Effect of Curing Temperature on Mechanical Performance and Acoustic Emission Properties of Cemented Coal Gangue-Fly Ash Backfill

2019 ◽  
Vol 37 (4) ◽  
pp. 3241-3253 ◽  
Author(s):  
Di Wu ◽  
Runkang Zhao ◽  
Chunlai Qu
Keyword(s):  
Acoustic Emission ◽  
Fly Ash ◽  
Mechanical Performance ◽  
Coal Gangue ◽  
Curing Temperature ◽  
Emission Properties

Mechanical Properties and Structure of Fly Ash Modified Basic Oxygen Furnace Slag Based Geopolymer Masonry Blocks

2020 ◽  
Vol 46 (3) ◽  
pp. 372-383
Author(s):  
N.T. Sithole ◽  
F. Okonta ◽  
F. Ntuli
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Coal Fly Ash ◽  
Basic Oxygen Furnace ◽  
Curing Temperature ◽  
Basic Oxygen ◽  
Load Bearing ◽  
Minimum Requirement ◽  
Basic Oxygen Furnace Slag ◽  
Furnace Slag

The objective of this research was to investigate the effect of Fly ash as a source of Si and Na on the mechanical performance of the Basic Oxygen Furnace Slag based (BOFS) geopolymer. BOFS has the lowest SiO2, Al2 O3, Na2 O content compared to other aluminosilicate sources (fly ash, metakaolin, granulated blast furnace slag and mine tailings); which have been used to effectively in geopolymer synthesis. SiO2 and Al2 O3, contents of BOFS are respectively 5-7 times and 6-8 times lower than those of fly ash, metakaolin and granulated furnace slag (GBFS). This study evaluated the potential use of fly ash as a source of Si and Al to improve the mechanical performance of a BOFS based geopolymer. The influence of varying amount of Coal Fly Ash (FA) (10–50%) on UCS was studied. The effects of several factors on the UCS of BOFS geopolymer were also investigated. The test variables were molarities of sodium hydroxide (NaOH) (5 M, 10 M and 15 M); the solid to liquid ratio (20 %, 25 % and 30 %); and the curing temperature (20°C, 40°C, 80°C and 100°C). It was established that most favorable conditions for the geopolymer synthesis were FA was 10% of the mixture, 5M NaOH and 80°C curing temperature. Attempts has been made to relate the microstructure of BOFS/FA based composite with properties of geopolymer. Aggregation was identified as the main particulate process as established by the evolution of the particle size distribution (PSD) and its derived moments during the geopolymerisation process. The morphology of the particles appeared flaky and fluffy. The developed composite met the minimum requirement of ASTM C34-13 for a structural clay load bearing non exposed masonry and load bearing exposed side construction masonry.

scholarly journals Effects of Corn Stalk Fly Ash (CSFA) on the Mechanical and Deformation Properties of Cemented Coal Gangue Backfill

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Tingye Qi ◽  
Haochen Wang ◽  
Guorui Feng ◽  
Xianjie Du ◽  
Zehua Wang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Shear Strength ◽  
Fly Ash ◽  
Substitution Rate ◽  
Drying Shrinkage ◽  
Coal Gangue ◽  
Corn Stalk ◽  
Surface Stability ◽  
Deformation Properties

To reduce the amount of cement used in cemented coal gangue backfill (CCGB, a mixture of coal gangue, cement, fly ash, and water), mechanical and deformation properties of CCGB in which CSFA partially replaces the cement (0, 10, 20, 30, and 40 wt%) were studied. Compressive strength, acoustic emission during uniaxial loading, shear strength, and drying shrinkage were analysed. The compressive strength, shear strength, and drying shrinkage tests were performed at different curing times. The results showed that cemented coal gangue and corn stalk fly ash backfill (CGCAB) presented better performance, and the CGCAB with a 20% substitution rate had the best performance at day 28. Despite having the largest drying shrinkage value, 20% is the best choice for the substitution rate of CSFA. A 20% CSFA addition can enhance the bearing capacity of CGCAB and improve its failure mode, which is of great significance to support the upper overburden load and maintain the surface stability of the goaf.

scholarly journals Monitoring and Assessment of Cemented Paste Backfill Containing Coal Gangue and Fly Ash in an Underground Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xinguo Zhang ◽  
Jinhai Zhao ◽  
Lin Xin ◽  
Kun Wang ◽  
Haiyang Pan
Keyword(s):  
Fly Ash ◽  
Monitoring System ◽  
Field Monitoring ◽  
Surface Subsidence ◽  
Coal Gangue ◽  
Longwall Face ◽  
Curing Temperature ◽  
Deformation Stage ◽  
Paste Backfill ◽  
Stable Stage

