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

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.