scholarly journals Effects of Erosion Form and Admixture on Cement Mortar Performances Exposed to Sulfate Environment

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 774
Author(s):  
Peng Liu ◽  
Ying Chen ◽  
Zhiwu Yu
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Pore Diameter ◽  
Energy Dispersive Spectrometer ◽  
Sulfate Solution ◽  
Crystal Form ◽  
High Concentration ◽  
Pore Characteristics ◽  
Average Pore ◽  
Before And After

The effects of the admixtures, erosion age, concentration of sulfate solution, and erosion form of sulfate attack on the mechanical properties of mortar were investigated. Simultaneously, the microstructure, pore characteristics, kinds and morphologies of erosion products of mortar before and after sulfate attacks were performed by Mercury Intrusion Porosimetry (MIP), Environment Scanning Electronic Microscope and Energy Dispersive Spectrometer (ESEM-EDS). In addition, the crystal form and morphology characteristics of crystallization on mortar surfaces attacked by partial immersion form were studied. The results showed that the compressive and flexural strengths of mortar attacked by sulfate for four months decreased with the increase of the replacement of cement with fly ash, and the corresponding strength of mortar containing slag first increased and then decreased. The admixtures can improve the microstructure and mechanical properties of mortar within the replacement ratio of 10%. Although the change laws of the mortar specimens containing different admixtures were similar, the mortar containing slag had an excellent sulfate resistance under the same condition. Compared with the complete immersion form, the strength variation of the mortar containing fly ash attacked by semi-immersion form was less. The porosity and average pore diameter of mortar attacked by sulfate for four months increased, and the percentage of micropore with the pore diameter less than 200 nm increased. Plenty of rod-like and plate-like erosion products were generated in mortar attacked by a sulfate solution with a high concentration. A larger number of fibrous and flocculent crystallization covered the mortar’s surface containing fly ash, but it was a granular and dense crystallization formed on the mortar’s surface containing slag. Much dendritic erosion product was generated in the mortar attacked by semi-immersion form, and ESEM-EDS analysis revealed that it may be scawtite, spurrite, and residue of the decomposed calcium silicate hydrate (CSH) in the inner mortar; however, the crystallization sodium sulfate was crystallized on mortar surface.

Pore Structure and Mechanical Properties of ZrC/SiC Multi-Components Modified C/C Composites

2013 ◽  
Vol 833 ◽  
pp. 159-164 ◽  
Author(s):  
Xiu Qian Li ◽  
Hai Peng Qiu ◽  
Jian Jiao
Keyword(s):  
Mechanical Properties ◽  
Pore Diameter ◽  
Testing Machine ◽  
Average Pore Diameter ◽  
Flexural Properties ◽  
Matrix Interface ◽  
Polymeric Precursor ◽  
Average Pore ◽  
Fiber Matrix Interface ◽  
Injection Apparatus

The ZrC/SiC multi-components modified C/C composites were prepared by using a hybrid precursor containning polycarbosilane and organic zirconium-contained polymeric precursor as impregnant and C/C composites of low density as preform. The porosity, microstructure and mechanical properties of samples were characterized with mercury injection apparatus, scanning electron microscopy and universal electron testing machine respectively. The results show that the porosity and average pore diameter decrease firstly and increase subsequently with the increase of organic zirconium content of the precursor. When the content of organic zirconium is 50%, the porosity and average pore diameter reach minimum which were7.27% and 0.0795um respectively. The most probabilistic pore diameter shifted from 10-100um to 1-10um at the same time; Meanwhile, the flexural properties also increases and drops immediately as the content of organic zirconium in the precursor adds. When the content of organic zirconium is 25%, the flexural strength reaches maximum of 245.20MPa.The improved flexural properties is attributed to the proper bonding of fiber-matrix interface and the low porosity of samples.

scholarly journals The development of technology for production of zeolites from fly-ash from Troitskaya power plant

