Ordinary concrete mixtures are not ideal for pumping. The pressure used to pump the concrete mixture often times forces water out of the cement leaving some portions dry and others wet. The friction caused by fine particles in the mixture is another concern. Typically higher pumping pressures are needed in order to overcome the problem. Simply modifying the mix by adding more sand, cement, or water to achieve pumpability often leads to undesirable physical properties and/or increased cost. Admixtures called pumping aids are commonly used to improve the pumpability of concrete and to reduce the overall cost of placement.
What is a Pumping Aid?
Simply put, a pumping aid is an admixture that makes concrete mixtures easier to pump through a line. They act as a lubricant for the mix and ultimately reduce the pressure necessary to pump the concrete without having to alter the sand. cement, water, and aggregate content.
POLYOX™ WSR-301 is a high molecular weight polyethylene oxide polymer that improves concrete pumpability by thickening the mix water and provides a pseudoplastic (shear thinning) rheology. To test the performance of POLYOX™ WSR-301, two typical concrete mixes were compared side by side.
The 25 ppm of POLYOX™ WSR-301 included in Formulation A reduced the pumping pressure of the mix by 16% without effecting the compressive strength or shrinkage upon drying. In addition, POLYOX™ WSR-301 stabilized air content. This stabilization allows for a 20-30% reduction of air entraining agents without any detriment to the workability of the concrete. Concrete that has POLYOX™ WSR-301 added is easier to pump, shows reduced rebound, and is easily workable in any temperature.
Added Benefits of POLYOX™ WSR-301 in Concrete
Improved water retention and distribution with highly porous and harsh aggregate
Pump longer distances at lower pressures
Prevents aggregate segregation
Stabilizes sprayed concrete
"Waterproofs" underwater concrete to improve setting qualities