A strain-hardening cementitious composites with the tensile capacity up to 8%

Fiber reinforced concrete (FRC) has advantage in tensile ductility over the normal concrete. Among the family of FRC, engineered cementitious composites (ECCs) are known for their strain-hardening behavior and high tensile capacity. However, even the ductility of normal ECC is not sufficient to support it to be a solo structural material. To improve the tensile capacity of ECC to a higher level, a new cementitious material, ultra-high ductile cementitious composites (UHDCCs), is developed with the specially selected polyethylene (PE) fibers. The present paper introduces the mixture process and a series of mechanical tests on UHDCC with 3 different mixtures. Uniaxial tension test indicated the outstanding strain hardening and saturated multiple cracking properties of UHDCC. At ultimate state, the crack spacing of UHDCC was generally less than 2 mm with the residual crack widths less than 100 μm. The tested UHDCC exhibited the averaged tensile strain at peak stress over 8% with some mixture even exceeding 12%. UHDCC had the compressive strength ranging from 45.9 MPa to 121.5 MPa. The strain hardening behaviors were observed in the compression test of UHDCC-1 and UHDCC-2. To figure out the formation of tensile capacity, comparative studies were conducted on the pseudo-strain hardening (PSH) indexes of UHDCC. The test results demonstrated that the ultra-high ductility of UHDCC originates from the ultra-high crack bridging capacity. It implies that with sufficient bridging provided by fibers, UHDCC can maintain the tensile ductility at an amazing level, despite the high fracture toughness of matrix. Additionally, analysis demonstrates that the classic PSH criterion is still valid for quantifying the tensile capacity of UHDCC.