Credit for making pumping economically attractive must be given to a variety admixtures which control the way in which concrete behaves, from mixing to final cure. Concrete admixtures have met with such success in recent years that some ready mixed concrete producers will now guarantee the pumpability of their products. One of the first admixtures found to be beneficial for pumping concrete was an air-entraining agent. The small, stable bubbles developed by an approved air-entraining agent act as flexible ball bearing in the mix. These enable the sand particles to move by each other more freely thus increasing the plasticity of the mix without the need of extra water. The bubbles also supplement the sand grading which is very important in concrete mixes that are to be pumped. In other words, they reduce particle interference and the effects of gap grading. The development of water-reducing agents and water reducing retarding admixtures has provided further benefits to the concrete pumping industry. These materials are commonly known as dispersing agents. When introduced into a concrete mix they disperse the cement grains and increase the plasticity of the mix by minimizing agglomeration. Thus, for a given amount of cement a better coated aggregate is provided for the pump to handle. Pumping aids represent a new development in the role played by admixtures in the pumpability of concrete, one which promises to be a significant advance in concrete pumping technology. A pumping aid is a lubricant that improves the ease with which a given mix can be pumped through a line. This means lower pump pressures, reduced pressure on the mortar phase of the concrete, less chance of segregation and a reduction in internal friction. One of the major advantages of pumping aids is the fact that in most cases they enable mixes designed in accordance with ACI 211.1 to be pumped without alteration.