Effect of Alkaline Electrolyzed Water on Performance Improvement of Green Concrete with High Volume of Mineral Admixtures

The strength and durability of concrete will be significantly reduced at high volume of mineral admixture,and the poor early strength of concrete also still needs to be solved.In this investigation,a highly active alkaline electrolyzed waters was used as mixing water to improve the early strength and enhance the durability of green concrete with high volume mineral admixture,the influences of alkaline electrolyzed water(AEW)on hydration activity of mineral admixture and durability of concrete were determined.The results showed that compared with natural tap water,AEW can accelerate early hydration process of cement in concrete and produce comparatively more hydrated products,leading to a 13.6%higher compressive strength than that of ordinary concrete at early age,but the improvement effect of AEW concrete was relatively reduced at long-term age.Meanwhile,the activity of mineral admixtures could be stimulated by AEW to some extent,the strength and durability performance of AEW concrete after double doping 25%slag and 25%fly ash can still reach the level of ordinary cement concrete without mineral admixtures.The SEM micromorphology of 7 d hydrated natural tap water cement paste was observed to be flaky and tabular,but the AEW cement pastes present obvious cluster and granulation phenomenon.The SEM microstructure of AEW concrete with mineral admixtures is more developed and denser than ordinary tap water concrete with mineral admixtures.Therefore,the AEW probably could realize the effective utilization of about 50%mineral admixture amount of concrete without strength loss,the cement production cost and associated CO_(2) emission reduced,which has a good economic and environmental benefit.

INFLUENCE OF MINERAL ADMIXTURES ON MECHANICAL PROPERTIES OF HIGH-PERFORMANCE CONCRETE

The improvements of the mechanical properties, including bulk density of fresh mixtures, elastic modulus, and compressive strengths of four high-performance concrete mixtures, made with the addition of fly ash, refined ground blast - furnace microslag (microslag) and silica fume are studied. The concrete mixtures were determined based on the dispersion testing results. The study indicates that the elastic modulus at 28 and 91 days, and compressive strengths of the concretes are improved a lot when fly ash and microslag by 25 percent by weight of cement are added into the mixtures individually. The improvement is especially evident when silica fume by 5 percent and fly ash by 25 percent by weight of cement are added together into the mixture, while the fresh concrete mixture keeps a good workability. Through the analysis of chemically combined water ratios of the four mixtures at various hydration ages, it is found that the addition of all these mineral mixtures are beneficial to the hydration process, especially, at later stages, which might be one of the reasons for the improvement of mechanical properties. (Author abstract) 4 Refs.

Effects of Curing Systems on Properties of High Volume Fine Mineral Powder RPC and Appearance of Hydrates

The effects of different curing systems on the properties of high volume fine mineral powder RPC （reactive powder concrete） and the appearances of hydrates were studied. The experimental results show that dry-heating curing promotes the development of pozzolanic reactivity of fine mineral powder; due to low cement content, 0.20 water-bind ratio and high reactive fine mineral powder content, the strength of RPC increases by around 200% after steam curing and subsequent dry-heating curing. Scanning electron microscopy and energy spectrum diagram showed that： after the high volume fine mineral powder RPC with 0.16 water-bind ratio underwent steam curing and dry-heating curing, there was no significant change in the appearance of hydrates; after the RPC with 0.20 water-bind ratio, the cement content of 150 kg/m3 and more steel slag powder underwent dry-heating curing, there was a certain change in the appearance of C-S-H, the structure of gel was more compact and was uniformly distributed, and the Ca/Si of C-S-H gel decreased from 1.41 to around 1.20.

EFFECT OF COMPOSITE MINERAL ADMIXTURES ON RESTRAINING ALKALI-SILICA REACTION

The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot absolutely diminish the ASR of mortar bars with the low-alkali cement and a highly reactive aggregate. But the expansion rate and the deleterious expansion of the mortar bar are mostly reduced with increasing composite mineral admixture. The influence of mineral admixtures on the fluidity of the paste and the strength of the mortar is also studied.

