Advanced Materials Research Vol. 982

Abstract: This article deals with thermal properties of selected kinds of timber. Wood, generally, is one of often used natural materials in building structures. For our research, woods were selected according to frequency of utilization in civil engineering branch. Four different timbers were chosen, and experimental determinations of their properties were performed. Basic physical properties as well as thermal properties belong among studied characteristics. From achieved results, it is obvious, that the bulk density of studied wood ranges between 373 kg m^-3 and 649 kg m^-3, the open porosity differ by 13%. Regarding thermal properties, values of the thermal conductivity as well as the specific heat capacity are influenced mainly by the open porosity and moisture content. The thermal conductivity in dry state varies by about 31% while in the case of the specific heat capacity the difference is about 19%. Obtained date will be used in the mathematical analysis of heat transport in building structures.

Abstract: Clay brick was perhaps to be the first artificial structural material. First bricks were dried by sun; later people had started to burn bricks by fire and in that time further enhancements appeared. This article deals with two kinds of fired clay bricks; basic physical properties, pore system characteristics and thermal properties are studied. The values of basic physical properties by water vacuum saturation vary slightly; bulk density shows values around 1880 kg/m³ and in the case of open porosity it is around 27%. Regarding thermal properties the difference is higher, obtained results of thermal conductivities in dried state vary by about 33%.

Abstract: New type of foamed gypsum-based material is described. Lightweight material, prepared from the gypsum as a main binder and hydrated lime as a secondary binder was foamed by the aluminum powder. The materials with the bulk density about 650 kg.m^-3, compressive strength about 1 MPa and thermal conductivity 0,22 W.m^-1.K^-1 were prepared. Basic physical, mechanical, thermal and water vapor properties were investigated.

Abstract: Fly ashes collected in Air Pollution Control lines of Municipal Solid Waste Incinerators (MSWI) differ highly from fly ashes generated during coal burning what complicates their utilization in building materials production. Nevertheless after a treatment such ashes can have properties relatively comparable with coal fly ashes and thus can be used as Supplementary Cementitious Material (SCM). The water extracted MSWI fly ash was used as partial Portland cement replacement in mortars. The mortars strength evolution in time was monitored; behavior typical for pozzolans – slower increase of strength – was observed. Influence of thermal load on strength of mortars was studied as well. It can be concluded that water extracted MSWI fly ash can be used as 10 % Portland cement substitute without loss of mechanical properties.

Abstract: This paper describes influence of different mechanical properties to the concrete penetration resistance. The resistance is evaluated on the basis of the presented experimental program. In the experiment, non-deformable ogive-nose projectiles with diameter of 7.92 mm and mass of 8 g with impact velocity of about 700 m/s were hitting center of the specimens. Determination of the concrete penetration resistance was than based on projectile residual velocity obtained from high-speed camera record. The specimens were made from high strength concrete, steel fiber-reinforced concrete, ultra-high performance concrete and ultra-high performance fiber-reinforced concrete with different fiber content. The concrete penetration resistance was evaluated on total 32 specimens. Influence of mechanical properties, addition of coarse aggregate and steel fibers were discussed. Mechanical properties of the tested materials were investigated on total 125 specimens. Data from the measurements were used for creation of new RHT concrete models in Autodyn. In order to confirm experiment's setup and results, numerical analysis was performed in Autodyn. Results of the numerical simulations were compared to the experimental program.

Abstract: This paper summarizes the results of an experimental program aimed at investigating of the mechanical properties of composites based on aluminous cement for high-temperature applications and deal with the influence of high-thermal loading on polycarboxylate superplasticizing (PCSP) additive contained in the composite. The intent of this examination was caused by the suspicion that the action of high-temperatures can lead to burnout of the PCSP additive and thus subsequently affecting the mechanical properties of the final composite. Silica composites based on Portland cement and silica aggregates are not able to resist the effects of high-temperatures [1]. For high-temperature composites was therefore used aluminous cement Secar®71 (Lafarge S.A.) in combination with crushed basalt aggregates of fraction 0/4 and 2/5 mm. The flexural strength was greatly improved thanks combinations of basalt fibers with lengths of 6.35 mm and 12.7 mm. The values ​​of flexural strength and compression strength were investigated on samples dried at temperature 105 °C or loaded for 180 minutes with high-temperature of 600 °C or 1 000 °C.

Abstract: Application of HPC (High performance concrete) is very popular and modern solution in current architecture. Higher mechanical and durability properties allow using of thin-walled cross-sections bringing savings of materials and internal space of buildings. This paper deals with development of HPC and UHPFRC (Ultra high performance fiber reinforced concrete) mix design and impact of composition to final mechanical properties. Mix design is focused first on the influence of various additives such as fly ash, silica fume and quartz flour and then to different dosage of steel fibers.

Abstract: Application of agricultural waste materials as building materials not just provides solutions of environmental problems related to the waste management, but it also decreases the use of limited available natural resources and energy. The research in this work is focused on using coconut waste, in the form of natural and chemically treated coir pith, as admixture partially replacing cement in cement composites. The coir pith is the residue acquired during the extraction coir fiber from the outer protective husk of the coconut. Basic physical properties, mechanical, thermal and hygric parameters of several mixtures were studied. The results of measurements showed the influence of amount of coconut addition primarily on parameters such as the bulk density, open porosity, mechanical strengths, moisture transport parameters and thermal parameters. Restrictions for utilization of this waste material relate primarily with its low adhesion ability to the cement matrix.

Abstract: The following article deals with the relations between rheological behavior and strength characteristics of high aluminous cement paste. There were investigated the values of flow of fresh mixture (tested with Högermann ́s table), tensile strength in bending and compressive strength at the age of 28 days on specimens 40 x 40 x 160 mm. The influence of high temperature was examined by exposure to 600 °C and 1000 °C. The results of provided experimental program confirm the fact that with increasing water-cement ration decreases compressive and tensile strength before and after temperature loading. Also was shown the effect of high temperature on refractory aluminous cement paste properites.

Abstract: The main aim of this contribution lies in the description of mechanical properties fiber cement composites after exposure to high temperatures. Destructive and non-destructive methods were used to investigate the influence of heat loading. The effect of refractory binder compared to common Portland cement binder was observed. Widespread non-destructive testing method can describe the changes of mechanical properties due to influence of external load e.g. high temperature at the level of 1000 °C. The tensile strength and compressive strength were investigated on specimens 40 x 40 x 160 mm. Before these destructive tests dynamic modulus of elasticity and tentative compressive strength were provided.