Cementing properties of steel slag activated by sodium silicates and sodium hydroxide

Steel slag which is mainly composed of γ-Ca2SiO4 and other silicates or alumino-silicates is activated by sodium sificates and sodium hydroxide. The powders of such steel slag are usually inert to hydrate and subsequently have very low ability of cementing. But when sodium silicates and sodium hydroxide are used as activators the steel slag shows very good properties of cementing. When activated with NaOH solution the hardened slurry of the steel slag has a compressive strength of 11.13 MPa after being cured for 28 days. When activated with Na2SiO3 solution the samples after being cured for 28 days have an average compres- sive strength of 40.23 MPa. While the steel slag slurry which is only mixed with water has a compressive of 0.88 MPa after being cured for 28 days.

Selecting the Technology of Sodium Silicate Modified Poplar with the Highest Performance by Fuzzy Orthogonal Method

Sodium silicate modification can improve the overall performance of wood.The modification process has a great influence on the properties of modified wood.In this study,a new method was introduced to analyze the wood modification process,and the properties of modified wood were studied.Poplar wood was modified with sodium silicate by vacuum-pressure impregnation.After screening using single-factor experiments,an orthogonal experiment was carried out with solution concentration,impregnation time,impregnation pressure,and the cycle times as experimental factors.The modified poplar with the best properties was selected by fuzzy mathematics and characterized by SEM,FT-IR,XRD and TG.The results showed that some lignin and hemicellulose were removed from the wood due to the alkaline action of sodium silicate,and the orderly crystal area of poplar became disorderly,resulting in the reduction of crystallinity of the modified poplar wood.FT-IR analysis showed that sodium silicate was hydrolyzed to form polysilicic acid in wood,and structural analysis revealed the formation of Si-O-Si and Si-O-C,indicating that sodium silicate reacted with fibers on the wood cell wall.TG-DTG curves showed that the final residual mass of modified poplar wood increased from 25%to 67%,and the temperature of the maximum loss rate decreased from 343℃ to 276℃.The heat release and smoke release of modified poplar wood decreased obviously.This kind of material with high strength and fire resistance can be used in the outdoor building and indoor furniture.

Reclamation of CO_(2) sodium silicate used sands by steam leaching

The bond film on the surface of the CO_(2) sodium silicate used sands is not easy to decompose,therefore,it is difficult to reclaim used sands.A new reclamation method of CO_(2) sodium silicate used sands was developed by steam leaching,which can reduce the water consumption of reclamation and improve the removal effect of sodium silicate bond film.Firstly,the leaching effect of the sodium silicate sands after 20/200/400/600/800/1,000°C heat preservation treatment was simulated.Furthermore,the influence of the leaching time on the removal effect of the sodium silicate bond film was studied.Finally,the casting properties of the reclaimed sands after the leaching reclamation treatment were tested.The results show for simulated used sands after 30 min of steam leaching,the removal ratio of the alkali exceeds 84.1%,the removal ratio of silicate is 86.2%,and the removal ratio of carbonate is 93.6%.The removal rate of alkali,silicate and carbonate is relatively low in the leaching time of 30-50 min.Considering the reclamation effect and cost,the leaching time is controlled in 30 min.Water consumption is only 60%of the mass of used sands for 30 min steam leaching,while it is 200%for wet reclamation.Morphological analysis shows that most of the hazardous substances in the used sands are removed in 30 min steam leaching,and the reclaimed sands surface after steam leaching in 50 min is as smooth as new sands.After 30 min of steam leaching,the alkali removal effect of the factory used sands can reach 81.5%,the water consumption by the steam leaching reclamation is 58%of the mass of the used sand,which is similar to the result of simulated used sands.The performance of reclaimed sands obtained after 30 min steam leaching is better than that of new sands when the amount of sodium silicate added is 6%of the mass of the reclaimed sands and the CO_(2) blowing time is 15 s:the 24 h ultimate compressive strength of reclaimed sands is 5.6 MPa(equated with new sands),and the collapsibility compressive strength is 5.2 MPa,which is lower than the collapsibility compressive strength of new sands(7.7 MPa).This indicates that the reclamation of CO_(2) sodium silicate used sands by steam leaching is a feasible method.

