Admixtures

Alkali silica reaction (ASR) is the reaction between the alkali contained in cement and silica containing aggregate. There are two parts of this equation. ASR does not necessarily have to be of concern if one of the constituents is missing. Using potentially reactive aggregate in conjunction with low alkali cement or slag or flyash does not necessarily have to lead ASR damage.
Another variable is the type of the structure and location. For ASR to happen moisture is required. If the structure (for example a concrete retaining wall) has continuous access to moisture then ASR damage is going to be more detrimental and treatment of the structure might be very expensive.
If the structure is accessible and exposed only to rain for example, than ASR can be slowed down by reducing the moisture penetration into the structure. There are "breathable" coatings available on the market that allow diffusion of moisture out of the structure but do not allow moisture to enter the structure. Applying such a coating to a structure that shows signs of ASR can reduce the rate of ASR. There are also Lithium salts available in the market that are used to reduce the occurrence of ASR, These product are available as admixtures for new structures or as spray applied products to be used in existing structures.
None of these products are final solutions that eliminate ASR, but can be successfully used to manage the risk of severe damage from ASR.

A 6 in 12 pitch roof is pretty steep. It would take a very stiff mix to be able to place it and not sag.

One alternative would be to precast panels for the roof.

I would consider cellular concrete for the weight considerations but I would first contact a roofer for more information on constructing a roof of this nature.

It may have been done successfully but my knowledge of roofing is limited.

Efflorescence is in its matter migration of soluble salts from the inside concrete to the surface. The transportation media in this case is water and salts migrating to the surface because there is higher evaporation rate at the surface. Highest contributor to efflorescence is cement.

In order to fight efflorescence we have to be able to reduce the volume of water migrating to the surface. The most effective way, in my opinion, is to fight it from the inside and actually prevent water migration.

Some admixtures currently available fight efflorescence but all of them (to the best of my knowledge) are liquid.

A powered High Range Water Reducer would help by reducing the water demand and could be used to reduce the cement content but I don’t think any are commercially available.

In short, I don’t know of a powdered efflorescence control product that is available.

Since the water/cement ratio was not changed and the final slump was achieved by using a superplasticizer or another water reducing admixture, the compressive strength should not be affected in negative way , neither should any other property of the concrete be significantly altered.
According to ASTM C 143 slump measurement values are rounded to closest ¼” (5mm). Therefore a variation of 20mm (approx ¾ inch) is not a significant change.

The only question is concerning the conditions under which the concrete was placed. If there was no segregation from the higher slump and the distance the concrete was allowed to free fall, the concrete should be structurally sound.

If the conditions are in a saturated environment that will only help the long term strength development.

The only problem I see is that the slump was out of spec, other than that I don’t see anything that should cause a problem.

Putting a heavy track vehicle on concrete is probable expecting more from the concrete than it is capable of delivering, even a high quality 4000 PSI concrete.

Diamonds are the hardest substance in the world but if you hit a diamond with a hammer it will shatter. The same thing is happening with the concrete under the point load of a track vehicle. The aggregate as well as the cement paste is being shattered.

Concrete is hard but it is also brittle. What is needed is something that can absorb the impact and transfer the load to the concrete. A ductile and malleable surface treatment such as a metallic aggregate floor hardener would help. A surface treatment that can be compressed instead of being brittle would help protect the base concrete.