基于颗粒最紧密堆积理论的超高性能混凝土配合比设计

Mix Design of Ultra-High Performance Concrete Based on Particle Densely Packing Theory

针对修正的Andreasen-Andersen(MAA)颗粒堆积模型设计超高性能混凝土(UHPC)时会存在两个弊端,(即未验证湿堆积状况下的可靠性、未考虑钢纤维掺入对颗粒堆积体系的扰乱),采用二次饱和D-最优化模型和钢纤维等效颗粒直径模型对其进行优化与完善,并利用UHPC材料性能对提出的新思路进行反向验证。结果表明:基于建立的湿堆积密实度二次饱和D-优化设计模型有效验证了MAA模型在湿堆积状态下的适用性和可靠性;同时,通过评价钢纤维和等效替代颗粒对湿堆积密实度的影响,确定了长13 mm、直径0.2 mm的钢纤维的等效颗粒直径为5.65 mm;将钢纤维以球形颗粒的形式纳入MAA模型中,可以制备出基体密实、抗压强度较高的UHPC材料。

There are two inherent drawbacks in designing ultra-high performance concrete(UHPC) by the modified Andreasen-Andersen(MAA) model, i.e., unproven reliability under wet conditions and ignorance of disturbing effect of steel fiber on particle packing skeleton. In this work, the D-optimal mixture design model and the equivalent spherical diameter of steel fires were adopted to verify and optimize the MAA model, and the properties of the optimized UHPC were utilized to verify the feasibility of the new proposed method. The results reveal that the MAA model is also suitable to be utilized under wet conditions. Moreover, the equivalent spherical diameter of steel fibers(L=13 mm, d=0.2 mm) is 5.65 mm, which is determined by evaluating the effect of screening particles and steel fibers on wet packing density. In addition, the employed steel fibers that are treated as spheroidal particles can be implanted into the MAA model for the optimized design of new UHPC, which has a densely packing structure and an admirable compressive strength.