SEM investigation of microstructures in hydration products of portland cement
نویسندگان
چکیده
Portland cement is the one of the main ingredients in the manufacture of many building materials include concrete composites. The phase composition of hydration products is controlled by means of XRD and DTA/TG analysis. Observations of phase changes and microstructure of maturing cement pastes can also be observed using scanning electron microscopy (SEM) techniques combined with chemical analyzes in microareas (EDS analysis). Hydrating in time cement paste is composed mainly of hydrated silicates of calcium so called C-S-H-phase accompanied with a calcium hydroxide (portlandite) and hydration products of calcium aluminate i.e. ettringite. SEM analysis of changes in the morphology and microstructure of cement pastes allow to track the hydration progress observed mainly by changes in the C-S-H phase. The initial stages of hydration of this phase is characterized by radial concentration of fibers or needles, often narrowed at the ends. This fibers grow from the surface of the cement grains. The increase in the degree of C-S-H structure orientation is shown by formation of fibers lattice, sometimes three-dimensional plates so called "honeycomb", which is transformed into the form of a closely-packed, isometric grains. In addition, besides CS-H cement phase investigation, scanning electron microscopy can also be applied to observation of the crystals formation of tobermorite, ettringite and relicts of portlandite, that often can’t be detected by XRD and DTA/TG due to their small amount in mineral composition of concrete.
منابع مشابه
Effect of FeSO4.7H2O and SnCl2.2H2O added as Chromium (VI) Reducers in Ordinary Portland Cement
The paper compared the effect of additives such as FeSO4.7H2O and SnCl2.2H2O on reduction of water soluble Cr(VI), in ordinary Portland cement (43 grades). The determination of water soluble Cr(VI) from cement samples was precisely conducted by DPC-Spectrophotometer technique. The compressive strength testing of the cement mortar samples was carried out. In addition, hydration properties of cem...
متن کاملInteraction of tartaric acid during hydration of Portland cement
Hydration of Ordinary Portland cement (OPC) in the presence of tartaric acid has been studied by using different techniques. Calorimetric studies have shown a rapid enhanced heat evolution within 5 min of hydration in presence of 1.0 wt% tartaric acid with a strong retardation of silicate phase hydration. DSC and X-ray diffraction studies have confirmed the formation of calcium tartarate hydrat...
متن کاملHydration mechanisms of mineral trioxide aggregate.
AIM To report the hydration mechanism of white mineral trioxide aggregate (White MTA, Dentsply, Tulsa Dental Products, Tulsa, OK, USA). METHODOLOGY The chemical constitution of white MTA was studied by viewing the powder in polished sections under the scanning electron microscope (SEM). The hydration of both white MTA and white Portland cement (PC) was studied by characterizing cement hydrate...
متن کاملHydration Study of Ordinary Portland Cement in the Presence of Zinc Ions
Hydration products of Portland cement pastes, hydrated in water and in the presence of zinc ions were studied comparatively at different ages. Hydration products were studied by X ray diffractions (XRD) and infrared spectroscopy (IR). Although IR is not frequently used in cement chemistry, it evidenced a new phase Ca(Zn(OH) 3 ) 2 . 2H 2 O formed during cement hydration in the presence of zinc. ...
متن کاملDetermining the water - cement ratio , cement content , water content and degree 1 of hydration of hardened cement paste : Method development and validation on 2 paste samples
7 We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) 8 of hardened cement-based materials made with Portland cements that have unknown mixture proportions and 9 degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the 10 volumetric fractions of capillary pores, hydration products and unr...
متن کامل