Research Articles | Challenge Journal of Concrete Research Letters

Characterization of Calcium Hydroxide (CH) crystals in Nano Modified Binder (NMB)

Norsuzailina Mohamed Sutan, Ibrahim Yakub, Sinin Hamdan, Chuo Sin Kiong

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Abstract


With the advent of nanotechnology, such nano scale materials have been developed for the application in binding material namely cement.A new synthetic material, namely Nano-SiO2(nS), has been produced and available in the market. It is based on silica particles of 5-50 nm which is much smaller than those of silica fume (microsilica) with particles of 0.1-1 μm. Previous studies have shown that due to the very high specific surface area (80-1000 m2/g) and the spherical shape of silica particles,it can potentially enhance the performance of cement mainly due to its reaction with calcium hydroxide (CH) to develop more of the strength-carrying compound in cement structure namely calcium silica hydrate (C-S-H). This reaction namely pozzolanic reaction is crucial in the mitigation of efflorescence by its relation to CH leaching. The early hydration behaviour of a Nano Modified Binder (NMB) that hypothetically affects efflorescence has been investigated through physicochemical characterization namely Puddle Test (PT), Standard Chemical Method (SCM), Compressive Strength Test (CS), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). NMB mortar samples were prepared with water-to-cement ratio (w/c) of 0.50. nS of 10-20 nm particle size was used as 2%, 3% and 5% replacement of cement by weight. Samples were cured at room temperature (32o C) and average relative humidity (90%). Powdered and polished samples were prepared and tested at 28 days of binder hydration. Results from CS, XRD analysis and SEM images show that compare to conventional binder, NMB exhibited a lesser efflorescence where validation from CS, XRD analysis and SEM images show the evidence of the pozzolanic reaction.

Keywords


Nano-SiO2; Efflorescence; pozzolanic; XRD; SEM

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