Browse Forums Paving & Concreting 1 Aug 18, 2011 7:42 pm For a 100mm thick driveway slab, typical mesh size is F62, 72 for 125mm and 82 for 150mm. However. Have you increased your mesh size but remained at the same thickness? Eg. do you have 100mm concrete with 72 mesh size? Obviously, increasing the mesh size willy-nilly is not recommended, but there are no hard rules that I can find. Can I still have 100mm with F72? Will the concrete actually crack easier if thickness is not increased? My signature is distracting people from my wise posts ... Re: Thickness of concrete vs. mesh size 3Aug 18, 2011 8:30 pm Basically the more reinforcement you have the less likely the concrete is to crack (as long as you have weakened the steel a the joints) Basically its just going to cost more. If you are going to have a polished concrete surface it can be worth using more reinforcement. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Thickness of concrete vs. mesh size 5Aug 19, 2011 8:59 am My driveway was specifeid for SL72. However I upgraded it to SL82 just to make it that little bit stronger. Didn't cost much (and was probably unnecessary). From what I can gather you can mix concrete strength, mesh thickness and concrete thickness to you hearts content as long as to go equal to or better than the engineer's specification. (I also increased my driveway concrete strength from 20 MPa to 32 MPa just because I could.) Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Thickness of concrete vs. mesh size 6Aug 19, 2011 9:45 am Casa2 just because I could We also don't want anything under 25. Tried to get some concretors to go 32, but they made some excuses like hard to finish or something like that, so we gave up on 32. We were thinking 72 mesh too, but by the looks of it, even if they "promise" a 100mm thick concrete, it may very well be 60 or 80 at places, and apparently thicker mesh could then cause more issues than not My signature is distracting people from my wise posts ... Re: Thickness of concrete vs. mesh size 8Aug 19, 2011 3:31 pm Lex Casa2 just because I could We also don't want anything under 25. Tried to get some concretors to go 32, but they made some excuses like hard to finish or something like that, so we gave up on 32. We were thinking 72 mesh too, but by the looks of it, even if they "promise" a 100mm thick concrete, it may very well be 60 or 80 at places, and apparently thicker mesh could then cause more issues than not Wasn't aware of any mesh thickness relative to slab thickness variation. Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Thickness of concrete vs. mesh size 9Aug 19, 2011 5:50 pm Thanks Aiah Apparently, thicker concrete requires thicker mesh and vice versa. It kinda doesn't matter for a single layer of mesh, but makes sense when it comes to overlapping - if you imagine how mesh has to be overlapped, and sometimes it even looks like there are more than 2 layers of mesh at some points - all that mesh takes room (height) and if there isn't enough concrete around it, I think that area is "weakened" from insufficient concrete mass ... dunno, just my theory ... And when I think what a "100mm" concrete can actually become in practice ... My signature is distracting people from my wise posts ... Re: Thickness of concrete vs. mesh size 11Aug 19, 2011 8:32 pm Aiah My sisters house slab was double layer of SL92 @ 100mm thick. The slab was to be polished, she had the engineer drop the spec to one layer of 82, she wanted some cracking... she got it. From 2 x SL92 down to 1 x SL82. that's a big drop! Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Thickness of concrete vs. mesh size 13Aug 20, 2011 8:26 am Casa2 Aiah My sisters house slab was double layer of SL92 @ 100mm thick. The slab was to be polished, she had the engineer drop the spec to one layer of 82, she wanted some cracking... she got it. From 2 x SL92 down to 1 x SL82. that's a big drop! The 82 was standard for the H class slab, the engineer beefed it up because she was having it polished Re: Thickness of concrete vs. mesh size 16Aug 24, 2011 3:26 pm i think most have address this thread. SL 72 standard in most slabs. 72 stands for 7mm and 200mm squares 100mm standard for most slabs. You are really splitting hairs about the amount of concrete is covering the steel mesh whether sl62 up to sl91, 3mm difference. 32mpa is bloody hard work, I now use a water reducer to reach 32mpa, higher water content lower mpa but easier to work. If you can keep the concrete nice and cool, now is a good time of year, for 30 days you will get 32mpa concrete. Good Luck Pulpo Re: Thickness of concrete vs. mesh size 18Aug 24, 2011 6:14 pm Well, you won't believe this coincidence Today I walked over a driveway which has a few parts of mesh exposed, maybe about 15 cm long each. The top layer of concrete (at least at that area) is so thin, around 10mm absolute max. Very close to this exposed mesh area were a few reo bars, also exposed The interesting thing is that there is no other visible degradation. The exposed parts probably haven't rusted enough yet for that to happen My signature is distracting people from my wise posts ... Re: Thickness of concrete vs. mesh size 19Aug 24, 2011 7:05 pm You will notice if mesh is too close to the surface with mesh pattern on the concrete slab showing through, but the actual mesh is not visible. A mesh layer closer to the surface will help with no cracking. I like to have 25mm cover min. In regards to MPa and water. Its something like 1 water to 2 cement produce 35mpa. 1 water to 1 cement produces 10 mpa. 20kg of cement to 10 litres of water is harder to work than 1:1. Use water reducers and the mix can be like 2 water for 1 cement but yet its strength can still be 35mpa. However water reducers add more dimensions to the equation and can be tricky. Good Luck Pulpo MATE!!! I've checked their website and it's a 90% match at least. I've just called them and sent the pic through to confirm it's the same product. 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