Considerations on the efficiency of Portland cement concrete mixtures based on the particle packing concept

ABSTRACT Concrete is the most widely used building material and, recently, studies have been developed in pursuit of materials with superior mechanical performance and durability. In order to cover the reality of the civil works regarding the on-site production of conventional and high strength concrete, several mix design methods are proposed. Although these methods allow obtaining the ideal proportion between the constituent materials of the mixture, it is possible to optimize the composition by applying the concept of particle packing. Therefore, this paper aims to measure the efficiency of the particle packing of Portland cement concrete mixtures widely used in civil construction´s practice, obtained by traditional mix design methods. For this, three concrete mixtures were produced using the traditional IPT/EPUSP mix design method, being two of conventional strength and one of high strength. By knowing the proportion and particle size distribution of the constituent materials of these concretes, the distribution´s coefficient of each mixture was determined considering Alfred´s particle packing model. Thereafter, maintaining the same distribution coefficient, the concrete mixtures were optimized by applying the particle packing concept, determining the physical and mechanical properties of the concrete. During the optimization process, there were gaps between the particle size distributions of the component materials normally considered in the production of concretes, characterizing a lack in packaging. Regarding the properties of the hardened concrete, the optimized mix design generally presented superior physical and mechanical properties than the reference concrete.

摘要 混凝土是目前应用最广泛的建筑材料，近年来相关研究均致力于开发力学性能与耐久性能更优异的建筑材料。为覆盖土木工程领域常规及高强度混凝土现场生产的实际场景，现有多种配合比设计方法被提出。尽管此类方法可实现混合料组分间的理想配比，但借助颗粒堆积理论可进一步优化混合料组成。本文旨在量化当前土木工程实践中广泛采用的、通过传统配合比设计方法制备的硅酸盐水泥混凝土混合料的颗粒堆积效率。为此，采用传统IPT/EPUSP配合比设计方法制备了三组混凝土混合料，其中两组为常规强度混凝土，一组为高强度混凝土。在明确上述混凝土各组分材料的配比与粒径分布后，基于阿尔弗雷德（Alfred）颗粒堆积模型计算各组混合料的分布系数。此后，在保持相同分布系数的前提下，通过应用颗粒堆积理论对混凝土混合料进行优化，并测定优化后混凝土的物理与力学性能。优化过程中发现，常规混凝土生产中常用的组分材料粒径分布存在间隙，即存在堆积缺陷。相较于基准混凝土，经优化的配合比设计方案通常可获得更优异的硬化混凝土物理及力学性能。