Nanoindentation characteristics of calcium hydroxide-metakaolin blended with sodium hydroxide solutions

Abstract

In order to determine the active mechanism of metakaolin (MK) as partial replacement of cement in concrete from the nanoscale structure perspective, nanoindentation characteristics of calcium hydroxide (CH)-MK blended with 5 M sodium hydroxide (NaOH) solutions simulating the condition of MK in concrete has been studied. The results indicate that three distinct phases are found by the nanoindentation and BSE tests, such as HD C-S-H gel, LD C-S-H gel and the reaction products with the network structure, the residual unreacted MK and CH, respectively. The volume fraction of HD C-S-H gel is about 96% of all reaction product phases. This means that the use of MK in concrete can increase the volume fraction of HD C-S-H gel and thus will improve the properties of concrete.

Keywords

nanoindentation / metakaolin / calcium hydroxide / C-S-H gel / elastic modulus

References

[1] Rafat S, Juvas K Influence of Metakaolin on the Properties of Mortar and Concrete: A Review[J]. Applied Clay Science, 2009, 43: 392-400.

[2] Sabir B B, Wild S, Bai J Metakaolin and Calcined Clays as Pozzolans for Concrete: A Review[J]. Cement & Concrete Composites, 2001, 23: 441-454.

[3] Love C A, Richardson I G, Brough A R Composition and Structure of C-S-H in White Portland Cement-20% Metakaolin Pastes Hydrated at 25 °C [J]. Cement and Concrete Research, 2007, 37: 109-117.

[4] Vikas S, Rakesh K, Agarwal V C, . Effect of Silica Fume and Metakaolin Combination on Concrete [J]. International Journal of Civil and Structural Engineering, 2012, 2(3): 893-900.

[5] Mehmet G Influence of Steam Curing on the Properties of Concretes Incorporating Metakaolin and Silica Fume[J]. Materials and Structures, 2010, 43: 1 123-1 134.

[6] Paramita M, Surendra P S, Laurence D M, . Comparative Study of the Effects of Microsilica and Nanosilica in Concrete [J]. Journal of the Transportation Research Board, 2010, 10: 6-9.

[7] Jiří N, Vít Lubomír K Nanoindentation Characteristics of Alkaliactivated Aluminosilicate Materials [J]. Cement & Concrete Composites, 2011, 33: 163-170.

[8] Silva P S D, Glasser F P Hydration of Cements Based of Metakaolin: Thermochemistry [J]. Advances in Cement Research, 1990, 12: 167-177.

[9] Santiago A, Angel P Calorimetric Study of Alkaline Activation of Calcium Hydroxide-metakaolin Solid Mixtures [J]. Cement and Concrete Research, 2001, 31: 25-30.

[10] Maria L G, Santiago A, Maria T B, . Alkaline Activation of Metakaolin: Effect of Calcium Hydroxide in the Products of Reaction [J]. Journal of the American Ceramic Society, 2002, 85: 225-231.

[11] Oliver W C, Pharr G M R An Improved Technique for Determining Hardness and Elastic Modulus Using Load and Displacement Sensing Indentation Experiments[J]. Journal of Materials Research, 1992, 7: 1 564-1 583.

[12] Wang X H, Jacobsen S, He J Y, . Application of Nanoindentation Testing to Study of the Interfacial Transition Zone in Steel Fiber Reinforced Mortar [J]. Cement and Concrete Research, 2009, 39: 701-715.

[13] Constantinides G, Chandran K S R, Ulm F J, . Grid Indentation Analysis of Composite Microstructure and Mechanics: Principles and Validation[J]. Materials Science and Engineering A, 2006, 430: 189-202.

[14] Constantinides G, Ulm F J The Nanogranular Nature of C-S-H [J]. Journal of the Mechanics and Physics of Solids, 2007, 55: 64-90.

[15] Matthieu V, Ulm F J, Fonollosa P Nanogranular Packing of C-S-H at Substochiometric Conditions [J]. Cement and Concrete Research, 2010, 40: 14-26.

[16] Chen J J, Sorelli L, Vandamme M, . A Coupled Nanoindentation/SEM-EDS Study on Low Water/cement Ratio Portland Cement Paste: Evidence for C-S-H/Ca(OH)₂ Nanocomposites [J]. Journal of the American Ceramic Society, 2010, 93(5): 1 484-1 493.

[17] Allen A J, Thomas J J, Jennings H M Composition and Density of Nanoscale Calcium-silicate-hydrate in Cement[J]. Nature Materials, 2007, 6(4): 311-316.