Densified silica fume: particle sizes and dispersion in concrete

Characterization of morphology and texture of several amorphous nano-silica particles used in concrete

“…For example, Diamond and Sahu [35] found that the agglomerates from micro-silica can be broken down into separated linked clusters of spheres, similar to the cluster identified in the present research, by sufficiently severe ultrasonic treatment. However, sintered spheres-spheres contacts are permanent.…”

“…The results of slump-flow tests on the pastes made with the micro-and nano-silica produced by different routes support this explanation. It was, furthermore, demonstrated, similarly to the present study for samples PmS-4 and PmS-6 that the nano-particles in silica powders are often in an aggregated (firmly-held clusters) or agglomerated (loosely-held clusters) form with a final cluster size from nanometers to as high as 100 lm due to their very high specific surface area [35]. Even in a well-dispersed colloidal dispersion, the nano-particles still exist as aggregates when they are incorporated into the highly alkaline environment that exists in the cement pastes [45].…”

“…Nevertheless, the production route also influences the aggregated state, as with the samples PmS-4, PmS-5 and PmS-6, which are produced at high temperatures. Consequently, the small particles are irreversibly clustered (sintered or welded), as was demonstrated by Diamond and Sahu [35] for similar type of silicas. This is evident in the particle size ranges determined by LLS (Table 3).…”

Intensified Pozzolanic Reaction on Kaolinite Clay-Based Mortar

“…Used SF (SiO 2 > 96.9%) has a density of 2.2 g/cm 3 and specific surface area of 200,000 cm 2 /g. In this study, the particle size distribution of SF was measured again using image-processing technique to correct its agglomeration effect during the laser diffraction measurement [35]. To obtain more accurate particle size distribution of SF, 20 SEM images containing total 3720 SF particles were analyzed under various magnifications (30,000×-100,000×).…”

Study of interfacial microstructure, fracture energy, compressive energy and debonding load of steel fiber-reinforced mortar

“…On top of that, some small microcracks that do not initiate from any pores are also seen in the ITZ or the bulk matrix in mortars with w/b 0.3 due to dessication. No agglomeration of silica fume was found in the specimens for both w/b [32]. Therefore, for the quantitative analysis of porosity and cement hydrates using the BSE-IA and the SEM-EDX, we selected the steel fiber that was located as far away as possible from any interaction of aggregate to avoid ITZ aureole and with no microcrack so that the intrinsic properties of the paste in the ITZ extending to the bulk matrix could be studied.…”