Min concrete strength needed

[Jruggi]

I have a concrete pad, reinforced and 15" thick, it has been specified a min of 4500 psi, however I have been supplied the 5 day test breaks (reaching 3300 to 3500 psi) and asked can this support an 18 wheeler loaded (80,000#) can drive on this at day 5 and day 6. I have declined but told to "research it more" so the question is, is this something that can be achieved or steer clear of and wait.

 

[dik]

Not a good idea to put maximum design load on something that has been designed for a 28 day strength...

From a flexural view, you likely have minimum flexural reinforcing and a low concrete strength has little influence on flexural strength. The slab is likley stiff enough that flexural tensile strength is providing much of the strength and this will crack at an early loading condition in particular with 'channelised' loading. Best not to.

Dik

 

[miningman]

Yep I tried something like this a few years ago when I tried running my mining equipment over freshly poured concrete....... must admit that at the time I was surprised how much damage I was able to inflict. Luckily this was a temporary installation to be used by my own crews only so there were no long term technical or financial consequences for myself.

 

[BigInch]

Well fortunately it seems to have at least made a long-term consequence in your memory chip.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[Ron]

A 15" thick section with standard 18k axle load is not stressed very highly, particularly if few repetitions. Check the bending stress at the bottom of the concrete using elastic layer analysis. For typical 4500 psi concrete, you can expect a modulus of rupture of about 500 to 550 psi, assuming it was NOT designed as a flexural mix. Given this, if your flexural stress levels are 250 to 275 psi at the bottom of the concrete....you're ok. If higher, don't do it.

 

[racookpe1978]

Would it help the OP if he places the "standard" 3/4" road-hole cover plates over the concrete before the trucks drive over the concrete? That would spread the load out more.