Microscopic Pore and Filling Performance of Coal Gangue Cementitious Paste

To obtain the influence laws of the fine gangue rate on the properties of coal gangue cementitious paste, the slump, divergence, stratification, bleeding, setting time and mechanical strength with the change of fine gangue rate were studied on the basis of keeping the amount of cementing material and slurry concentration unchanged. The porosity and the distribution of pore diameter of the filling specimen for curing 28 d were tested by a mercury injection instrument under different fine gangue rate conditions. It was shown that the slump, divergence, setting time and compressive strength of the paste firstly increased and then decreased with increasing fine gangue rate. The stratification and bleeding rate decreased with increasing fine gangue rate. The smaller the critical pore size of the paste was, the smaller the porosity was, the smaller the average pore size was. When the fine gangue rate was 40%, the maximum critical pore diameter of the paste was 55.79 μm, and the corresponding porosity was 17.54%, and the properties of filling paste were the best. When the fine gangue rate further increased, the aggregate surface area increased, and the reaction product of cementitious materials could not effectively fill the pores. It weakened the agglomeration effect. The particles surface of coal gangue was fragmental and flake deposit with irregular shape and uneven fold morphology. It was easy to be bonded with the surface of other filling material. The hydration products of coal gangue cementitious material were a large number of C-S-H gel with fibrous shape and ettringite（AFt） with compact block structure. The theoretical reference was provided for the preparation of low cost gangue cemented filling materials in coal mines.

Pore structure characteristics of the relative water-resisting layer on the top of the Ordovician in Longgu Coal Mine

In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 × 10^-3-2.782762× 10^-3, 4.1092 × 10^-3 -7.3387 × 10^-3 and 2.0891 ×10^-3-3.2705 × 10-3 μm^2, respectively, and porosity of that is 0.6786-0.9197%, 0.3109-0.3951% and 0.9829-1.8655%, respectively. The results indicate that： （I） the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 μm; （2） the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; （3） the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m; and （4） the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting lavers.

New insights into the effect of hard carbons microstructure on the diffusion of sodium ions into closed pores

Closed pores formed in hard carbons play an essential role in sodium storage at plateau region.However,the effect of different structural features on the diffusion of sodium ions into closed pores remains unclear.Herein,a precursor reconstruction strategy is conducted to regulate carbon microstructures including interlayer spacing,defect concentration,and closed pore volume by changing the ratio of aromatic and polysaccharide components.Aromatic structure parts tend to develop disordered carbons with fewer defects,larger interlayer spacing,and smaller closed pore volume,while polysaccharide components prefer to form disordered carbons with more defects,smaller interlayer spacing,and larger closed pore volume.Through the correlation analysis of microstructure features and the sodium storage capacity below 0.1 V.It finds that the intercalation capacity is proportional to the ratio of pseudo-graphitic domains,whereas the pore filling capacity appeared at lower potential gradually decreases with the increasing defect concentration due to homo-ionic repulsion effect,without linear correlation with shortrange microcrystalline and closed pore volume.The optimized sample with suitable interlayer spacing and defect concentration exhibits a high plateau capacity of 241.7 m Ah/g.This work provides insights into the exploitation of closed pore sodium storage performance.

Pore-fillings of dolomite reservoirs in Sinian Dengying Formation in Sichuan basin

The Sinian Dengying Formation in the Sichuan basin is an important potential reservoir for oil and gas exploration in the periphery of the Sichuan basin.Its reservoirs were well developed.And many kinds of fillings which lead to the decrease of pores can be seen in reservoir pores and caves.In this paper,the pore fillings of the Dengying Formation reservoir in Sichuan basin are the object of study.The types and characteristics of the fillings are studied in detail by means of rock slices analysis,cathode luminescence,trace elements and inclusion temperature measurement.The study shows that the fillings include dolomite fillings and siliceous quartz fillings and bitumen fillings.Among them,dolomite fillings can be divided into botryoidal dolomite fillings,foliated dolomite fillings,finely-medium crystalline dolomite fillings and coarse crystalline dolomite fillings.50%–80%of the pores are filled by the dolomite fillings with botryoidal structure,and the pores can be partially full filled;0%–20%of pores are filled by foliated dolomite fillings;20–80%of the pores are filled by finely-medium dolomite fillings;20–80%of the pores are filled by coarse crystalline dolomite fillings.1%–5%of secondary pores are often filled by siliceous quartzs,and the pores can be partially full filled.Bitumen fillings often occur after the above-mentioned fillings,and the residual pores are often semi-filled by bitumens,which makes the original pores and throat smaller and reduces the effective porosity and permeability of the reservoir.So,it is a destructive diagenesis.The pore fillings make the secondary porosity in the reservoir significantly lower,which is not conducive to the formation and preservation of the Dengying Formation reservoir.