The effect of sodium silicate concentration on microstructure and corrosion properties of MAO-coated magnesium alloy AZ31 in simulated body fluid

In recent years,magnesium and its alloys are considered as biodegradable implants.However magnesium implants may rapidly corrode before the natural healing process of the tissue is completed.In this investigation,micro arc oxidation process has been studied for avoiding primary corrosion of the magnesium alloy in simulated body fluid.Anodized coating was formed on AZ31 alloy in nontoxic silicate-alkaline solution at constant current.The effects of silicate concentration and conductivity of electrolyte solution on microstructure and corrosion properties of coating were evaluated.Scanning electron microscopy showed that a thick and condensed coating is formed after enough anodizing period.Energy dispersive spectroscopy showed that Si,O and Mg are the main components of the coating.Corrosion resistance of the coated and uncoated samples was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy tests in SBF at 37℃ and pH of 7.4.Maximum corrosion resistance was achieved at 30 g/L concentration of sodium silicate in anodizing solution.It was observed that further increase in silicate concentration decreased the corrosion resistance.

Wet reclamation of sodium silicate used sand and biological treatment of its wastewater by Nitzschia palea

The massive amount of sodium silicate in the used sand was a pollution source,especially in the waste water from the wet reclamation of used sand.A new process of wet reclamation by biologically treating the waste water produced during the wet reclamation process of used sand was studied in the paper.In the work,the pre-cultivation of N.palea was performed firstly,and three different scrubbing solutions:(1) tap water,(2) modified medium for N.palea,and (3) filtrate of the broth treated by N.palea for 15 days,were used.The results of the primary investigation show that a de-skinning ratio of 90% is obtained when using the scrubbing solution containing modified medium for N.palea at the ratio 1:2 of sand and scrubbing solution,and the maximal concentrations of Na+ and SiO32are 1.49 g·L-1 and 0.51 g·L-1,respectively.The results of the optimal biomass,pH value decrease and Na+ and SiO32consumption indicate the optimal incubation conditions are at the irradiance of 5,000 lux and 25 oC.Using the filtrate of the broth treated by N.palea for 15 days as the scrubbing solution directly,a de-skinning ratio of 93% is the highest compared to the results of the tap water and the modified medium for N.palea.In the biological process using N.palea,less water is used and little wastewater is produced,which is advantageous to the purpose of green manufacturing and environmental protection.

Evaluation of the effect of sodium silicate addition to mine backfill,Gelfill-Part 2:Effects of mixing time and curing temperature

The effects of mixing time and curing temperature on the uniaxial compressive strength （UCS） andmicrostructure of cemented hydraulic fill （CHF） and sodium silicate-fortified backfill （Gelfill） wereinvestigated in the laboratory. A series of CHF and Gelfill samples was mixed for time periods rangingfrom 5 min to 60 min and cured at temperatures ranging from 5 C to 50 C for 7 d, 14 d or 28 d.Increasing the mixing time negatively influenced the UCS of Gelfill samples, but did not have a detectableeffect on CHF samples. The curing temperature had a strong positive impact on the UCSs of both Gelfilland CHF. An elevated temperature caused rapid UCS development over the first 14 d of curing. Mercuryintrusion porosimetry （MIP） indicated that the pore size distribution and total porosity of Gelfill werealtered by curing temperature.

Effectiveness of sodium silicate as gangue depressants in iron ore slimes flotation

The recovery of iron from the screw classifier overflow slimes by direct flotation was studied. The relative effectiveness of sodium silicates with different silica-to-soda mole ratios as depressants for silica and silicate bearing minerals was investigated. Silica-to-soda mole ratio and silicate dosage were found to have significant effect on the separation efficiency. The results show that an increase of Fe content in the concentrate is observed with concomitant reduction in SiO2 and A1203 levels when a particular type of sodium silicate at a proper dosage is used. The concentrate of 58.89wt% Fe, 4.68wt% SiO2, and 5.28wt% A1203 with the weight recovery of 38.74% and the metal recovery of 41.13% can be obtained from the iron ore slimes with 54.44wt% Fe, 6.72wt% SiO2, and 6.80wt% A1203, when NazSiO3 with a silica-to-soda mole ratio of 2.19 is used as a depressant at a feed rate of 0.2 kg/t.

