Dynamic testing of the sub-base layer made from foam concrete using light weight deflectometer

Foam concrete (FC) is little used material in construction practice and it has very good potential for utilization in the civil engineering and building construction. Nowadays, it is primarily used as a leveling layer in the floor of the buildings, but its utilizability is much wider because of its particular properties. Its main characteristics are its material property and that it consists of void pores. This allows to achieve the low bulk density and saving of material inputs. As a building material, it has adequate mechanical characteristics and low thermal conductivity. A series of dynamic testing using light weight deflectometer (LWD) was carried out to estimate the reliable value of the dynamic deformation modulus that can represent the quality of the sub-base made from foam concrete beside the bulk density investigation. Static strain moduli from the second load cycle is the common required value for the sub-base design. Due to larger stiffness and thus larger deflection radius, conventional PLT apparatus is not suitable for foam concrete testing. On the other hand, when adequate dynamic modulus based on the conventional strain modulus is determined, LWD testing is quick method for the foam concrete testing. This paper presents the first attempts to estimate this relation

Numerical Approach to Pile Load Test Using 3D Finite Element Method

Despite the various design approaches, the design of the pile foundations is still to be verified by the in-situ load tests to check the design stage assumptions. This paper presents the results of the study aimed at the soil properties and interaction between piles and soil. Calibration of the numerical model is based on the in-situ pile load test. It represents the case study, how variation of soil characteristics acting in interaction with pile and numerical technics can attain the coinciding results with tested outputs. Moreover, this study is contribution to the effort of designing the pile foundations more accurately with limiting occurrence of potential risks

Experimental and computational dynamic analysis of the foam concrete as a sub-base layer of the pavement structure

Dynamic properties of the new materials represent the actual problem, which is solved at many departments in the world at this time. Foam concrete (FC) is a material that has wide application in the civil engineering structures. Currently, it's mainly used in the floor structures of the buildings but its usability can be much wider thanks to its specific properties. The foam concrete contains closed air pores, what achieves its low volume weight (density) and saving of material inputs. It's a building material with good mechanical properties and low thermal conductivity and at the same time with high-tech processing. Nowadays, a research aimed at the application of the foam concrete in the pavement structures takes place at the University of Zilina. Foam concrete could be utilized as a sub-base layer at the road reconstructions, excavations or as a regular layer of the new constructed pavements. The submitted paper is dedicated to the numerical simulation based on the Finite element method (FEM) in pursuance of the outputs of the experimental investigation of the dynamic effect on the pavement structure which contains the foam concrete layer. Obtained dynamic parameters will be a background for the pavement design using the foam concrete

Experimental and computational dynamic analysis of the foam concrete as a sub-base layer of the pavement structure

Dynamic properties of the new materials represent the actual problem, which is solved at many departments in the world at this time. Foam concrete (FC) is a material that has wide application in the civil engineering structures. Currently, it's mainly used in the floor structures of the buildings but its usability can be much wider thanks to its specific properties. The foam concrete contains closed air pores, what achieves its low volume weight (density) and saving of material inputs. It's a building material with good mechanical properties and low thermal conductivity and at the same time with high-tech processing. Nowadays, a research aimed at the application of the foam concrete in the pavement structures takes place at the University of Zilina. Foam concrete could be utilized as a sub-base layer at the road reconstructions, excavations or as a regular layer of the new constructed pavements. The submitted paper is dedicated to the numerical simulation based on the Finite element method (FEM) in pursuance of the outputs of the experimental investigation of the dynamic effect on the pavement structure which contains the foam concrete layer. Obtained dynamic parameters will be a background for the pavement design using the foam concrete

Osseointegration of resorbable magnesium screws – A SRμCT Study

The development of resorbable osteofixation materials that degrade upon substitution by regenerated tissue is highly desirable in orthopaedics. Magnesium is promising as implantable material, because of its biocompatibility, osteoconductivity and biodegradation under physiological conditions [1]. Through the selection of alloying elements, the mechanical properties and corrosion behaviour of magnesium can be modulated for application in load-bearing situations. The aim of our research was to investigate the bone integration and the corrosion process of Al-free Mg-alloys in vivo. Our hypothesis was that Mg-based implants stimulate bone growth.METHODS: Mini-screws of two different Mg- alloys, Mg10Gd and Mg-Y-RE (WE43) were manufactured at HZG. The cytocompatibility of the selected alloys was formerly tested and validated in vitro [2, 3]. The mini-screws were implanted in rats after ethical approval. After 1 and 3 months of healing, cylindrical bone-implant blocks were retrieved. Samples were imaged at the P05 Imaging Beamline (IBL) operated by HZG at PETRA III – DESY (Hamburg). We used monochromatic X-rays at 25 keV to take 900 projections and a field of view of 7mm x 1.8 mm, which resulted in 5X magnification with a resolution of ~2.5 μm. 3D data sets were computed using filtered back projection algorithms.RESULTS: The inserted implants healed without any observable adverse effect. On the basis of tomographic data, we were able to compute three- dimensional renderings of dvrscrews and bone with high contrast-to-noise ratios. A qualitative evaluation of the data revealed inhomogeneous surface corrosion of the screws, which maintained their original shape within the study period. New bone formation was observed in all of our samples. We found a considerable increase of implant-bone contact sites with progressing healing time. A quantitative analysis of the tomographic data indicated spatial differences in bone density. In proximity of the implant, newly formed bone matured and became dense after 3 months.Top: Horizontal (left) and vertical (right) sections of a screw after 3 months of healing. Fragments of implants, completely integrated in the bone, are visible. Bar 0.25 mm. Bottom: Orthogonal cut planes (left) and volume rendering (right), showing an implant (gray) into the bone (purple).DISCUSSION & CONCLUSIONS: The SRμCT showed osseointegration of Mg10Gd and WE43. Although the spatial resolution was not sufficient to fully elucidate the alloys microstructure, we observed the distribution of the high absorbing regions in the materials, possibly intermetallic phases and Y or RE oxides. The corrosion of the alloys was slow. Biocompatibility of the tested materials was confirmed by bone growth in intimate contact with the implants.REFERENCES: 1 Witte F,2 et al (2005) Biomaterials 26:3557-3563. Feyerabend F, Fischer J, et al (2010) Acta Biomater. 6:1834-1842. 3Johnson I, et al. H (2011) JBMR-A.ACKNOWLEDGEMENTS: Founding from the People Programme (Marie Curie Actions) Seventh Framework Programme FP7/2007-2013/ under REA grant agreements n° 289163 and n° 312284