3102 results about "Cement paste" patented technology

The invention discloses a device and method for preparing nitrogen foam cement. The preparing device comprises a foam cement producer, a liquid nitrogen evaporator, a liquid nitrogen plunger pump, a foam liquid plunger pump, a foam liquid tank, a heat exchange system, a liquid nitrogen pipeline, a high-pressure cement paste pipeline, a first pipeline, a foam cement discharge pipeline and a densitydetecting device. The heat generated by a power unit, a hydraulic system and other devices in a nitrogen foam well fixing device is recovered through the heat exchange system, the recovered heat is used as a heat source of the liquid nitrogen evaporator, energy conservation and environment protection are realized, the energy utilization rate is high, and equipment input is low. Liquid nitrogen and foam liquid are pressurized through a high-pressure liquid nitrogen plunger pump and a high-pressure foam liquid plunger pump, the mixing uniformity is increased, and the density of foam cement is reduced. The density of the foam cement is detected in real time through the density detecting device, the flow of the liquid nitrogen and / or foam liquid is adjusted according to the density, and the density is simply controlled. By arranging a clear water tank, after operation ends, the equipment and pipelines are flushed, and the service life is polonged.

An injectable mixture for substituting bone tissue in situ comprises: A) a two-component powder / liquid bone cement which upon mixing forms a self-hardening cement paste; and B) a third component consisting of a liquid which essentially is non-miscible with the cement paste and which is suitable to be washed out after hardening of said mixture in situ, resulting in a porous bone substituting material; and C) an X-ray contrast agent which is an organic substance. The injectable bone substitute material for bone augmentation has adaptable mechanical properties, an optimal radio-opacity without any inorganic X-ray contrast agent and therefore good biocompatibility.

The invention relates to a preparation method of a slow-setting polycarboxylic acid water reducing agent, which is implemented by carrying out free radical copolymerization reaction on allylsulfonate monomers, acrylic monomers, polyethylene glycol nono-methyl ether methacrylate macromonomers and maleic anhydride grafted beta-cyclodextrin macromonomers. The invention is characterized in that a beta-cyclodextrin side chain is introduced into a polycarboxylic acid main chain, so that the polycarboxylate water reducing agent has favorable slow setting property, micro air-entraining property and better fluidity. The obtained polycarboxylic acid water reducing agent has the advantages of stable product performance, strong adaptability to cement and favorable compatibility; and the cement paste fluidity is up to higher than 290mm (W / C=0.29), the water reducing rate of concrete is up to 30-40%, and the slump protection time is 3-5 hours. The preparation method provided by the invention has the characteristics of unique technique, excellent product performance and the like.

The invention relates to a preparation method of a star polycarboxylic acid high-performance water reducing agent. Polybasic alcohol and (methyl) acrylic acid used as main raw materials for esterification are esterified and polymerized to prepare the star polycarboxylic acid high-performance water reducing agent material: the (methyl) acrylic acid and polybasic alcohol used as reactants are esterified under the action of a catalyst to firstly prepare a star polymerizable active terminal, and free-radical polymerization reaction is carried out with unsaturated polyethenoxy ether, molecular weight regulator and unsaturated carboxylic acid monomer under the action of an initiator to prepare the star polycarboxylic acid high-performance water reducing agent. The invention is easy to control, and has the advantages of high polymerization degree, low cost and no pollution; the esterification reaction is carried out form an active core, and the free-radical polymerization is carried out to generate the chain arm, thereby implementing the polycarboxylic acid high-performance water reducing agent in a star molecular structure; and under the condition of common doping amount and low doping amount, the star polycarboxylic acid high-performance water reducing agent has better cement paste flowability and holding capacity than the traditional linear and comb polycarboxylic acid water reducing agents, and has favorable cement adaptability and concrete application performance.

The invention discloses a bionic concrete artificial fish reef arranged on the seafloor. According to the fish reef, C40 concrete is used for pouring to form an artificial fish reef base body, the surface of the base body is covered with a protective layer which is composed of cement mortar, biological calcium carbonate and oyster shells, the biological calcium carbonate is made of eggshells, corals, seashells and fishbone and is used as an additive to be added into the cement mortar, the cement mortar mixture is smeared on the surface of the fish reef base body to form cement paste after the biological calcium carbonate and the cement mortar are evenly stirred together, and the oyster shells are inlaid in the cement paste in a convex face outward mode. According to the artificial fish reef, the environment-friendly function, the durable function and the trapping function are integrated, the cement mortar covering layer doped with the biological calcium carbonate and the coating of the oyster shells can attract marine organisms to inhabit, and thus the trapping effect of the artificial fish reef can be better achieved; compared with a traditional concrete fish reef, the artificial fish reef has good waterproof property and chloride ion resistance, surface roughness and alkalinity of the surface of the fish reef are appropriate, bionic performance is achieved, and the fish collecting effect is excellent.