2021 ◽  
Vol 8 (1) ◽  
pp. 20218111
Author(s):  
V. A. Snegirev ◽  
V. M. Yurk
Keyword(s):  
Fly Ash ◽  
Power Plant ◽  
Pore Diameter ◽  
Silicon Oxide ◽  
Exchange Capacity ◽  
Static Exchange Capacity ◽  
Average Pore ◽  
Hydrochemical Synthesis ◽  
Bet Method ◽  
Zeolite Production

The study examines the technology of processing fly ash from Troitskaya power plant for the production of zeolite. The paper presents the results of laboratory studies evaluating the suitability of fly ash from Troitskaya power plant for the production of zeolites and the development of the zeolite production process. Fly ash contains a small amount of heavy metals that can complicate processing, but contains a large amount of silicon oxide. The technology consists of high-temperature alkaline activation of fly ash and hydrochemical synthesis. The resulting powder has a specific surface area of 89.7 m2/g, determined by the BET method, and an average pore diameter of 0.345 μm. The static exchange capacity was 220 mg/g.

Microstructure and Mechanical Behavior of CaCu3Ti4O12 Ceramics Hollow Fiber Prepared via Dry/Wet Spinning Method

2020 ◽  
Vol 1010 ◽  
pp. 239-243
Author(s):  
Mohsen Ahmadipour ◽  
Tunmise Ayode Otitoju ◽  
Mohammad Arjmand ◽  
Zainal Arifin Ahmad ◽  
Swee Yong Pung
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Hollow Fiber ◽  
Outer Layer ◽  
Pore Diameter ◽  
Hollow Fibers ◽  
Wet Spinning ◽  
Outer Diameter ◽  
Average Pore ◽  
Elongation At Break

Dry/wet method was used to prepare CaCuTi4O12 (CCTO) hollow fibers (HFs) and then the structural and physico-mechanical properties of HFs were characterized by XRD, FESEM, BET and tensile strength, respectively. The outer diameter and thickness of CCTO HFs were found to be 650 μm and 390 μm, respectively. A finger-like macrovoids and sponge-like was observed inside the membrane with a denser structure in the outer layer. It was observed that the crystallite size was increased from 28.5 nm to 37.0 nm while the average pore diameter was decreased from 34.65 nm to 29.16 nm in CCTO hollow fiber with 1.0 wt.% CCTO. In addition, the tensile strength of HFS was significantly improved from 4.84 MPa to 5.54 MPa and elongation at break was decreased from 6.97 % to 5.09 % which is ascribed to the reduction in porosity. All the results indicated the significant effect of CCTO content on properties of CCTO hollow fibers. The finding in this study could lead to a new direction to enhance the properties of HFS with potential application in membranes.

scholarly journals Damage Constitutive Model and Mechanical Performance Deterioration of Concrete under Sulfate Environment

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Peng Liu ◽  
Ying Chen ◽  
Zhiwu Yu ◽  
Zhaohui Lu
Keyword(s):  
Mechanical Properties ◽  
Bearing Capacity ◽  
Elasticity Modulus ◽  
Mechanical Performance ◽  
Sulfate Solution ◽  
Concrete Surface ◽  
Ultimate Bearing Capacity ◽  
Stress Strain ◽  
Before And After ◽  
Relationship Model

The effects of erosion mode, erosion age, and concentration of sulfate solution on mechanical properties of concrete were investigated. The dimensionless relationship model of the stress-strain of concrete on the basis of randomness was proposed. The variation of the elasticity modulus and Poisson’s ratio of the concrete surface attacked by sulfate was studied, and a novel method of using a superficial parameter to characterize the performance change of the concrete surface was recommended. The results showed that the dimensionless relationship model of stress-strain of concrete could be used to represent the variations of mechanical properties of concrete. The differences of load-displacement of concrete before and after sulfate attack were reflected as the change of curve’s slope and ultimate bearing capacity, and the slope of a straight section of the lateral and longitudinal strain curves of concrete surface also varied. The increment rates of ultimate bearing capacity of concrete attacked by 1% and saturated sulfate solution were about 30% and 10%, respectively. However, the decreasing ratio of the ultimate bearing capacity of concrete attacked by saturated sulfate solution was approximately 25%. The damage factor of the elasticity modulus of the concrete surface of C20 and C40 was 0.185 and −0.19, respectively. The obtained results could provide a support for investigating the variations of stress-strain relationship and mechanical performance of concrete under a sulfate environment.

