5 sack mix is only a 3000psi mix a 7 sack mix is 5000 psi if you add fiber mesh, 1/8 steel reinforcement mats and Plasticizers the PSI jumps dramatically. Contractors add to much water to the mix it makes it easy for THEM and the finishers have more CREAM to make it look good but strength is weakened. With the Plasticizers the need of water is reduced to achieve the same effect but with FAR MORE STRENGHT . At the entrance doors to our shop there is a 25 x 25 sq ft pad that is only 2x4 thick it has 7 sack mix with the 1/8 inch reinforcement mats fiber mesh and the Plasticizers mentioned above fly ash was also added. I have had a Prevost motor home and several class 8 trucks at well over 80K cross over and park on them and NO CRACKS, if a guy does his own work IT GETS DONE THE RIGHT WAY, a contractor will blame the ready mix the ready mix will blame the contractor and YOUR LEFT HOLDING THE BAG!!!
For concrete [edit]
Plasticizers or water reducers, and superplasticizer or high range water reducers, are chemical admixtures that can be added to concrete mixtures to improve workability. Unless the mix is "starved" of water, the strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added (without "starving" the mix), which makes the concrete mixture less workable and difficult to mix, necessitating the use of plasticizers, water reducers, superplasticizers or dispersants. [3]
Plasticizers are also often used when pozzolanic ash is added to concrete to improve strength. This method of mix proportioning is especially popular when producing high-strength concrete and fiber-reinforced concrete.
Adding 1-2% plasticizer per unit weight of cement is usually sufficient. Adding an excessive amount of plasticizer will result in excessive segregation of concrete and is not advisable. Depending on the particular chemical used, use of too much plasticizer may result in a retarding effect.
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