Topping for Existing 6.5" Slab-on-Grade 2

[ThorenO]

Hello everyone,

I've got an existing 6.5" interior slab on grade that I would like to add a 4" topping get additional capacity for heavy wheel loading.

What are some of the general considerations to get increased capacity in terms of mix, reinforcement, surface preparation, dowels, etc.

Thanks in advance,

 

[KootK]

Do you need extra bending capacity, extra punching shear capacity, or both? What does the existing slab have for reinforcement and where is positioned vertically?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[SlideRuleEra]

See this link: Resurfacing Concrete Floors by the Portland Cement Association.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[ThorenO]

Thanks KootK - Looking for bending capacity. With the large wheel contact area, the punching shear is OK.

Wire mesh was picked up by the GPR at 6" o.c. near the bottom of the slab.

 

[oldestguy]

If this is really needed, treat it like you for the treatment I recommend for parking ramp slabs that have been affected by salt action. There the weakened upper part is removed. The remaining surface is vacuumed clear of all loose material. So in your case you need to roughen that surface some how. There are numerous machines suitable for that, even hand held jack hammers. LEAVE THAT SURFACE DRY!!! Have ready the new overlay mix, preferably a 5 bag mix or better. Just ahead of placement brush on the roughened surface a paste made from Portland cement and water. Immediately place your concrete overlay. Do the usual moist curing.

Some time later core out some samples. Take a chisel and try to break them apart at the joint. My bet is that none will break at the joint.

 

[ThorenO]

@SlideRuleEra - thanks for the info