Advanced Materials Research Vol. 982

Abstract: Thermal conductivity of lime-pozzolan plaster is analyzed in the paper. At first, determination of basic physical properties of tested material is done for its basic characterization, as well as for the assessment of input parameters in the subsequent analysis of measured data by different homogenization techniques. The measurements of thermal conductivity are performed in dependence on moisture content from the dry state to the fully water saturated state using transient pulse method. Among the homogenization techniques based on effective media theory, Lichtenecker’s and Dobson’s models are used. The measured data presented in this paper can find utilization in practical applications of the studied plaster. The analyzed homogenization techniques are found to be applicable for a rapid evaluation of moisture dependent thermal conductivity.

Abstract: Mineral wool materials are widely used for thermal insulation of buildings due to their low thermal conductivity and high fire resistivity. On this account, they are popular materials for passive fire protection of buildings. Thermal insulation boards are usually provided with hydrophobic admixtures that ensure their functional properties even in the contact with moisture. In this paper we focused on investigation of hygric transport properties of hydrophilic mineral wool materials that could find application in interior thermal insulation systems as well as in desalination and drying of salt laden materials and building structures. The obtained results give evidence of the effect of fiber orientation on studied material properties and reveal that fiber orientation perpendicular to board surface is a perspective way of materials development.

Abstract: Possible applicability of TDR method for continuous monitoring of moisture content in porous building materials is studied in the paper. TDR method, originally proposed for application in soil science, represents prospective tool for long time monitoring of moisture content in laboratory as well as in-situ conditions neglecting the effect of salts presence in researched material on accuracy of measured moisture content. The basic experimental setup of the TDR method is adjusted to the measurement of water content in building materials. The practical application of the method is presented on the measurement of moisture profiles in rod-shaped sample of cellular concrete.

Abstract: In this paper, water vapor adsorption in sandstone is analyzed using different measurement setting of dynamic vapor sorption device. Basic physical properties of tested material are determined. The vapor sorption is measured using different experimental time and dm/dt setting. It is shown that the device setting can influence the results of equilibrium moisture content in high relative humidities, whereas the differences are of about 20%. The measurement also indicates that the difference in hysteresis can be up to 50% for non-equilibrium measured sample compared to the one under equilibrium state. Both measurements are compared with the steady state desiccator method. The sandstone samples containing a certain concentration of inorganic water soluble salt which just only emphasizes the low hygroscopicity of silica grains are studied as well. The measured data can be used in evaluating of results obtained by dynamic vapor sorption device under equilibrium states although the measurement takes significantly longer time.

Abstract: Effect of porosity on mechanical and hygric properties of high performance concrete (HPC) with natural pozzolan as partial Portland cement replacement up to 40% is studied in the paper. The reference HPC mixture is researched as well in order to evaluate the influence of pozzolan usage on concrete performance. For the studied materials, measurement of compressive strength, sorptivity, apparent moisture diffusivity, and water vapor diffusion permeability is done. The obtained data shows that application of the pozzolan as partial cement replacement leads to increase of concrete porosity that is related to the lower mechanical strength and higher moisture transport properties. Therefore, the applied natural pozzolan has a potential to replace a part of Portland cement in concrete manufacturing but its content in concrete mixture has strict limitations.

Abstract: This paper aims at computational simulation of effect of zeolite admixture on service life of concrete building envelope from point of view of freeze/thaw resistance. Hygrothermal behavior of two types of concrete is studied in this paper: reference concrete without any admixtures and zeolite concrete with 40 % zeolite as cement replacement. The computations are performed using computer simulation tool HEMOT, which processes the input parameters using finite element method. The simulation is assumed under dynamic climatic conditions of Prague. As the results of the computational simulations showed, assuming analyzed amount of zeolite, any positive effect of on freeze/thaw resistance was not found related to unprotected building envelope. However, the results indicated, hygrothermal performance of zeolite concrete can be very considerate to applied external layers and thus extend their service life.

Abstract: This paper is focused on behavior of fiber reinforced cement composites (FRC) and ultrahigh-performance fiber reinforced cement composites (UHPFRC) in dependence on the direction of casting. Almost fifty prismatic samples of size of 400 x 100 x 100 mm were cast into horizontal and vertical moulds. Forty of them with most corresponding results were used in this paper – twenty for FRC and twenty for UHPFRC. In each mixture three samples of both series were cast in the common horizontal direction and the other three in the vertical way. It was found that specific fracture energy of horizontally cast prisms was approximately four and half times higher for both materials than the vertically cast ones. The peak loads of FRC were very similar for both ways of casting. On the other hand the UHPFRC behaved differently, the peak load of horizontally cast prisms was approximately three times higher than the vertically cast ones. It was demonstrated that these differences are caused by the way of casting and vibration.

Abstract: The aim of this study was to quantify the restrained shrinkage of high performance concrete (HPC). Ring test was used for the measurement of restrained shrinkage. Mechanical properties of the HPC as well as free shrinkage were determined for assessment of theoretical stress in shrinkage restrained material. The results from the ring test showed a lot of information about material such as development of actual residual stress, cracking potential, microcracks and relaxation.

Abstract: Retention curve is the basic material property used in models for simulation of moisture storage in porous materials. The measurement of retention curves (also called suction curves, capillary potential curves, capillary-pressure functions and capillary-moisture relationships) is described in this paper. The water storage of different types of sandstone, the materials frequently used on the Czech territory for many centuries mainly for architectonic details and sculptures, is studied in using pressure plate apparatus. The obtained data gives information on materials behaviour in contact with liquid water and on their absorption capacity.