Abstract
It is well known that hydration and hardening of Portland cement are associated with complicated physical and chemical processes, in particular the interaction of clinker minerals with water to form new hydrate phases of different composition. Sometimes the presence of various substances can affect these processes leading to self-destruction of the hydrated cement stone. The morphology and composition of damaged cement stone modified with an additive and with a nanoscale aluminum oxide were studied. It is shown that in the presence of the ‘Linamix PC’ plasticizer and a nanoscale aluminum oxide, well-crystallized Ca(OH)2 plates with an average thickness of 1.5 microns and a length and width equal to 300–400 microns are formed. Also, a network of thread-like ettringite with a diameter of less than 1 micron on the surface of microcracks of cement stone is formed. Most likely the cement stone sample could be damaged by the forces of crystallization pressure during the growth of both Ca(OH)2 and ettringite crystals.
Highlights
Hydration and hardening of Portland cement is a complex of physical and chemical processes that is accompanied by the formation of hydrate phases when clinker minerals interact with water
For a more detailed study micrographs of cement stone were made with the determination of the chemical composition at some points
The morphology of the samples and their chemical composition were studied using a JEOL JSM-6390LA scanning electron microscope equipped with an 'EDS Inca Enegy 250’ X-ray spectrometer
Summary
Hydration and hardening of Portland cement is a complex of physical and chemical processes that is accompanied by the formation of hydrate phases when clinker minerals interact with water. Ettringite is the first stable hydration product that is formed by the reaction of C3A, calcium sulfate (gypsum) and water [1, 4]. It is reported in [2, 4,5,6,7] that plasticizer molecules are usually adsorbed primarily on the surface of both C3A and new formed ettringite. This leads to a change in its morphology.
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