Rheological characterisation of clay-cement sealing suspensions with fractionated coal fly ashes
These videos have been matched automatically. Contact us if they are not relevant.
These videos have been matched automatically. Contact us if they are not relevant.
View abstract on PubMed
Summary
This summary is machine-generated.Fractionated coal fly ash significantly alters clay-cement slurry rheology. High-calcium ashes enhance sealing properties, while siliceous ashes improve pumpability, offering tailored solutions for sustainable geotechnical applications.
Area Of Science
- Geotechnical Engineering
- Materials Science
- Civil Engineering
Background
- Clay-cement suspensions are crucial for sealing applications in geotechnical and hydraulic engineering.
- Coal fly ash is a sustainable supplementary cementitious material, but its impact on rheology depends on its properties.
- Controlling slurry rheology is essential for effective placement and long-term performance.
Purpose Of The Study
- To investigate the influence of size-fractionated coal fly ash on the rheological behavior of clay-cement sealing suspensions.
- To understand the combined effects of fly ash chemistry (high-calcium vs. siliceous) and particle size on rheological properties.
- To identify optimal fly ash compositions for specific sealing applications, balancing rapid sealing and pumpability.
Main Methods
- Preparation of clay-cement suspensions with dry size-fractionated coal fly ashes (S1: high-calcium, S2: siliceous) in ultrafine, fine, and middle fractions.
- Rheological characterization using rotational and oscillatory rheometry to measure parameters like Bingham yield stress (τ₀) and storage modulus (G').
- Investigation of rheological response to sodium-silicate activation.
Main Results
- High-calcium (S1) fly ash fractions, especially ultrafine ones, significantly increased yield stress and storage modulus, indicating rapid structuration and sealing potential.
- Siliceous (S2) fly ash fractions dispersed the clay-cement network, reducing yield stress and maintaining moderate viscoelastic stiffness, enhancing pumpability.
- Particle fineness amplified chemical effects: S1.UF promoted early hydration, while S2.UF maintained fluidity.
- Sodium-silicate activation induced a sol-gel transition in S1 systems at low concentrations, while S2 systems showed a gradual response.
Conclusions
- Fly ash chemistry and particle size are critical design parameters for tailoring the rheology of low-cement sealing slurries.
- High-calcium, fine-fraction fly ashes are suitable for rapid sealing applications.
- Siliceous, fine-fraction fly ashes are effective for achieving long-distance pumpability.
- Fractionated fly ash offers a versatile tool for developing sustainable and high-performance sealing materials for hydraulic and geotechnical engineering.
These videos have been matched automatically. Contact us if they are not relevant.
These videos have been matched automatically. Contact us if they are not relevant.
Related Concept Videos
Hydration of cement is a chemical reaction between cement particles and water. This process occurs primarily through two mechanisms: through-solution and topochemical. In the through-solution process, anhydrous compounds dissolve into their constituents, hydrates form in the solution, and then precipitate from the supersaturated solution. The topochemical process involves solid-state reactions at the cement particle surface. The through-solution process dominates the topochemical process at the...
The soundness of cement refers to the ability of cement paste to retain its volume after setting. Unsound cement can lead to expansion and structural damage due to the presence of free lime, magnesia, and calcium sulfate. Free lime hydrates very slowly, expanding and causing unsoundness, which is difficult to detect because it intercrystallizes with other compounds. Magnesia also reacts with water, forming crystals that can disrupt the cement's structure. Calcium sulfate can create...
Portland cement is the essential binding ingredient in concrete, made from finely ground materials including lime, iron, silica, and alumina. Lime is derived primarily from limestone, marble, marl, seashells, and clays, which also supply iron and alumina, while silica is sourced from sand, chalk, and bauxite. Contemporary manufacturing of Portland cement is a significant source of carbon dioxide emissions, prompting research into reducing its content in concrete through alternative...
The fineness of cement directly influences the rate of hydration, as the hydration begins at the surface of the cement particles. In addition to hydration, the fineness of cement is vital for various properties of concrete including workability, gypsum requirement, and long-term behavior. The fineness of cement is represented in terms of the specific surface of cement which is typically measured in square meters per kilogram, with several methods available for this determination.
Direct...
Strength tests for cement are not performed directly on neat cement paste due to difficulty in obtaining consistent, reliable specimens. Instead, cement is typically tested in the form of cement-sand mortar.
For compressive strength tests, ASTM C 109-05 standards prescribe a cement-sand mix ratio of 1:2.75 and a water/cement ratio of 0.485 for making 2-inch cubes. These cubes are mixed, cast, and cured in saturated lime water at 23°C until testing. Flexural strength testing, outlined in...
Portland cement comes in several types, each with distinct properties and applications based on their chemical composition and hydration characteristics:
Type I (Ordinary Portland Cement) is widely used for general construction where special properties are not required. It has moderate sulfate resistance and heat of hydration.
Type II (Modified Cement) offers moderate resistance to sulfate attack and a lower rate of heat development compared to Type I. It is suitable for structures in...