Improving the durability and performance of spun-cast concrete poles

The causes for the formation of longitudinal cracks and other types of damage in spun-cast concrete poles are investigated. From on-site inspection of several damaged poles and laboratory tests on existing and new pole segments, ii has been established that the differential shrinkage caused by the segregation of fines from the coarse aggregate is the primary cause for cracking. In order to develop the technology of spun-cast concrete poles, a large number of trial mixes consisting of normal weight concrete, lightweight concrete, and blended concrete have been produced in a specially fabricated spinning machine and tested for strength and durability. Fly ash, silica fume and admixtures such as super-plasticizers, air-entraining agents and set retarders have been used to improve the performance of the concrete. Based on the results, two mixes, one for normal weight concrete and one for lightweight concrete, are recommended for production of spun-cast concrete poles.