基于最紧密堆积理论的超高性能混凝土配比设计

Mix proportion design of ultra-high performance concrete(UHPC)based on closest packing theory

实际生产过程中,超高性能混凝土(UHPC)的配制及性能往往受到原材料品质波动的制约。为此,基于最紧密堆积理论,采用改进Andreasen模型和最小二乘拟合算法,对现有UHPC基体中的粉料材料最紧密堆积配比进行了计算。随后参考计算结果设计了不同UHPC配比,用最大固相含量法测试了不同配比UHPC基体的堆积密度,根据相关标准测试了各个配比UHPC的力学性能、收缩性能,采用化学结合水法对胶凝材料水化程度进行了测试,采用SEM对基体3 d和28 d龄期的微观形貌进行了分析。结果表明:根据最紧密堆积理论进行配比设计,UHPC中的水泥用量大幅降低;优化后不同配比UHPC及其基体的力学性能与最大固相含量法测试的结果相吻合,得到的UHPC基体最大抗压强度为136.1MPa。总而言之,结合最紧密堆积理论和最大固相含量法进行UHPC配比设计,可以克服材料局限性,得到水泥用量较少并且性能更优的UHPC配比。

In the actual production process,the preparation and performance of ultra-high performance concrete(UHPC)are often restricted by the raw material quality.Therefore,based on the closest packing theory,the improved Andreasen model and the least square fitting algorithm were used to calculate the closest packing ratio of powder in the existing UHPC matrix.Then different UHPC mix proportions were designed according to the calculation results.The bulk density of UHPC matrix with different mix proportions was tested by maximum solid loading method.The mechanical properties and shrinkage properties of UHPC with different mix proportions were tested according to relevant standards.The hydration degree of cementing materials was tested by chemical combined water method,and the micro-morphology of the matrix at 3 d and 28 d was analyzed by scanning electron microscope.The results showed that the cement content in UHPC decreased significantly according to the proportion design based on the closest packing theory.The mechanical properties of UHPC and its matrix with different proportions after optimization were consistent with the test results of maximum solid loading method,and the maximum compressive strength of UHPC matrix was 136.1 MPa.In summary,UHPC proportion design based on the closest packing theory and the maximum solid loading method can overcome the limitations of materials and obtain UHPC proportion with less cement content and better performance.