Questions you ask a flatwork contractor

[jcarapet]

So I will happily close this if there is already a relevant thread, but search was unable to pull up something in line to what I'm looking for.

The sticky for what to demand for a concrete slab has been an invaluable resource for me while building a shop. I selected a flatwork contractor and was able to use that for questions to ask and things to review AFTER the project started. Unfortunately I picked a contractor on the recommendation of my pool crew and a bad referral call, and I'm finding that was a mistake after 2+ months of delays, catching numerous errors, and blatant dishonesty.

My question is simple. What do you ask a flatwork contractor when trying to vet them for your job? Hoping I can learn a thing or two to ask someone who is taking over the work that is now abandoned by the people I hired and paid a good chunk of money to do.

 

[ConCretin]

I started thinking about technical questions to assess a contractor's workmanship and business questions to assess the likelihood they'll otherwise perform but if I had to ask one question, it would be; "Have you done any other projects like this and who did you do them for?". It's time consuming to check references and it's not foolproof but it's probably the best way to root out a bad actor before it's too late.

If I had to ask one technical question, it would be; 'What slump are you going to place my concrete at?' If a finisher doesn't have an understanding of mix water and it's affect on a concrete slab and more specifically, it's surface, you don't want them. The first clue will be if he knows what slump is. lol.

Many standard concrete mix designs are based on enough water to produce a 4" slump. The reality is that very few finishers are going to place concrete that stiff. They are going to add more water. The results of this range from lower strengths and a less durable surface to wide range of surface defects.

If he says he'll place at a 4 or 5 inch slump, that's an acceptable answer. If he says anything higher, ask if he's using a water reducer, which is a chemical admixture that increase the slump to workable ranges without extra water. If he says "no what's that?", walk away. If he says "yes", then it's probably fine. Use of water reducers, particularly mid range water reducers has become pretty common but it's still important to understand the allowable slump in the mix design.

As with anything, trust but verify. A phone call to the plant and a conversation with the driver can glean a lot of information.

 

[jcarapet]

I agree on all points, especially at this point trust and verify.

According to potential replacement contractor, most of the plants this time of year in Texas have a "summer mix" that does come with a reducer already.

I went through the effort of buying a cheap slump cone and a set of test cylinders as a way of trust and verify, and to keep people honest. Fully understand that water will likely have to be added, but want to be in control of what, and be able to verify the result.

One of my favorite points of trust and verify is calling the concrete plant to verify the mix ticket.

"uhh, sir we have no order for that address or under that contractor". Okay, fun.

 

[Half-fast eddie]

. Fully understand that water will likely have to be added,

Not necessarily. Specify 5” slump at whatever psi you prefer, and they can add a plasticizer on site. And ask the driver to show you the batch ticket before unloading.