Tests Research on Grouting Materials of Waste-Concrete-Powder Cement for Goaf Ground Improvement

Waste concrete powder (WCP) is proposed to replace part of the cement to seek environmentally friendly grouting materials for ground improvement in mine goaf. The optimal mixing proportion was selected based on the performance indexes of the water-separation ratio, stone rate, viscosity, setting time, and compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were also conducted to analyze mineralogical phases and investigate the microscopic mechanism. Test results show that the slurry prepared by the substitution rate of 70% and adding 0.05% water-reducing agent meets well the requirements of ground grouting in mine goaf. The WCP produced by grinding mainly exerts microaggregate effect in the slurry due to low activity. A lot of pores on the surface of WCP were shown by SEM which can absorb the water in the slurry and increase the stone rate. The WCP application for ground grouting in mine goaf can not only recycle WC but also provide new grouting materials for goaf ground.

On Smoothed MWSD Estimation of Mixing Proportion

The problem considered in the present paper is estimation of mixing proportions of mixtures of two (known) distributions by using the minimum weighted square distance (MWSD) method. The two classes of smoothed and unsmoothed parametric estimators of mixing proportion proposed in a sense of MWSD due to Wolfowitz(1953) in a mixture model F(x)=p (x)+(1-p) (x) based on three independent and identically distributed random samples of sizes n and , =1,2 from the mixture and two component populations. Comparisons are made based on their derived mean square errors (MSE). The superiority of smoothed estimator over unsmoothed one is established theoretically and also conducting Monte-Carlo study in sense of minimum mean square error criterion. Large sample properties such as rates of a.s. convergence and asymptotic normality of these estimators are also established. The results thus established here are completely new in the literature.

Numerical Simulation of Combustion of Natural Gas Mixed with Hydrogen in Gas Boilers

Hydrogen mixed natural gas for combustion can improve combustion characteristics and reduce carbon emission, which has important engineering application value. A casing swirl burner model is adopted to numerically simulate and research the natural gas hydrogen mixing technology for combustion in gas boilers in this paper. Under the condition of conventional air atmosphere and constant air excess coefficient, the six working conditions for hydrogen mixing proportion into natural gas are designed to explore the combustion characteristics and the laws of pollution emissions. The temperature distributions, composition, and emission of combustion flue gas under various working conditions are analyzed and compared. Further investigation is also conducted for the variation laws of NOx and soot generation. The results show that when the boiler heating power is constant, hydrogen mixing will increase the combustion temperature, accelerate the combustion rate, reduce flue gas and CO2 emission, increase the generation of water vapor, and inhibit the generation of NOx and soot. Under the premise of meeting the fuel interchangeability, it is concluded that the optimal hydrogen mixing volume fraction of gas boilers is 24.7%.

A Photometric Study of Regolith Intimate Mixing with Ice-Like Impurity

Surfaces of solid solar system objects are covered by layers of particulate materials called regolith originated from their surface bedrock. They preserve important information about surface geological processes. Often regolith is composed of more than one type of particle in terms of composition, maturity, size, etc. Experiments and theoretical works are being carried out to constrain the result of mixing and extract the abundance of compositional end-members from regolith spectra. In this work we have studied, photometric light scattering from simulated surfaces made of two different materials – one is highly bright quartz particles ≈ 80µm and the other moderately bright sandstone particles ≈ 250µm. The samples were mixed with varying proportions and investigated at normal illumination conditions to avoid the shadowing effect. Said combinations may resemble ice mixed regolith on various solar system objects and therefore important for in situ observations. We find that the combinations show a linear trend in the corresponding reflectance data in terms of their mixing proportion and some interesting facts come out when compared to previous studies.

Experimental investigation on buffer/backfill materials for radioactive waste repository downward facing sorption additivity of cesium, strontium and cobalt with different concentrations

Buffer/backfill materials for radioactive waste disposal sites consist of pure bentonite or bentonite-rock mixtures. In this study, the batch test method was used to obtain the sorption characteristics of important radionuclides such as Cs, Sr and Co on buffer/backfill materials; i. e., mixing Wyoming MX-80 bentonite or local Taiwanese Zhi-Shin bentonite with possible host rock (argillite and granite) in different proportions (0∼100%). The distribution coefficients (Kd) for Cs, Sr and Co were obtained from the experiments. The distribution coefficient for the bentonite-rock mixtures were found, with more than 50% of mixing proportion of bentonite to argillite or granite, to have very similar values to that of pure bentonite. Furthermore, it was clearly found that the sorption of Cs, Sr and Co to bentonite-rock mixtures is decreased as ionic strength of the liquid phase is increased from 0.001M to 1M for NaCl solutions. According to the experimental results, in synthetic groundwater, it is quite convenient and helpful to assess the distribution coefficients (Kd) of Cs, Sr and Co for buffer/backfill materials using batch sorption experiments with bentonite-rock mixtures of fixed mixing proportions.

