Non-Shrink Grout Shrink distance

[sedonas]

I let Sika recommended installer put non-shrink grout under the 10mm gap base plate. They sealed the formworks and put hose into it and pumped the grout using a large floor based cement pump. They know it's full when every side overflows as seen from above. Sika 215 is required since this is pumpable.. not Sika 212. Procedure looked ok. I'll know in two days when I removed the watertight formwork..

However something worries me. The concrete surface is not pre-wet.

Now supposed the dry concrete absorbs the water from the non-shrink grout. Would the non-shrink grout shrink? What's the distance it would shrink and sink. how do you compute for it? I'd like to know if the 10mm gap just becomes 9.99 with 0.01 shrink distance or even larger??

 

[JStructsteel]

Before we delve into this with you, can you post what Sika's response was? Thanks.

 

[sedonas]

Before we delve into this with you, can you post what Sika's response was? Thanks.

They don't know how to compute for the shrink distance. The installer doesn't seem to put importance into prewetting. Fortunately (depending on the theoretical and method of computation). It rained hard 2 days before the pour. However it's covered with base plate but some rain managed to touched the side of the column and some open holes (in some base plates).. so can the concrete absorb the rain at the side by capillary action, how much can it reach inside perpendicular to the side?

For Sika 215 with about 8000 psi final strength. I just need 300 psi. So don't mind any strength reduction as long as there is no gap and it doesn't shrink enough for any bolt to go into tension at yield strength or concrete pullout.

 

[hokie66]

You worry too much about trivial things. You have done the right thing. Move on.

 

[sedonas]

But if the dry concrete has absorbed the water in the non-shrink grout.. the non-shrink grout may sink.. and when it does.. it's like you didn't put any because there is no compression block and the tension bolts may be stress.

Therefore I need to know the shrinkage distance in the event computation support it, I can hire anchor experts to design post-in-anchor bolts that can also act as compression block, etc.

The raining 2 days before is just to let me feel better.. but then it is very sunny next day and the water in the concrete microstructure has already probably evaporated so let's assume dry concrete condition.

 

[Ron]

You indicated that the grout flowed above the forms, thus there was a positive head on the grout. The non-shrink grout is formulated to accommodate some absorption into the concrete. You cannot calculate the loss of height from the installation as there are too many variables; however, you can expect that it is insignificant with respect to the bearing. As hokie66 noted, stop worrying about such trivia and move on.