SCHUNDLER V+16, ULTRA MIX AND ULTRA MIX II

Compared to Sand Cement or Grout Mixes

To solve problems caused by steeper slopes and using plain, packed sand, many installers in the pool industry began to use vermiculite concrete as a permanent base for vinyl lined pools. During the last thirty years, vermiculite concrete has proven to be an effective, permanent solution to many potential vinyl pool problems. Using vermiculite may cost a little more, but it is the only alternative with long lasting advantages.

Unfortunately as in many industries, there are slightly less expensive alternatives available to contractors such as sand/cement or grout bottoms. Although sand/cement grout bottoms can work in some instances and may be less expensive, they do have long-term liabilities and can cost more money eventually:

1. Sand/Cement grout mixes produce a concrete that is not porous, and that will not let water pass through it when hydrostatic pressures build up under the bottom of your pool. These kinds of pressures caused by high water tables and heavy rain can break the concrete and leave small hairline cracks and larger more obvious flaws. The sharp, brittle edges of broken concrete will cut and wear down soft vinyl liners eventually requiring liner replacements. And when the liner is replaced, the bottom also will have to be patched and repaired.

2. Pools with sand/cement grout bottoms tend to be very hard and offer no cushioning. This not only feels harder and rougher on your feet, it also contributes to more long-term degradation of the liner.

3. Sometimes installers will boast about how much stronger sand concrete is compared to vermiculite concrete. Consider the facts.

• Sand/cement concrete does provide more compressive strength than vermiculite concrete (2000 psi or more compared to 100 psi for vermiculite concrete.) But in this application, the "weakness" or resiliency of vermiculite concrete works to its advantage.
  

• Like a willow compared to an oak tree, you want the pool bottom to give and bend a little. Just as your house "settles", there is movement in pools. When subjected to tensile stresses and hydrostatic pressures, it is better to have a bottom that will flex when necessary and will not crack. Without reinforcing bars and thicknesses of six to eight inches as done in regular concrete (gunite) pools, sand concrete is very fragile and vulnerable to cracking, chipping, and breaking.
  

• There is no doubt that 2000 psi sand/cement concrete can hold more weight than 100 psi vermiculite concrete; if subjected to just compressive pressures, sand/cement could withstand the weight of 288,000 lbs of water per square foot vs. 14,400 lbs per square foot with vermiculite concrete. But a pool doesn't need that much compressive strength; vermiculite concrete with its low 100 psi rating can still support a water column of over 221 feet!