Evaluation of Electric Field Integral Voltage Measurement Method of Transmission Line Based on Error Transmission and Uncertainty Analysis.

Electric field numerical integration algorithms can realize the non-contact measurement of transmission line voltage effectively. Although there are many electric field numerical integration algorithms, lack of a comprehensive comparison of accuracy and stability among various algorithms results in difficulties in evaluating the measurement results of various algorithms. Therefore, this paper presents the G-L (Gauss-Legendre) algorithm, the I-G-L (improved Gauss-Legendre) algorithm, and the I-G-C (improved Gauss-Chebyshev) algorithm and proposes a unified error propagation model of the derived algorithms to assess the accuracy of each integration method by considering multiple error sources. Moreover, evaluation criteria for the uncertainty of transmission line voltage measurement are proposed to analyze the stability and reliability of these algorithms. A simulation model and experiment platform were then constructed to conduct error propagation and uncertainty analyses. The results show that the G-L algorithm had the highest accuracy and stability in the scheme with five integral nodes, for which the simulation error was 0.603% and the relative uncertainty was 2.130%. The I-G-L algorithm was more applicable due to the smaller number of integral nodes required, yet the algorithm was less stable in achieving the same accuracy as the G-L algorithm. In addition, the I-G-C algorithm was relatively less accurate and stable in voltage measurement.

A Review on the Application of Lignocellulosic Biomass Ash in Cement-Based Composites.

With the development of society, the demand for cement-based composites is increasing day by day. Cement production significantly increases CO2 emissions. These emissions are reduced when high volumes of cement are replaced. The consideration of sustainable development has prompted people to search for new cement substitutes. The lignocellulosic biomass ash obtained from burning lignocellulosic biomass contains a large number of active oxides. If lignocellulosic biomass ash is used as a partial cement substitute, it can effectively solve the high emissions problem of cement-based composites. This review summarizes the physicochemical properties of lignocellulosic biomass ashes and discusses their effects on the workability, mechanical properties, and durability (water absorption, acid resistance, etc.) of cement-based composites. It is found that appropriate treatments on lignocellulosic biomass ashes are beneficial to their application in cement-based composites. Meanwhile, the issues with their application are also pointed out.

Bonding Properties between Fly Ash/Slag-Based Engineering Geopolymer Composites and Concrete.

Concrete infrastructure repair remains a formidable challenge. The application of engineering geopolymer composites (EGCs) as a repair material in the field of rapid structural repair can ensure the safety of structural facilities and prolong their service life. However, the interfacial bonding performance of existing concrete with EGCs is still unclear. The purpose of this paper is to explore a kind of EGC with good mechanical properties, and to evaluate the bonding performance of EGCs with existing concrete using a tensile bonding test and single shear bonding test. At the same time, X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were adopted to study the microstructure. The results showed that the bond strength increased with the increase in interface roughness. For polyvinyl alcohol (PVA)-fiber-reinforced EGCs, the bond strength increased with the increase in FA content (0-40%). However, with the change of FA content (20-60%), the bond strength of polyethylene (PE) fiber-reinforced EGCs have little change. The bond strength of PVA-fiber-reinforced EGCs increased with the increase in water-binder ratio (0.30-0.34), while that of PE-fiber-reinforced EGCs decreased. The bond-slip model of EGCs with existing concrete was established based on the test results. XRD studies showed that when the FA content was 20-40%, the content of C-S-H gels was high and the reaction was sufficient. SEM studies showed that when the FA content was 20%, the PE fiber-matrix bonding was weakened to a certain extent, so the ductility of EGC was improved. Besides, with the increase in the water-binder ratio (0.30-0.34), the reaction products of the PE-fiber-reinforced EGC matrix gradually decreased.

Bond Properties of Magnesium Phosphate Cement-Based Engineered Cementitious Composite with Ordinary Concrete.

A magnesium phosphate cement-based engineered cementitious composite (MPC-ECC) was developed using polyvinyl alcohol (PVA) fibers and fly ash. In this study, the bond behavior of MPC-ECC with ordinary concrete was evaluated through single and double shear bond strength tests. The effects of the water to solid mass ratio (W/S), the sand to binder mass ratio (S/B), the molar ratio of MgO to KH2PO4 (M/P), the fly ash content (F), the borax dosage (B), the volume fraction of PVA fibers (Vf), and curing age on the bond behavior of MPC-ECC with ordinary concrete were examined. The results showed that as the W/S increased, the single and double shear bond strengths were gradually reduced. As the S/B increased, the double shear bond strength increased; the single shear bond strength first decreased up to an S/B of 0.1 and then increased. With the increase of M/P, the single and double shear bond strengths increased. With the increase of F, the single shear bond strength first increased up to an F of 30% and then decreased; the double shear bond strength decreased. With the increase of B, the single and double shear bond strengths increased first and then decreased, and their strength reached its maximum at a B of 6%. The increase of Vf improved the single and double shear bond strengths. The research results can provide some technical guidance for repairing concrete structures with MPC-ECC.

Mechanical Properties and Water Stability of High Ductility Magnesium Phosphate Cement-Based Composites (HDMC).

In this study, the compressive test and four-point flexural test were carried out to explore the water stability as well as mechanical properties of high ductility magnesium phosphate cement-based composites (HDMC). The effects of ambient curing age (7 d and 28 d), water immersion age (7 d, 28 d, and 56 d), water/binder ratio (W/B), and magnesium oxide/potassium dihydrogen phosphate ratio (M/P) on the mechanical properties (compressive strength, first-crack strength, ultimate flexural strength, ductility index, and toughness index) and water stability of the HDMC were examined. The results showed that the 28-day ambient curing could lead to higher retention rates of strength, ductility, and toughness than 7-day ambient curing, indicating better water stability; however, it did not result in significant improvement in the mechanical properties of the HDMC. As the water immersion age increased, the mechanical properties of the HDMC with 7-day ambient curing showed an obvious downward trend; the mechanical properties of the HDMC with 28-day ambient curing did not show an obvious decrease and even could be increased in many cases, especially when the water immersion age was 56 days; and the change of water stability was consistent with that of the mechanical properties. If all indexes and their corresponding retention rates were considered comprehensively, the W/B ratio of 0.16 and the M/P ratio of 5 seemed to be the optimum values for the HDMC. The scanning electron microscopy analysis confirmed that the water immersion had a large adverse effect on the HDMC and thus reduced their mechanical properties.

A Review on the Application of Nanocellulose in Cementitious Materials.

The development of the concrete industry is always accompanied by some environmental issues such as global warming and energy consumption. Under this circumstance, the application of nanocellulose in cementitious materials is attracting more and more attention in recent years not only because of its renewability and sustainability but also because of its unique properties. To trace the research progress and provide some guidance for future research, the application of nanocellulose to cementitious materials is reviewed. Specifically, the effects of cellulose nanocrystal (CNC), cellulose nanofibril (CNF), bacterial cellulose (BC), and cellulose filament (CF) on the physical and fresh properties, hydration, mechanical properties, microstructure, rheology, shrinkage, and durability of cementitious materials are summarized. It can be seen that the type, dosage, and dispersion of nanocellulose, and even the cementitious matrix type can lead to different results. Moreover, in this review, some unexplored topics are highlighted and remain to be further studied. Lastly, the major challenge of nanocellulose dispersion, related to the effectiveness of nanocellulose in cementitious materials, is examined in detail.