The invention relates to a method for directly synthesizing a pure solid high-performance polycarboxylate water-reducer in one step, belonging to the field of water-reducers. According to the method, the pure solid high-performance polycarboxylate water-reducer is prepared by taking an acrylic compound and unsaturated polyoxyethylene ether as polymerization reaction monomers, adding a molecular weight regulator and carrying out free-radical polymerization reaction under the action of an initiator and under a solvent-free environment. The method disclosed by the invention is strong in controllability, high in polymerization degree, low in cost, environment-friendly and pollution-free, achieves the purpose of preparing the absolutely anhydrous pure solid polycarboxylate water-reducer by bulk polymerization, not only has the fluidity and holding property of cement paste, cement adaptability and concrete application performance which are similar to those of a polycarboxylate water-reducer prepared from a common solution by polymerization and can be prepared into any concentration of solution according to actual demands as the pure solid high-performance polycarboxylate water-reducer prepared by direct polymerization is an anhydrous pure solid, but also is free of postprocessing working procedures, such as heat drying or solvent separation and is more convenient to transport, saved in transport cost and favorable in market competitiveness and application prospect.

The invention discloses a method for exchanging a tool of a shield machine for tunnel construction, which comprises the steps of: (1) soil cabin replacement filling: performing the process of soil cabin replacement filling by using a spiral excavating machine and a slip casting system synchronously working with the spiral excavating machine; (2) advanced slip casting inside the machine: beating a plurality of slip casting pipes into the soil on the upper part of the shield machine from inner to outer inside the shield machine by respectively passing through a plurality of advanced geologic holes and then synchronously injecting cement paste into the soil on the upper part of the shield machine through the slip casting pipes by using a slip casting device till the cement paste cannot be injected any more; (3) cleaning cabin and exchanging tool synchronously: manually cleaning the cement plaster solidified inside the soil cabin and synchronously exchanging the tool mounted on the shield machine; and (4) getting rid of the difficult position of the shield machine and recovering the process. The method provided by the invention has the advantages of reasonable design, convenience for operation, low cost, high safety factor, good use effect and capable of solving the problem that the tool cannot be exchanged in the traditional tool exchanging mode under severe tool exchanging conditions.

The invention belongs to the technical field of building materials, and particularly relates to an early-strength composite foam concrete foaming agent and a preparation method thereof. The early-strength composite foam concrete foaming agent comprises the following components in percentage by mass: 40%-80% of composite foaming components, 1.0%-5.0% of foam stabilizing components, 3.3%-22% of early-strength components and 10%-45% of water, wherein the composite foaming components are formed by compounding synthesized surface active agent foaming agents and protein foaming agents. The early-strength composite foam concrete foaming agent prepared through the method disclosed by the invention has the advantages of high foam expansion, excellent foam stability and good compatibility with general cement pastes; the early-strength composite foam concrete foaming agent disclosed by the invention is applied to foam concrete; the prepared foam concrete has no recess phenomenon and is fast enhanced in early strength, and the foam concrete with a density grade equal to 300 kg / m<3> or above is more easily prepared.

Methods for design-optimization of concrete compositions having workability optimized gradation and fixed cement paste volume are disclosed. In particular, the methods allow for designing and manufacturing of concrete compositions having target compressive strengths and slumps and having a fixed volume of cement paste based on target compressive strengths and / or target slump amounts using improved methods that more efficiently utilize all the components from a performance standpoint.

