青藏高原气候环境对混凝土强度和抗渗性的影响

为了研究青藏高原气候环境对混凝土性能的影响，在高原和平原地区完成相同配比混凝土的制备与养护工作，并结合强度、抗渗性、气孔结构、显微硬度以及扫描电镜与原子力显微镜分析等测试对比研究混凝土性能的差异，从宏观、细观和微观多个角度揭示高原气候条件对混凝土性能与内部结构带来的影响与作用机理。结果表明：高原地区制备且标准养护组混凝土的抗压强度与抗渗性都最优，其次是平原地区制备且标准养护组，高原地区制备且室外自然养护组性能最差；低气压导致混凝土拌合物含气量降低和工作性下降；高原标准养护下硬化混凝土含气量最低，平均孔径最小，而高原室外自然养护下硬化混凝土含气量最大，平均孔径最大；高原地区制备的混凝土，在标准养护条件下界面过渡区密实程度最高，结构均匀，其显微硬度最大，而室外自然养护条件下界面过渡区密实程度最差，微裂纹密布，结构粗糙，其显微硬度最小；而高原地区制备且室外自然养护条件下，混凝土气孔结构参数和界面过渡区微结构整体最差，以上原因的综合作用给混凝土力学和抗渗性带来极为不利的影响。总体来讲，青藏高原气候环境对混凝土性能的负面影响主要源于室外养护条件，而非制备过程。

Impact of Qinghai-Tibet Plateau's Climate on Strength and Permeability of Concrete

To explore the impact of the Qinhai-Tibet plateau's climate on the performance of concrete, the processes relating to the preparation and curing of concrete were completed and simulated on the plateaus and plains. Furthermore, the difference in concrete performance was studied by combining the tests of strength, impermeability, pore structure, micro-hardness, scanning electron microscopy, and atomic force microscopy. The influence and mechanism of high altitude climate conditions on concrete performance and internal structure were revealed with respect to macroscopic, mesoscopic, and microscopic aspects. The test results show that the compressive strength and impermeability of the concrete, prepared on the plateau, and cured under the standard condition are the best, followed by that prepared on the plain under similar conditions. The group prepared on the plateau and cured outdoor under natural environmental conditions have the worst performance. Low air pressure leads to the reduction of air content and workability of the concrete mixture. Hardened concrete cured under the standard condition on the plateau has the lowest air content and smallest average pore size. In contrast, the hardened concrete cured outdoors has the highest air content and largest average pore size. The interfacial transition zone (ITZ) of concrete, cured under standard conditions, on the plateau has the highest density, the least pore distribution, a uniform structure, and the greatest micro-hardness. In contrast, the ITZ of concrete cured outdoors has the worst density, the most micro-cracks, a rough structure, and the smallest micro-hardness. The poor pore structure of concrete combined with the deterioration of the microstructure in the ITZ has an extremely unfavorable effect on the mechanical and impermeability to the concrete prepared on the plateau and cured outdoor under natural environmental conditions. In general, the negative effect of the climate on the concrete performance in the Qinghai-Tibet plateau is mainly due to outdoor curing conditions rather than the preparation process.