Determination of Iron in Layered Crystal Sodium Disilicate and Sodium Silicate by Flame Atomic Absorption Spectrometry with Boric Acid as a Matrix Modifier

The effects of matrix silicate and experimental conditions on the determination of iron in flame atomic absorption spectrometry （FAAS） were investigated. It was found that boric acid as a matrix modifier obviously eliminated silicate interference. Under the optimum operating conditions, the determination results of iron in layered crystal sodium disilicate and sodium silicate samples by FAAS were satisfactory. The linear range of calibration curve is 0-10.5 μg.mL^-1, the relative standard deviation of method is 1.2%-2.2%, the recovery of added iron is 96.0%- 101%, the sensitivity is 0.19 μg.mL^-l and the detection limit is 77 ng.mL^-1. The effect of the determination of iron of the standard curve method, standard addition calibration and colorimetry method was the same, but the first has the merits of rapid sample preparation, reduced contamination risks and fast analysis.

Evaluation of the effect of sodium silicate addition to mine backfill,GelfillLPart 1

In this paper, the mechanical properties of sodium silicate-fortified backfill, called Gelfill, were investigated by conducting a series of laboratory experiments. Two configurations were tested, i.e. Gelfill and cemented hydraulic fill（CHF）. The Gelfill has an alkali activator such as sodium silicate in its materials in addition to primary materials of mine backfill which are tailings, water and binders. Large numbers of samples of Gelfill and CHF with various mixture designs were cast and cured for over 28 d. The mechanical properties of samples were investigated using uniaxial compression test, and the results were compared with those of reference samples made without sodium silicate. The test results indicated that the addition of an appropriate amount of an alkali activator such as sodium silicate can enhance the mechanical（uniaxial compressive strength） and physical（water retention） properties of backfill. The microstructure analysis conducted by mercury intrusion porosimetry（MIP） revealed that the addition of sodium silicate can modify the pore size distribution and total porosity of Gelfill, which can contribute to the better mechanical properties of Gelfill. It was also shown that the time and rate of drainage in the Gelfill specimens are less than those in CHF specimens made without sodium silicate. Finally, the study showed that the addition of sodium silicate can reduce the required setting time of mine backfill, which can contribute to increase mine production in accordance with the mine safety.

The Use of Sodium Silicate as a Corrosion Inhibitor in a Saline Drilling Fluid: A Nonaggressive Option to the Environment

The function of a corrosion inhibitor in drilling mud compositions is the corrosion protection of the equipment involved in drilling operations. Many compositions involve environmentally several products such as fatty amines of high molecular weight, polyoxylated amines, amides, imidazolines, nitrogen heterocyclic products, etc. The potential advantages of the use of silicates are the effective protection of carbon steel, especially in aerated saline fluids, low costs and non-aggressive behavior to environment. Gravimetric and electrochemical tests were carried out using an aerated solution of 3.5% NaCl and the addition of sodium silicate (Na2SiO3·9H2O) as a corrosion inhibitor at concentrations of 250 to 2000 mg/L. The efficiencies of the corrosion protection of carbon steel using silicate concentrations greater than 1250 mg/L were greater than 92%.

Formation of Na_(1+x)V_3O_8 Nanoribbon Thin Film from V_2O_5 Xerogel on Sodium Silicate Glass Substrate

Na1＋xV3O8 nanoribbon thin film was successfully fabricated by annealing the V2O5 xerogel film on sodium sili-cate glass substrate at 450℃. It has been identified that the amount of sodium ions diffused into the V2O5 xerogel film increases with the high temperature of annealing treatment. The sodium glass substrate serves as a limited sodium source to induce the transformation from V2O5 to Na1＋xV3O8.

Synthesis and characterization of A1 doped δ-laminar crystal sodium silicate

An modified laminar crystal sodium silicate （A1-SKS-6） was synthesized by spray drying and high temperature crystallization using sodium silicate as silicon source, A1 atom as inorganic source and hexadecyltrimethy ammonium bromide （CTMAB） as the structure template. The hydrothermal stability of product was at least 1 h. The synthesized material was characterized by XRD and SEM. The results indicated that shape and intensity of XRD diffraction peak at 20 took changes, but raw material 8 phase crystal form kept unchanged, and assured high Ca^2＋ and Mg^2＋ binding capacity of the products. The Ca^2＋ and Mg^2＋ binding capacity of product is up to 380 mg Ca/g and 410mg Mg/g respectively. It was found that the hole of product became smaller and appeared rod structure based on SEM. The hydrothermal stability was increased due to the pillaring of AI atom.

