The nanogranular nature of C–S–H

By Georgios Constantinides, Franz-Josef Ulm. 2007

880 citations recorded by the source corpus.

Abstract Despite its ubiquitous presence as binding phase in all cementitious materials, the mechanical behavior of calcium–silicate–hydrates (C–S–H) is still an enigma that has deceived many decoding attempts from experimental and theoretical sides. In this paper, we propose and validate a new technique and experimental protocol to rationally assess the nanomechanical behavior of C–S–H based on a statistical analysis of hundreds of nanoindentation tests. By means of this grid indentation technique we identify in situ two structurally distinct but compositionally similar C–S–H phases heretofore hypothesized to exist as low density (LD) C–S–H and high density (HD) C–S–H, or outer and inner products. The main finding of this paper is that both phases exhibit a unique nanogranular behavior which is driven by particle-to-particle contact forces rather than by mineral properties. We argue that this nanomechanical blueprint of material invariant behavior of C–S–H is a consequence of the hydration reactions during which precipitating C–S–H nanoparticles percolate generating contact surfaces. As hydration proceeds, these nanoparticles pack closer to center on-average around two characteristic limit packing densities, the random packing limit ( η = 64 % ) and the ordered face-centered cubic (fcc) or hexagonal close-packed (hcp) packing limit ( η = 74 % ), forming a characteristic LD C–S–H and HD C–S–H phase.

Subfields: Ceramics and Composites, Civil and Structural Engineering, Mechanics of Materials

View Paper: https://www.semanticscholar.org/paper/5b3b0b8af51ffc86b574660bbc6b6ae8b7bd804f

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Ceramics and Composites

1. M. Vandamme
2. Franz-Josef Ulm
3. Zongjin Li
4. Chuanlin Hu
5. H. Brouwers
6. C. Bobko
7. Y. Abousleiman
8. R. Pellenq

In Civil and Structural Engineering

1. H. Brouwers
2. Zongjin Li
3. P. Spiesz
4. Chuanlin Hu
5. R. Yu
6. Franz-Josef Ulm
7. M. Vandamme
8. Jeffrey J. Thomas

In Mechanics of Materials

1. Franz-Josef Ulm
2. M. Vandamme
3. Zongjin Li
4. Chuanlin Hu
5. Y. Abousleiman
6. J. A. Ortega
7. Philip Fonollosa
8. C. Bobko

Citations in the corpus

• A review on the mechanical properties of cement-based materials measured by nanoindentation (2015, methodology): “Thus, statistical nanoindentation technique was widely used in cement-based materials [5,6,8–10,12,28,30,31,39,40,47,48,57–60, 72,74,89,91–94,97,100,101,109,110].”
• Pore structure characterization of cement pastes blended with high-volume fly-ash (2012, background): “Moreover, with hydration process the LD C–S–H can progressively change into HD C–S–H [41,42].”
• Statistical indentation techniques for hydrated nanocomposites: concrete, bone, and shale (2007, methodology): “[27];[28];[5];[7];[3];[6] For such a disordered porous material system, linear micromechanics provides the following relations for the dimensionless indentation modulus function (10):[3] M (rs; ; 0 = 1=2) = G (9 rs + 4G + 3rs) (3rs + 4) 4 (4G + 3rs) (3rs + 1) (12)”
• Micromechanical investigation of Portland cement paste (2014, background): “14 SNT Constantinides and Ulm [9] HD 29.”
• Long-term creep properties of cementitious materials: Comparing microindentation testing with macroscopic uniaxial compressive testing (2014, methodology): “In order to measure mechanical properties of individual phases of heterogeneous materials, the indentation technique proves to be well-suited [6,7,30,36,20,21].”
• Physical Origins of Thermal Properties of Cement Paste (2015, background): “[16] Georgios Constantinides and Franz-Josef Ulm, The nanogranular nature of C-S-H, J.”