Preparation and activity research of ecological nano mineral admixture from rice husk charcoal

The rice husk ash （ RHA） and silica （ Si02） nanoparticles are prepared from rice husk charcoal （RHC） by the methods of ventilated calcining and chemical precipitation, respectively, to remove the residual carbon which is harmful to cement composites. The structures and morphologies of these products are investigated by the Fourier transform infrared spectroscopy, X-ray diffraction, scanning/ transmission electron microscopy and N2 adsorption- desorption analyzer. The results show that the as-produced RHA and Si02 nanoparticles exist in amorphous phase without residual carbon, and exhibit porous structures with specific surface areas of 170.19 and 248. 67 m2 /g , respectively. The micro particles of RHA are aggregated by numerous loosely packed Si02 gel particles with the diameter of 50 to 100 nm. The Si02 nanoparticles are well dispersed with the average size of about 30 nm. Both the RHA and Si02 nanoparticles can significantly reduce the conductivity of saturated Ca（OH）2 solution and increase the early strength of the cement composites. They also exhibit high pozzolanic activity, indicating that they can be used as ecological nano mineral admixtures.

Influence of Cement Types and Mineral Admixtures on Resistance of Mortar to Sulfate Attack under Lower Temperature

Mortar prisms made with different cements or mineral admixtures plus 30% mass of limes tone filler were stored in 2% magnesium sulfate solution at 5±1 ℃ for 1 year and their visual appearance,strength development were measured at intervals.The formation of thaumasite was checked and confirmed by XRD and FTIR.The results show that the relative resistance to thaumasite form of sulfate attack of the cements is outlined below,from best to worst:sulphoaluminate cement,sulfate resisting Portland cement,OPC.The resistance to thaumasite form of sulfate attack of mortar is remarkably improved by the addition of silica fume or ground granulated blastfurnace slag (SL),and the better the resistance to thaumasite form of sulfate attack,the more the addition of SL is.The thaumasite form of sulfate attack is decreased to a certain degree by a lower replacement of cement with fly ash,but it is accelerated by the addition of a higher amount of fly ash due to its lower reactivity.

Grey Clustering Theory to Assess the Effect of Mineral Admixtures on the Cyclic Sulfate Resistance of Concrete

Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%, ground blast furnace slag with the replacement of 15% or 30%, or 15% fly ash and 15% ground blast furnace slag were made and exposed to a cyclic sulfate environment. Concrete properties including relative dynamic elastic modulus, chloride ion diffusion coefficient, compressive strength and flexural strength were measured. Effect of mineral admixtures on the cyclic sulfate resistance of concrete was assessed based on the grey clustering theory. The experimental results indicate that the cyclic sulfate resistance of concrete incorporating ground blast furnace slag belongs to the higher grey grade, which exhibits that it possesses excellent cyclic sulfate resistance. With increasing addition of fly ash, the cyclic sulfate resistance of concrete changes from the medium grey grade to the lower grey grade, which shows that incorporation of fly ash is disadvantageous for the cyclic sulfate resistance of concrete.

Preparation of High Impermeable and Crack-resistance Chemical Admixture and Its Mechanism

A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: (1) perfect workability: slump is more than 22cm, theslump afar 3h is about 16cm; (2) high impermeability:for the mortar, the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2. 2cm;(3) high crack-resistance: there is a micro-expansion at the age of 90d; (4) high compressivestrength: compared with the controlled concrete, the compressive strengths at the age of 3d and 2Sd are improved by 66.4% and 62.0% , respectively. At the same time, the effects of different curing condition on mortar and concrete expansive andshrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism, was investigatedin the present paper.

Properties and Microstructure of Marine Concrete with Composite Mineral Admixture

The influences of compositing mineral admixtures on the regularity of mechanical property, workability, durability and microstructure of C50 marine concrete were investigated. The results show that the incorporation of mineral admixtures can improve the mechanical properties and workability of C50 marine concrete, 3 min-doped mineral admixture had excellent resistance to chloride ion permeability. The microscopic structure mixing mineral admixtures system was well-distributed and compact, little macroporeare can be found.

Influence of coal blending on mineral transformation at high temperatures

Transformation of mineral matter is important for coal utilization at high temperatures.This is especially true for blended coal.XRD and FTIR were employed together to study the transformation of mineral matter at high temperature in blended coals.It was found that the concentration of catalytic minerals, namely iron oxides, increases with an increasing ratio of Shenfu coal, which could improve coal gasification.The transformation characteristics of the minerals in blended coals are not exactly predictable from the blend ratio.This was proved by comparing the iron oxide content to the blending ratio.The results from FTIR are comparable with those from XRD.FTIR is an effective method for examining variation in mineral matter.

Mineralogy and Geochemistry of the High-Cr Podiform Chromitite from the Cuobuzha Ophiolite, Yarlung Zangbo Suture Zone, Western Tibet, China: Implication for its Origin

The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements(PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios(<0.1). In mid-ocean ridge basalts(MORB)-normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral(PGM) grains were discovered from the samples, including laurite, erlichmanite, Os-Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os-Fe alloy and increased thereafter, with the fall in temperature. Primary Fe-Ni and Fe-Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high-pressure and low-pressure chromites. Low-pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high-pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites.

