Distribution of Cement Content Across Wall Thickness of Spun-Cast Concrete Poles and Its Implications for Their...

The durability of prestressed spun-cast concrete poles is typically assessed on the basis of the nominal mix design parameters and the assumption of material homogeneity. However, the centrifugal spinning of fresh concrete mix results in an uneven distribution of its components throughout the wall thickness, which may affect the actual cement content in individual layers and consequently, the durability. As part of this study, the distribution of cement content in spun concrete poles was analysed using an experimental approach based on the analysis of hardened concrete composition. Samples were taken from various locations along the height of the pole and divided into layers across wall thickness. Cement content, aggregate distribution, porosity, and water absorption were determined using a combination of chemical and physical methods. The results indicate that although the average cement content meets the design requirements (minimum amount of cement exceeds 300 kg/m³), there are significant local variations, particularly in the inner and outer layers of the cross section. The inner layer is characterized by increased cement content and porosity, while the outer layer is characterized by a higher coarse aggregate content and reduced cement content. It was also observed that the spinning program used in the production of the poles resulted in a homogeneous concrete structure at the top of the pole, where the spinning radius is smallest, with no signs of delamination. However, delamination of the concrete structure was observed at lower sections of the pole. These results highlight the limitations of assuming homogeneous material properties in durability design and suggest that the actual performance of spun concrete elements may deviate from predictions based on the standards. The results have direct implications for assessing the durability of spun concrete poles used in exposure classes such as XC4 and XD1.