In the last post, I explained the clear definition of different densities. Among these densities, bulk density and apparent density are the two most important values when performing mercury intrusion porosity (MIP) experiment.
Since samples that undergo MIP are usually irregular, the bulk volume is not possible to measure without being immersed in liquid. By the help of MIP, the bulk volume can be measured, thus the bulk density can be calculated simply dividing the mass by bulk volume.
The hydration kinetics of slag is generally divided into three stages: (1) a nucleation period during which product growth is accelerating, (2) a phase boundary controlled stage, and (3) a diffusion controlled stage.
The reaction degree of slag in blended cement is influenced by many factors. The main factors affecting the reaction of slag in blended system include the reactivity of slag that could be defined as (C+A+M)/S, the fineness of grinding (specific surface area), the vitreous fraction of slag, the replacement level of slag in blended system, the hydration temperature and the water/solids ratio.
Many XRD analysis results have shown the main hydration products of slag blended cement are essentially similar with that of pure Portland cement, except the amounts of CH found by this method or other are in varying degrees and less than those that should be given by the pure Portland cement constituent if the slag part did not participate the reaction.
Though the chemical reaction of the fine particles of limestone in cement paste is limited to a low extent due to its inert property, the addition of limestone particles has significant effect on the microstructure development. Research conducted by Sellevold et al. using mercury intrusion method showed that specimens containing 12% CaCO3, which have the main body of the particles smaller than 0.1 µm had finer pore structure and somewhat reduced total pore volume.
The extent of reaction of limestone with cement clinkers is relatively low than the corresponding values of cement clinkers, the probable cause for this as stated above arise from the low solubility and low reactivity of limestone particles, though other factors of limestone, including fineness, particle size distribution, etc., do have influence on its reaction degree in blended system.