Study on increasing the toughness of UHPC by emulsified asphalt

At present, cracking is the main form of damage to UHPC, and increasing flexural toughness is the main technical way to solve the cracking damage of UHPC. Currently, fiber, polymer or nanomaterial modification is usually used to improve the toughness of UHPC, and emulsified asphalt has been shown to have the potential to toughen and resist cracking. In order to investigate the toughening effect of emulsified asphalt in cementitious materials, this paper uses emulsified asphalt and water added simultaneously for wet mixing to prepare UHPC specimens. The effects of different types and dosages of emulsified asphalt on the working performance, mechanical strength and flexural toughness of UHPC were investigated by conducting the extensibility test, flexural toughness test, compressive strength, flexural strength and tensile strength tests. The results show that: in terms of work performance, the extension of UHPC mixes with two types of emulsified asphalt gradually decreased with the increase of emulsified asphalt dosage; when the dosage of two types of emulsified asphalt was more than 3%, the extension could not meet the specification requirements. In terms of mechanical strength, with the increase of two kinds of emulsified asphalt dosage, the mechanical strength of UHPC have a small decrease. In terms of bending toughness, both emulsified asphalt can make the bending toughness of UHPC enhancement, of which the bending toughness of anionic emulsified asphalt UHPC is better than cationic emulsified asphalt UHPC. compared with cationic emulsified asphalt, anionic emulsified asphalt UHPC work performance and mechanical strength is better than cationic emulsified asphalt UHPC, toughening effect is more significant; comprehensive consideration of mechanical properties and performance, the use of anionic emulsified asphalt UHPC is recommended. UHPC recommended the use of anionic emulsified asphalt, and the optimal dosage of 3%. Through the scanning electron microscope to observe the microstructure of UHPC specimens without the addition of emulsified asphalt and UHPC specimens doped with 3% anionic emulsified asphalt, found that the emulsified asphalt can fill the original micro-cracks in the UHPC, to improve the internal structure of the matrix, to a certain extent, increase the effective contact area between the steel fibers and the substrate, and give full play to the toughening effect of the steel fibers. On the other hand, the viscoelastic property of emulsified asphalt makes the cracks need to consume more energy to expand, which effectively reduces the generation and development of microcracks, and serves as a buffer for the destabilization damage of hydration products.