scholarly journals Experimental Study on the Evolution Law of Mesofissure in Full Tailing Cemented Backfill

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Yufan Feng ◽  
Guanghua Sun ◽  
Xuejian Liang ◽  
Chenyang Liu ◽  
Yue Wang
Keyword(s):  
Mechanical Properties ◽  
Pore Diameter ◽  
Failure Process ◽  
Hole Diameter ◽  
Fracture Density ◽  
Surface Porosity ◽  
Characteristic Parameters ◽  
Average Pore ◽  
Cemented Backfill ◽  
Lower Structure

To understand the mechanical properties of the backfill, to reveal the evolvement of micromechanical fissure of backfill, a uniaxial compression experiment was carried out for the full tailing cemented backfill. After loading, the microstructure of the specimens was observed by microscope and the pore characteristic parameters were analyzed. The results showed that the diameter of the initial damage hole of the backfill was mostly between 0 and 40 μm, the hole diameter increases gradually with the increase of pressure, and the hole diameter reached more than 5000 μm in the postpeak damage stage. The upper structure of the backfill specimen is compact while the lower structure is relatively loose. The cracks and interfaces between tailings particles and cement paste are mechanical weak surfaces, where the cracks are mainly generated and propagated. The tip of microfractures in the backfill is damaged by the influence of stress concentration. In the failure process, both surface porosity and fracture density decrease first and then increase, and the average pore diameter increases gradually. The results have guiding significance for the study of backfill mechanical properties and goaf filling design.

scholarly journals Study on Crack Development and Micro-Pore Mechanism of Expansive Soil Improved by Coal Gangue under Drying–Wetting Cycles

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6546
Author(s):  
Hongxing Zhu ◽  
Yan Zhang ◽  
Zhuhan Li ◽  
Xiaoyu Xue
Keyword(s):  
Soil Sample ◽  
Pore Volume ◽  
Pore Diameter ◽  
Expansive Soil ◽  
Soil Samples ◽  
Coal Gangue ◽  
Pore Density ◽  
Pore Characteristics ◽  
Average Pore ◽  
Road Engineering

Expansive soil is prone to cracks under a drying–wetting cycle environment, which brings many disasters to road engineering. The main purpose of this study is use coal gangue powder to improve expansive soil, in order to reduce its cracks and further explore its micro-pore mechanism. The drying–wetting cycles test is carried out on the soil sample, and the crack parameters of the soil sample are obtained by Matlab and Image J software. The roughness and micro-pore characteristics of the soil samples are revealed by means of the Laser confocal 3D microscope and Mercury intrusion meter. The results show that coal gangue powder reduces the crack area ratio of expansive soil by 48.9%, and the crack initiation time is delayed by at least 60 min. Coal gangue powder can increase the internal roughness of expansive soil. The greater the roughness of the soil, the less cracks in the soil. After six drying–wetting cycles, the porosity and average pore diameter of the improved and expanded soil are reduced by 37% and 30%, respectively, as compared to the plain expansive soil. By analyzing the cumulative pore volume and cumulative pore density parameters of soil samples, it is found that the macro-cracks are caused by the continuous connection and fusion of micro-voids in soil. Coal gangue powder can significantly reduce the proportion of micro-voids, cumulative pore volume, and cumulative pore density in expansive soil, so as to reduce the macro-cracks.

scholarly journals Influence of curing age on high-temperature properties of additive manufactured geopolymer mortar

2020 ◽  
Vol 218 ◽  
pp. 03019
Author(s):  
Xiaohong Yin ◽  
Xiaodong Wang ◽  
Yuan Fang ◽  
Zhu Ding
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Temperature ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Flexural Strength ◽  
High Temperature Properties ◽  
Before And After ◽  
3D Printed ◽  
Curing Age

