Due to their small size and large surface area, nanoparticles are susceptible to agglomeration without appropriate handling. Proper dispersion is essential. This session is to share insights and key outcomes from a recently completed State-of Art report developed by ACI Committee 241, and it will focus on discussions on (1) the available techniques, such as high-energy mechanical mixing or chemical dispersants, for dispersing nanomaterials in cement-based materials, (2) characterization methods for the degree of the dispersion, and (3) effects of dispersion on material properties, including cement hydration, workability, strength, and durability of nanoparticle-modified concrete. It is expected that this session will help foster more efficient use of nanoparticles in sustainable concrete applications.
Learning Objectives:
(1) Discover available techniques for nanoparticle dispersion in cement-based systems;
(2) Understand how nanoparticle dispersion influences cement hydration and overall concrete performance;
(3) Explore practical methods for achieving uniform dispersion and characterizing dispersion quality;
(4) Realize the key issues, benefits, and challenges in nanoparticle dispersion and practical applications.
Techniques for Achieving Effective Nanoparticle Dispersion
Presented By: Pengkun Hou
Affiliation: University of Jinan
Description: Effective dispersion of nanoparticle is a critical factor governing their influences on the performance of cementitious materials. Various techniques have been explored to disperse nanoparticles, including mechanical dispersion, chemical dispersion and other methods, which aim to separate agglomerated solid nanoparticles and generate stable interfaces between the liquid dispersion medium and nanoparticles surface. This talk systematically summarizes and discusses the advantages and limitations of the most practical dispersion techniques, including mechanical milling, intensive mixing, sonication, use of dispersants, and in-situ nCaCO3 formation. The effectiveness of these dispersion methods strongly depends on the physicochemical properties of the nanoparticles, and combinations of multiple techniques are required to achieve enhanced and stable dispersion in cementitious materials. In addition, HRWRA has demonstrated effectiveness in the dispersion of nanoparticles when combined with other methods, particularly during pre-dispersion stages, as well as enabling the desired workability. This review could provide practical guidance for optimizing nanoparticles dispersion strategies in nano-modified cementitious materials.
Methods for Characterizing Nanoparticle Dispersion and Stability
Presented By: Yogiraj Sargam
Affiliation: IIT Jodhpur India
Description: Nanoparticles offer significant potential to enhance the properties of cementitious systems; however, their widespread adoption is often hindered by challenges in achieving uniform dispersion. While effective dispersing agents and techniques are essential for improving nanoparticle stability and distribution, equally critical is the ability to characterize the degree of dispersion within both suspensions (aqueous and cement) and hardened cement matrices. This presentation will provide an overview of analytical techniques commonly employed to evaluate nanoparticle dispersion and stability, discussing their underlying principles, sample requirements, sample preparation challenges, and respective advantages and limitations. Techniques spanning sensing (optical), light scattering (e.g., DLS, SAXS), and microscopic (e.g., SEM, TEM) approaches will be explored, with examples drawn from recent cement and concrete research. The presentation aims to stimulate discussion among researchers and practitioners on best practices and emerging methodologies for nanoparticle characterization in cementitious systems.
Effects of Nanoparticle Dispersion on Fresh Properties of Cement-Based Materials
Presented By: Jae Hong Kim
Affiliation: KAIST
Description: Assessing nanoparticle dispersion in hydrating cement is challenging due to the lack of real-time observation techniques. Reported studies in this section have demonstrated that the dispersion of nanoparticles can profoundly influence the early age cement hydration, setting, water demand, and rheological properties of the resulting cement-based materials. A multitude of mechanisms at play encompass water adsorption, surface charge interactions, seeding and filler effects, as well as alterations in the viscosity of fresh mixtures, leading to reduced particle segregation. Proficient comprehension and control of these factors are imperative for optimizing both the water-to-cement ratio and water content, thereby ensuring the desired performance of nanoparticle-modified cement-based materials. Poor dispersion of nanoparticles may compromise the uniformity of the concrete mix, disrupt cement hydration process, result in material inconsistent properties, and diminish the benefits associated with nanoparticles use.
Effects of Nanoparticle Dispersion on Hardened Material Properties and Durability
Presented By: Shiho Kawashima
Affiliation: Columbia University
Description: It has been well documented that nanoparticles can improve the physical, mechanical, and durability-related properties of cement-based materials by filling fine pores, providing seeding sites for the nucleation of cement hydration products, and interacting with cement-based materials through processes such as pozzolanic reactions. However, reported work that focuses specifically on the aspect of nanoparticle dispersion and its impact on hardened concrete properties is limited. This is largely because of the complex interactions between nanoparticles and cement-based materials and the inability to effectively characterize nanoparticle dispersion within the cement matrix. This talk will provide a review of reported work that has investigated the impact of dispersion on resultant hardened properties, including strength, pore structure, and shrinkage, and highlight research needs in this area.
Nanoparticles in Concrete Practice: Case Studies and Observations
Presented By: Gilson Lomboy
Affiliation: Rowan University
Description: The transition of nanotechnology from the laboratory to the job site represents a critical step forward for the construction industry. Moving nanoparticles from the controlled environment of a laboratory to real-world field applications is the critical "bridge" that turns scientific discovery into societal benefit. While a lab can prove a concept, the field proves its viability, durability, and scalability. The presentation will provide case studies on the implementation and observed performance benefits of colloidal silica (CS), nanotitanium dioxide (nTiO2), and nanoclay (nClay) in field pavement applications. CS was applied to an airfield pavement with the goal of improving concrete mechanical properties. The nTiO2 was on a two-lift construction with a focus on air quality testing. The nClay was used in developing semi-flowable concrete for slipform paving. The presentation will include information on dispersion, incorporation in concrete, construction, and their effects on fresh and hardened properties.
Outlook of Nanoparticles in Cement-Based Materials
Presented By: Konstantin Sobolev
Affiliation: University of Wisconsin-Milwaukee
Description: The future research on nanoparticles in cement-based materials will transfer existing laboratory studies toward integrated nanoparticle incorporation in multifunctional, intelligent, and sustainable cementitious systems. Large-scale implementation will depend on resolving dispersion challenges, reducing cost, and establishing reliable performance under field conditions. Moving beyond current findings, this presentation will discuss the future direction of the field, emerging opportunities, and remaining challenges.