h i g h l i g h t s Crack self-sensing ability of concrete beam added with SF, CB and CF is studied. Two models for FCI-COD curve are found for deflection softening/hardening beam. Signal noise of FCI-COD curves has been analyzed by the fractal geometry method. Hybrid use of CB and SF is an optimization option for crack self sensing concrete.

The multiphasic conductive admixtures like macro steel fiber (SF), nano carbon black (NCB) and carbon fiber (CF) are incorporated into concrete to improve the conductivity and mechanical properties. In this study, the mechanical and conductive properties of the concrete beam are explored by the hybrid use of different conductive admixtures. The deflection hardening (multiple cracking) behavior of concrete beam with different fiber content, monitoring of single and multiple cracks of diphasic (SF+NCB) and triphasic (SF+CF+NCB) conductive concrete beam through resistance measurement is investigated. Moreover, the relationship between fractional change in resistance (FCR) and crack opening displacement is established to study the influence of different types and amounts of electric conductive admixtures on self-sensing behavior of concrete beam. Results reveal that the deflection hardening (multiple cracking) behavior is obtained with 70 kg m −3 SF content. The single and multiple cracks monitoring is illustrated through load-time and FCR-time relationship. In addition, FCR improved linearly with an increment of NCB with triphasic conductive admixtures.

No abstract

No abstract

In this paper, the radial deformation of fiber reinforced self‐compacting concrete (SCC) pipes under cyclic fire conditions is studied. A series of experimental study on the temperature fields and radial deformation properties of steel mesh, polypropylene fiber (PP fiber), and macro steel fiber (SF) reinforced SCC pipes subjected to fire is carried out. A novel method for measuring the deformation of pipes under high temperature has been proposed. The results indicate that both micro PP fiber and macro SF are effective in decreasing the temperature difference and reducing the radial deformation in each thermal cycle. A significant positive synergistic effect on decreasing the residual radial deformation can be achieved by combined use of macro SF and micro PP fiber. The elastic theory is used to estimate the elastic portion in the total radial deformation, and the elastic radial deformation is about 22.3% of the maximum radial deformation in the first thermal cycle. Based on the elastic calculation and observed experimental results, a simplified method for estimating the maximum radial deformation in the first thermal cycle is proposed.