This paper reports on a study of physical properties of lightweight cement composite. We investigate the possibility of replacing traditional aggregate with Granulated Ash Aggregate (GAA) and above all with Granulated Expanded Glass Aggregate (GEGA). For this purpose, 15 specimens of different percentage share of each aggregate in total aggregate volume were tested: 0%, 25%, 50%, 75% or 100% of foam glass aggregate (GEGA) partially replaced by ash aggregate (GAA) content in the cement composite. The water-cement ratio was constant and equal to w/c=0.5. Three grain sizes were analyzed: 2mm, 4mm (both GEGA) and 8mm (GAA). Numerical simulations of concrete specimen behavior under static loading were conducted with the implementation of elastic plastic model of each component. The study shows a significant impact of grain type and size on physical properties of lightweight concrete. Due to lower density of foamed glass aggregate, specimens shows various apparent density and porosity, which affect concrete properties. Compressive strength of concrete decreases with the increase in foam glass aggregate content; however specimens show different workability and in consequence porosity of lightweight concrete.

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High requirements for the properties of construction materials and activities directed at environment protection are reasons to look for new solutions in concrete technology. This research was directed at solutions affecting the reduction of energy consumption and CO2 emissions. The use of lightweight concretes (LWCs) allows one to meet both conditions at the same time. The purpose of the research presented in this paper was to investigate the abilities of using lightweight aggregates (LWAs) of the following types: 2 and 4 mm granulated expanded glass aggregate (GEGA) as ingredients with excellent insulating properties and 8 mm granulated fly ash aggregate (GAA) as an ingredient with a relatively high resistance to crushing. The influence of the percentage participation of each aggregate in all LWCs was variable and amounted to 0%, 25%, 50%, 75%, and 100%. A series of 15 LWC mixes were prepared for various LWA participations and for a constant water–cement ratio (w/c = 0.5). Concrete tests were carried out for the following criteria: density, porosity, compressive strength, and the modulus of elasticity. In order to fully analyze fracture processes in LWCs with the participation of GEGA and GAA and to assess the correctness of the results obtained during the experiments, numerical models that corresponded to both geometrical and load diagrams of elements under research were created. The numerical analyses of the LWCs were conducted by means of the conventional finite element method (FEM).

ObjectiveThe purpose of this study was to evaluate the influence of a change in the meniscus cross sectional shape on its position and on the biomechanics of a knee joint.MethodsOne main finite element model of a left knee joint was created on the basis of MRI images. The model consisted of bones, articular cartilages, menisci and ligaments. Eight variants of this model with an increased or decreased meniscus height were then prepared. Nonlinear static analyses with a fixed flexion/extension movement for a compressive load of 1000 N were performed. The additional analyses for those models with a constrained medio-lateral relative bone translation allowed for an evaluation of the influence of this translation on a meniscus external shift.ResultsIt was observed that a decrease in the meniscus height caused a decrease in the contact area, together with a decrease in the contact force between the flattened meniscus and the cartilage. For the models with an increased meniscus height, a maximal value of force acting on the meniscus in a medio-lateral direction was obtained. The results have shown that the meniscus external shift was approximately proportional to the meniscus slope angle, but that relationship was modified by a medio-lateral relative bone translation. It was found that the translation of the femur relative to the tibia may be dependent on the geometry of the menisci.ConclusionsThe results have suggested that a change in the meniscus geometry in the cross sectional plane can considerably affect not only the meniscal external shift, but also the medio-lateral translation of the knee joint as well as the congruency of the knee joint.