Quality Control Of Grouting For Post-Tensioned Tendons: In-Line Density Measurements

Abstract

Cementitious grout has proven to be an effective corrosion protection method in post-tensioning systems. While successful grouting has been used in numerous post-tensioned (PT) bridges, quality control of the material and placement in the field remains a challenge. During the grouting process on-site, ensuring that the grout being placed in the tendon is representative of the intended grout design is critical for the performance of the system. Inconsistencies in the placed grout can be attributed to varying mixing procedures used in the field (such as the addition of water above the design value). In some cases, grout passing the laboratory tests differs significantly from grout placed in the field. To alleviate these discrepancies, it is imperative that the PT industry improves quality control to ensure materials and products meet project requirements throughout production and placement - not just during the grout’s initial qualification. Advancements in the quality of in-place grouts can be made by refining specifications and developing a procedure to continuously measure the density of the grout as it is pumped into the tendon. The objective of this research is to develop a quality control measure that can be used during pumping to ensure suitable and consistent grout quality. Continuous monitoring and recording of the grout density will ensure the grout is of uniform quality throughout the project and meets the water content requirements provided by the grout manufacturer to meet project specifications. Recommendations for procedure and associated specification language is provided.