The Impact of Secondary Phyllosilicate Minerals on the Engineering Properties of Various Igneous Aggregates from Greece

Abstract

This paper investigates the effect of alteration on the physicomechanical properties of igneous rocks used as aggregates, from various areas from Greece. The studied lithologies include serpentinized dunites, serpentinized harzburgites, serpentinized lherzolites, metamorphic gabbros, diabases, dacites and andesites. Quantitative petrographic analysis shows that the tested samples display various percentages of secondary phyllosilicate minerals. Mineral quantification of the studied rock samples was performed by using the Rietveld method on X-ray diffraction patterns. The samples were also tested to assign moisture content (w (%)), total porosity (n t (%)), uniaxial compressive strength (UCS (MPa)) and Los Angeles abrasion test (LA (%)). The influence of secondary phyllosilicate minerals on the physicomechanical behavior of the tested samples was determined using regression analysis and their derived equations. Regression analysis shows a positive relationship between the percentage of the phyllosilicate minerals of the rocks and the moisture content as well as with the total porosity values. In mafic and ultramafic rock samples, the relationships between the secondary phyllosilicate minerals and their physicomechanical properties have shown that the total amount of the secondary phyllosilicate minerals results negatively on their physicomechanical properties. On the other hand, the low percentage of phyllosilicate minerals in volcanic rocks can't be able to define their engineering properties.

Does the Methylene Blue Test Give Equally Satisfactory Results in All Studied Igneous Rocks Relative to the Identification of Swelling Clay Minerals?

“…Petrounias et al [12] have proved that minor amounts of smectite (<3%) in andesites can cause failures and detachments of the aggregates from the cement paste, thus significantly reducing the final strength of the produced concretes. In general, the influence of phyllosilicate minerals, both in the form of swelling and non-swelling types, has been a subject that concerned many researchers (e.g., References [19,28]), because they have a significant effect upon the engineering properties of rocks that are used as aggregates and hence on the applications in which they participate. The influence of swelling phyllosilicate mineral types is understandable by engineering application scientists.…”

The Effect of Petrographic Characteristics and Physico-Mechanical Properties of Aggregates on the Quality of Concrete

“…In this process, olivine and pyroxene transform to serpentine, a laminate soft mineral that belongs to the phyllosilicate subclass of minerals and forms smooth surfaces [10,51,52]. The influence of serpentine on the aggregate strength as well as on the final compressive strength of concrete specimens has been investigated by several researchers [10,17,46,53,54].…”

“…For the same quality cement, different lithotypes of coarse aggregates characterized by different micro-roughness, mineralogical composition, structure and compressive strength may result in different concrete compressive strength [10,11].Mineralogical composition of the aggregates, and more specifically their alteration degree, strongly influence their mechanical behavior and their in-service performance [10,[12][13][14][15][16][17]. Increased percentages of certain secondary minerals negatively affect the physical, as well as the mechanical properties of aggregates due to their smooth layers, cleavage and platy or fibrous crystal habit [10,17], which have an adverse effect on their performance as concrete aggregates [10]. The increased number of construction failures has highlighted the importance of understanding that mineralogy is a mean to diagnose problems in engineering constructions.…”

The Effect of Petrographic Characteristics and Physico-Mechanical Properties of Aggregates on the Quality of Concrete

“…Τhe mineralogical composition of the aggregates and more specifically their alteration degree strongly influence their mechanical behavior and their in-service performance [10,[12][13][14][15][16][17]. Increased 2 of 21 percentages of certain secondary minerals affect negatively the physical, as well as the mechanical properties of aggregates due to their smooth layers, cleavage and platy or fibrous crystal habit [10,17]. The increased number of construction failures has highlighted the importance of understanding that mineralogy is a mean to diagnose problems in engineering constructions.…”

“…Physicomechanical properties depend on the petrographic characteristics (mineralogical composition, texture, size, shape and arrangement of mineral grains, nature of grains contact, and degree of grain interlocking), alteration and deformation degree of the source rock [18][19][20][21][22]. Τhe mineralogical composition of the aggregates and more specifically their alteration degree strongly influences their mechanical behavior and their in-service performance [10,[12][13][14][15][16][17]. Increased percentages of certain secondary minerals affect negatively the physical, as well as the mechanical properties of aggregates due to their smooth layers, cleavage and platy or fibrous crystal habit [10,17], which definitely have an adverse effect on their performance as concrete aggregates [10].…”