Analysis of Hydration Mechanism and Microstructure of Composite Cementitious Materials for Filling Mining

To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum（CS）. The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO4 completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.

Temperature and strain registration by fibre-optic strain sensor in the polymer composite materials manufacturing

The presence of process-induced strains induced by various manufacturing and operational factors is one of the characteristics of polymer composite materials(PCM).Conventional methods of registration and evaluation of process-induced strains can be laborious,time-consuming and demanding in terms of technical applications.The employment of embedded fibre-optic strain sensors(FOSS)offers a real prospect of measuring residual strains.This paper demonstrates the potential for using embedded FOSS for recording technological strains in a PCM plate.The PCM plate is manufactured from prepreg,using the direct compression-moulding method.In this method,the prepared reinforcing package is placed inside a mould,heated,and then exposed to compaction pressure.The examined technology can be used for positioning FOSS between the layers of the composite material.Fibre-optic sensors,interacting with the material of the examined object,make it possible to register the evolution of the strain process during all stages of polymer-composite formation.FOSS data were recorded with interrogator ASTRO X 327.The obtained data were processed using specially developed algorithms.

Viscoelastic behavior of nanotube-filled polycarbonate:Effect of aspect ratio and interface chemistry

A combined experimental and modeling study on the solid-state rheology of multi-walled carbon nanotube(MWNT)/polycarbonate composites as a function,independently,of MWNT aspect ratio and interface chemistry was carried out.Shorter aspect ratio nanotubes lead to greater broadening of the loss modulus peak in frequency space,but there was no effect of aspect ratio on the glass transition temperature.The breadth of the loss modulus peak was found to correlate with the free space parameter,a measure of the spacing between the MWNTs.A new model that accounts for the aspect ratio and distribution in a representative volume element was developed to study these parameters in a controlled setting where morphology was precisely known.Micromechanics modeling was found to correlate well with experimental data.These results shed light on the separate impacts of aspect ratio,dispersion,and interface modification on the solid-state rheology of nanofilled polymers.