Characterisation of briquettes from forest wastes: Optimisation approach

: Waste from a forest environment constitutes an enormous quantity of renewable energy resources. In this study undesirable forest materials, such as jatropha seed shells (JSSs) and Eucalyptus camaldulensis wood shavings (EcWSs) were used in the production of briquettes with Acacia senegal as the binder using mixing proportions of 0 : 100, 25 : 75, 50 : 50, 75 : 25 and 100 : 0 while the binder was varied from 50, 60, 70, 80 to 90 g. Some physical properties, such as the density, moisture content, water resistance and shatter index, were optimised using the response surface methodology at these mixing proportions. The outcome of the production showed the briquettes to have mean values of 0.66 kg·m^–3, 11.51, 91.12 and 99.7 % for the density, moisture content, water resistance and shatter index, respectively. The optimum mixing ratio and binder quantity of 75 : 25 and 60 g, respectively, would result in a briquette having a 0.70 kg·m^–3, 10.88, 98.11 and 99.86% density, moisture content, water resistance and shatter index, respectively. It has been revealed that the JSS and EcWS are potential organic wastes which could be used as a feedstock for the production of briquettes. It could be concluded that the variation in the mixing proportion of the JSSs, EcWSs and A. senegal significantly affected the properties of the produced briquettes.

Optimization of Technological Parameters for Preparation of Geopolymers Fabricated with Pulverized Fly Ash

Geopolymer is widely considered as an important direction for the comprehensive utilization of fly ash with its production increasing sharply year by year. The effect of mixing proportion including SiO2/Al2O3 molar ratio, Na2O/SiO2 molar ratio and water-solid ratio on the performances of geopolymer fabricated with pulverized fly ash with a median particle size of 3.3 μm was investigated by an orthogonal test in this work, and the optimum preparation technics were also obtained. Results indicated that the compressive strength of geopolymer reached the maximum of 61.0 MPa when SiO2/Al2O3 molar ratio was 3.3, Na2O/SiO2 molar ratio was 0.11 and the W/S ratio was 0.30 under the optimum preparation technics of aging time of 3h, mixing time of 3min and curing at 80℃ for 24h. Overall, Na2O/SiO2 molar ratio played the most important role on the compressive strength of geopolymer, but SiO2/Al2O3 molar ratio had a minimal impact. FTIR spectrum demonstrated that the sample with the optimum proportion exhibited a more complex asymmetric stretching vibration peak, which indicated that there were more activated silicon/aluminum monomers and dimers in fly ash depolumerized and repolymerized and tetrahedral phase transitions, and then geopolymer paste with denser microstructure was formed.

98 Impact of social mixing on feedlot steer eating and lying behavior

This study evaluated the impact of mixing cattle from two sources of feedlot steers (n = 96) on feeding and lying behavior. Angus crossbred steers (n = 48 McG and n = 48 BCS), similar in genetic composition, were transported (833.64 ± 85.29 km) to a feedlot 39-d prior to mixing where the two sources were housed without visual or tactile contact. Steers, blocked by source and stratified by d -34 body weight, were randomly assigned to one of 12 pens (n = 8 steers/pen) for the 42-d study. Pens were assigned to one of two treatments (n = 6 pens/treatment): 1) NOMIX—100% of cattle from McG (n = 3 pens) or BCS (n = 3 pens) and, 2) MIX—50% of cattle from BCS and 50% from McG (n = 6 pens). Instantaneous scan sampling (n = 61 scans/d; 10 min intervals) recorded the number of steers per pen eating and lying on d1, 2, 3, 4, 5, 6, 7, 8, 9, 14, 15, 16, 21, 22, 23, 28, 29, 36, and 37 after mixing. Proportion of steers lying varied across time (P < 0.0001); however, a greater proportion of steers laid down on d1 compared to d7, 8, 9, 16, and 28 (P < 0.03). The proportion of steers observed eating increased over time (P < 0.0001). Fewer steers ate on d1 than d9, 14, 15, 28, 29, and 36 (all P < 0.01). More steers were observed eating on d8 and 16 than the first seven days (all P < 0.01) and on d37 than the first 6 days (all P < 0.02). While there was no impact of mixing, data indicate that handling and sorting cattle into new pens impacts eating and lying behavior and it takes approximately a week for behavior to stabilize.

99 Impact of social mixing on feedlot steer eating and lying behavior

This study evaluated the impact of mixing cattle from two sources of feedlot steers (n = 96) on feeding and lying behavior. Angus crossbred steers (n = 48 McG and n = 48 BCS), similar in genetic composition, were transported (833.64 ± 85.29 km) to a feedlot 39-d prior to mixing where the two sources were housed without visual or tactile contact. Steers, blocked by source and stratified by d -34 body weight, were randomly assigned to one of 12 pens (n = 8 steers/pen) for the 42-d study. Pens were assigned to one of two treatments (n = 6 pens/treatment): 1) NOMIX—100% of cattle from McG (n = 3 pens) or BCS (n = 3 pens) and, 2) MIX—50% of cattle from BCS and 50% from McG (n = 6 pens). Instantaneous scan sampling (n = 61 scans/d; 10 min intervals) recorded the number of steers per pen eating and lying on d1, 2, 3, 4, 5, 6, 7, 8, 9, 14, 15, 16, 21, 22, 23, 28, 29, 36, and 37 after mixing. Proportion of steers lying varied across time (P < 0.0001); however, a greater proportion of steers laid down on d1 compared to d7, 8, 9, 16, and 28 (P < 0.03). The proportion of steers observed eating increased over time (P < 0.0001). Fewer steers ate on d1 than d9, 14, 15, 28, 29, and 36 (all P < 0.01). More steers were observed eating on d8 and 16 than the first seven days (all P < 0.01) and on d37 than the first 6 days (all P < 0.02). While there was no impact of mixing, data indicate that handling and sorting cattle into new pens impacts eating and lying behavior and it takes approximately a week for behavior to stabilize.