Effects of curing age on compressive and tensile stress-strain behaviors of ecological high ductility cementitious composites

To obtain the design parameters of the structure made by ecological high ductility cementitious composites(Eco-HDCC),the effects of curing age on the compressive and tensile stress-strain relationships were studied.The reaction degree of fly ash,non-evaporable water content and the pH value in pore solution were calculated to reveal the mechanical property.The results indicate that as the curing age increases,the peak compressive strength,peak compressive strain and ultimate tensile strength of Eco-HDCC increase.However,the ultimate compressive strain and ultimate tensile strain of Eco-HDCC decrease with the increase in curing age.Besides,as the curing age increases,the reaction degree of fly ash and non-evaporable water content in Eco-HDCC increase,while the pH value in the pore solution of Eco-HDCC decreases.Finally,the simplified compressive and tensile stress-strain constitutive relationship models of Eco-HDCC with a curing age of 28 d were suggested for the structure design safety.

Dynamic regimes of cemented backfill at early-age

In view of the mechanics characteristic of cemented tailings backfill(CTB)at early age,the separation Hopkinson pressure bar test device was used to explore the effects of curing age and impact energy.A total of 48 CTB samples with diameter of 50 mm and length of 25 mm were prepared with curing ages of 3,5,7 and 9 d.Impact tests under different impact energy(10,20,30 and 40 J)were carried out.The microstructure of CTB at different ages was analyzed by scanning electron microscopy(SEM).The results show that,the curing age mainly affects the mechanical properties and internal structure of early-age CTB.With increasing curing age,the mechanical properties of early-age CTB change from viscoelasticity to brittleness.The impact energy mainly affects the response of dynamic peak compressive strength to strain rate.Under low strain rate,the structure of CTB is broken,but still has bearing capacity,affecting the formation of later strength.It is concluded that the structural loses completely under the action of high strain rate.Therefore,the control of impact energy and the protection of curing age should be fully considered in actual production process.

Experimental Study on Electric Properties of Carbon Fiber Reinforced Concrete

According to the phenomenon that the physical properties have,a great effect on the electric capability of carbon fiber reinforced concrete, the author researched the relationship between DC resistance of carbon fiber reinforced concrete and curing age using the two-probe method. Then the effect of insulative area, location and quantity on DC resistance of carbon fiber reinforced concrete was investigated at different curing age with analysis of hydration. The results suggest that DC resistance increases greatly with its curing age, which illustrates the relationship like Gaussian curve. In every curing ages the electric capability of carbon fiber reinforced concrete weakenes with the increase of insulative area. In same curing ages, section and insulative area, the more the quantity of insulation, the stronger the conductibility. The insulative location in optimal position can only result in optimal conductibility.