一年龄期内超高泵送SCC力学性能时变研究

Time Variation of Mechanical Properties of Ultra-High Pumped Self-Compacting Concrete Within One Year of Age

为揭示施工龄期内超高层建筑泵送自密实混凝土(SCC)轴心抗压强度、弹性模量以及劈裂抗拉强度等力学性能的时变规律,提供超高层建筑施工阶段力学性能分析的基础依据,依托某一超400 m高层建筑泵送SCC制作了120个试件,包括96个圆柱体件和24个立方体试件,并对其进行了不同时间龄期的力学性能测试,获取了超高层建筑泵送SCC的应力-应变曲线,提出了各力学性能指标时变及关系计算公式.研究结果表明:超高层建筑泵送SCC在免振条件下具有良好的密实性;随着龄期的增长,超高层建筑泵送SCC的峰值应力增大,且其峰值应变显著大于普通混凝土的;早期14 d内为各项性能增长的关键阶段,弹性模量在90 d后趋于稳定,而轴心抗压强度和劈裂抗拉强度在28 d后仍有大幅增长;龄期T≤60 d时,超高层建筑泵送SCC的轴压刚度随龄期增长呈增大趋势,而相对韧性则呈减小趋势,龄期T>60 d时,二者均变化较小趋于稳定;超高层建筑泵送SCC强度的提高能增快早期性能的发展,且能增大轴压刚度和相对韧性;提出的各力学性能指标时变计算公式能为超高层建筑泵送SCC的力学性能预测与评估提供可靠依据.

In order to reveal the time-varying laws of the axial compressive strength,elastic modulus and splitting tensile strength of the pumped self-compacting concrete(SCC)in super high-rise buildings during the construction period,and to provide a basis for mechanical performance analysis of super high-rise buildings in construction stage,120 specimens,including 96 cylindrical specimens and 24 cube specimens,were fabricated by pumping the SCC of a high-rise building over 400 m,their mechanical properties were tested at different ages,and the stress-strain curves of the ultra-high pumped SCC were obtained.Based on the tested results,formulas for calculating the time-varying relationship of the mechanical properties were proposed.The results show that the ultra-high pumped SCC has good compactness under vibration-free conditions.With the increase of age,the peak stress of the ultra-high pumped SCC increases,and the peak strain is significantly greater than that of ordinary concrete.The period of early 14 d is the key stage for the growth of various properties;the elastic modulus tends to stabilize after 90 d,while the axial compressive strength and split tensile strength still increase significantly after 28 d.When the age T≤60 d,the axial compressive stiffness of the ultra-high pumped SCC increases with time,while the relative toughness decreases.When T>60 d,both of them change little and tend to be stable.The improvement of strength of the pumped SCC in super high-rise buildings can accelerate the development of its early performance,and increase the axial compressive stiffness and relative toughness.The proposed calculation formulas of time-varying mechanical properties can provide a reliable basis for prediction and evaluation of mechanical performance of the pumped SCC in super high-rise buildings.