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Method for Assessment of Changes in the Width of Cracks in Cement Composites with Use of Computer Image Processing and Analysis

Abstract

Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.

Open access
Preliminary Investigations of Creep Strain of Neogene Clay from Warsaw in Drained Triaxial Tests Assisted by Computed Microtomography

Abstract

The study concerns soil creep deformation in multistage triaxial stress tests under drained conditions. High resolution X-ray computed microtomography (XμCT) was involved in structure recognition before and after triaxial tests. Undisturbed Neogene clay samples, which are widespread in central Poland, were used in this study. XμCT was used to identify representative sample series and informed the detection and rejection of unreliable ones. Maximum deviatoric stress for in situ stress confining condition was equal 95.1 kPa. This result helped in the design of further multistage investigations. The study identified the rheological strain course, which can be broken down into three characterizations: decreasing creep strain rate, transitional constant creep velocity, and accelerating creep deformation. The study found that due to multistage creep loading, the samples were strengthened. Furthermore, there is a visibly “brittle” character of failure, which may be the consequence of the microstructure transformation as a function of time as well as collapse of voids. Due to the glacial tectonic history of the analyzed samples, the reactivation of microcracks might also serve as an explanation. The number of the various sizes of shear planes after failure is confirmed by XμCT overexposure.

Open access
Structural and Textural Characteristics of Selected Copper-Bearing Rocks as One of the Elements Aiding in the Assessment of Gasogeodynamic Hazard

Abstract

The characteristics of copper-bearing rocks that include the structural and textural parameters are an important factor determining a possible gas accumulation in those rocks. In September 2009, in the Rudna copper mine in Poland, an outburst of gases and dolomite occurred. The analysis of the outburst mass showed that one of the main causes of the outburst was the different structural properties such as high porosity and presence of gas in the pores. This paper presents data from the structural analysis of dolomite from the Polkowice-Sieroszowice copper mine and the Rudna copper mine. Seven rock samples from various areas of the mines were tested by the following methods: mercury porosimetry (MIP), low pressure gas adsorption (LPNA), scanning electron microscopy (SEM), computed microtomography (micro-CT). The SEM analyses of the rock samples allowed pores of various sizes and shapes to the observed. The porosity (MIP) of the dolomite changed in the range of 3-15%. The total micro and mesopore volume (LPNA) was from 0.002 cm3/g to 0.005 cm3/g. The macropore volume (MIP) was from 0.01 cm3/g to 0.06 cm3/g and the mean macropore diameter was from 0.09 μm to 0.18 μm. The dolomite samples varied in the surface area (LPNA) (0.7-1.5 m2/g) and the pore distribution. The structure of dolomite determines the possibility of the occurrence of gasogeodynamic phenomena and hence it is urgent that research be conducted into its changeability. To better understand the gasogeodynamic processes in copper-bearing rocks, it is necessary to constantly monitor and analyse in detail those areas that have different structural properties.

Open access
Temperature Changes in the Vicinity of Thermally Loaded Structure Embedded in the Soil: Effect of Sand Content and Saturation Degree

Abstract

Due to the rapid development of geothermal technologies, the problem of efficient and proper evaluation of soil thermal conductivity becomes extremely important. Factors mostly affecting the soil conductivity are the conductivity of solid phase and the degree of saturation. The former one is mainly affected by the mineral composition, in particular, by the content of quartz whose conductivity is the highest one among all the minerals forming soil skeleton. Organic matter, because of its relatively low conductivity, influences the solid conductivity as well. The problem addressed in the paper is the influence of mentioned factors on temperature changes in the vicinity of thermally loaded structure embedded in the soil medium. Numerical simulations are carried out for different values of soil thermal conductivity resulting from various quartz contents and degrees of saturation. In addition, a weak coupled - heat and water transport - problem is considered.

