing compounds in hot weather.