Orthogonal test design for optimization of synthesis of super early strength anchoring material

Calcination of calcium sulphoaluminate cement using flue gas desulfurization gypsum as whole calcium oxide source

Carbonates and bicarbonates are two groups of accelerators which can be used in sprayed concrete. In this study, the effects of the two accelerators sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) (0%, 1%, 2%, 3%, and 4% by weight of ordinary Portland cement OPC) on the properties of OPC paste were compared. The results show that both of them could accelerate the initial and final setting time of OPC paste, but the effect of the two accelerators on the compressive strength were different. After 1 day, sodium bicarbonate at 3% had the highest strength while sodium carbonate at 1% had the highest strength. After 7 days, both of the two accelerators at 1% had the highest compressive strength. After 28 days, the compressive strength decreased with the increase of the two. The improved strength at 1 and 7 days was caused by the accelerated formation of ettringite and the formation of CaCO3 through the reactions between the two with portlandite. The decrease of strength was caused by the Na+ could reduce the adhesion between C-S-H gel by replacing the Ca2+. NaHCO3 was found be a better accelerator than Na2CO3.

Comparison of Effects of Sodium Bicarbonate and Sodium Carbonate on the Hydration and Properties of Portland Cement Paste.

Effects of calcium bicarbonate on the properties of ordinary Portland cement paste

Grouting materials are used frequently in grouting reinforcement projects, such as mining and coastal engineering. Double liquid grouting materials are mostly used because of the fast setting and high early strength properties when the two slurries are mixed together but high fluidity when the two slurries are separated. In our study, double liquid grouting materials were developed from CSA cement (slurry A), quicklime and fluorgypsum (slurry B). Aluminum sulfate was added in slurry B in order to counteract any adverse effects caused by the fluorgypsum, such as the decreased early compressive strength and the prolonged setting time. The effects of aluminum sulfate content and the quicklime/fluorgypsum ratio on the setting time, hydration heat, and compressive strength of the double liquid grouting materials were investigated, and the hydration products were characterized through thermogravimetry-differential thermal analysis (TG-DTA), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM) tests. The results show that the addition of aluminum sulfate can shorten the setting time and increase compressive strength at both early and later ages. Considering the setting time and compressive strength of double liquid grouting material at the same time, the optimum content of aluminum sulfate was found to be 2%, and the optimum ratio of quicklime/fluorgypsum was found to be 2:8. The values of the optimum content of aluminum sulfate and ratio of quicklime/fluorgypsum were verified from theoretical analysis.

Effects of Aluminum Sulfate and Quicklime/Fluorgypsum Ratio on the Properties of Calcium Sulfoaluminate (CSA) Cement-Based Double Liquid Grouting Materials.

Effects of lithium carbonate on performances of sulphoaluminate cement-based dual liquid high water material and its mechanisms

The invention discloses a sectional grouting method for a broken coal rock deep hole of a fully mechanized coal mining face. The method sequentially comprises the following steps of forming holes in advance, inserting tubes, sealing holes, and grouting in an advanced abutment pressure area. The sectional grouting method disclosed by the invention has the advantages that firstly a hole sealing bag is matched with a one-way explosion valve, so that full-hole multi-sectional hole sealing can be realized, multi-sectional grouting can be realized, and whole-hole grouting is converted into sectional grouting, therefore the utilization efficiency of the deep hole is greatly improved, the uniformity of grouting a coal rock body in a full-hole area is further guaranteed, and the grouting effect is improved; secondly, a double-liquid quick-coagulating grouting material is adopted for sealing holes and grouting, so that the hole sealing time can be greatly shortened and the demand of quick proceeding of a working face is met due to quick coagulating time and fast strength increment of the material.

Sectional grouting method for broken coal rock deep hole of fully mechanized coal mining face

The utility model relates to a technical field is administered in colliery face fall district's slip casting, the utility model discloses a colliery face fall district's slip casting treatment system. This system is mainly including gentle mould bag, slip casting pipe, hydraulic prop, layer board, bracing piece etc. And hydraulic prop and hydraulic support top be the layer board, and layer board upper portion is gentle mould bag, and the bracing piece setting is internal at gentle mould bag, and the slip casting pipe is inserted and internal and stretched into to the roof fall and distinguish the commanding point at gentle mould bag. The utility model discloses the gas that the security is poor in the time of can solving the processing of colliery face fall district, intensity of labour is high, construction speed is slow and caused by roof fall district gas accumulation transfinites or even the explosion problem. The simple structure of this system, simple to operate, reasonable in design, the security performance is good, construction speed is fast, can the roof fall of reliable assurance colliery distinguish filling quality, and the economic technology benefit is showing. , the colliery face fall has good popularization prospect in distinguishing the improvement field.

Colliery face fall district's slip casting treatment system

The sealing wall is a main facility for ventilation of a coal mine. The sealing wall which has the functions of insulation and sealing is widely used underground. Multiple modes, such as shotcrete, masonry, and so on are used for building the sealing wall. At present, the sealing wall adopting the concrete and the masonry is widely used, is rich in practical and technical experience, is widely known by design personnel, but is complex in technology, high in labor intensity, low in building speed, hard in material transport, and serious in material waste. Besides, the sealing wall adopting the above modes has no buffering performance and is easy to crack and fail under the dynamic pressure. The serving time of the permanent sealing wall for the coal mine is long, the rigid sealing wall is easy to damage and fails after a long period of loading, and the surrounding rock stratum is easy to crack, so that an air leakage channel is formed, and the sealing wall fails, and the sealing wall is difficult to repair and has safety hidden hazards. The constructing system and method for the coal mine permanent sealing wall have the advantages of simple process, rapid construction speed, strong adaptability, low cost, and high reliability.

Constructing system and method for coal mine permanent sealing wall

The invention provides a fluorgypsum-based high-water and super high-water filling material and a preparation method thereof. The material is prepared from a component A and a component B, wherein the component A is prepared from, by weight percentage, aluminoferic cement clinker, calcium bentonite, an accelerator, a suspending agent and a thickening agent; the component B is prepared from, by weight percentage, fluorgypsum, calcium oxide, metakaolin, a compound early strength agent, the suspending agent and calcium carbonate. The material has the advantages of achieving early strength and rapid hardening and being high in water-cement ratio, adjustable in initial setting time and less in material consumption, after the component A and the component B are mixed, no bleeding happens, and the initial setting time is 3-25 minutes and can be adjusted according to field needs.

Sun Yapeng

Papers

Effects of lithium carbonate on performances of sulphoaluminate cement-based dual liquid high water material and its mechanisms

Sectional grouting method for broken coal rock deep hole of fully mechanized coal mining face

Colliery face fall district's slip casting treatment system

Constructing system and method for coal mine permanent sealing wall

Fluorgypsum-based high-water and super high-water filling material and preparation method thereof