weak actual concrete strength of retaining wall 1

[marl2017]

Good day everyone,

this topic is about my project which is "construction of retaining wall" with a height of 4 meters, and 10 meters long. its footing has a base width of 2 meters, base length of 10 meters and a thickness of 0.60 meters. During our concrete pouring i told my workers to use class B mixture when in fact the design mixture is Class A (1:2:3). Before the material engineers came to inspect the site for concrete pouring, i told them to use class A so they used it. When the materials engineer have tested the concrete in cylindrical mold, the result was shocking because it fails. and it is far from the design strength which is 3500 psi. Note that payment for this project doesn't applies to weak actual concrete strength so we did another testing through hammer test. The result was another tragedy again which is 1500 psi, it failed, and it doesn't meat the design strength which is 3500 psi so the result for this project is either retrofitting or no payment otherwise, remove and replace. As a contractor, i want to retrofit in an economical method. as advice to me from the agency, i need to retrofit and test again the concrete (new structure of retrofitting). My question is what is the best method to retrofit the said retaining wall for the sake of my capital and gained even the structure seems needs to remove and replace as this actual strength which is ranging from 1000 psi to 1500 psi can not match the required design strength which of 3500 psi? do you have any suggestion? note: the retaining wall's face is a lot boundary so additional volume of concrete doesn't apply in the retaining wall face.

MARL2017

 

[oldestguy]

How old was the first concrete sample tested? Was that sample kept wet all the time before testing? Answer that question and also run a calculation as to the safety factor you have for concrete that is well over 28 days strength. I'd core another sample rather than using an impact hammer test. Your wall may have a low safety factor, yet passable. I'd do an analysis of the backfill and determine the active soil pressure. If there still is a problem, what can be done to lower the pressure on the wall? That may be replace the current backfil with a light weight material such as Styrofoam.

 

[Obregon]

Not only you will not get paid but are gonna get sued. The mixed concrete at the construction site looks very poor and with excess of water as a result of bad quality control and lack of supervision. Frankly, this should had never happened for such an easy and small job.

You got no more than one third of the specified compression strength for the concrete. The only way yoy can avoid the need of demolishing this structure is to retrofit it by means of installing Soil Nails and leave the wall as the facade of the retaining system. I've done it a few times for retaining structures showing incipient structural failure due to bad design or poor construction practices as it is your case. Do it quick before the situation becomes more awkuard once the cracks satart showing up.

 

[miningman]

Rip it out , replace with a properly prepared concrete mix, CUT BACK ON THE WATER, apologise profusely to the owner , and whosoever was supervising this job should be terminated.

 

[oldestguy]

Noting the pictures, this was obviously very wet concrete. Far too much water. Note the level liquid in the mixer and the horizontal footing surface against the form. I'd see if the owner would accept another wall and footing placed over the present, of course all FREE.

 

[TerryScan]

I'm sorry, but I laughed a little at what appears to be photo editing of a hard hat.