The invention relates to a fishbone-shaped anchor rod. The fishbone-shaped anchor rod comprises an anchor head, an anchor rod body and a sleeve pipe. A movable conical propelling body is arranged in the anchor head and connected to the front end of the anchor rod body through a thread. The anchor head is connected to the front end of the sleeve pipe through a thread. Spine holes are evenly distributed in the anchor head and internally provided with short-rod-shaped anchor head bore spines. Two or more pairs of fishbone-shaped blade mechanisms are evenly distributed on the anchor rod body. Each blade mechanism comprises blades and a clamp. When the fishbone-shaped anchor rod is not used, the blades are folded, abut against the anchor rod body and are located in the sleeve pipe. When the fishbone-shaped anchor rod is used, a roof bolter rotates forwards, and the fishbone-shaped anchor rod is drilled into rock soil. Pressure is exerted on the rear end of the anchor rod body, the propelling body in the anchor head extrudes the anchor head bore spines out of the anchor head, and the anchor head bore spines are embedded in a rock soil body. The roof bolter rotates reversely till the sleeve pipe is separated from the anchor head. Then, outward pull force is provided for the anchor rod body till the blades evenly distributed on the anchor rod body are in a completely unfolded state. Finally, a grouting machine is aligned with the anchor rod body and pours cement paste into the anchor rod body till a cavity between the anchor rod body and the rock soil body is completely filled. Then, installation of the anchor rod body is finished.

Floor, ceiling and wall covering (01) material, consisting of natural stones, i.e. marble, granite, limestone, onyx, travertine and sandstone, cement based tiles, softwood and hardwood, wood fiber HDF, MDF, agglomerated cork, rubber, and composite tile materials, such as stone, quartz or vinyl composition tiles, in format of tile slabs. Which the thickness is between 4 mm and 35 mm in which at the two opposite edges or sides are jointed together and interlocked by mechanical locking means, by connecting or inserting, (A6 to A5) and connecting or pressing downward (A8 to A9) using polyvinyl chloride (PVC) couplings, connecting in the form of a tongue and a groove which will prevent shifting of two interlocked tiles and or slabs into the opposed direction of each section tile or slab, with an integrated backing layer consisting of cork syntactic foam material, The invention relates to a natural stone core tile slab, allowing for an installation without the use of cement, adhesives or grout, provided with such a mechanical locking system jointed to the core (A4) according to the invention.

A device for injecting a cement paste into a bone cavity and forming a hardened cement in-situ under pressure includes a syringe having an injection end; a pocket having an inlet and a body for containing the paste entering the inlet; and a mounting mechanism at the injection end for connecting the inlet of the pocket to the injection end so that the body of the pocket can contain the paste through the syringe. The device further includes a leaking mechanism provided at the injection end of the syringe for allowing liquid contained in the paste inside the pocket to be expelled from the pocket under pressure, and an opening mechanism which can be operated at a location away from the injection end to open the body of the pocket.

The invention discloses a synthesis method of a polycarboxylic acid high-performance water reducing agent of a star-like structure, belonging to the field of a water reducing agent. According to the synthesis method, polybasic alcohol, (methyl) acrylic acid, a polyethylene glycol compound and the like are used as esterification raw materials, and the polycarboxylic acid high-performance water reducing agent of the star-like structure is prepared through a sequential esterification and polymerization method, i.e., the (methyl) acrylic acid and the polybasic alcohol are used as reactants, a star-like polymerizable active end is prepared through esterification reaction under the action of a catalyst, and then the polycarboxylic acid high-performance water reducing agent is prepared from the star-like polymerizable active end and esterification macromolecule, a molecular weight regulator and an unsaturated carboxylic acid monomer under the action of an initiator through free radical polymerization reaction. The synthesis method has the advantages of simplicity, easiness in control, high polymerization degree, low cost, no pollution, capability of realizing the polycarboxylic acid high-performance water reducing agent of the star-like structure connected with a plurality of polycarboxylic acid molecules, and more superior cement paste fluidity and holding capacity, good cement adaptability and concrete application performance compared with the conventional linear and comb-shaped polycarboxylic acid water reducing agent in the case of normal and low added amount.

The invention discloses a method for synthesizing polycarboxylic acid high-property water reducer by copolymerization of amidated active monomers, belonging to the field of water reducer. In the invention, the polycarboxylic acid high-property water reducer material is prepared by a method of first amidation and second copolymerization, namely, taking a (methyl) acrylic monomer and methoxyl polyoxyethylene ether with the other end containing amino as reactant, preparing a polymerizable monomer by amidation reaction under the action of catalyst, then copolymerizing the polymerizable monomer with the (methyl) acrylic monomer and a chain transfer monomer in water solution under the action of initiator, and then neutralizing with alkaline solution, thus preparing the polycarboxylic acid high-property water reducer. The method is low in cost, environment-friendly and free from pollution and achieves high polymerization degree and strong controllability; by copolymerization of amidated active monomer, an amide structure is introduced into the molecular structure of polycarboxylic acid water reducer, cement can obtain good flowing property, the flowing capacity maintaining capability of neat cement paste is improved obviously, excellent cement adaptivity is shown, and excellent flowing effect can be obtained under low doping quantity and low water-ash ratio.

