scholarly journals Influence of Binder Types and Temperatures on the Mechanical Properties and Microstructure of Cemented Paste Backfill

2021 ◽  
Vol 2021 ◽  
pp. 1-10 ◽  
Author(s):  
Zhaowen Du ◽  
Shaojie Chen ◽  
Sheng Wang ◽  
Rui Liu ◽  
Dehao Yao ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Microstructural Evolution ◽  
Red Mud ◽  
Hydration Product ◽  
Curing Temperature ◽  
Hydration Reaction ◽  
Burial Depth ◽  
Cemented Paste Backfill ◽  
Paste Backfill

In order to study the influence of burial depth or fire on the core area of cemented paste backfill (CPB), the experiment of CPB with different types of binder and temperature was carried out. Three types of binders, red mud (RM), Portland cement (PC), and slag cement (SC), are used and tested at 20°C, 40°C, 60°C, and 80°C. The macroperformance and microstructural evolution of CPB are analyzed using slump, uniaxial compressive strength (UCS), X-ray diffraction, and scanning electron microscopy (SEM). The results show that the coupled effects of binder type and temperature have a significant impact on the macroscopic performance and microstructural evolution of CPB. The CPB slump prepared with three types of binder meets the production requirement of the mine. Regardless of curing temperature and curing time, the uniaxial compressive strength of CPB samples with PC and SC is much higher than that of CPB samples with red mud. When cured for 12 hours, the uniaxial compressive strength of CPB samples containing PC and SC increases first, then decreases, and finally increases again with the increase of temperature. However, with the increase of temperature, the uniaxial compressive strength of CPB samples containing RM only increases first and then decreases. When the curing temperature is less than 40°C, the main reason for the increase in UCS was attributed to the fact that the temperature increase accelerates the hydration reaction and improves the density of the sample. When the curing temperature is 60°C, the main reason for the decrease in UCS is the formation of the expansive ettringite (AFt) which destroys the internal spatial structure of the sample. When the curing temperature is 80°C, the UCS increases again due to the fact that such high temperature can destroy the crystal structure of AFt and harden the hydration product C-S-H gel.

scholarly journals Experimental Investigation on Strength and Failure Characteristics of Cemented Paste Backfill

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhihong Zhang ◽  
Jiacheng Li
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Uniaxial Compressive Strength ◽  
Cement Content ◽  
Confining Pressure ◽  
Curing Temperature ◽  
Cemented Paste Backfill ◽  
Upward Trend ◽  
Paste Backfill ◽  
Curing Age

The strength characteristics of cemented paste backfill (CPB) in mining areas are key control factors for the safety assessment of overlying strata. A series of experiments about uniaxial compression and triaxial compression were carried out to study the influence of cement content of filling slurry, curing age, and curing temperature on strength behavior of CPB specimens. The failure mechanism and damage feature of CPB have been investigated. The results show the following: (1) The uniaxial compressive strength of CPB specimens exhibits an upward trend with the increase of cement content and curing age. When the cement content is high, the uniaxial compressive strength increases sharply with increasing curing age. (2) The cohesion of CPB specimens increases with the increase of cement content of filling slurry, curing age, and curing temperature. The cohesion of CPB specimens with curing age 7 days and 14 days increases linearly with increasing cement content. At the later stage of curing age, the strength growth of high cement content backfill is significantly greater than that of low cement content. The internal friction angle of the filling increases slightly with increasing filling cement content, curing age, and curing temperature. (3) The shear strength of CPB specimens at curing age 7 days exhibits an upward trend with the increase of confining pressure, while the shear strength at 14 days and 28 days curing age decreases slightly as the confining pressure increases. (4) With the increase of cement content in backfill, the brittleness increases significantly when the backfill is damaged. The failure mode of CPB specimens changes from monoclinic section shear failure to X-type failure with increasing curing age, and the failure process is divided into four stages: pore compaction, linear elastic deformation, plastic deformation, and post-peak failure.

scholarly journals Strengthening Behavior of Cemented Paste Backfill Using Alkali-Activated Slag Binders and Bottom Ash Based on the Response Surface Method

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 855
Author(s):  
Qi Sun ◽  
Xueda Wei ◽  
Tianlong Li ◽  
Lu Zhang
Keyword(s):  
Response Surface ◽  
Bottom Ash ◽  
Hydration Product ◽  
Cemented Paste Backfill ◽  
Alkali Activated Slag ◽  
Surface Method ◽  
Optimal Mix ◽  
Paste Backfill ◽  
Activated Slag ◽  
Alkali Activated

A new type of cemented paste backfill (CPB) was prepared by using the bottom ash (BA) from a thermal power plant as an aggregate, alkali-activated slag as a binder, and an air-entraining agent as an admixture. Based on the central composite design (CCD) response surface method, the mix ratio was optimized, and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was performed on the optimal mix ratio. ImageJ software was utilized to determine the porosity of the experimental samples at various curing ages. The results indicate that the optimal mix ratio of the aggregate-binder ratio is 3.28, the alkali dosage is 3%, the solid content is 67.44%, and the air-entraining agent dosage is 0.1%. As the curing age increases, the porosity of CPB gradually decreases. A calcium aluminosilicate hydrate (C-A-S-H) gel is the main hydration product of alkali-activated slag. At the beginning of the hydration reaction, the slag gradually dissolves, and the C-A-S-H product binds the BA together. At 14 d, complete calcium hydroxide (CH) crystals appeared in the hydration product. Finally, the degree of C-A-S-H crystallization increased further to form a dense structure.

scholarly journals Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 172
Author(s):  
Mamert Mbonimpa ◽  
Parrein Kwizera ◽  
Tikou Belem
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Room Temperature ◽  
Freezing Temperature ◽  
Curing Temperature ◽  
Strength Development ◽  
Short Term ◽  
Practical Applications ◽  
Humidity Chamber ◽  
Paste Backfill

When cemented paste backfill (CPB) is used to fill underground stopes opened in permafrost, depending on the distance from the permafrost wall, the curing temperature within the CPB matrix decreases progressively over time until equilibrium with the permafrost is reached (after several years). In this study, the influence of declining curing temperature (above freezing temperature) on the evolution of the unconfined compressive strength (UCS) of CPB over 28 days’ curing is investigated. CPB mixtures were prepared with a high early (HE) cement and a blend of 80% slag and 20% General Use cement (S-GU) at 5% and 3% contents and cured at room temperature in a humidity chamber and under decreasing temperatures in a temperature-controlled chamber. Results indicate that UCS is higher for CPB cured at room temperature than under declining temperatures. UCS increases progressively from the stope wall toward the inside of the CPB mass. Under declines in curing temperature, HE cement provides better short-term compressive strength than does S-GU binder. In addition, the gradual decline in temperature does not appear to affect the fact that the higher the binder proportion, the greater the strength development. Therefore, UCS is higher for samples prepared with 5% than 3% HE cement. Findings are discussed in terms of practical applications.

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