STUDY ON PROPERTIES OF RECLAIMED SODIUM SILICATE SAND

SEM shows that flowers and plants like sodium carbonate exists on the surface of sodium silicate sand grains when hardened by carbon dioxide, baculiform sodium acetate exists not only on sand surface but also inside sodium silicate film when hardened by ester method. The strength of sodium silicate sand mainly depends on the point bridge connecting strength of dewatered sodium silicate film. The performance of reclaimed sodium silicate sand is determined by the extent of which salinous crystal is eliminated and reasonableness of relevant technological methods.

Effect of depressants on flotation separation of magnesite from dolomite and calcite

The flotation separation of magnesite from calcium-containing minerals has always been a difficult subject in minerals processing.This work studied the inhibition effects of carboxymethyl cellulose(CMC),sodium lignosulphonate,polyaspartic acid(PASP)and sodium silicate on flotation behaviors of magnesite,dolomite and calcite,providing guidance for the development of reagents in magnesite flotation.The micro-flotation results showed that among these four depressants,sodium silicate presented the strongest selectivity due to the highest recovery difference,and the flotation separation of magnesite from dolomite and calcite could be achieved by using sodium silicate as the depressant.Contact angle measurement indicated that the addition of sodium silicate caused the largest differences in surface wettability of the three minerals,which was in line with micro-flotation tests.Furthermore,zeta potential test,the Fourier transform infrared(FT-IR)spectroscopy and atomic force microscope(AFM)imaging were used to reveal the inhibition mechanism of sodium silicate.The results indicated that the dominated component SiO(OH)3
of sodium silicate could adsorb on minerals surfaces,and the adsorption of sodium silicate hardly affected the adsorption of NaOL on magnesite surface,but caused the reduction of NaOL adsorption on dolomite and calcite surfaces,thereby increasing the flotation selectivity.

Experimental Study on Ratio and Performance of Coal Gangue/Bottom Ash Geopolymer Double-Liquid Grouting Material

Mine grouting reinforcement and water plugging projects often require large amounts of grouting materials.To reduce the carbon emission of grouting material production,improve the utilization of solid waste from mining enterprises,and meet the needs of mine reinforcement and seepage control,a double-liquid grouting material containing a high admixture of coal gangue powder/bottom ash geopolymer was studied.The setting time,fluidity,bleeding rate,and mechanical properties of grouting materials were studied through laboratory tests,and SEM analyzed the microstructure of the materials.The results show that the total mixture of calcined gangue does not exceed 60%.And the proportion of bottom ash replacing cement should be within 30%.At the same time,the volume mixture of sodium silicate is 20%.And the water-solid ratio does not exceed 0.6.The stability of the slurry prepared under this ratio is good.The microstructure of the stone body is dense,and its strength can meet the requirements of rock reinforcement and seepage control.Its economic and environmental benefits are more significant than the traditional cement-silicate double-liquid grouting material.

Preparation of fly ash and rice husk ash geopolymer

The geopolymer of fly ash （FA） and rice husk ash （RHA） was prepared. The burning temperature of rice husk, the RHA fineness and the ratio of FA to RHA were studied. The density and strength of the geopolymer mortars with RHA/FA mass ratios of 0/100, 20/80, 40/60, and 60/40 were tested. The geopolymers were activated with sodium hydroxide （NaOH）, sodium silicate, and heat. It is revealed that the optimum burning temperature of RHA for making FA-RHA geopolymer is 690oC. The as-received FA and the ground RHA with 1%-5% retained on No.325 sieve are suitable source materials for making geopolymer, and the obtained compressive strengths are between 12.5-56.0 MPa and are dependent on the ratio of FA/RHA, the RHA fineness, and the ratio of sodium silicate to NaOH. Relatively high strength FA-RHA geopolymer mortars are obtained using a sodium silicate/NaOH mass ratio of 4.0, delay time before subjecting the samples to heat for 1 h, and heat curing at 60oC for 48 h.

