RMC roof slab and Waterproofing

[riturajmnit]

Hi Folks,

I will be doing exposed Slab also with RMC and thus wants to ensure proper strength and waterproofing. Does it makes sense to add Dr Fixit at site on the concrete load ?
What is the ideal process ?

[Nivas]

The waterproofing admixture should be added at the RMC plant at your request for a small additional price. It is not possible to add waterproofing admixture at site to RMC (I am assuming Dr Fixit LW+ ) for the reasons below.

(a) since its a water additive and needs proper mixing. They are useless if added to mixed concrete and if not homogeneously mixed. Lets assume if you dissolve it additional water and ask the guy to turn on the mixer at site , you will be altering the strength of concrete and slump (Note : adding water to concrete decreases its strength drastically and these admixture also work as plasticizer). Hence it needs proper dosing and water is adjusted at the plant appropriately.

(b) More over the RMC might be using better waterproofing admixtures that is not available to retail consumer in small packs. Also you could get the job done at a lower cost , retail packs have lot of margin.

Since its a exposed slab , after the roof is laid , further you should explore using surface waterproofing (aka paint \ membrane etc ) .as the admixtures are not fail safe , they are necessary and right step but not adequate and waterproofing does not end at it.

[riturajmnit]

Thank you Nivas sir, that helps a lot