The invention discloses a method for extracting gas from a separation layer below an overlying strata, draining water and grouting through a combined drill hole and belongs to a mine disaster prevention method. The method for extracting gas from the separation layer below the overlying strata, draining water and grouting through the combined drill hole includes that installing a drill site at a transportation roadway of a preparatory work face adjacent to a coalface, constructing the combined drill hole in the part about to generate the separation layer below the overlying strata above the gob of the coalface in a mode of keeping away from a caving zone, wherein the combined drill hole is composed of an inside gas extraction pipe and a water draining-grouting pipe; after the separation layer is generated, preventing the mine disaster according to the stages that firstly, draining water from the separation layer through the combined drill hole; secondly, after the gas is gathered in the separation layer after the water in the separation layer is emptied, using the primary combined drill hole to extract the gas from the separation layer; finally, after the water and gas are completely drained and extracted from the separation layer, filling cement paste to the separation layer through the primary combined drill hole. The method for extracting gas from the separation layer below the overlying strata, draining water and grouting through the combined drill hole is capable of solving the mine disasters of water bursting in mine, gas outburst (gas emission), rock burst, surface subsidence and the like through the combined drill hole, the separation layer water and gas extraction rate is high, and the grouting effect is good.

The invention relates to an inorganic foam heat insulating material and a preparation method thereof. Raw materials for preparing the inorganic foam heat insulating material comprise cement paste and foam. The cement paste is mainly formed by Portland cement, sulphoaluminate cement, pulverized coal ash, silica fume, expanding agent, coagulant enhancer, water reducing agent, waterproof agent, fiber and water according to a certain proportion. The foam is mainly formed by foaming agent, foam stabilizer and water according to a certain proportion. Compared with the prior art, the inorganic foam heat insulating material has the advantages of high heat insulating performance, light weight, high strength, low water absorbability, high crack resistance, high fireproof performance and long service life.

A method for increasing working time / setting time of monolithic tetracalcium phosphate (TTCP) cement paste formed by mixing a TTCP powder with an aqueous solution, which includes heating the TTCP powder, prior to the mixing, so that the TTCP powder is maintained at a temperature of 50-350° C. for a period of time which is greater than one minute, and that a TTCP cement paste formed by mixing the resulting heated TTCP powder with the aqueous solution has a prolonged working time in comparison with that formed by mixing TTCP powder that has not been subjected to such heating with the aqueous solution.

The invention relates to a high-temperature-resistant copolymer oil well cement retarder and a preparation method thereof. The preparation method comprises: respectively weighing four polymerization monomers such as 2-acrylamide-2-methylpropanesulfonic acid, diallyldimethylammonium chloride, maleic anhydride or itaconic acid or fumaric acid, and acrylic acid or methacrylic acid according to the mass ratio of 45-80:5-17:7-18:8-20, dissolving the first three monomers in water, then adding sodium polyphosphate and diphenylcarbazide, then successively adding a chain transfer reagent and an initiator, and finally dropwise adding the forth monomer, performing heating reaction and adjusting the pH value, so as to obtain the copolymer retarder. The invention also provides the high-temperature-resistant copolymer oil well cement retarder prepared by the above preparation method. The retarder is resistant to a high temperature up to 230 DEG C and is weak in dispersibility at a high temperature, the cement paste strength develops fast at a low temperature, the addition amount of the retarder has good linear relation with the cement paste hardening time, and the cement paste comprehensive performance is good.

The invention discloses a lightweight aggregate cellular concrete block and a preparation method thereof. The lightweight aggregate cellular concrete block comprises cement, lightweight aggregate, water, a foaming agent and an additive. The lightweight aggregate is multihole lightweight aggregate with the stacking density of less than 1200kg / m3. The foaming agent is the substance, with which foam is formed in a material, thus forming a material in a closed pore or a connected pore structure. The additive is one, several or none of concrete common additives and mineral additives. In the preparation method, the cement, the additive, the chemical foaming agent (or not involved) and water are weighted and fed into an agitator, and beaten into a mixed cement paste; the mixed cement paste is manufactured into a foamed cement paste through a foaming device; after the lightweight aggregate is added to the foamed cement paste, the mixture is beaten and poured. Subsequently, the mixture is moulded at one step and cured. The manufacturing cost of the lightweight aggregate cellular concrete block is low; the manufacturing process is simple and easy to control; regions, which are able to invest on the production of the lightweight aggregate cellular concrete block, are wider.