Preparation and Characterization of Nano-Structured SiO_(2) Thin Films on Carbon Steel

Nano-structured SiO2 thin films were prepared on the surface of carbon steel for the first time by LPD. The compositions of the films were analyzed by XPS, and the surface morphology of the thin films were observed by AFM. The thin films were constituted by compact particles of SiO2, and there was no Fe in the films. In the process of film forming, the SiO2 colloid particles were deposited or absorbed directly onto the surface of carbon steel substrates that were activated by acid solution containing inhibitor, and corrosion of the substrates was avoided. The nano-structured SiO2 thin films that were prepared had excellent protective efficiency to the carbon steel.

Comparative Study on the Properties of Inorganic Silicate and Organic Phenolic Prepolymer Modified Poplar Wood by Vacuum Cycle Pressurization

To enhance mechanical properties and improve flame retardancy and smoke suppression of fast-growing poplar wood in wood applications,the wood was impregnated and modified.An organic phenolic prepolymer and inorganic sodium silicate was used as contrasting impregnation modifiers and wood samples were impregnated by a bionic“respiration”method with alternating positive and negative pressure.The weight percentage gain,density increase ratio,mechanical properties(bending and compressive strength and hardness),and water absorption rate of inorganic and organic-impregnated modified poplar wood(IIMPW and OIMPW,respectively)were compared and these properties in IIMPW were found to be higher than those of OIMPW with the exception of the water absorption rate which was lower than the OIMPW.This was attributed to the superior absorption of sodium silicate that also improved the impregnation,reinforcement,and dimensional stability in the IIMPW.The chemical structure,crystalline structure,internal morphology,flame retardancy,smoke suppression,and thermal stability of IIMPW and OIMPW were characterized by FT-IR,XRD,SEM,CONE,and TGA.FT-IR and XRD results showed that,although IIMPW cellulose crystallinity reduced the most,more chemical bonds were come into being in IIMPW,which explained the better physical and mechanical properties of IIMPW.Compared with OIMPW,IIMPW had better flame retardant and smoke suppression performance.

Investigation on the Thermo-dynamics of Alkali-activated Carbonatite

The thermo-dynamics of reactions between carbonatite and sodium silicate solution at ordinary temperature （25℃） were investigated. The calculated results indicate that at ordinary temperature, the reactions between dolomite, calcite, Ca2＋ and Mg2＋ in carbonatite and H4SiO4, tl3SiO4- and H2SiO42- in sodium silicate solution to form the cementitious products of hydrated calcium silicate or hydrated magnesium silicate all possibly happen; among these reactions, the reactions to form gyrolite （2CaO.3SiO2.2.5H2O） and serpentine （3MgO.2SiO2-2H20） are the most possible to occur. Further, the dissociation degree of dolomite and calcite and the activity of H3SiO4 , H2SiO42- and H4SiO4 ions are the key factors to influence the reactions.

Application and Properties of Organic Emulsion Coated Phosphogypsum in Aluminous Rock Based Mineral Polymer Composite

A polarizing microscope,X-ray diffraction(XRD),fourier transform infrared spectrometer(FTIR),scanning electron microscope and energy dispersive spectrometer(SEM-EDS),X-ray photoelectron spectroscopy(XPS),and micro computed tomography(Micro CT)were used to investigate the relation between the structure and properties of the composite.Meanwhile,the physical properties,mechanical properties and strength mechanism were researched.The experimental results show that the structure and morphology of coated phosphogypsum remain intact in the composite,which shows good compatibility and forms a clear interface layer of transition zone between the coated phosphogypsum and the matrix,conforming to the structure of particle reinforced inorganic composites.The emulsion coated phosphogypsum has a certain strengthening effect on the aluminous rock mineral polymer composite.The compressive strength of the composite can reach 16.5 MPa when the amount of coated phosphogypsum is 40%,and the apparent density is 1.75 g·cm^(-3),which is significantly lower than that of common concrete;the thermal stability of the composite is also improved to a certain extent.Some certain chemical reactions occur in the process of forming the matrix of aluminous rock mineral polymer materials,with a structure of three-dimensional network.The research will provide a new way for the comprehensive utilization of phosphogypsum and low-grade aluminous rock.