Use of Strain-Hardening Cement-Based Composites (SHCC) for Retrofitting

Strain-hardening cement-based composites (SHCC, or Engineered Cementitious Composites, ECC) were developed in the early 1990th and have been since then an object of numerous investigations which number increases every year. Under tensile loading SHCC exhibit fine and well distributed cracking accompanied by large inelastic deformations prior to reaching ultimate strain capacity. Such behaviour makes SHCC suitable for repair and strengthening. The present article reports on the transfer of SHCC from laboratory tests to a practical application and on monitoring this application over several years. At the laboratory scale, neutron radiography was used to visualize the capillary water suction by a specimen made of a multiple cracked SHCC repair layer and a cracked RC substrate. The obtained results led to a practical implementation on a concrete water reservoir in Germany. The presented project served the purpose of testing the new technology in real scale and investigating challenges arising when laboratory scale is left for a larger one, especially resulting from the real mixing and placement conditions. The application was brought into life by industrial partners under close supervision of the authors. The repair layer is in service for several years now and under observation by the TU Dresden with respect to cracking behaviour and material deterioration.