Open access
The Use of a Unipore Diffusion Model to Describe the Kinetics of Methane Release from Coal Spoil in the Longwall Environment

Abstract

The unipore methane diffusion model based on the solution of the second Fick’s law describes effectively the kinetics of methane release from coal grains. The knowledge of the model describing the kinetics of methane release from coal, the coalbed methane content, the sorption isotherm, the effective diffusion coefficient and the coal particle size distribution, enables the calculation of the volume of methane which is released from the coal spoil as a function of time. These assumptions became the basis for building the software that enables the analysis of methane emissions from coal during the longwall mining. Simulations were performed to determine the temporal and spatial methane inflow to the longwall. The share of methane emission from coal grains (taking into account both the emission kinetics and mass participation) of various classes has been analyzed. The results of the analysis showed that the methane from the small grains, in particular less than 0.1 mm in size, prevails. The mass fraction of these grains in the total weight does not exceed 5%. For the typical parameters determining the mining, geological and technological conditions of methane emissions at different moments of time and position of the longwall were determined.

Open access
Application of Anaerobic Digestate as Inoculum for Treatment of the Plant-Derived Wastes: Case Study

Abstract

The aim of this study was to characterize the digestate from an activated sludge biogas reactor (IDARS) as an inoculum for enzymatic hydrolysis and biogas production from organic wastes. Aerobic and anaerobic bacteria are represented in IDARS with H’ index 3.1 and 2.5, respectively. IDARS stimulated the enzymatic hydrolysis of wood and leaves, preferably broadleaf tree species. The results demonstrated the potential of IDARS for improvement of the technological parameters for conversion of organic wastes into biogas.

Open access
Characterization and Applications of Organic Coagulant KOHIDRAC

Abstract

Low cost, effective and water soluble organic coagulant is offered for the extraction of charged clay particles. Coagulation with KOHIDRAC results in simultaneous concentration and purification of the clay fraction. After treatment with KOHIDRAC the obtained clay samples were free of carbonates and feldspar. Moreover, the amount of quartz decreased significantly in finished samples. The proposed coagulant and the patented methodology can be successfully used as purification procedure or as pretreatment for qualitative and quantitative analysis of clay minerals. The possible structure of the active compound KOHIDRAC was investigated in this paper. Real applications of the coagulant were provided.

Open access
Clay Ceramic Filter for Water Treatment

Abstract

Ceramic water filters were prepared from different proportions of kaolin and soft wood and sintered at 900 °C, 950 °C, and 1000 °C. The flow rate, conductivity, pH of filtered water and removal efficiency (microbial, water hardness agent’s, nitrite and turbidity) were analysed. The ceramic filter with 15 % saw dust, 80 % clay and 5 % grog that was fired at temperature of 950 °C or 1000 °C showed the best removal efficiency. Statistical ANOVA tests showed a significant difference between ceramic filters with various compositions in their removal efficiencies.

Open access
Facile Synthesis of Spinel Nanocrystalline ZnFe2O4: Enhanced Photocatalytic and Microbial Applications

Abstract

Spinel ZnFe2O4 was developed successfully as a heterogeneous-Fenton catalyst for the degradation of Reactive Yellow 86 (RY 86) under UV light. The ZnFe2O4 was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and UV-diffuse reflectance spectroscopy (UV-DRS). FE-SEM reveals that the some of the particles sizes are in the range from 10 nm to 50 nm. The photocatalytic performance of ZnFe2O4 was evaluated by degradation of RY 86 dye solution under UV light. The degradation rate was highly influenced by pH, initial concentrations of H2O2 and catalyst concentration. The results indicated that ZnFe2O4 could be used as a photocatalyst for treatment of industrial coloured wastewater. The catalyst was reused for five consecutive runs without significant change in its activity. Moreover, the antibacterial effects were investigated.

Open access
Glass Formation and Crystallization in P2O5-Nb2O5-CaO-Na2O System

Abstract

There is a lack of studies on a wide composition range for calcium phosphate glasses containing transition elements, e.g. niobium. Addition of Nb2O5 increases mechanical and chemical strength of calcium phosphate glasses and glass ceramics.

Glass is formed in a wide range of compositions. CaO promotes batch melting. The oxidation state of niobium has important role in glass forming. Solid state reactions between P2O5 and Nb2O5 during batch melt change the oxidation state of niobium. Nb5+ in this system acts as an intermediate or conditional glass former (glass is yellow) while Nb4+ is a glass modifier (glass is blue). It is possible to obtain glass with Nb2O5 (Nb5+) content up to 70 mol%. The glass ceramics obtained by reheating powdered glass contained niobium in crystalline phases. The composition of crystalline phases depends on the phosphate amount.

Open access