不同期龄塑性混凝土力学性能试验研究

对养护期龄为7,14,28,90 d的塑性混凝土进行三轴压缩试验,实测不同围压状态下试件的应力-应变曲线及强度参数,分析不同养护期龄及试验围压对强度、应力-应变关系的影响。试验结果表明:塑性混凝土在低围压时表现出软化性,破坏偏应力与破坏应变较小,随着围压提高塑性混凝土应力应变曲线软化趋势减弱,并且随着围压的提高其破坏偏应力显著提高。塑性混凝土在不同围压下均表现出先剪缩后剪涨的特点,且随着围压升高其剪缩的趋势增大剪涨的趋势减小。双曲线模型参数K值随养护期龄的发展而增大,双曲线模型参数n、F、破坏比Rf值随养护期龄的发展而减小。相同养护期龄内塑性混凝土破坏偏应力随围压的增大而增大,相同围压下其破坏偏应力随养护期龄的发展而增大。凝聚力随期龄发展而增大,内摩擦角受养护期龄变化影响较小。

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.

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.

Study on influence factors of cement-stabilized soil compressive strength

The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.