Low E Modulus Early Strength Engineered Cementitious Composites Material

For a reliable repair solution to be provided for the sinkage of concrete pavement slabs caused by the subsidence of subgrade, low E modulus early strength high ductility engineered cementitious composites (LMES-ECC) material was developed for ultrathin whitetopping overlay application. Low modulus of the topping material is advantageous for deformation compatibility with the existing substrate concrete without the experience of high stress. The high tensile ductility of LMES-ECC further increases the deformation compatibility and suppresses the reflective cracking, which is a major failure mechanism of pavement repair. Experimental studies were conducted on LMES-ECC with respect to its compressive strength, tensile properties, cracking behavior under restrained shrinkage, and flexural properties. The compressive strength and flexural strength of LMES-ECC at 3 days reached 31 MPa and 7 MPa, respectively, which satisfied both the requirement necessary to reopen traffic and the design strength of concrete pavement material. Unlike the brittle fracture of normal concrete, multiple microcracks (i.e., average crack width below 60 μm) developed in LMES-ECC before final fracture under tension and bending; this deformation resulted in a tensile strain capacity as high as 4% (about 400 times that of normal concrete) and large vertical deflection capacity. In addition, the E modulus of LMES-ECC was measured at 14 GPa, which was significantly lower than for normal concrete. The low modulus and high deformation capacity of LMES-ECC greatly improved the deformation compatibility of the topping overlay with the old concrete substrate, avoided brittle failure or large cracks of the overlay, and contributed to more effective pavement repair.