Influence of strain rate and water content on mechanical behavior of dam concrete

Compressive behaviour of brick masonry triplets in wet and dry conditions

“…Although obtained for samples of different geometry, such strength can be considered comparable to the 28 days value reported above, hence the hardening of CEM mortar seems to have occurred mostly in the first month at high relative humidity. When water saturated, CEM mortar undergoes a marked peak strength decrease (À29.2%) and a slight E increase (which is fairly in agreement with other studies on concrete [29][30]). The fact that CEM mortar shows a higher sensitivity to water presence than brick cannot only be explained on the basis of the amount of pores of these two materials (indeed, the total porosity in brick is almost double than in CEM mortar), but it should be linked to their different microstructural features.…”

“…Fired-clay bricks exhibit mostly cylindrical [46] and coarse pores (average pore radius around 0.4 lm, Table 2), where the effect of moisture in enhancing crack propagation at the fissure tip seems lower than in other materials having thin intergranular microcracks (decayed marble, highly sensitive to moisture [24]) or subcritical cracks (glass [22]). Conversely, CEM mortar exhibits much thinner pores respect to brick (about one fourth) and presumably also a lower water mobility through capillaries (due to adhesive forces with pore walls), which causes water pressure arising in the water-filled voids under quasi-static loading [30] and thus an earlier crack propagation.…”

“…The strain rate sensitivity of concrete strength to water was explained through different concepts, such as the 'viscous cohesive stress' of free water in the pores (e.g., [30]) or the wave propagation concept [31]. An increase in both static and dynamic elastic modulus in wet concrete was found as well [30].…”

“…The combined effect of moisture and strain rate was specifically investigated also for concrete [29][30] and a marked reduction in compressive and flexural strength for increasing water contents was found, especially at lower displacement rates (static conditions) [29][30], while saturation seems to cause much higher strength at high strain rates and for impact loads [31]. The strain rate sensitivity of concrete strength to water was explained through different concepts, such as the 'viscous cohesive stress' of free water in the pores (e.g., [30]) or the wave propagation concept [31]. An increase in both static and dynamic elastic modulus in wet concrete was found as well [30].…”

Experimental study and analytical formulation of mechanical behavior of concrete

“…Testing conditions include variables such as stiffness of testing machine [4][5][6], shape and size of the specimen [7,8], strain rate [9][10][11], type of strain gauge and gauge length [6,12]. Concrete characteristics depend on many interrelated variables such as water-cement ratio [13,14], the mechanical and physical properties of the cement [15,16] and aggregate [17,18], and the age of the specimen when tested [19,20].…”