Some researches have been conducted on the application of geopolymer in 3D printing. However, there is no publication about the high-temperature properties of 3D printed geopolymer made from fly ash, slag, and metakaolin. This paper presents the experimental research on the mechanical properties of 3D printed geopolymer after being exposed to elevated empratures. The effects of curing age on high-temperature properties are analyzed. The heating temperasures were 300 °C, 600 °C, and 900 °C, and the holding time was one hour. After exposure to temperatures, the flexural strength of 3D printed geopolymer exhibited different change trends with increasing curing age for different exposure temperatures. Before and after exposure to elevated temperature, the 3D printed geopolymer experienced significant anisotropic compressive strengths. The change trends of compressive strength at different exposure temperatures wit hincreasing curing ages were different from each other on different loading directions.

scholarly journals Synthesis of zeolite from fly ash and its adsorption of phosphorus in wastewater

2021 ◽  
Vol 10 (1) ◽  
pp. 349-360
Author(s):  
Kecheng Zhang ◽  
Lizelle Van Dyk ◽  
Dongsheng He ◽  
Jie Deng ◽  
Shuang Liu ◽  
...  
Keyword(s):  
Fly Ash ◽  
Regression Coefficient ◽  
Coal Fly Ash ◽  
Synthetic Zeolite ◽  
Order Kinetic ◽  
Adsorption Model ◽  
High Concentration ◽  
Average Pore ◽  
Phosphorus Adsorption ◽  
And Performance

Abstract Using synthetic zeolite from fly ash to treat high concentration phosphorus wastewater does not only improve the utilization of fly ash as solid waste but also reduce the environmental pressure caused by eutrophication. A synthetic zeolite was prepared from coal fly ash by one-step hydrothermal synthesis and applied for phosphorus adsorption from industrial wastewater (∼8,000 mg-P/L), and its adsorption characteristics and performance were studied. The results indicated that the product was a well-crystallized Na-P1 zeolite with typical morphology of plate- and rod-shaped crystals. Compared with the original fly ash, the specific surface area and average pore volume of the synthetic zeolite were nine and six times larger than the fly ash, reaching 43.817 m2/g and 0.122 cm3/g. The results from phosphorus adsorption onto the synthetic zeolite showed that the synthetic zeolite had good phosphorus adsorption properties. The adsorption process highly conformed to the pseudo-second-order kinetic model with the regression coefficient R 2 of 0.998. Phosphorus adsorption on the synthetic zeolite was fitted to the Langmuir monolayer adsorption model, and the regression coefficient R 2 was 0.989. The maximum phosphorus adsorption capacity was 84.4 mg-P/g-zeolite.

scholarly journals Possibilities of Graphitization of Unburned Carbon from Coal Fly Ash

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1027
Author(s):  
Zdzisław Adamczyk ◽  
Joanna Komorek ◽  
Barbara Białecka ◽  
Joanna Całus-Moszko ◽  
Agnieszka Klupa
Keyword(s):  
Fly Ash ◽  
Pore Volume ◽  
Pore Diameter ◽  
Coal Fly Ash ◽  
Total Pore Volume ◽  
Starting Material ◽  
Unburned Carbon ◽  
Active Carbons ◽  
Average Pore ◽  
Graphite Phase

The paper presents the characteristics of products annealing at the temperatures of 2400 and 3000 °C of unburned carbon from coal fly ash in terms of its possible use as a starting material in the graphitization process. An amorphous substance (organic substance) with an admixture of some minerals has been found in samples subjected to graphitization. However, the graphite phase is dominant in products subjected to graphitization. Studies have also shown a diverse grain morphology in individual samples. The presence of plate-shaped and tube-shaped grains was found. As the graphitization temperature of the starting material increases (2400 and 3000 °C), the specific surface area in the graphitization products decreases. The total pore volume in the samples after the graphitization process was significantly lower than the pore volume of active carbons produced from other unburned carbon. Average pore diameter is similar to the pore diameter in active carbons. The reflectance value of the matrix for the sample graphitized at 3000 °C is characteristic for graphite. Unburned carbon from Polish fly ash can be used as the starting material for graphitization.

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