Hydration–Strength–Workability–Durability of Binary, Ternary, and Quaternary Composite Pastes

At present, reducing carbon emissions is an urgent problem that needs to be solved in the cement industry. This study used three mineral admixtures materials: limestone powder (0–10%), metakaolin (0–15%), and fly ash (0–30%). Binary, ternary, and quaternary pastes were prepared, and the specimens’ workability, compressive strength, ultrasonic pulse speed, surface resistivity, and the heat of hydration were studied; X-ray diffraction and attenuated total reflection Fourier transform infrared tests were conducted. In addition, the influence of supplementary cementitious materials on the compressive strength and durability of the blended paste and the sustainable development of the quaternary-blended paste was analyzed. The experimental results are summarized as follows: (1) metakaolin can reduce the workability of cement paste; (2) the addition of alternative materials can promote cement hydration and help improve long-term compressive strength; (3) surface resistivity tests show that adding alternative materials can increase the value of surface resistivity; (4) the quaternary-blended paste can greatly reduce the accumulated heat of hydration; (5) increasing the amount of supplementary cementitious materials can effectively reduce carbon emissions compared with pure cement paste. In summary, the quaternary-blended paste has great advantages in terms of durability and sustainability and has good development prospects.

Epoxy Casting Systems with Harmless Hardeners for Outdoor Applications

Presented thesis is focused on studying of electro-insulating casting systems based on epoxy resin. The aim of the article is to acquaint the reader with the development of this systems – epoxy resin with hardeners that comply with REACH authorization. The temperature and frequency dependence of complex permittivity, complex electric modulus, loss factor and inner and surface resistivity of the given samples are investigated.

Growth and some surface characterization of tin Sulphide (SnS) thin film by two-electrode cell arrangement for photo absorption

This study presented deposition of tin sulphide (SnS) thin film using a two-electrode electrochemical cell arrangement. The bath electrolyte comprised tin sulphate (SnSO4 ), hydrated sodium thiosulphate (Na2S2O3∙5H2O) and sulphuric acid (H2SO4 ). The acid was used to adjust the pH of the bath. The deposited film was characterised using Surface Profilometer, X-Ray Diffractometer (XRD), Uv-Visible Spectrophotometer and four point probe technique. Surface profiling revealed that the film is continuous with thickness of about 60 nm. The XRD result showed that the film has orthorhombic crystal structure. Film's crystallite size was estimated as 0.61 nm and interplanar spacing as 0.29 nm. The Uv-visible Spectrophotometer result reveals that, the film has good absorbance but poor reflectance and transmittance in the visible light region. The film has direct allowed transition with energy band gap of 1.69 eV. Values of surface resistivity and conductivity were deduced from data obtained from Four-point probe studies as 5.12 x 10-4Ω-cm and 1.96 x 103Ω-1cm-1 respectively. The I-V characteristics curve of ITO/SnS/Ag structure is linear indicating an Ohmic contact between the substrate electrode and the deposited layer. It can therefore be suggested that the film can allow pathway for photoabsorption and also aid charge transfer in photovoltaic process. Keywords: tin sulphide, orthorhombic, electrochemical deposition, characterization, photovoltaic and surface resistivity.

Three-Dimensional Inversion of Borehole-Surface Resistivity Method Based on the Unstructured Finite Element

The electromagnetic wave signal from the electromagnetic field source generates induction signals after reaching the target geological body through the underground medium. The time and spatial distribution rules of the artificial or the natural electromagnetic fields are obtained for the exploration of mineral resources of the subsurface and determining the geological structure of the subsurface to solve the geological problems. The goal of electromagnetic data processing is to suppress the noise and improve the signal-to-noise ratio and the inversion of resistivity data. Inversion has always been the focus of research in the field of electromagnetic methods. In this paper, the three-dimensional borehole-surface resistivity method is explored based on the principle of geometric sounding, and the three-dimensional inversion algorithm of the borehole-surface resistivity method in arbitrary surface topography is proposed. The forward simulation and calculation start from the partial differential equation and the boundary conditions of the total potential of the three-dimensional point current source field are satisfied. Then the unstructured tetrahedral grids are used to discretely subdivide the calculation area that can well fit the complex structure of subsurface and undulating surface topography. The accuracy of the numerical solution is low due to the rapid attenuation of the electric field at the point current source and the nearby positions and sharply varying potential gradients. Therefore, the mesh density is defined at the local area, that is, the vicinity of the source electrode and the measuring electrode. The mesh refinement can effectively reduce the influence of the source point and its vicinity and improve the accuracy of the numerical solution. The stiffness matrix is stored with Compressed Row Storage (CSR) format, and the final large linear equations are solved using the Super Symmetric Over Relaxation Preconditioned Conjugate Gradient (SSOR-PCG) method. The quasi-Newton method with limited memory (L_BFGS) is used to optimize the objective function in the inversion calculation, and a double-loop recursive method is used to solve the normal equation obtained at each iteration in order to avoid computing and storing the sensitivity matrix explicitly and reduce the amount of calculation. The comprehensive application of the above methods makes the 3D inversion algorithm efficient, accurate, and stable. The three-dimensional inversion test is performed on the synthetic data of multiple theoretical geoelectric models with topography (a single anomaly model under valley and a single anomaly model under mountain) to verify the effectiveness of the proposed algorithm.

Surface Resistivity of Silicone Rubber Formulations Tested in Room Ambient Conditions: The Case of Silicone Rubber Formulations With and Without Filler Materials

Silicone rubber formulations in the form of thin discs have been studied under room ambient conditions for their surface characteristics. The samples were silicone rubber manufactured in laboratory and those industrially manufactured. The measurements were done using an electrometer high resistance meter, applying dc voltage under normal room ambient conditions. The results show that the silicone rubber samples show higher values of surface resistivity when the dc voltage was applied. Silicone rubber samples manufactured in laboratory seem to exhibit erratic behaviour unlike their corresponding silicone rubbers manufactured in industry; this could be due to manufacturing shortcomings in laboratory and the irregularities in the way the silicone rubber adhered to the concentric ring electrodes. The empirical current traversing the surface of the silicone rubbers does not decay exponentially but rather it decays as an exponential power of the energization time.

Engineering Properties of Colorful Mortar with Inorganic Color Paste

Color cement directly exposes the surface of a concrete building through concrete materials or adding color additives and other technologies to achieve a special aesthetic effect of the overall building’s appearance. The multifunctionality of materials is paid increasing attention with time. This study uses additional 5%, 10% and 15% inorganic color paste and 20% polyacrylic emulsion to colorize mortar, and discusses the fresh properties (slump, slump flow), hardened properties (compressive strength, flexural strength, tensile strength and ultrasonic pulse velocity and durability (surface resistivity, thermal conductivity and length change) of mortar. The results show that the slump and slump flow increase with the content of inorganic color paste; the slump flow is larger than the control group and larger than 25 cm, meaning the inorganic color paste can effectively enhance the workability of mortar. The compressive strength, flexural strength and tensile strength decrease as the inorganic color paste increases. The addition of 5% inorganic color paste still maintains certain engineering properties. The addition of polyacrylic emulsion can improve the tensile strength of mortar, which is higher than the control group. The ultrasonic pulse velocity is a little different from compressive strength, but they have similar trends, and it is higher than 3500 m/s. The durability decreases as the inorganic color paste and polyacrylic emulsion increase, meaning the content of inorganic color paste has relatively significant influence. The surface resistivity at the age of 7 days was higher than 20 kΩ-cm. The findings show that different contents of inorganic color paste and 20% polyacrylic emulsion have different degrees of influence on the engineering properties of colorful mortar.