Basic mechanical behavior and flexural toughness evaluation#br#
method of coarse aggregate UHPC
Shi Zhanchong1 Su Qingtian1，2 Shao Changyu3 Chen Liang3
1. Tongji University, Shanghai 200092, China;2. Shanghai Engineering Research Center of High Performance Composite Bridges, Shanghai 200092, China;
3. Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., Shanghai 200092, China
Abstract：In order to investigate the basic mechanical behavior and free-shrinkage behavior of coarse aggregate UHPC (CA-UHPC), the tests on basic mechanical behavior and free-shrinkage of CA-UHPC were designed and conducted, and the behaviors of CA-UHPC were compared with those of UHPC and steel fiber reinforced concrete (SFRC). The advantages and disadvantages of flexural toughness evaluation methods currently used for fiber reinforced concrete were discussed. The offset method to quantitatively capture the first-crack point of UHPC beam under bending and tension actions was proposed. Furthermore, a new method of evaluating flexural toughness of CA-UHPC from the perspectives of energy and equivalent flexural-tensile strength was optimized, and the flexural toughness of CA-UHPC, UHPC and SFRC were evaluated based on the proposed evaluation method. The results show that the elastic modulus of CA-UHPC is 10% higher than that of UHPC, while cubic compressive strength and flexural strength are 15% and 6% lower respectively. The flexural-tensile strength of CA-UHPC is 1.8 times that of SFRC. The free shrinkage of CA-UHPC during 91 days is almost the same as that of SFRC, while the shrinkages of CA-UHPC at the age of 3 days and 91 days are 63% and 55% lower than that of UHPC. Accordingly, adding coarse aggregates to UHPC may reduce the risk of earlyage cracking of UHPC. The proposed evaluation method can effectively evaluate the flexural toughness of the UHPC beam during its whole loading process. In addition, the flexural toughness of UHPC and CA-UHPC is significantly better than that of SFRC. The maximum decreasing amplitudes of pre-peak flexural toughness index and flexural toughness ratio ofCA-UHPC are 28% and 22% lower than that of UHPC, while the decreasing amplitudes of the post-peak flexural toughness index and flexural toughness ratio are within 11%.
