Abstract Three nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.

中文翻译：

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通过加入纳米碳酸钙提高蒸压混凝土的碳化和氯化物抗性

摘要 在蒸压混凝土中使用了三种纳米 CaCO3 (NC) 替代水平，分别为 1%、2% 和 3%（按水泥重量计）。在 28、90、180 和 300 天龄时定期测试硬化混凝土的加速碳化深度和库仑电通量。此外，还通过X射线衍射、热重法和压汞孔隙率法研究了水泥水化产物和混凝土微观孔隙结构在高压釜固化下的变化。结果表明，适当水平的NC置换可发挥充填和加速作用，促进水泥水化产物的产生，降低孔隙率，细化蒸压混凝土的微孔。这些效果显着提高了蒸压混凝土的碳化和氯化物抵抗力，并使材料具有接近或超过标准固化混凝土的抵抗力。在三种NC替代比例中，3%的NC替代是提高混凝土长期抗碳化和耐氯化性的最佳用量。