Effect of Mineral Admixture on Fracture Behavior of Concrete under Freeze-Thaw Cycles

According to GBJ82-85 test method for frost resistance of concrete,four-point bending tests were used to examine the effects of mineral admixture(silica fume and fly ash)on fracture toughness,fracture energy and dynamic elastic modulus of concrete subjected to rapid freeze-thaw cycles The microstructure of the concrete was also analyzed.The results show that with the increase of the number of freeze-thaw cycles,the fracture toughness of concrete,and the loss of fracture energy as well as the l0ss of relative dynamic elastic modulus showed a downward trend.The air content of fresh concrete is the most important parameter to improve frost resistance of concrete There existed distinct difference for silica fume and fly ash to enhance fracture performance and microstructure of the concrete under freeze-thaw cycles.The l0ss of fracture energy and the loss of relative dynamic elastic modulus kept a good linear relationship.

Early-age Electrical Resistivity and Reactive Capacity of Mineral Admixtures in Mortars

A non-contacting electrical resistivity measurement device was used to investigate the effect of different types and contents of mineral admixtures on the hydration perfrormanee of mortars during early age. The experimental results show that the changes of measured resistivity with time of hydration can be used to describe the hydration characteristics of cement-based materials, as well as the physical and chemical behavior of fly ash; blast furnace slag and silica fume at the very early ages. With an increasing replacement ratio of mineral admixtures, for the specimens blended with fly ash or slag, the resistivity increases firstly, then the following flatting period extends and after setting the resistivity increasing becomes slow and consequently a lower resistivity value at 24 hours occurs. This is due to the dilution effect and lower pozzolanicl hydraulic activity of fly ash and slag. However, for the samples incorporated with silica fume, the resistivity value through 24 hours is lower with shorter flatting period and larger slope in the resistivity curves, which is because of its particle size effect and higher pozzolanic activity of silica fume. Moreover, non-contacting resistivity measurement might provide a helpful information to predict the long term performanee including the durability of cement-based materials at early ages.

Influence of Mineral Admixtures on the Permeability of Lightweight Aggregate Concrete

The permeability of lightweight aggregate concrete was studied. Some efforts were taken to increase the resistance of lightweight aggregate concrete (LC) to water penetration by using the mineral admixtures of fly ash, granulated blast furnace slag or silica fume. Accelerated chloride penetrability test and liquid atmosphere press method were used to study the anti-permeability of lightweight aggregate concrete. The experimental results show that fly ash, granulated blast furnace slag and silica fume can decrease the permeability of lightweight aggregate concrete, but the effect of granulated blast furnace slag is poor. According to the SEM and pore structure analyzing results,an interface self-reinforcing effect model was presented and the reinforced mechanism of mineral mixture on LC was discussed according to the model described by authors.

Demineralization mechanism and influence of parameters on high ash Indian coal by chemical leaching of acid and alkali solution

The current research was investigated the mechanism of coal demineralization and the effect of leaching parameters on high ash coal and study the characterization of pre and post-treated coal. The two high ash Indian coal selected from Mahanadi Coalfield Limited, Odisha, pulverized to 375, 230 and 180 gm particle size were undergone simultaneous acid and alkali treatment at a different concentration, temperature and time. The percent demineralization was increased with decrease the size of the particle and rises with leaching parameters. The investigation suggested 180 μm particle size offers efficient demineralization for both coals at 30% NaOH and 30% H2SO4 concentration. The alkali leaching leads to obtaining the demineralization 46% and 42% whereas acid treatment resulted in 34% and 32% of the original coal samples. The extent of demineralization was improved the calorific value of coal. Besides, the degree of demineralization was proved from the FTIR, XRF and FESEM-EDX analysis results. FTIR analysis result showed that the peak intensity of mineral band decreased by the leaching effect and the degree of demineralization was significantly obtained to large extent by the X-ray Fluorescence spectrometer; which elucidates major minerals removed from coal by the leaching effect of acid and alkali solution.

