Advanced Materials Research Vol. 1054

Abstract: Experimental investigation of the effect of phase change material (PCM) admixture on thermal properties of composite plaster is researched in the paper. Due to its latent heat storage, the applied PCM represents promising way for reduction of buildings energy consumption spent for heating and air conditioning. The investigated composite material is based on commercial dry plaster mixture modified by microencapsulated PCM admixture Micronal DS 5038 produced BASF. The particle size distribution of PCM admixture, original dry plaster mixture, and particular dry mixture with PCM addition are measured on laser diffraction principle. For characterization of the developed materials, measurement of their basic physical properties is done. Specific attention is paid to thermal properties of research materials, whereas the heat transport parameters are measured using transient impulse device, and the DSC (difference scanning calorimetry) analysis is applied for determination of temperatures of phase transitions, enthalpy of fusion and crystallization, and temperature dependent specific heat capacity. The obtained results show significant improvement of the heat storage capacity of PCM modified plasters in dependence on temperature, what can be beneficially used for regulation of the indoor climate.

Abstract: The aim of the presented study was to find a relationship between PVA concentration and properties of cement pastes. The PVA solution was added into fresh mortar in the amount equal to 1.4 and 2.8 % of cement weight. The produced samples were consequently stored in different curing conditions – exposed to air in common laboratory environment or submerged in water. The development of the dynamic Young’s and shear moduli was monitored using the non-destructive resonance method during first 28 days of hardening. The obtained data were compared to the measurements of a pure cement reference paste.

Abstract: The main aim of this contribution is description of the static and the dynamic modulus of elasticity of concrete containing recycled aggregate. Recycled construction and demolition waste, especially recycled concrete, is able to use as an aggregate for concrete, but using of recycled aggregate has a negative impact of concrete characteristic. This paper presents results of non-destructive measurement of recycled aggregate concrete properties. Series of concrete samples with 100% replacement ratios of coarse natural aggregate by coarse recycled aggregate from different sources were prepared for this study. The static and the dynamic modulus of elasticity were investigated on specimens 100 x 100 x 400 mm. All tested mixtures were also tested on compressive strength.

Abstract: Currently, the emphasis is put on sustainable buildings; simultaneously, the emphasis is put on energy efficiency in buildings, with respect to this fact of necessity to test thermal properties of new building materials. This article deals with the thermal properties of concrete containing recycled concrete aggregate. Four types of recycled concrete aggregate were used for the production of the concrete. For the testing of concrete, a total of ten concrete mixtures were made, one of which was a reference mixture and the natural aggregate was replaced by recycled aggregate of varying ratio in the other mixtures. Finally, it is possible to say that according to the thermal properties of the recycled aggregate concrete is possible to be used in the same applications as conventional concrete.

Abstract: The presented study addresses the mechanical performance of micro-filler cement-based material produced from recycled concrete sleepers. Such material can be considered both, as a binder and filler at the same time. The main advantage of such material is the energy efficiency of the production process, since there is no demand for increased temperature. Compression and flexural strength parameters of such material are compared with those of a composite based on commonly used Portland cement. Moreover, the influence of curing conditions on the strength parameters was investigated as well. The results indicate that the recycled sleepers can be used in the form of micro-filler cement-based to replace a certain portion of cement in concrete and reduce cost of concrete structures.

Abstract: Agricultural waste materials can often find an application in the production of concrete or mortar. In this paper, several composites containing waste coir pith are studied. A reference material without coir pith is analyzed as well, for the sake of comparison. The investigated material parameters include the basic physical properties determined by the water vacuum saturation method and helium pycnometry, compressive strength, bending strength, and thermal properties.

Abstract: This paper aims at determination of mechanical properties of 28 years old concrete with various nondestructive and destructive testing methods. All investigated parameters were determined on drilled cores with diameter 79.8 mm gained from existing bridge. On these samples Schmidt rebound testing and destructive force loading test were performed. Static (from loading test) and dynamic (measured by ultrasonic device) modulus of elasticity was also measured. The evaluation of destructive and nondestructive testing was according to the Czech Standards. Testing of old concrete from real structures is important especially prior to the reconstruction, strengthening or repair of the structure, when the structural engineer needs to know the characteristics. The compressive strength measured destructively on cylinders achieved average value 28 MPa, while the Schmidt rebound hammer test showed strength 44 MPa. The average value of static modulus of elasticity was 26 GPa.

Abstract: In this paper the possibilities of colouring concrete and the use of pigments are presented. There are two groups of pigments with respect to its manufacture (organic and inorganic) and three different forms available on market: powder, granulates and slurry. Next to the influences of other concrete components the effects of fine pigment particles on the properties of fresh and hardened concrete are introduced. Because of the higher need of water the workability of each mixture is affected. With the increasing specific surface area of pigment the flow of fresh concrete decreases. On the other hand this characteristic feature causes slightly higher density of concrete matrix which results in better durability. Optimal dosages differs depending on the form of pigment, for powders it is about 5% of the weight of cement content. Higher amounts don ́t bring about higher tinting strength and in the case of more than 10 % its mechanical properties can be negatively affected. An example of colour evaluation as well as utilization of recycled materials as colouring agents are also mentioned.

Abstract: This paper is focused on the problem of the lightweight concretes made of the Municipal Solid Waste Incineration (MSWI) bottom ash. Their basic, mechanical and thermal properties were investigated. According to the requirements were designed 7 mixtures and reference made just from natural aggregates. The first 4 mixtures had a higher porosity, which explained good thermal properties, but it had low mechanical parameters. Next 4 mixtures had lower level of porosity and had shown good ultimate stress data.

Abstract: This paper describes some of tests of mechanical properties of rammed earth which have been held at CTU in Prague. Influence of size of specimen was examined in two tests, conversion factor is counted. Size factor is discussed comparing to concrete, influence of layer depth is also mentioned.