Engineered Cemenitious Composites (ECC) are cementitious composites with high pseudo-ductility. ECC's can be made with relatively low sand/cement ratio and 1.5-2% of polyvinyl alcohol (PVA) fiber. In this research investigation, three potential applications of ECC in concrete structures are considered. These include 1) Precast ECC for region of high local stress at the anchorage zone of a post-tensioned concrete member, 2) Precast ECC for region of high local stress around anchor bolt and 3) A protective layer to prevent the falling of spalled concrete from external walls of concrete buildings. In each application, to optimize performance/cost, ECC is only employed in the most critical locations of the structural component....[ Read more ]

Engineered Cemenitious Composites (ECC) are cementitious composites with high pseudo-ductility. ECC's can be made with relatively low sand/cement ratio and 1.5-2% of polyvinyl alcohol (PVA) fiber. In this research investigation, three potential applications of ECC in concrete structures are considered. These include 1) Precast ECC for region of high local stress at the anchorage zone of a post-tensioned concrete member, 2) Precast ECC for region of high local stress around anchor bolt and 3) A protective layer to prevent the falling of spalled concrete from external walls of concrete buildings. In each application, to optimize performance/cost, ECC is only employed in the most critical locations of the structural component.

For the first application, based on the tensile stress distributions from 3-D FEM analysis, critical splitting tension is found on the outer surface of the post-tensioned member. To increase the load capacity under concentrated stress, it is necessary to apply ECC over the whole anchorage zone, rather than just within an internal core of the zone. With the use of ECC, experiment results show that the ultimate load capacity improve more significantly over that of plain concrete when the load becomes more concentrated. When the loaded area is one-quarter of the total cross sectional area, the improvement can be up to 50%.

For the second application, over 25% of load improvement can be obtained when a precast ECC disc is placed above the bolt of a steel anchor. Test results indicate that the improvement in load capacity is not necessary proportional to the compressive strength of the disc. The ductility of the disc material may play a more important role. The improvement of anchor performance with material ductility is supported by results from FEM analysis.

For the third investigation, the feasibility of using a thin (5mm) ECC repair layer to prevent the falling spalling concrete cover is studied. To assess the ability of the ECC layer in preventing concrete spalling, a new testing set-up has been designed. Depending on the bond between the ECC layer and the concrete, the ECC layer is either so strong that it is impossible to fail under the loading from spalled concrete of common size, or exhibits a progressive failure with a 'hardening' load vs displacement behaviour that provides a lot of warning. From the results, the feasibility of preventing concrete spalling with an ECC layer is demonstrated.