Surface irregularities in concrete wall 5

[concreteworld]

Hello All,

We are troubled with change in color of concrete in METRO tunnel wall. The wall is 30 m long and casted in multiple lifts 500-1000mm thick at one time. In this 6.5m meter wall, we see color layers have different colors, from light to dark grey. The concrete supplier says that it is due to varying color of flyash in the mix and the surface and color of formwork used.

what could be other possible reasons for such changes in color of concrete other than inconsistent W/C in different batches?

 

[concreteworld]

Please see another wall photo with same concrete but different surface. This time nice regular shade !!

Please need your support to find the root cause...

 

[epoxybot]

Are both contractors using the same ready mix supplier? Are they both using form faces made of the same material? If one contractor is delivering consistently acceptable results and each is using a different ready-mix supplier, then require the contractor who is having the discoloration issues, use the ready-mix supplier and mix design, that the better results contractor is using for at least one section. What type of vibrators are being used? The photo of the highly discolored concrete, from bottom up has 6 or 7 lift lines, that I can see. Whether or not the discoloration can be attributed to poor vibration, there is definitely a poor workmanship issue regarding placement of concrete. How is the concrete being placed, via a pump rig or a bucket?

 

[TehMightyEngineer]

The problem is one contractor is able to give a great surface and another cannot.

Simple solution, get rid of the contractor that isn't performing the work sufficiently or get them to do the same things that the better contractor is doing (what epoxybot said).

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/