Rheological and mechanical properties of microfine-cement-based grouts mixed with microfine fly ash, colloidal nanosilica and superplasticizer

The development and application of nondestructive testing technology for prestressed reinforced concrete structures in the field of infrastructure construction were summarized in this study via the analysis of relevant literature worldwide. The detection methods, detection principles, and detection instruments in quality evaluation of prestressed reinforced concrete structures were analyzed and compared, based on which, acoustic emission detection technology, impact echo detection technology, ultrasonic detection technology, infrared thermography detection technology, ground-penetrating radar detection technology, piezoelectric transducer detection technology, and X-ray detection technology were summarized. Additionally, the advantages, disadvantages, and application scope of each detection method were focused upon and analyzed comparatively. It is indicated that further improvement in the detection visualization, accuracy, and efficiency for most nondestructive testing technologies is available by optimizing the algorithm and combining artificial intelligence technology with neural network deep learning, precise positioning, and imaging analysis of the quality defects in prestressed reinforced concrete structures. The results of this study can provide technical reference for the further application and research of nondestructive testing technologies in the quality inspection of prestressed reinforced concrete structures.

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Application of Nondestructive Testing Technology in Quality Evaluation of Plain Concrete and RC Structures in Bridge Engineering: A Review

High-performance cementitious grout with fly ash for corrosion protection of post-tensioned concrete structures

To ensure the sealing effect of gas extraction borehole in underground coal mine and improve the concentration of gas extraction, a kind of high-flow sealing material which can be injected into the microcracks around borehole was developed The ultrafine cement as the base material, with water-reducing agent, expansion agent, retarder, the material, and water combined stir, will form a kind of colloid with high fluidity and slightly expansibility This paper analyzes the differences between the new high-fluidity sealing material and ordinary cement materials in expansion performance, compressive strength, and sealing performance Scanning electron microscope and mercury intrusion method were used to analyze the differences in microscopic morphology and pore structure of these two materials The experimental results show that the new high-fluidity sealing material has an excellent fluidity of 2955 mm with an expansion rate of 60 d being 1562% The new high-fluidity sealing material is convenient for grouting with strong material permeability and superior sealing performance Field test results show that the effect of the new high-fluidity sealing material is better than the ordinary cement materials The average drainage concentration and flux during the drainage period were 5907% and 0243 m3/min, respectively, which showed that the drainage efficiency was significantly improved This novel sealing material is of great significance for improving the efficiency of drilling and drainage

/pdf/experimental-research-on-performance-of-new-gas-drainage-5gdx672e4g.pdf

Experimental Research on Performance of New Gas Drainage Borehole Sealing Material with High Fluidity

The rheology of cement grouts often plays a crucial role in the success of rock grouting. In practice, the rheological parameters should be timely adjusted according to the evolution of grouting pressure, flow rate and injection time. However, obtaining the magnitude of rheological parameters is not easy to achieve under site conditions. More importantly, the ground temperature in deep rock masses is elevated higher than that on the surface or under room conditions, which has been demonstrated to strongly influence the rheological properties of grouts. Reasonable understanding and control of the rheological behavior of cement grouts at true ground temperatures is very important to the quality of grouting. This paper aims to propose a simplified method to approximately estimate the initial yield stress and viscosity of cement grouts for rock grouting under elevated ground temperature that actually exists in deep rock masses, on the basis of the flow spread test. The temperature investigated was controlled between 12 °C and 45 °C to simulate the true ground temperature in rock masses with a maximum depth of 1500 m below the surface. Taking the influences of elevated temperatures into account, a temperature-based model for estimating the initial viscosity of cement grout was successfully developed on the basis of Liu’s model and the results of the flow spread test. However, the yield stress failed to be estimated by the Lapasin model due to the absence of plastic behavior of cement grouts. In contrast, yield stress can be linearly correlated to the measured relative flow area. In this work, it was also found that the dependence of yield stress of cement grouts on relative flow area is a strongly exponential law. The temperature dependence of the viscosity of water was accounted for in both estimations of viscosity and yield stress of grouts. Significantly, it was found that the packing density of cement is dependent on the grout temperature, especially when the temperature is up to 45 °C. The proposed method in this work offers an alternative solution for technicians to reasonably control the rheological properties in the increasing applications of deep rock grouting.

https://www.mdpi.com/1996-1944/13/13/2939/pdf

Estimation of Viscosity and Yield Stress of Cement Grouts at True Ground Temperatures Based on the Flow Spread Test.

Factors affecting the performance characteristics of cementitious grouts for post-tensioning applications

It is possible to reduce distribution losses by strategically placing and sizing DG and BESS sources. Assuring low loss requires strategically placing the aforementioned devices; otherwise, the system may experience either under- or overvoltage. It is preferable to choose bus stations with less risk for loss. The proposed approach tries to pinpoint the optimal BESS size and placement to cut down on investment and operating expenses while still achieving the desired level of energy reduction. The development of optimisation algorithms for finding and scaling BESS units is the fundamental focus of this study. Two such strategies are being explored here: the Genetic Algorithm (GA) and the Ant Colony Optimization Algorithm (ACOA). The goal function, like the original issue, seeks to minimise system-wide power losses while adhering to specified levels of equality and inequality. This article explores the appropriate capacity and placement of the DGs in a 33-bus radial distribution grid to reduce power dissipations. Matlab code is used to perform a simulation, and the results are put to use gauging the method's sturdiness.

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Ramya Thirunavukkarasu

Papers

Factors affecting the performance characteristics of cementitious grouts for post-tensioning applications

Power Loss Minimization in a Radial Distribution Network by Optimal Sizing and Placement of Energy Storage Units