Effect of Supplementary Cementitious Materials on Mechanical Properties and Self-Healing Efficiency of Engineered Cementitious Composite

Concrete is considered as a fundamental construction material as it has high compressive strength and fairly low cost. However, brittleness behavior and limited tensile strength can be remarkably observed in conventional concrete and accordingly, crack formation easily occurs. Many researchers have dedicated considerable efforts to adjust the brittleness characteristic and other weak points of conventional concrete and thus, they come up with the development of a new type of concrete, which is named engineered cementitious composite (ECC). In this experimental study, it is aimed to investigate the effects of replacing slag (S) 100% with fly ash (FA), in different proportions with limestone powder (LSP), and glass powder (GP); on workability, mechanical properties, microcracking behavior and self-healing efficiency of ECC. For this purpose eight different ECC mixtures were prepared; at first reference sample is produced with a certain amount of cement and slag as a binder, then slag is replaced 100% with fly ash, 5, 20 and 40% with LSP and 20, 40 and 60% with GP by total mass of slag. In order to determine and compare the effects of slag, fly ash, LSP and GP on workability, mechanical properties and behavior and self-healing efficiency of ECC; flow test, compressive and splitting tensile strength tests at different compressive loading levels, stress-strain diagrams tests under compression were conducted. In addition, self-healing efficiency of eight different ECC produced were determined by means of ultrasound readings and stereomicroscope measurements. Here, cracks were created on the surface of specimens by preloading them up to ultimate splitting tensile strength. After that, microscope and ultrasonic test were utilized to observe and determine the self-healing recovery rate. Overall, replacing slag with LSP up to 5% and with GP up to 20% displayed significant improvement on mechanical properties of ECC and a high relative comparative of self-healing efficiency with ECC-Ref. Calcium carbonate and C-S-H gels were observed to be the prominent healing products.