Browse Forums Building A New House 1 Sep 03, 2014 10:41 pm Hi All, If my land is affected by salinity, does it definitely 100% require a "H Class" slab? Reason I ask is because my geotech report came back with a "S" Classification, however the entire area is salinity affected. One of the reasons why I think it was classified as "S" was because of rock that was found 400mm below surface, so obviously less "movement" as rock has less movement and changes than clay. Does this mean there is less salt (saline) in the ground because of the amount of rock and therefore I won't require an H Class slab? Or would I require a H class slab anyway as the whole area is still salinity affected? Thanks in advance! BB $395 Fixed Priced Landscape Plans for DA M: 0435 127 244 | W: bluegumdesign.com.au | E: info@bluegumdesign.com.au Residential | Commercial | Industrial Re: H Class Slab Question! 3Sep 05, 2014 12:54 am Thanks very much! $395 Fixed Priced Landscape Plans for DA M: 0435 127 244 | W: bluegumdesign.com.au | E: info@bluegumdesign.com.au Residential | Commercial | Industrial Re: H Class Slab Question! 4Sep 16, 2014 1:53 am Hi Brahma Bull, Another useful suggestion I hope - wrapping strip footings in underlay is often a requirement for H site footings and that may be why H was stipulated... but make certain that the taping is complete I suggest... and for a slab make the underlay turn up the concrete slab edge and get tucked into the rebate. Leonardo_23 Re: H Class Slab Question! 5Sep 16, 2014 2:57 am Hi Brahma Bull Are you removing the clay and putting down a sandpad for class S? If salinity is a problem then I suggest you refer to AS3600- Table 4.10.3.5 a & b -Durability you may wish to also increase the concrete cover around the reo as well. HTH Designer,Engineer (Civil,Const & Envir),Builder,Concrete & Masonry Contract.Struct Repairs Re: H Class Slab Question! 6Sep 16, 2014 7:16 am We've built in Saline soil with an M slab. Increased concrete MPA, layer of sand and thicker membrane were needed (might be more but thats all I can remember ATM). Our council has some standard requirements for saline soils, it might be worth checking yours our. http://camdenbuild.blogspot.com.au/ by invite only please pm me Re: H Class Slab Question! 7Sep 16, 2014 7:22 am Leonardo_23 Hi Brahma Bull, Another useful suggestion I hope - wrapping strip footings in underlay is often a requirement for H site footings and that may be why H was stipulated... but make certain that the taping is complete I suggest... and for a slab make the underlay turn up the concrete slab edge and get tucked into the rebate. Leonardo_23 If you are going to wrap building plastic under the slab up over slab edge and into rebate you will conceal slab edge and provide potential concealed termite entry opportunity. Ideally exposed slab edge should be used as perimeter termite inspection zone and you won't have to use chemicals. I think that increased cement content will make concrete much more impermeable and protective of reinforcing. I built concrete factories and 35MPA concrete is very very hard and dense. I would avoid fly ash as it is corrosive to reinforcing. Some of the reported concrete cancer in high rise buildings is due to use of fly ash. Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: H Class Slab Question! 8Sep 16, 2014 7:34 am Hi BE I disagree that the fly ash is highly corrosive to the reo if the slab is designed correctly. If that was the case then our Road authorities are in a lot of trouble. I worked and did extensive testing with flash concrete and if the mix design is correct you have nothing to worry about. Problem is people cut corners that's when issues arise. The oxygen and water is what will corrode the reo. If you have the correct reo cover you are eliminating the contact of water and air hence eliminating the corrosion. With the absence of air and moisture you won't get corrosion simple, that being said I've not included galvanic corrosion. That's different. In essence OP I think the answers being given above should answer your questions Re: H Class Slab Question! 9Sep 16, 2014 7:57 am Crazyk Hi BE I disagree that the fly ash is highly corrosive to the reo if the slab is designed correctly. If that was the case then our Road authorities are in a lot of trouble. I worked and did extensive testing with flash concrete and if the mix design is correct you have nothing to worry about. Problem is people cut corners that's when issues arise. The oxygen and water is what will corrode the reo. If you have the correct reo cover you are eliminating the contact of water and air hence eliminating the corrosion. With the absence of air and moisture you won't get corrosion simple, that being said I've not included galvanic corrosion. That's different. In essence OP I think the answers being given above should answer your questions I think you are right, the contributing cause of concrete cancer is poor workmanship and also fly ash in use on roads may be OK but it's use in buildings is dangerous. This is what I lifted from internet "As you might expect, coal ash is a cocktail of toxic chemicals -- it contains the same heavy metals that are found in coal, only in higher concentrations. Fly ash typically contains heavy metals like arsenic, lead and selenium that are known to cause cancer and other health problems. Because of the known risks, environmentalists have long fought to have fly ash categorized as a hazardous material, but they have faced stiff resistance from the energy industry, and now the construction industry." and also emission of Radon gas can cause lung cancer, have a look at this http://www.caee.utexas.edu/prof/Siegel/ ... 1_1015.pdf I would not use fly ash in construction of any home or building. If you live in concrete building, such as multi storey dwellings then: ventilate, ventilate ,ventilate (not only because of fly ash but also because of Radon in concrete) Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: H Class Slab Question! 10Sep 16, 2014 8:01 am Good bit of info and all things considered. I will admit we were concentrating on the durability benefits of fly ash not health impacts. Also not that concrete dust is just as bad for your health as well so if mixing concrete...wear a mask! All in all higher MPa concrete and additional concrete cover will be the way to go. Re: H Class Slab Question! 11Sep 17, 2014 1:04 am Hi Brahma Bull, Agreed if you take the underlay up the side of the slab to the rebate (and fold into the rebate) the folds could well give a chance for termites to get to the rebate unseen; and with poor workmanship there could well be an avenue through under the first mortar bed - very good point by B-E. However I partly disagree with the next bit of advice because with 150mm rebates, the ground under the 100mm slab and its 50mm sand bed equals the rebate level for raft slabs, and so there may well be no slab edge to inspect when you think about it - perhaps a little for waffle pod slabs. The thing to keep clear of termite attack are the weep holes. Paving and garden and soil must be below these holes or it is an open invitation to termites and this entry point is outside the treated area. The important thing with salinity is to separate the brackish water from the slab with the underlay turned up to ground level as was the rule for all raft slabs until about 1994 I believe. That simple thing should be sufficient, but the taped joints in the underlay must be well done and the concretor must tape up around all pipe penetrations really well and there must not be any puncture holes caused by sloppy workmen. So all up it may be advised to have this secondary safeguard as well as a more durable slab discussed at length. Leonardo_23 The Soil classification has little to do with piers. The purpose of the classing of the soil is to identify the clay content and the "average expected range of movement… 2 7887 I am not sure whether Perth has its own way of doing things in regards to this. Most of Perth has class A (sandy soil), except for some areas near rivers or hills. 2 8248 I don’t think so as the floor area over 300 square meters then it is class 3…. 12 15868 |