Principle and Method of Optimization Design for Soft Soil Stabilizer

A stabilized soil structure formation model was introduced. In order to form compact stabilized soil structure, cementitious hydrates were needed to wrap and bind the soil aggregates. Meanwhile, expansible hydrates were needed to squeeze and fill the pores, especially the pores in the aggregates. The experimental results show that the influences of various chemical characteristic factors of soil on the strength of the stabilized soil are boiled down, for the influence on the concentration of Ca（OH）2 in the pore solution of the stabilized soil, and the amount of CSH generated by cement. Finally an optimization design method is proposed, with which the stabilizer can be designed according to characteristics of soil samples.

Assessing soil nitrous oxide emission as affected by phosphorus and nitrogen addition under two moisture levels

Agricultural soils are deficient of phosphorus （P） worldwide. Phosphatic fertilizers are therefore applied to agricultural soils to improve the fertility and to increase the crop yield. However, the effect of phosphorus application on soil N2O emissions has rarety been studied. Therefore, we conducted a laboratory study to investigate the effects P addition on soil N2O emissions from P deficient alluvial soil under two levels of nitrogen （N） fertilizer and soil moisture. Treatments were arranged as follows： P （0 and 20 mg P kg-1） was applied to soil under two moisture levels of 60 and 90% water filled pore space （WFPS）. Each P and moisture treatment was further treated with two levels of N fertilizer （0 and 200 mg N kg-1 as urea）. Soil variables including mineral nitrogen （NH4＋-N and NO3--N）, available P, dissolved organic carbon （DOC）, and soil N2O emissions were measured throughout the study period of 50 days. Results showed that addition of P increased N2O emis- sions either under 60% WFPS or 90% WFPS conditions. Higher N2O emissions were observed under 90% WFPS when compared to 60% WFPS. Application of N fertilizer also enhanced N2O emissions and the highest emissions were 141 μg N2O kg-1 h-1 in P＋N treatment under 90% WFPS. The results of the present study suggest that P application markedly increases soil N2O emissions under both low and high soil moisture levels, and either with or without N fertilizer application.

Sulfate Attack Resistance of Air-entrained Silica Fume Concrete under Dry-Wet Cycle Condition

Based on the erosion resistant coefficient,the effects of water-cement ratio,air-entrained,silica fume content and sand ratio on the sulfate attack resistance of air-entrained silica fume concrete were studied by orthogonal experiments in order to explore its sulfate attack resistance under dry-wet condition.A more significant model of concrete resistance to sulfate attack was also established,thus this work provided a strategy reference for quantitative design of sulfate attack resistant concrete.The experimental results show that dry-wet cycle deteriorates the concrete resistance to the sulfate attack,and leads to the remarkable declines of concrete strength and sulfate resistance.Air bubbles in the air-entrained silica fume concrete lower and delay the damage resulted from the crystallization sulfate salt.However this delay gradually disappears when most of the close bubbles are breached by the alternative running of the sulfate salt crystallization and the permeating pressure,and then the air bubbles are filled with sulfate salt crystallization.The concrete is provided with the strongest sulfate resistance when it is prepared with the 0.47 water-binder ratio,6.0% air-entrained,5% silica fume and 30% sand ratio.The erosion resistant coefficients K80 and K150 of this concrete are increased by 9%,7%,9%,and 5% respectively as compared with those of concretes without silica fume and air entraining.

Sorption of triclosan on electrospun fibrous membranes: Effects of pH and dissolved organic matter

Three hydrophobic and polyporous electrospun fibrous membranes(EFMs)were prepared by electrospinning methoxy polyethylene glycol-poly(lactide-co-glycolide)(MPEG-PLGA),poly(D,L-lactide-co-glycolide)(PLGA)and poly(D,L-lactide)(PDLLA).The effects of pH and dissolved organic matter(DOM)on triclosan(TCS)sorption by EFMs in aqueous solution were investigated.The results indicated that hydrogen bonding,hydrophobic and π-π bonding interactions led to fast adsorption,which governed the adsorption rates of TCS onto EFMs.The maximum sorption capacities of MPEG-PLGA,PLGA and PDLLA reached 130,93 and 99 mg g^-1,respectively,which were in positive correlation with their pore volumes and influenced by pore filling processes.The solution pH could significantly influence the TCS sorption by EFMs.In acid condition,protonated TCS facilitated their sorption onto EFMs.No obvious sorption was observed in alkaline condition due to repulsive forces between negatively charged EFMs and deprotonated TCS(pKa=7.9).The presence of DOM inhibited TCS sorption onto EFMs due to competitive adsorption.The results could be due to the occupation of the adsorption sites and the blockage of the pore entrance by DOM.