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This article presents, for the first time, the study of diabases from various ophiolite complexes from Greece and Cyprus to identify their performance as concrete aggregates. Within this scope, in the first step, diabase samples from four selected ophiolite complexes of Greece (Veria-Naousa, Edessa and Guevgueli) and Cyprus (Troodos) were collected in order to estimate their suitability as concrete aggregates by means of their petrographic and physicochemical characteristics. In the next step, concrete specimens were prepared and their mechanical strength was measured in order to investigate their mechanical performance. Additionally, their petrographic characteristics in relation to the mechanical strength of the created concretes were investigated for the first time. Concrete specimens prepared by employing diabases from the Veria-Naousa and Guevgueli complexes as aggregates were reckoned as the most durable ones in contrast to those derived from the Edesssa complex and even more so than those from Cyprus, with the latter containing the most altered diabases (rodingitised). The overall conclusion of this research is that the engineering properties of the aggregates were dependent on their petrographic characteristics and hence they influenced the final mechanical behaviour of each produced concrete. [ABSTRACT FROM AUTHOR]

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 (nt (%)), 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. [ABSTRACT FROM AUTHOR]

The sustainable use of agricultural, industrial and human waste products as raw materials in the construction industry has been extensively investigated. This study aimed to conceive an innovative concrete composition mainly using recycled materials, which, as a result as waste from human activities and natural organic growth, such as animal bones and human hair, will be used in different mixtures in order to prepare concrete specimens. More specifically, the effect of these materials upon the final concrete strength was investigated, as well as how their petrographic characteristics may influence the durability of concrete specimens. Special emphasis was placed on the effect of the artificial increase in bone and hair microroughness and how these can improve the mechanical strength of the final product. The research results point towards the fact that the percentage of the replacement of natural aggregate rocks by animal bones tends to be enhanced by the increase in their microroughness using quartz primer. In addition, the use of bones with increased artificial microroughness and a certain percentage of human hair with increased microtopography seems to be the ideal mixture for the replacement of natural aggregates for the production of normal concrete. [ABSTRACT FROM AUTHOR]

This case study investigates the influence of the mineralogical composition of ultramafic rocks derived from two ophiolite complexes from Greece (Veria-Naousa and Gerania) on their mechanical, physical and physicochemical properties. The investigated lithologies include lherzolite, harzburgite, dunite and olivine-orthopyroxenite with variable degrees of alteration. The ratio of secondary minerals to primary minerals (SEC/PR) of the studied ultramafic rocks shows good correlations with their physical, physicochemical and mechanical properties, suggesting that alteration has a negative effect on the engineering performance of the ultramafic rocks. Among the secondary minerals, serpentine plays the most critical role in determining the moisture content, the total porosity and hence the soundness of the host rocks, due to its phyllosilicate structure, which allows more water/solutions to be captured. The high percentage of serpentine creates surfaces of weakness, and as a result, it decreases the rock strength. The low microtopography of highly serpentinized rocks results in their reduced mechanical performance. [ABSTRACT FROM AUTHOR]

This study aims at the interpretation of the adverse effects of the secondary products in two types of rocks during their performance as concrete aggregates. Serpentinised peridotites contain serpentine, as the dominant secondary phase, which creates low microroughness on the particles and therefore unfavorable surfaces for cement paste to adequately adhere to. Moreover, its soft and platy nature contributes to the development of platy defects along the contacts of the aggregate particles with the cement paste. Poor adherence of the paste, failures along the contacts of the aggregate particles and potential propagation of the defects into the concrete during curing (and perhaps subsequently in-service) explain the poor performance of highly serpentinised rocks as concrete aggregates. Andesites show a different composition with a variety of secondary products including albite, chlorite, calcite, Fe-oxides and clay minerals. The role of all these products was investigated and it appears that only smectite is important, as even small amounts of it may be detrimental to the quality of the rocks as concrete aggregates. It is likely that abnormal hydration reactions and considerable swelling of the smectite result in the appearance of defects in the concrete, hence contributing to its low performance. [ABSTRACT FROM AUTHOR]