The invention refers to an intelligent and high-efficiency brick paving machine comprising a walking track and a trolley body arranged on the walking track; the trolley body is composed of a transmission mechanism, a three-dimensional brick-transmission mechanism, a roller brushing mechanism, a cam locking mechanism, a hexagonal brick placing mechanism, a brick compaction mechanism and a control module. The transmission mechanism is used for transmitting power to the track, the three-dimensional brick-transmission mechanism, the cam locking mechanism, the hexagonal brick placing mechanism and the like. The three-dimensional brick-transmission mechanism is used for separating the vertically-piled bricks and delivering the bricks forwards one by one. During transmission of the bricks, the roller brushing mechanism is used for smearing cement paste to backs of the bricks uniformly. The hexagonal brick placing mechanism is used for continuously and exactly putting the bricks on the floor from an upper place. The bricks are evenly pressed and compacted by the compaction mechanism. The control module is used for controlling the operation of the whole machine. The brick paving job can be finished by the intelligent and high-efficiency brick paving machine instead of human beings, time and effort are saved, and meanwhile, the brick paving quality is ensured.

The invention relates to a curable leaking stoppage spacer fluid and a preparation method thereof. The spacer fluid comprises the following components according to parts by weight: 450 parts of fresh water, 400-600 parts of curing agent, 3-10 parts of stabilizing agent, 2-20 parts of suspending agent, 10-40 parts of activating agent, 10-60 parts of activating auxiliary agent and 10-700 parts of density regulator, wherein the curing agent is slag powder; the stabilizing agent is clay; the suspending agent is sodium bentonite or calcium bentonite; the activating agent is the mixture of sodium hydroxide and sodium carbonate; the activating auxiliary agent is the mixture of sodium silicate and calcium oxide; and the density regulator can be iron ore powder for well cementation or coal ash hollow microsphere. After the curable leaking stoppage spacer fluid is cured, the lamination capability can reach more than 5MPa, the spacer fluid shows good chemical compatibility with mud and cement paste and good curing performance between 30-130 DEG C; after the spacer fluid is cured, the appearance of a formed cured body has non volume contraction; therefore, the spacer fluid can effectively pack a stratum dropping passage and provides guarantees for the follow-up operation of oil and gas wells.

The invention relates to self-compacting concrete which is used for overcoming the contradiction between flowability and stability, early strength and delayed coagulation, contraction and expansion and the like of the self-compacting concrete in the prior art. In the invention, by means of combination of an aliphatic (hydroxyl) sulfonate superplasticizer and a polycarboxylic acid superplasticizer, selection and collocation of a cementing material and coarse and fine aggregates as well as specific mix design, the self-compacting concrete (more than C40) with low consumption of the cementing material is prepared from coal ash, mineral powder and tailings, wherein, a ketoaldehyde condensate is taken as the main component of the aliphatic (hydroxyl) sulfonate superplasticizer; and when the superplasticizer is added to cement paste, the mixed concrete has the advantages of good construction workability, less possibility of bleeding and segregation, no crystallization precipitate at low temperature and the like. Compared with the prior art, the self-compacting concrete prepared by the method provided by the invention has the advantages of lowering cement consumption by at least 70kg / m<3>, reducing consumption of the cementing material by at least 70kg / m<3>, comprehensively utilizing at least 470kg / m<3> of solid waste, and lowering concrete cost by at least **yuan / m<3>.

The invention provides a high-temperature-resistant dispersed fluid loss agent for oil well cement and a preparation method thereof. The fluid loss agent prepared with the method is used for reducing a fluid loss of cement paste in oil and natural gas well drilling and cementing processes. The fluid loss agent prepared with the method is a quadripolymer; comonomers are 2-acrylamide-2-methyl propanesulfonic acid (AMPS), N,N'-dimethylacrylamide (DMAA), acrylamide (AM), and maleic anhydride (MA); and an initiator is a mixed solution of ammonium persulfate and sodium hydrosulfite. The fluid loss agent provided by the invention has good capacities of controlling fluid loss and improving the rheologic property of the cement paste, and has good temperature-resistant and salt-resistant capabilityand wide application range.

