Papers by Keyword: Gneiss

Abstract: Two polyphase gneiss samples (Western Alps, Switzerland) consisting of quartz, albite, muscovite and microcline have been investigated with respect to anisotropic physical properties - residual and applied strain - and crystallographic preferred orientations. The samples were taken in close vicinity to a fault structure. For texture evaluation the 'Rietveld texture analysis' has been applied, because reliable texture analysis of polyphase rocks from pole figures is problematic due to multiple peak overlaps. The quartz textures of both samples are strong and rather similar, whereas albite and microcline show a nearly random distribution. In contrast, the mica texture is pronounced and complex. The basal plane normals of muscovite are preferably oriented parallel to [-direction of the structural reference frame and switch to [-direction with residual orientations in [ and a transition into the [-[-plane within the fault. This might be the result of quartz recrystallization, if mica is used as reference according the applied stress field. A residual strain scan has been carried out along the axis of a cylindrical sample (d = 30 mm, l = 60 mm). Residual strain values of quartz have been detected with a minimum of-1.6×10^-3, and maximum strain values of 1.2×10^-3. Uniaxial compression experiments in discrete steps up to 53 MPa were performed, for each step the applied and residual strains were determined. The strain increases up to 28 MPa; surprisingly, lower strain values are detected at higher applied stresses.

Abstract: Bitumen pavement suffers from moisture damage mainly due to loss of durability and stability in a short span of service life. Filler is known to be capable of increasing the stiffness of bitumen binder, contributing to improvement of moisture sensitivity of bitumen mixture. In this paper a new type of filler named 'Compound Fly Ash Modifier' (CFAM) was introduced in order to enhance the bond strength between acidic aggregate with bitumen. The primary object is to determine the effect of CFAM on the moisture sensitivity of bitumen mixtures prepared by gneiss and granite respectively, which are termed acidic aggregate. Modified Lottman test and fatigue test were conducted. The results show that CFAM improves the resistance of mixes to moisture damage in the increase in indirect tensile strength and the extension of fatigue life. Finally the mechanism of modified effects for CFAM is discussed.

Abstract: The use of gneiss as aggregates might help meet the pavement constructing demands. However, the study of the pavement performances of gneiss asphalt mixture is few. In this paper, the microstructure of gneiss aggregate was studied by Scanning Electron Microscopy (SEM). And the pavement performances of gneiss asphalt mixture with different improving measure were characterized by means of Indirect Tensile Strength Test and Four-Point Bending Fatigue Test. Gneiss is flaky, surface texture rougher and imporosity characteristic in microstructure, resulting to its adhesion and processing property are poor. Experiment results indicate that the use of hydrated lime replacing limestone power partly in filler can improve pavement properties of the gneiss asphalt mixtures distinctly.

Abstract: Construction of the pavement has consumed a huge amount of high grade aggregates, such as basalt, limestone etc. In some region, these aggregates are very scarce and have to be produced and transported from far aggregate quarries which would cause the waste of energy and resources as well as the increase of cost. Large quantities of gneiss exist in China, the use of gneiss as aggregates might help meet the highway constructing demands and save. In this paper, the feasibility is analyzed with respect to different aspects. Physical properties of gneiss aggregate were evaluated using Los Angeles abrasion, specific gravity and flakiness index. Mixture properties were characterized in terms of Marshall stability, moisture susceptibility, soak wheel track and low temperature cracking resistance property. Experiment results indicate that the physical properties of gneiss aggregates can satisfy the related specifications and these gneiss materials as aggregates can be used in asphalt pavement. Results also show that the optimal gradation component of the mixture consists of the gneiss as coarse aggregate and the limestone as fine aggregate. The use of hydrated lime can improve the moisture susceptibility of the mixtures containing gneiss aggregates.