Particle packing density models have allowed for enhancing infrastructure performance and durability through optimized solid structure of concrete ingredients. However, the widespread applications of the theoretical packing models in industrial practices are still limited due to the complexity of the theoretical packing models. This session discusses the recent advancements in the packing models with emphasis on practical approaches for mixture proportioning. Attendees will understand the theoretical background and mechanisms behind optimized packing density, including advancements in numerical and analytical modelling, industry practices, and tools available for aggregate packing optimization. Also, successful application of theoretical packing models in optimizing mixture proportioning of various types of concrete will be presented.
(1) Define various experimental and analytical approaches of particle packing density;
(2) Identify the impact of particle packing on rheology and workability of fresh concrete;
(3) Enhance material and durability aspect of concrete through aggregate optimization;
(4) Implement particle packing optimization approaches in mixture proportion design.
This session has been AIA/ICC approved for 2 CEU/PDH credits.
Drying Shrinkage and Cracking Tendency of Concrete Pavement Mixtures with Variable Packing Densities of Aggregates and Paste Contents
Presented By: Jan Olek
Affiliation: Purdue University
Description: Excessive drying shrinkage, and associated cracking, can lead to serious durability problem in concrete pavements and bridges. The presentation will describe the study which was conducted in order to explore the potential to transition from prescriptive to performance-based specifications for concrete pavements. An essential part of such transition process would be the ability to optimize the composition of concrete mixtures to enhance the performance characteristics of pavements, especially with respect to durability. In the course of this study, the magnitude of drying shrinkage and cracking potential was evaluated for several concrete pavement mixtures as a function of packing density of the aggregate and paste contents. The results indicated that both, the shrinkage and the cracking potential, depend on the volume of voids between aggregate particles (packing density), paste content of concrete mixture, and the paste-aggregate void saturation ratio.
Optimizing Concrete Mixtures for Performance and Sustainability Through Improved Aggregate Packing
Presented By: Karthik Obla
Description: The presentation will discuss the outcome of a study with the following objectives. 1. Develop a new approach to experimentally determine the combined aggregate voids content with good precision. 2. Experimentally evaluate a model that determines the combined aggregate voids content based on packing theory. 3. Determine a correlation between the optimum combined aggregate void content and paste volumes for mixtures for optimum performance.
Investigation of Concrete Workability Through Characterization of Aggregate Gradation in Hardened Concrete Using X-Ray Computed Tomography
Presented By: Tyler Ley
Affiliation: Oklahoma State University
Description: This presentation will show how existing 3D packing models have challenges predicting the workability of concrete in laboratory testing. This work shows that the parameters in the Tarantula Curve correlate to workability and the actual packing in concrete. The actual packing of aggregates in concrete is measured by using 3D X-ray CT scanning. This work provides important data that can be used to improve future packing models to improve aggregate properties.
Effective Reduction of Cement Content in Concrete Mixtures Based on Theoretical and Experimental Particle Packing Methods
Presented By: Jiong Hu
Affiliation: University of Nebraska-Lincoln
Description: The effective reduction of cement content in concrete without compromising its fresh, mechanical, and durability properties can lead to more economical and sustainable pavement engineering. Because a reduction in cement content in concrete can be achieved by improving the particle packing of aggregates, this study attempted to improve a practical mix design procedure based on both theoretical and experimental particle packing methods. In this study, optimum aggregate blends were first identified using the Modified Toufar Model, which indicated a good correlation with the experimental packing results based on a combined void content test. Successful examples of the approach used for slipform pavement concrete, bridge deck concrete and fiber-reinforced concrete are presented.
The Use of Continuous Particle Packing Models (PPMs) to Mix- Proportion Eco-Efficient Concrete with Suitable Fresh and Hardened State Properties
Presented By: Leandro Sanchez
Affiliation: University of Ottawa
Description: Concrete, the major construction material used in the construction industry worldwide, presents a huge environmental impact producing about 7% of the global carbon dioxide. Given the concerns related to global warming, studies have been focusing on distinct approaches aiming to reduce the amount of Portland cement (PC), which is the least sustainable ingredient of the mixture, by adopting alternative mix-design strategies such as the use of particle packing models (PPMs). However, there is currently a lack of data on the efficiency of the use of continuous PPMs to reduce PC while maintaining or improving concrete fresh and/or hardened properties. This work aims to investigate the impact of current and modified versions of continuous PPMs on the fresh (rheological behavior) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state of mixtures designed with low and moderate amounts of PC and inert fillers. Results demonstrate that eco-efficient concrete may be produced through current and modified continuous PPMs without compromising the fresh and hardened properties of the material. Nevertheless, further durability and long-term investigations must be performed on systems with reduced PC contents.
Theoretical Particle Packing Models in Practice
Presented By: Nicolas Ali Libre
Affiliation: Missouri University of Science Tech
Description: Despite the benefits of solid particle optimization in concrete, the widespread application of the theoretical packing models in industrial practices is still limited due to the complexity of the theoretical packing models. This presentation discusses the recent advancements in the packing models with emphasis on numerical tools for mixture proportioning. The accuracy of the theoretical packing models in predicting the void content is verified through an extensive experimental program. Practical approaches will be presented and discussed for a successful application of theoretical packing models to achieve optimum performance in the fresh and hardened concrete.