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• Adding appropriate amount of dredged sand can improve the frost resistance of concrete. • Adding appropriate amount of dredged sand can improve the fracture performance of concrete. • AE count, energy and b-value can well reflect the fracture process of concrete. • The damage model of dredged sand concrete established based on the AE events obeys Weibull distribution. In order to investigate the frost resistance and fracture behaviors of dredged sand concrete, three kinds of concrete with different dredged sand contents (0%, 25%, and 50%) by weight were designed and subjected to different freeze–thaw cycles (0, 25, 50, 75 and 100). Three-point bending fracture tests were performed on the frozen concrete specimens combined with acoustic emission (AE) technique. The results show that the mass loss of dredged sand concrete increases, the relative dynamic elastic modulus and compressive strength decreases with the increase of the freeze–thaw cycles. With the increase of dredged sand content, the pore structure is improved, so the fracture behavior and frost resistance of concrete are improved. With the increase of the dredged sand content of concrete, the fractal dimension of the fracture surface decreases. With the increase of the freeze–thaw cycles, the fractal dimension of the fracture surface increases, and the fracture surface is rougher. The higher the freeze–thaw cycles, the lower the peak load, fracture toughness and fracture energy of dredged sand concrete. The higher the content of dredged sand, the greater the fracture energy of dredged sand concrete. The accumulate AE counts, AE energy and AE b -value can reflect three-stage failure process of dredged sand concrete. The damage model of dredged sand concrete established based on the AE events obeys Weibull distribution, which can reflect the effect of freeze–thaw cycles on damage. [ABSTRACT FROM AUTHOR]

In view of devastating outcomes of post-earthquake fires, it is imperative to propose a model for the fire-resistance capacity of a seismically-damaged concrete structure. For this purpose, the effects of cyclic damage and high temperature on residual tensile behavior of normal strength concrete are investigated in this paper. Monotonic tensile tests are performed on cylindrical concrete specimens which have been initially subjected to strain-controlled cyclic tensile load or have been exposed to high temperature. Residual mechanical behaviors are expressed in terms of cyclic damage or high temperature, respectively. Test results indicate that the residual tensile strength and stiffness decrease while residual peak strain and post-peak strain increase with the increase of damage and temperature. Finally, a modified stress-strain model is proposed to describe the residual tensile stress-strain relationship of concrete considering the effect of cyclic damage and high temperature. The modeling results fits well with the experimental curves. • The residual tensile behavior of concrete was studied. • Cyclic tensile test and exposure to high temperature test were carried out. • The residual tensile strength decreased with the damage and temperature rose. • The residual peak strain increases as the damage and temperature rose. • A residual tensile stress-strain model of concrete was proposed. [ABSTRACT FROM AUTHOR]

• The time variation of fresh properties of cementitious suspension containing BGA and GBA were investigated. • The effects of BGA and GBA on structural build-up were explained from the perspective of flocculent structure. • Bond strength coefficient (BSC) was an important parameter to determine the structural build-up parameters(t perc and G' rigid). In this paper, the structural build-up characteristics of cementitious suspensions containing attapulgite were explored from the perspective of flocculent structure. Firstly, the fluidity, rheology, adhesiveness, and segregation resistance of cementitious suspensions containing two kinds of attapulgite (burning followed by grinding (BGA) and grinding followed by burning (GBA)) were investigated. Then the small-amplitude oscillating shear tests were used to examine the structural build-up of cementitious suspension in different time periods. The percolation time (t perc) and the rigidification rate (G' rigid) of the percolated structures were measured. Finally, the bonding strength coefficient (BSC) was used to characterize the flocculent structures's size and strength, and its relationship with macroscopic experimental parameters and structural build-up characteristic parameters were investigated. The results indicated that GBA and BGA affected the flow expansion, plastic viscosity, yield stress, and adhesiveness of the cementitious suspension by changing the flocculent structures, and the BSC was the key property that determined these parameters. While the bleeding rate was affected by the combined effect of BSC and standing time. GBA and BGA were found to have different effects on the flocculent structures with different standing time periods. The BSC was strongly correlated with G' rigid and t perc , which could characterize the structural build-up of cementitious suspension. [ABSTRACT FROM AUTHOR]