The invention relates to a retarder for cement paste used in petroleum drilling, completion or well cementing operation, which comprises two components. The two components are a multipolymer containing carboxylic acid groups accounting for 60 to 90 portions by weight and an organic phosphonic acid and salts thereof accounting for 10 to 40 portions by weight. The average relative molecular mass of the multipolymer containing carboxylic acid groups is 2,000 to 20,000. The applicable temperature scope of the cement retarder is wide, and the cement retarder can be applied at high temperature, medium and low temperatures. The applicable temperature scope ranges from 30 DEG C to 230 DEG C. The cement retarder can be matched with various additives and is very compatible, which is applicable for oil well cement of various grades. The retarder can resist salt well, which is applicable for fresh water, brine, seawater, concentrated water and so on. The retarder can be widely applied in various shallow holes, moderate-depth holes, deep holes and superdeep holes. An excess amount of retarder is not sensitive in brine and seawater; the construction safety is ensured; the retarder does not adversely affect the strength development of cement.

The invention discloses an evaluation device and method capable of eccentricity testing of cementation quality of a cement-casing interface. The cement-casing interface is a well cementation first interface. Currently, evaluation of the first interface only considers the cementation situation of the outer surface of a casing and a cement ring, however, in a realistic multi-drilled well bore structure, cementation exists between the inner surface of the casing and the cement ring, and the cementation quality between the inner surface of the casing and the cement ring also determines the success or not of cement ring sealing. Besides, when consideration is given to the inner and outer surfaces, consideration also needs to be given to the influence of eccentricity of the casing on cementation. Aiming at the problems, according to the solving scheme, the technology and working condition well cementation on the spot are simulated as far as possible, including forming of mud cake, washing, downhole maintenance of cement, downhole pressure and temperature and the like. The evaluation device and method capable of eccentricity testing of cementation quality of the cement-casing interface are high in simulation degree, can evaluate the cementation situation of the outer surface of the casing and the cement, can simulate the casing cementation situation of random degrees of eccentricity, and can simulate the plugging strength of slug injection of colloids of cement paste and the like. An experimental result and analysis can provide important reference for the evaluation of cementation quality of the well cementation first interface, provide important basis for an engineering design, and can be applied to the evaluation of cementation strength of other material systems and the casing as well.

The invention relates to a plugging thixotropic cement paste for an oil-gas well and a preparation method for the same. The plugging thixotropic cement paste is composed of the following constituents in parts by weight: 100 parts of oil-gas cement, 0.5-10 parts of a thixotropic agent, 0-200 parts of a density regulator, 0-35 parts of a stabilizer, 0-6 parts of a coagulation time regulator, 0-5 parts of an expander, 0.5-3 parts of a dispersant, 0-2 parts of a defoamer, and 60-150 parts of water. Via the plugging thixotropic cement paste disclosed by the invention, the technical problem of loss during the well construction process and the production process of the oil-gas well can be effectively solved on the premise of meeting the various engineering performances needed by the plugging cement paste for the oil-gas well, thus providing a guarantee on the subsequent drilling and completion as well as the safety production of the oil-gas well.

The invention discloses a layered hydraulic fracturing method of underground coal mine multiple coal seams. The layered hydraulic fracturing method of the underground coal mine multiple coal seams is suitable for layered air-permeability-increasing operation in soft and low-air-permeability coal seam groups and includes the following steps: (1) punching a hydraulic fracturing drilling hole penetrating all coal seams; (2) installing a coal seam hydraulic fracturing sleeve pipe in the hole, and then fixing the hole to the bottom with cement paste; (3) in the mode of hole sealing with capsules, sealing the hole to a top plate of the coal seam to be fractured, and then through a high-pressure sealing drill rod, sending a special perforating gun to the coal seam to be fractured in the hole; (4) calibrating the position of the perforating gun, aiming at the coal seam to be fractured, through the high-pressure sealing drill rod, pumping perforating liquid to the perforating gun to shoot through the sleeve pipe and a cement sheath, and a perforating orifice is formed in the coal seam; (5) taking the perforating gun and the high-pressure sealing drilling rod out of the sleeve pipe; (6) leading high-pressure water in the sleeve pipe to carry out hydraulic fracturing on the coal seam in the position of the perforating orifice; and (7) after a coal seam is fractured, repeating the steps (3) to (6) to carry out hydraulic fracturing on a next coal seam until all the coal seams are fractured. Effective pressure relief and air-permeability increasing in layered coal seam groups can be achieved, and the method of the underground coal mine multiple coal seam layered hydraulic fracturing is simple, good in effect and low in cost.

A cement powder is disclosed that contains reactive tricalcium phosphate nanoparticles and other ingredients required to form a cementous material. Methods of making the reactive tricalcium phosphate nanoparticles, the cement powder, the cement paste, and cured cement are also provided, as are methods and articles for using the cement.