Dry Mix Slag—High-Calcium Fly Ash Binder. Part Two: Durability

This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na2CO3): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.

Performance of a synthetic resin for lithium adsorption in waste liquid of extracting aluminum from fly-ash

In this study,we investigated the performance of a synthetic resin for the adsorption of Li from predesilicated solution which is the waste liquid produced by extracting aluminum from fly ash.The adsorption kinetics and isotherms of the resin were obtained and analyzed.The saturated adsorption sites of the resin were in agreement with the quasi-second-order kinetic model.Then,the pore diffusion model(PDM)was applied to represent the lithium adsorption kinetics which confirming that the external mass is the limiting step.Moreover,we evaluated the adsorption properties of this resin in fixed-bed mode.We established a feasible extraction process for Li from strong alkaline solutions with low Li concentrations.The process parameters,such as the flow rate,initial adsorption solution concentration,water washing process,desorption agent concentration,and flow rate were studied.The desorption rate of the Li;ions was directly proportional with the concentration of the desorption agent.The time required to accumulate Li decreased as the hydrochloric acid concentration and flow rate increased.Time of the peak appeared increased from 0.5 bed volume(BV)to 2.5 BV as the concentration was increased from 1 to3 mol·L^(-1),and the peak increased from 231 to 394 mg·L^(-1).The resin presented good selectivity for Li;ions and could effectively separate impurity ions from the pre-desilication solution.

LOW TEMPERATURE SINTERING OF FLY-ASH CERAMICS AND ITS MICROSTRUCTURE

In this paper, the fly-ash ceramics with prior physical propertieswas fabricated in a low sintering temperature range. XRD, SEM wereused to study the microstructure and sintering mechanism. The resultsshow that in this fly-ash ceramics, three kinds of matter form itsstructure frame such as the glass pearls from the fly-ash rawmaterials, quartz and mullite in which glass liquid phase wasproduced during sintering. And the sintering mechanism is that ofliquid sintering.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part One: Hydration and Mechanical Properties

High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na2CO3 into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.

Copper-Free Resin-Based Braking Materials:A New Approach for Substituting Copper with Fly-Ash Cenospheres in Composites

Copper particles emitted from braking have become a significant source of environmental pollution.However,copper plays a crucial role in resin-based braking materials.Developing high-performance braking materials without copper has become a significant challenge.In this paper,the resin-based braking materials were filled with flyash cenospheres to develop copper-free braking materials.The effects of fly-ash cenospheres on the physical properties,mechanical and friction and wear properties of braking materials were studied.Furthermore,the wear mechanism of copper-free resin-based braking materials filled with fly-ash cenospheres was discussed.The results indicate that the inclusion of fly-ash cenospheres in the braking materials improved their thermal stability,hardness and impact strength,reduced their density,effectively increased the friction coefficient at medium and high temperatures,and enhanced the heat-fade resistance of the braking materials.The inclusion of fly-ash cenospheres contributed to the formation of surface friction film during the friction process of the braking materials,and facilitated the transition of form from abrasive wear to adhesive wear.At 100-350℃,the friction coefficient of the optimal formulation is in the range of 0.57-0.61,and the wear rate is in the range(0.29-0.65)×10^(-7) cm^(3)·N^(-1)·m^(-1),demonstrating excellent resistance to heat-fade and stability in friction coefficient.This research proposes the use of fly-ash cenospheres as a substitute for environmentally harmful and expensive copper in brake materials,which not only improves the performance of braking materials but also reduces their costs.

Durability and Micro-structure of Reactive Powder Concrete

Durability of traditional reactive powder concrete （RPC） with rich cement and high volume of fly-ash reactive powder concrete （FRPC） were studied. The X-diffraction and scanning electron microscope （SEM） measurement was imployed to analyze the microstructure. The results show that both types of RPC have higher compressive strength, less volume shrinkage ratio and better carbonation-, chloride-, freezing-resistances than the conventional concrete. The results of X-diffraction indicate that they basically have C-S-H as the main composition without Ca（OH）2 crystal and ettringite. SEM results show that hydration products of FRPC is mainly Ⅲ-C-S-H which is piled up closely like densely arranged stone body and it has very compacted structure, in addition, Ca/Si ratio of C-S-H gel is lower than 1.5.

