Relationship between differences in silica fume additives and fine-scale microstructural evolution in cement based materials

Allen, Andrew J.; Livingston, Richard A.

doi:10.1016/s1065-7355(98)00015-7

Cited by 43 publications

(35 citation statements)

References 34 publications

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“…temperature curing, but the surface fractal scattering is more prominent with heat curing. This is indicative of a more heterogeneous microstructure, where the original cement grains do not blend smoothly into the outer hydration product [8]. This is consistent with observations of denser hydration product [9,10] and lower strength [11] in heat cured pastes.…”

Section: Small-angle Scattering Measurementssupporting

confidence: 87%

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A multi-technique investigation of the nanoporosity of cement paste

Jennings

Thomas

Gevrenov

et al. 2007

Cement and Concrete Research

363

140

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The nanometer-scale structure of cement paste, which is dominated by the colloidal-scale porosity within the C-S-H gel phase, has a controlling effect on concrete properties but is difficult to study due to its delicate structure and lack of long-range order. Here we present results from three experimental techniques that are particularly suited to analyzing disordered nanoporous materials: small-angle neutron scattering (SANS), weight and length changes during equilibrium drying, and nanoindentation. Particular attention is paid to differences between pastes of different ages and cured at different temperatures. The SANS and equilibrium drying results indicate that hydration of cement paste at 20°C forms a low-density (LD) C-S-H gel structure with a range of gel pore sizes and a relatively low packing fraction of solid particles. This fine structure may persist indefinitely under saturated conditions. However, if the paste is dried or is cured at elevated temperatures (60°C or greater) the structure collapses toward a denser (less porous) and more stable configuration with fewer large gel pores, resulting in a greater amount of capillary porosity. Nanoindentation measurements of pastes cured at different temperatures demonstrate in all cases the existence of two C-S-H structures with different characteristic values of the indentation modulus. The average value of the modulus of the LD C-S-H is the same for all pastes tested to date, and a micromechanical analysis indicates that this value corresponds to the denser and more stable configuration of LD C-S-H. The experimental results presented here are interpreted in terms of a previously proposed quantitative "colloid" model of C-S-H gel, resulting in an improved understanding of the microstructural changes associated with drying and heat curing.

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Section: Small-angle Scattering Measurementssupporting

confidence: 87%

“…1) can be fit with a model that includes appropriate terms for the volume and surface fractal scattering described above [6,8]. Here we focus on the volume fractal regime of the data (associated with the C-S-H gel), in which the scattered intensity varies as Q…”

Section: Small-angle Scattering Measurementsmentioning

confidence: 99%

A multi-technique investigation of the nanoporosity of cement paste

Jennings

Thomas

Gevrenov

et al. 2007

Cement and Concrete Research

363

140

View full text Add to dashboard Cite

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“…The kinetics of surface area development are similar in nature to the kinetics of the total heat evolution (see Figure 1 inset), confirming that CaCl 2 stimulates the formation of a greater amount of C-S-H hydration product at a given time during the early hydration period. Additional parameters related to the microstructure development of these pastes can be obtained by applying a previously developed fractal microstructure model 4,[21][22][23] to the SANS data over almost the entire accessible q-range. The model describes three separate scattering regimes present in the data.…”

Section: Analysis Of Hydration Kineticsmentioning

confidence: 99%

Hydration Kinetics and Microstructure Development of Normal and CaCl₂-Accelerated Tricalcium Silicate Pastes

2009

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Microstructure development and the kinetics of hydration of pure tricalcium silicate (C 3 S) and CaCl 2 -accelerated C 3 S pastes were investigated by performing isothermal calorimetry and in situ small-angle neutron scattering (SANS) measurements on parallel specimens during the first few days of hydration, as well as on 28-day old specimens hydrated under the same curing conditions (water/cement ratio ) 0.5, 20°C). Calorimetry experiments were also performed over a range of hydration temperatures from 10 to 40°C. The calorimetry data were analyzed by applying a previously described boundary nucleation and growth model. The model indicates that CaCl 2 significantly increases the rate of nucleation of hydration product on the surface of the C 3 S particles but has relatively little effect on the product growth rate. The SANS measurements indicate that the composition and density of the calcium-silicate-hydrate (C-S-H) nanoparticles is unchanged by the addition of CaCl 2 . However, in the CaCl 2 -accelerated paste the surface fractal scattering associated with the deposition of hydration product onto the initially smooth surfaces of the C 3 S particles rapidly declines in intensity and essentially disappears by the age of 1 day, while in the pure C 3 S paste the surface fractal scattering remains prominent throughout the hydration process. The key observations from both the calorimetry and SANS analysis can be explained if in a pure C 3 S paste the C-S-H hydration product forms initially with a low packing density and then densifies at later times.

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“…At that time the concept of surface fractals was introduced by Bale and Schmidt [7] when analyzing the surface of pores of lignite. Nevertheless, in a further work [8] the authors improved the interpretation of cement SANS data and included the concept of surface fractals as well. In that paper, surface and volume fractals were used for assessing effects of silica fume additives upon the development of the microstructure of cement-based materials.…”

Section: Sas Techniquementioning

confidence: 99%

“…Previous SANS studies [6,8,13] repeatedly highlighted their basic building role in forming the gel nano-structure. Although their existence is experimentally well evidenced, their own inner structure and properties remain almost un-Brought to you by | MIT Libraries Authenticated Download Date | 5/9/18 7:27 PM explored.…”

Section: Research Objectivesmentioning

confidence: 99%

A remark on nano-particle stability of cement C-S-H gel

Ficker¹,

Len²,

Martišek³

2011

Open Physics

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Abstract:Hydrated pastes of ordinary Portland cement prepared with different water-to-cement ratios were investigated by using the small-angle neutron scattering technique in the region of Q ∈ (0 0045 0 11) Å −1 . Samples of cement pastes were subjected to non-standard hydration conditions using a mix with D 2 O, low RH, and water-to-cement ratios spread over a very wide interval (0.4; 1.4). The investigation was focused on testing the structural stability of nano-metric particles in the cement C-S-H gel. Owing to the high structural stability of these nano-particles, their average diameter might be used as a microscopic parameter characterizing the nano-metric structure of C-S-H gels. The average diameter of the nano-particles of the studied ordinary Portland cement CEMI 42.5 R-SC was found to be close to the value of 4.2 nm and independent of the water-to-cement ratios. PACS

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Relationship between differences in silica fume additives and fine-scale microstructural evolution in cement based materials

Cited by 43 publications

References 34 publications

A multi-technique investigation of the nanoporosity of cement paste

A multi-technique investigation of the nanoporosity of cement paste

Hydration Kinetics and Microstructure Development of Normal and CaCl₂-Accelerated Tricalcium Silicate Pastes

A remark on nano-particle stability of cement C-S-H gel

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Relationship between differences in silica fume additives and fine-scale microstructural evolution in cement based materials

Cited by 43 publications

References 34 publications

A multi-technique investigation of the nanoporosity of cement paste

A multi-technique investigation of the nanoporosity of cement paste

Hydration Kinetics and Microstructure Development of Normal and CaCl2-Accelerated Tricalcium Silicate Pastes

A remark on nano-particle stability of cement C-S-H gel

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Product

Resources

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Hydration Kinetics and Microstructure Development of Normal and CaCl₂-Accelerated Tricalcium Silicate Pastes