Influence of microstructure on the physical properties of self-curing concrete

During the development of "self-curing" concrete, it has been found that one particular self-curing admixture used produces a number of effects with respect to particular physical properties and powder x-ray diffraction characteristics. This paper attempts to explain these observations at a microstructural level Two computer models are used to illustrate the influence the admixture is thought to have on hydrated cement microstructure. At low dosages, good strength and improved permeability characteristics are observed. At high dosages, it appears that the admixture has a detrimental effect on the concrete's compressive strength due to an alteration of the nature of calcium hydroxide at the cement-aggregate interface. However, it seems that at the same dosages the CSH gel structure is altered beneficially, producing a highly impermeable concrete. It is suggested that although a lowering of strength does occur at high dosage, a much lower permeability for a given strength can be obtained.