Investigation and Repair of a Megatall Building Transfer Mat

Construction of a megatall tower foundation was suspended in October 2016 over concerns related to concrete uniformity and the presence of surface water during construction operations. The foundation design consisted of a four meter thick reinforced concrete transfer mat set on a network of 136 drilled concrete piers. The authors were retained as third party advisors to independently assess the as-built conditions and assist the contractor and designer in the formulation of a repair plan. The investigation commenced in December 2016 and included documentation of cores extracted from the transfer mat as well as the development of procedures to effectively ascertain conditions within the core holes. Of particular concern to the construction team was the development of a sufficiently representative sampling plan, the relative shear strength and performance of concrete joints, and the evaluation of corrosion potential within the transfer mat. A plan to repair affected locations of the transfer mat was developed to address the nature and type of conditions identified during the investigation. The repair recommendations developed by the authors were widely approved by the construction team.