Yup! I always install a vapor barrier over concrete, either with a roll on membrane or with an anti coupling system such as Ditra Schluter. Hydrostatic pressure will blow Porcelain tiles (are vitreous) off the floor. To test if a slab has a vapor barrier you simply put a rubber floor mat on the floor and check under it in a day or so to see if it is wet under the mat. if so, you have no vapor barrier. If you store cardboard boxes, etc. directly on this you will get molding in the box.All modern day ready mix concrete companies, at least any that a reputable all use various water reducing admixs in their mix designs. This is the only way to maintain a proper Cement to water rate ratios. You must understand that to properly maintain these ratio's to get the proper yield on PSI at 7, 14, and 28 days a variety of factors come into play. Moisture contents of the aggregates are a highly variable factor from day to day and can have major impacts on the cement to water ratio which will greatly affect the ultimate achieved PSI.. We run moisture test daily in our labs. If it is going to be COLD storage you must also ensure the proper air entrainment in the mix. Air entraining agents should be added to any outside mix design. Make sure you are ordering a 3500 mininum to 4000 pound mix with full air. Ask that they run a Air test on your load and produce those results to you. Your desired air content should be around 5-7%. Air entrainment too is a variable that will change daily with things like moisture contents, Cementatious materials, Fly ash or Slag being part of the mix, ect. We run air test daily on all different mixes thru out the day. If you are truly wanting to get the most from the ready mix product (not cement, cement is a component of ready mix) aske for a 4000 lb mix, with full air. It is ok to use a mix with ash or slag but if the ready mix company does ask for a copy of the batch weights so you have them should you have isssues latter you could have an engineer inspect the mix design. As far as water use a good water reducer at the time of the batch. Try to keep your Slup, (wetness of the load) around a 3 to 4 inch slump. If your contractor doesnt want to do it right and wants to work with a "looser" product you can spend the extra money and ask that they use a Super Plastizer material in place of water. Super works by being added at the sight and will give you a big increase in your slump for a short period of time without throwing of the water ratio.
As far a plastic. It wil only work as long as it remains totaly in tack. To many times contractor put plastic down and it gets punctured, tore, ect. Once there is a break in the membrane the slap will eventually wick moisture back to a normal moisture content
All modern day ready mix concrete companies, at least any that a reputable all use various water reducing admixs in their mix designs. This is the only way to maintain a proper Cement to water rate ratios. You must understand that to properly maintain these ratio's to get the proper yield on PSI at 7, 14, and 28 days a variety of factors come into play. Moisture contents of the aggregates are a highly variable factor from day to day and can have major impacts on the cement to water ratio which will greatly affect the ultimate achieved PSI.. We run moisture test daily in our labs. If it is going to be COLD storage you must also ensure the proper air entrainment in the mix. Air entraining agents should be added to any outside mix design. Make sure you are ordering a 3500 mininum to 4000 pound mix with full air. Ask that they run a Air test on your load and produce those results to you. Your desired air content should be around 5-7%. Air entrainment too is a variable that will change daily with things like moisture contents, Cementatious materials, Fly ash or Slag being part of the mix, ect. We run air test daily on all different mixes thru out the day. If you are truly wanting to get the most from the ready mix product (not cement, cement is a component of ready mix) aske for a 4000 lb mix, with full air. It is ok to use a mix with ash or slag but if the ready mix company does ask for a copy of the batch weights so you have them should you have isssues latter you could have an engineer inspect the mix design. As far as water use a good water reducer at the time of the batch. Try to keep your Slup, (wetness of the load) around a 3 to 4 inch slump. If your contractor doesnt want to do it right and wants to work with a "looser" product you can spend the extra money and ask that they use a Super Plastizer material in place of water. Super works by being added at the sight and will give you a big increase in your slump for a short period of time without throwing of the water ratio.
As far a plastic. It wil only work as long as it remains totaly in tack. To many times contractor put plastic down and it gets punctured, tore, ect. Once there is a break in the membrane the slap will eventually wick moisture back to a normal moisture content