Technologies of oxygen supply for life support during the development of mineral resources in high altitude areas

In order to fulfill the needs of life-support oxygen supply during the development of plateau mineral resources,four oxygen supply patterns suitable for the plateau mine in specific environment were developed:tunnel face diffusive oxygen supply,tunnel oxygen-bar car,carried oxygen cylinder and portable oxygen generator. Through the study of safety oxygen supply experiments in low- pressure plateau areas,the mathematical relationship between maximum integration of secure oxygen volume and altitude has been achieved. Oxygen supply safety control should follow this relationship in plateau mines during the time of executing tunnel face or in room air diffusive oxygen supply. The application results of life-support oxygen supplement technologies in the development of mineral resources in high altitude areas show that the oxygen supply for tunneling miners in plateau mines can not only effectively enhance the oxygen saturation,reduce the pulse rate and the breath rate per minute,but also improve various symptoms caused by altitude hypoxia and high-intensity physical labor.

Anti-chloride permeability and anti-chloride corrodibility of a green high performance concrete admixture in concrete

The effects of green high performance concrete (GHPC) admixture on the anti-chloride permeability and anti- chloride corrodibility of concrete are studied by a series of experiments designed on the basis of the diffusion principle and electro-chemical principle. The GHPC admixture consists of fly ash, gangue, slag, red mud, etc., of which the mass fraction of industrial residues is over 96 %. The anti-permeabilities and anti-corrodibilities of the tested GHPC and normal concrete (NC) are evaluated by the Diffusion Coefficients of chloride which was obtained by measuring the concentration of chloride in the tested systems by the voltage difference method. It is found that the adoption of GHPC admixture greatly improves the anti-chloride permeability and anti-chloride corrodibility by modifying the inner structure and contracting the porosity of concrete to the reduce considerably the diffusion rate of chloride. The admixture is desirable regarding its engineering performances as well as economical and environmental interests.

Influence of Mineral Admixtures on the Electrodeposition Healing Effect of Concrete Cracks

Two types of solutions（Zn SO4, Mg SO4） were selected to study the influence of mineral admixtures on the electro-deposition healing effect of concrete cracks. Four parameters（i e, rates of weight gain, surface coating, crack closure and crack filling depth） were measured. The mineral composition of electro-deposits in the cracks was analyzed. The study shows that the healing effect of mortar specimens with 10% fly ash is the worst, while the healing effect of mortar specimens with 20% fly ash is better than that of the specimens without fly ash. The rates of weight gain, surface coating, crack closure and crack filling depth decrease with increasing content of the ground granulated blast-furnace slag（GGBS）. The mineral admixtures have no influence on the composition of deposits.

Influence of shrinkage-reducing admixture on drying shrinkage and mechanical properties of high-performance concrete

High-performance concrete （HPC） has specific performance advantages over conventional concrete in strength and durability. HPC mixtures are usually produced with water/binder mass ratios （mW/mB） in the range of 0.2-0.4, so volume changes of concrete as a result of drying, chemical reactions, and temperature change cannot be avoided. For these reasons, shrinkage and cracking are frequent phenomena. It is necessary to add some types of admixture for reduction of shrinkage and cracking of HPC. This study used a shrinkage-reducing admixture （SRA） for that purpose. Concrete was prepared with two different mW/mB （0.22 and 0.40） and four different mass fractions of SRA to binder （w（SRA） = 0%, 1%, 2%, and 4%）. The mineral admixtures used for concrete mixes were： 25% fly ash （FA） and 25% slag by mass of binder for the mixture with mW/mB = 0.40, and 15% silica fume （SF） and 25% FA for the mixture with mW/mB = 0.22. Tests were conducted on 24 prismatic specimens, and shrinkage strains were measured through 120 days of drying. Compressive strength, splitting strength, and static modulus of elasticity were also determined. The results show that the SRA effectively reduces some mechanical properties of HPC. The reductions in compressive strength, splitting tensile strength, and elastic modulus of the concrete were 7%-24%, 9%-19%, and 5%-12%, respectively, after 90 days, compared to concrete mixtures without SRA. SRA can also help reduce drying shrinkage of concrete. The shrinkage strains of HPC with SRA were only as high as 41% of the average free shrinkage of concrete without SRA after 120 days of drying.

Influence of Mineral Admixtures on Chloride Ion Permeation through Concrete

Through the rapid chloride ion penetration test,the influence of fly ash and slag on chloride ion permeability and microstructure of concrete was studied.The results indicate that the addition of fly ash increases concrete permeability at 28 days.With the slag content of 20% and 30%,the permeability of concrete at 28 days is reduced.The positive effect of slag is due to its relatively stronger pozzolanic reactive ability resulted in the most probable pore size and total porosity decreased.When the slag content reaches 40%,the concrete permeability showes the tendency ofincrease.