Cemented coal gangue paste backfill (CCGPB) containing coal gangue and fly ash is a backfilling technique newly developed in coal mines in China that allows environmentally hazardous products, such as gangue and fly ash, to be reused in underground stopes. CCGPB materials provide efficient ground support for the caving of strata and reduce surface subsidence. In this paper, field monitoring of CCGPB properties was conducted in an underground coal mine, which mainly included the measurement of the longwall face temperature, humidity, CCGPB internal hydration temperature, stress conditions inside the backfills, and displacement. First, the components of the backfills, paste technique, slurry generation procedures, coalfield geology, and mining conditions were introduced. Then, a monitoring system was designed in the field. An online monitoring system was installed. The results of the field monitoring showed that the curing temperature significantly varied, i.e., from 26°C near the main gate to 37°C near the tailgate. The curing humidity had the same trends, increasing from 60% relative humidity (RH) near the main gate to 81% RH near the tailgate. The internal hydration process of the paste was divided into four stages, i.e., the rapid hydration stage, slower hydration stage, rapid decline hydration stage, and relatively stable stage. The highest hydration temperature was 50°C, which was measured on the second day after the backfill process. The temperature approached stability at 41°C. The evolution of the roof stress applied on the CCGPB was divided into four stages: the development stage, regulation stage, rapid growth stage, and relatively stable stage. The maximum roof loading was 12 MPa in the middle of the longwall face. The deformation of the backfill experienced four stages, i.e., the rapid deformation stage, slow deformation stage, relatively stable stage, and long-term stable stage. The maximum deformation was 104.3 mm, appearing in the middle of the face. In addition, the compression ratio of the backfill was approximately 4%. The results of this study showed that the working conditions of backfills in the field were different from those in the laboratory. This paper provides guidance for the design of the CCGPB technique and the predictions of surface subsidence induced by the production process of underground mining.

scholarly journals Statistical Modelling of Ultrasonic Pulse Velocity of Fly Ash Based Geopolymer mortar using response surface methodology

2020 ◽  
Vol 2 (4) ◽  
Author(s):  
Muhammad Zahid ◽  
Nasir Shafiq ◽  
Muhammad Ali
Keyword(s):  
Response Surface Methodology ◽  
Fly Ash ◽  
Response Surface ◽  
Mechanical Performance ◽  
Statistical Modelling ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Curing Temperature ◽  
Significance Level

The fly ash based geopolymer has emerged as a capable and sustainable binder material in construction industry. Ultrasonic pulse velocity (UPV) method is a non-destructive technique for investigating the mechanical performance of concrete. Experimental investigation was performed for studying the effect of NaOH Molarity, Na2SiO3/NaOH and curing temperature on the ultrasonic pulse velocity of geopolymer mortar. Experiments were designed based on central composite design (CCD) technique of response surface methodology (RSM). Statistical model was developed and statistically validated and found significant as the difference between adjustable R-squared and predicted R-squared less than 0.2. Finally, the optimized mix proportion was assessed for maximized value of UPV. Experimental validation on the optimized mix reveals the close agreement between experimental and predicted values of UPV with significance level of more than 95%. The proposed technique improves the yield, the reliability of the product and the processes.

Mechanical performance and micro-structure of bentonite-fly ash and bentonite-sand mixes for landfill liner application

2021 ◽  
Vol 292 ◽  
pp. 126033
Author(s):  
Chandra Bhanu Gupt ◽  
Sanandam Bordoloi ◽  
Rakesh Kumar Sahoo ◽  
Sreedeep Sekharan
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Micro Structure ◽  
Landfill Liner

Long term mechanical performance of nano-engineered high volume fly ash concrete

2021 ◽  
pp. 103168
Author(s):  
Charith Herath ◽  
Chamila Gunasekara ◽  
David W. Law ◽  
Sujeeva Setunge
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
High Volume ◽  
Fly Ash Concrete ◽  
High Volume Fly Ash

Test and Study on Green High-Performance Marine Concrete Containing Ultra-Fine Limestone Powder

2013 ◽  
Vol 368-370 ◽  
pp. 1112-1117
Author(s):  
Jin Hui Li ◽  
Liu Qing Tu ◽  
Ke Xin Liu ◽  
Yun Pang Jiao ◽  
Ming Qing Qin
Keyword(s):  
Fly Ash ◽  
High Performance ◽  
Mechanical Performance ◽  
Chloride Ion ◽  
Limestone Powder ◽  
Ion Permeability ◽  
High Quality ◽  
Cracking Resistance ◽  
Slag Powder ◽  
Marine Concrete

In order to solve the environment pollution of limestone powder during production of limestone manufactured sand and gravel and problem of lack of high quality fly ash or slag powder in ocean engineering, ultra-fine limestone powder was selected for preparation of green high-performance marine concrete containing fly ash and limestone powder and that containing slag powder and limestone powder for tests on workability, mechanical performance, thermal performance, shrinkage, and resistance to cracking and chloride ion permeability. And comparison was made between such green high-performance concrete and conventional marine concrete containing fly ash and slag powder. Moreover, the mechanism of green high-performance marine concrete was preliminary studied. Results showed that ultra-fine limestone powder with average particle size around 10μm had significant water reducing function and could improve early strength of concrete. C50 high-performance marine concrete prepared with 30% fly ash and 20% limestone powder or with 30% slag powder and 30% limestone powder required water less than 130kg/m3, and showed excellent workability with 28d compressive strength above 60MPa, 56d dry shrinkage rate below 300με, cracking resistance of grade V, 56d chloride ion diffusion coefficient not exceeding 2.5×10-12m2/s. Mechanical performance and resistance to chloride ion permeability of limestone powder marine concrete were quite equivalent to those of conventional marine concrete. But it had better workability, volume stability and cracking resistance. Moreover, it can serve as a solution to the lack of high quality fly ash and slag powder.

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