Partially submerged water tank 1

[cvlenv]

we are to construct a partially submerged water tank. during the excavation we encountered groundwater level. after grading the subsoil, we poured "lean concrete" at 2500psi @ 28days. the thickness is 2". the next day after pouring, we observed that some portion of the concrete is "rubberized". we suspected that the soil underneath was not compacted as the level of the groundwater is almost the same with the level of the subsoil. what could be the corrective measure to repair the "rubberized" concrete. by the way, we established a sumpit to collect the groundwater but maybe the level is not enough to collect all water by gravity.

 

[kelowna]

Rubberized? Could you explain what you mean by that?

If you have only 2" the best approach would be to remove all suspect concrete and replace. You should try to keep the excavation dry when pouring the concrete and wet the concrete surface after it sets for a few days.

 

[cvlenv]

"rubberized" meaning that the concrete is still moving at some portion when the other portion/s had already started to harden. we are to construct a 12" thick mat foundation on the 2" lean concrete, thus, the lean concrete would act as "subbase" for the mat foundation.

 

[oldestguy]

You don't explain much, so you will not get reliable answers from those that can help you. For instance where is that 2" slab with respect to the natural ground water table?

Why only 2"?.

What is the size of the tank, height? width? etc.

What sort of a job is thus? Gas station, Cheese factory???? Refinery??

A more descriptive subject label would help also.

 

[fattdad]

What's so amazing to me is there is no ground water observation well data. Digging a hole and "encountering the ground water level" means alot of different stuff to different people. Some knowledge of the stratigraphy in conjunction with piezometer data would help too.

Not really sure why your concrete failed to set. However, if the project was properly designed with sufficient background information, you could just tell the contractor to redo failed work.

f-d

¡papá gordo ain’t no madre flaca!

 

[cvlenv]

thanks guys!
actually we did what kelowna had suggested...we redug the portion of the "rubberized" subsoil under the lean concrete and compacted with adequate backfill and tried to make the subsoil dry prior to lean concreting again. and the procedure worked...

to oldest guy; i have said it earlier, we are to construct a partially submerged water tank with a mat foundation. the 2"lean concrete was supposed to act as subbase for the mat foundation since the ground level where the mat foundation will rest is at same level with the groundwater we encountered...

to fattdad; before the commencement actually of the project, we requested some groundtest data from the construction management. it was speculated in the groundtest report that there was no groundwater but prior to the excavation work we did some test pits and encountered groundwater..there was a conflict of the report and actual condition of the soil [maybe the borehole(s) were not representative of the soil condition of the site]..
anyways, it was great communicating with you guys...