25分钟促凝压蒸法推定大掺量粉煤灰碾压砼后期强度试验研究

本文介绍了一种新型高效复合促凝剂的研制过程及配套促凝压蒸试验方法,运用该方法可使对碾压砼后期强度预测时间缩短到25分钟,比水利部规范(SL48-94)要求缩短了72％;同时进行了该方法的室内验证试验研究,取得R_快～R_(90d)强度关系式相关系数达0.946,满足使用要求,从而为大掺量粉煤灰碾压砼强度的质量控制提供了一条更为快捷有效的途径。

Spectroscopic, Kinetic Studies of Polyaniline-Flyash Composite

Polyaniline-fly ash (PANI-FA) composites were prepared by oxidative polymerization of aniline with fly ash in presence of ammonium persulphate (APS). The PANI-FA composites were prepared with different concentrations of fly ash to aniline ratio. The composites, so prepared, were characterized by UV-vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The thermal stability was studied by TGA and total weight loss of PANI, FA and PANI-FA composites having FA composition of 0.02%, 0.1%, 0.5% and 1.0% were found to be 82%, 39.%, 67% 65%, 62% and 61%, respectively. The UV-vis spectroscopy of the PANI-FA polymeric composite shows absorption maxima at 315 and 350 nm (due to π-π* transition of the benzenoid rings), and 578-712 nm (due to charge transfer excitations of the quinoid structure), which are characteristic of emeraldine base. FTIR spectra of the PANI-FA composite is similar to that of pure polyaniline (PANI) but with the bands for C=N, C=C and C-N shifted to lower wave numbers, i.e., 1585, 1494, 1327 and 1113 cm?1 due to strong interaction of Fe2O3 and PANI matrix. SEM shows the complexation of metal oxide with emaraldine base of PANI, significantly changing the aggregate state of polymeric molecular chain.

Characterization of Size and Density Separated Fractions of a Bituminous Coal as a Feedstock for Entrained Slagging Gasification

Coal is one of the main sources of energy in many parts of the world and has one of the largest reserves/production ratios amongst all the non-renewable energy sources. Gasification of coal is one among the advanced technologies that has potential to be used in a carbon constrained economy. However, gasification availability at several commercial demonstrations had run into problems associated with fouling of syngas coolers due to unpredictable flyash formation and unburnt carbon losses. Computer models of gasifiers are emerging as a powerful tool to predict gasifier performance and reliability, without expensive testing. Most computer models used to simulate gasifiers tend to model coal as a homogenous entity based on bulk properties. However, coal is a heterogeneous material and comminution during feedstock preparation produces particle classes with different physical and chemical properties. It is crucial to characterize the heterogeneity of the feedstocks used by entrained flow gasifiers. To this end, a low ash US bituminous coal that could be used as a gasifier feedstock was segregated into density and size fractions to represent the major mineral matter distributions in the coal. Float and sink method and sieving were employed to partition the ground coal. The organic and inorganic content of all density fractions was characterized for particle size distribution, heating value, ultimate analysis, proximate analysis, mineral matter composition, ash composition, and petrographic components, while size fractions were characterized for heating value, ash composition, ultimate and proximate analysis. The proximate, ultimate and high heating value analysis showed that variation in these values is limited across the range of size fractions, while the heterogeneity is significant over the range of density fractions. With respect to inorganics, the mineral matter in the heavy density fractions contribute significantly to the ash yield in the coal while contributing very little to its heating value. The ash yield across the size fractions exhibits a bimodal distribution. The heterogeneity is also significant with respect to the base-to-acid ratio across the size and density fractions. The results indicate that the variations in organic and inorganic content over a range of density and size classes are significant, even in the low ash, vitrinite rich coal sample characterized here. Incorporating this information appropriately into particle population models used in gasifier simulations will significantly enhance their accuracy of performance predictions.

