Properties of calcium sulfoaluminate cement made ultra-high performance concrete: Tensile performance, acoustic emission monitoring of damage evolution and microstructure.

• ES-UHPC exhibits significant tensile strain-hardening behavior at early age. • ES-UHPC obtain high ductility and bonding between steel fiber and matrix at 1 d. • Damage evolution was monitored by acoustic emission method. • AE analysis proves that the ES-UHPC exhibits multiple cracking behavior at 28 d. • Ettringite is the main hydrates and the content increases rapidly from 4 h to 1 d. The properties of early age strength ultra-high performance concrete (ES-UHPC) made with calcium sulfoaluminate (CSA) cement, including tensile performance, damage evolution monitored by acoustic emission (AE) and microstructure were evaluated in this work. Results show that the ultimate tensile strain ε Utu of ES-UHPC can reach to 0.199% at 1 d, which is 4.23 times larger than that of normal UHPC (N-UHPC) at the same testing age. AE testing results indicate that both types of UHPCs exhibit multiple cracking behavior at 28 d. With the tensile strain developing, the two UHPCs show a similar damage evolution trend and multiple microcracks with crack-width smaller than 0.01 mm generated after 0.046% strain reached. Microstructure tests demonstrate that ettringite presented after 4 h and the content increased significantly from 4 h to 3 d, which contributed to the early mechanical properties for ES-UHPCs. [ABSTRACT FROM AUTHOR]