Liu S.-J.,Hebei University of Science and Technology |
Li H.,Hebei University of Science and Technology |
Li H.,Institute of Building Materials |
Liu H.-J.,Hebei University of Science and Technology |
And 2 more authors.
Journal of Adhesion Science and Technology | Year: 2013
In this paper, a new polymer-modified adhesive mortar is prepared using the fine iron tailings, eco-cement, redispersible latex powder, additives, and water. In our study, the fine iron tailings are used to replace the natural river sand as the mortar aggregate and the optimal process conditions are determined by the orthogonal experiment. The obtained results are shown as follows: The ratios of cement-sand and polymer-cement are 1:2.5 and 4%, respectively, with the aggregate modulus 0.81 and water reducing agent 0.5% (cement-based). The properties of the polymer-modified adhesive mortar obtained under the optimal process conditions conform to JC/T 547-2005 (China Professional Standard: Ceramic Tile Adhesive). Moreover, the microstructure of the polymer-modified adhesive mortar is studied and discussed. The results show that the network formed by the intertwined polymer film can prevent the merger of micro-cracks and improve the adhesive mortars overall cohesion. Therefore, adding polymer to the adhesive mortar can improve its failure stress and enhance its bonding strength. © 2013 Taylor and Francis Group, LLC.
Hosser D.,Institute of Building Materials |
Hohm V.,Institute of Building Materials
Fire Safety Journal | Year: 2013
The application of numerical fire simulations to validate and to evaluate the propagation of fire and smoke is already a fundamental part of the preparation of fire protection or safety concepts, especially in the field of performance-based designs. Against this background, the GFPA-guideline "Ingenieurmethoden des Brandschutzes"  has been developed in the recent years, which describes and classifies the available possibilities, approaches and models as well as provides suitable support for their application. Those programs and models respectively have to provide reliable results on the one hand and have to be efficient on the other hand. Thus, it is mandatory to continuously improve and extend the available possibilities of numerical fire simulations also in the future to satisfy the rising requirements as sufficiently as possible. There is extensive need for improvement in numerical fire simulations especially in the field of heat transfer, both between the gas phase and the solid phase and within the solid phase itself. So far, the focus of further developments has mainly been on the modelling of the gas phase as well as pyrolysis and burning processes. In contrast to this, the physical processes of both convective heat transfer, in particular in the context of special configurations such as pipes or ducts (e. g. air ventilation ducts), and multidimensional heat conduction in solids have not been sufficiently accounted for so far. Hence, a heat transfer model for coupled processes in fire simulations was developed, which is able to represent the process of convective heat transfer between the gas phase and the solid phase for both horizontal and vertical, plane surfaces and in particular pipe and duct flows on the one hand and the process of heat conduction within multidimensional problems on the other hand physically correct. In addition to this the model is able to reproduce corresponding results using numerical simulation. The model was optimised both physically, by considering the specific fire effects and characteristics, and numerically, by selecting adequate numerical methods, for the integrated usage within numerical fire simulations. It has a modular design, so it is suitable for integration into current and future fire simulation codes. Additionally, a basis was established with and within this model for a later expansion with appropriate pyrolysis models. For that, an interface is provided with the embedded source term on the one hand and the required multidimensional temperature fields are determined precisely by the model on the other hand. A for the completion and demonstration concluding necessary integration of the developed heat transfer model for coupled processes into a state-of-the-art fire simulation code was exemplarily and successfully performed by means of the "Fire Dynamics Simulator" in its present and current version 5 . Finally, the model was successfully applied amongst others to real scale fire tests in the context of nuclear facilities within the international OECD PRISME project. In summary, the state-of-the-art was expanded with the heat transfer model developed and integrated into an internationally recognised CFD fire simulation code. Additionally, an important step was made on the way towards a fully coupled fire simulation imaginable in the future for instance for the purpose of the fire protection design of structures. Beyond that, the developed model can also make a valuable contribution in other fields, where extensions and improvements are still necessary in the future, in particular in upgrading pyrolysis models. Finally, the present possibilities in numerical fire simulations were expanded with the developed model also in such fields, where calculations in fact are performed at this stage, whereas the applicability of the present and available models or the transferability of their constituents is however questionable or even incorrect. © 2013 Elsevier Ltd.
Eggersdorfer M.L.,Institute of Process Engineering |
Kadau D.,Institute of Building Materials |
Herrmann H.J.,Institute of Building Materials |
Pratsinis S.E.,Institute of Process Engineering
Langmuir | Year: 2011
Multiparticle sintering is encountered in almost all high temperature processes for material synthesis (titania, silica, and nickel) and energy generation (e.g., fly ash formation) resulting in aggregates of primary particles (hard-or sinter-bonded agglomerates). This mechanism of particle growth is investigated quantitatively by mass and energy balances during viscous sintering of amorphous aerosol materials (e.g., SiO2 and polymers) that typically have a distribution of sizes and complex morphology. This model is validated at limited cases of sintering between two (equally or unequally sized) particles, and chains of particles. The evolution of morphology, surface area and radii of gyration of multiparticle aggregates are elucidated for various sizes and initial fractal dimension. For each of these structures that had been generated by diffusion limited (DLA), cluster-cluster (DLCA), and ballistic particle-cluster agglomeration (BPCA) the surface area evolution is monitored and found to scale differently than that of the radius of gyration (moment of inertia). Expressions are proposed for the evolution of fractal dimension and the surface area of aggregates undergoing viscous sintering. These expressions are important in design of aerosol processes with population balance equations (PBE) and/or fluid dynamic simulations for material synthesis or minimization and even suppression of particle formation. © 2011 American Chemical Society.
Siemon M.,Institute of Building Materials |
Hosser D.,Institute of Building Materials |
Zehfuss J.,Institute of Building Materials
Research and Applications in Structural Engineering, Mechanics and Computation - Proceedings of the 5th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2013 | Year: 2013
Although many commercial finite element programs are capable of coupling the thermal and mechanical calculation, the definition for an appropriate model for both calculations yields to several problems, especially in fire protection engineering. Due to high spatial and temporal temperature gradients, the resolution of the mesh has to be very high at edges and areas of a structure applied with fire load. This usually leads to problems in the mechanical calculation where a graded mesh results in deformed element geometries and convergence problems.An evenly spaced high resolution mesh on the other hand leads to excessive computational time consumption. By combining two different finite element models for the thermal and thermomechanical calculation with a transfer program, the contradictory mesh discretization requirements can be solved.As a second advantage, both models can be optimized for their purpose, the thermal or thermomechanical calculation. In this paper, this procedure is presented by an example of a simple geometry ultra high performance concrete column. Utilization ofUHPCallows for the design of slight building components and small cross-sectionswhen compared to traditional concrete components. When it comes to fire protection, these aspects yield to disadvantageous behavior under fire load. In this case, the assessment of the coupled thermomechanical approach using advanced finite element methodologies is capable of determining the behavior of such building components. © 2013 Taylor & Francis Group, London, UK.