Thermal Load Reduction with Green Building Envelope

Various studies have confirmed that high thermal resistance in roof & wall can reduce the heat transfer load of the buildings. In this study, experimental investigation of the effects of some sustainable features (such as green roof, reflective coated roof & Fly ash brick (FAB) etc.) on the building has been conducted in the Indian context. For the purpose, two scaled building models i.e. Model I (conventional design) & Model II (green design) have been examined with different design configurations. The sensible heat transfer (SHT) load of the building is reduced by 21% - 29% through the use of FAB with cavity wall in place of Fired clay brick (FCB) wall. The load reduction increases to 26% - 44% by using FAB cavity wall with reflective coating on the roof. This reduction further increases to 64% - 68% with FAB cavity wall along with green roof. In this final scenario, the monthly electrical energy saving for air-conditioning is approximately 5.1 kWhe/m2 per unit envelope area, with associated reduction in GHG emissions up to 6.36 kg CO2eq/m2 per unit envelope area, assuming continuous operation of HVAC systems.

Experimental Investigation on the Properties of Recycled Concrete Using Hybrid Fibers

Due to the inherent property of concrete being very weak in tension, efforts have been made to overcome this deficiency by adding various type of fibers like carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), polypropylene fiber (PPF) and stainlesssteel fiber (SSF) smeared into the concrete mix. The present study involves experimental investigation on the use of GFRP, CFRP and SSF fibers alone or as combination to improve the mechanical properties of concrete. Furthermore, concrete cylinders were cast and tested for compression and tension using 10% fly ash as cement replacement in all specimens. Besides fiber material types, fiber reinforcement ratios of 1% and 1.5% were tested to investigate the mechanical properties of concrete. In all concrete cylinder tests, the fiber reinforcement ratio of 1% had a significant contribution in increasing the tensile strength as oppose to compressive strength. As a result, the tensile and compressive strengths were increased by 26% and 11%, respectively as compared to the control specimen. Increasing the fiber reinforcement ratio from 1% to 1.5%, resulted in diminishing the mechanical properties of concrete. However, reduction in concrete compressive strength was more prominent than the tensile strength. Furthermore, it was observed that, the crack propagation was decreased with the increase of fiber content when compared to the control specimen.

Chemically modified silica gel with 1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone:Synthesis, characterization and application as an efficient and reusable solid phase extractant for selective removal of Zn(Ⅱ) from mycorrhizal treated fly-ash samples

1-{4-[（2-hydroxy-benzylidene）amino]phenyl}ethanone functionalized silica gel was synthesized and used as a highly efficient, selective and reusable solid phase extractant for separation and preconcentration of trace amount of Zn（II） from environmental matrices. The adsorbent was characterized by fourier transform infrared spectroscopy （FT-IR）, elemental analysis,~3C CPMAS NMR spectroscopy, scanning electron microscopy （SEM）, thermogravimetric analysis （TGA） and BET surface area analysis. The dependence of zinc extraction on various analytical parameters such as pH, type and amount of eluent, sample flow rate and interfering ions were investigated in detail. The material exhibited superior adsorption efficiency for Zn（II） with high metal loading capacity of 1.0 mmol/g under optimum conditions. After adsorption, the recovery （〉 98%） of metal ions was accomplished using 1.0 mol/L HNO3 as an eluent. The sorbent was also regenerated by microwave treatment in milder acidic environment （0.1 mol/L HNO3）. The lower detection limit and preconcentration factor of the present method were found out to be 0.04 ~tg/L and 312.5 respectively. The modified silica surface possessed excellent selectivity for the target analytes and the adsorption/desorption process remained effective for at least ten consecutive cycles. The optimized procedure was successfully implemented for the extraction of Zn（II） from mycorrhizal treated fly ash and pharmaceutical samples with reproducible results.