Mechanical processing of wet stored fly ash for use as a cement component in concrete

Wet storage effects on fly ash, mean processing may be necessary to achieve physical properties required for use in concrete. This paper considers drying, de-agglomeration and milling of various wet stored fly ashes at laboratory and pilot/benchtop scales, towards meeting these. In the laboratory, different batch quantities and milling times with as received/pre-screened materials were examined using a ball mill. Greater particle size reductions were obtained with increased milling time but at gradually reducing rates. Pre-screening and batch quantity had relatively minor effects on particle size reductions, with little difference found between these materials and dry stored fly ash. Extended milling time resulted in: a darkening of colour; slight increases in loss-on-ignition, the main oxides content, and crystalline components; reductions in water requirement (to a point); and greater reactivity. Similar effects were generally noted in concrete for the superplasticizing admixture dose to achieve a target slump and compressive (cube) strength. At pilot/benchtop scale, a dryer-pulverizer and jet mill were used, which gave general agreement with the behaviour noted in the laboratory, but with the effects tending to be less. Fineness levels in Standards were achievable, with subsequent performance appearing to depend on the milling process used

Mechanical processing of wet stored fly ash for use as a cement component in concrete

Wet storage effects on fly ash, mean processing may be necessary to achieve physical properties required for use in concrete. This paper considers drying, de-agglomeration and milling of various wet stored fly ashes at laboratory and pilot/benchtop scales, towards meeting these. In the laboratory, different batch quantities and milling times with as received/pre-screened materials were examined using a ball mill. Greater particle size reductions were obtained with increased milling time but at gradually reducing rates. Pre-screening and batch quantity had relatively minor effects on particle size reductions, with little difference found between these materials and dry stored fly ash. Extended milling time resulted in: a darkening of colour; slight increases in loss-on-ignition, the main oxides content, and crystalline components; reductions in water requirement (to a point); and greater reactivity. Similar effects were generally noted in concrete for the superplasticizing admixture dose to achieve a target slump and compressive (cube) strength. At pilot/benchtop scale, a dryer-pulverizer and jet mill were used, which gave general agreement with the behaviour noted in the laboratory, but with the effects tending to be less. Fineness levels in Standards were achievable, with subsequent performance appearing to depend on the milling process used

Evaluation of Fly Ash Reactivity Potential Using a Lime Consumption Test

The reactivity of fly ash (FA), for use in concrete, is normally evaluated in the UK/EU by means of the activity index test (on mortars at 28 and 90 d (BS EN 450-1)). This paper reports on the application of a lime consumption test, based on BS EN 196-5 (pozzolanic cement test), to determine FA reactivity more rapidly. The method uses a Portland cement (PC)/FA slurry, stored for 8 or 15 d at 40°C, and measures hydroxyl ion (OH−) and calcium oxide (CaO) concentrations of the filtrate. Seven FAs, including those produced using modern power station techniques (e.g. co-combustion, low nitrogen oxide emissions), and three PCs with different characteristics were tested. Early experiments gave acceptable repeatability for the test and revealed that pozzolanic reactions mainly occur during the initial 8 to 15 d storage. Similar behaviour for FA to that in thermogravimetric analysis and activity index tests from related studies was noted. Strong correlations were obtained for FA fineness and calcium oxide consumed (difference in calcium oxide content between PC and PC/FA with respect to that in PC). While there was general agreement for calcium oxide consumed and activity index, the correlations were poor. Similar types of effect were found to occur for mortar (activity index) and concrete. The lime consumption test can assess FA reactivity, but should be combined with measurements of the material's fineness. </jats:p

Oil-based mud waste reclamation and utilisation in low-density polyethylene composites

Oil-based mud (OBM) waste from the oil and gas exploration industry can be valorised to tailor-made reclaimed clay-reinforced low-density polyethylene (LDPE) nanocomposites. This study aims to fill the information gap in the literature and to provide opportunities to explore the effective recovery and recycling techniques of the resources present in the OBM waste stream. Elemental analysis using inductively coupled plasma–optical emission spectrometry (ICP-OES) and X-ray fluorescence analysis, chemical structural analysis by Fourier transform infrared (FTIR) spectroscopy, and morphological analysis of LDPE/organo-modified montmorillonite (LDPE/MMT) and LDPE/OBM slurry nanocomposites by scanning electron microscopy (SEM) have been conducted. Further analysis including calorimetry, thermogravimetry, spectroscopy, microscopy, energy dispersive X-ray analysis and X-ray diffraction (XRD) was carried out to evaluate the thermo-chemical characteristics of OBM waste and OBM clay-reinforced LDPE nanocomposites, confirming the presence of different clay minerals including inorganic salts in OBM slurry powder. The microscopic analysis revealed that the distance between polymer matrix and OBM slurry filler is less than that of MMT, which suggests better interfacial adhesion of OBM slurry compared with the adhesion between MMT and LDPE matrix. This was also confirmed by XRD analysis, which showed the superior delamination structure OBM slurry compared with the structure of MMT. There is a trend noticeable for both of these fillers that the nanocomposites with higher percentage filler contents (7.5 and 10.0 wt% in this case) were indicated to act as a thermal conductive material. The heat capacity values of nanocomposites decreased about 33% in LDPE with 7.5 wt% MMT and about 17% in LDPE with 10.0 wt% OBM slurry. It was also noted, for both nanocomposites, that the residue remaining after 1000°C increases with the incremental wt% of fillers in the nanocomposites. There is a big difference in residue amount (in %) left after thermogravimetric analysis in the two nanocomposites, indicating that OBM slurry may have significant influence in decomposing LDPE matrix; this might be an interesting area to explore in the future. The results provide insight and opportunity to manufacture waste-derived renewable nanocomposites with enhanced structural and thermal properties

Abrasion resistance of sustainable green concrete containing waste tire rubber particles

The development of new environmental friendly concretes such as rubberized concrete is being promoted due to the environmental problems created by the waste tire rubber. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. In this study, we analyse the potential of waste tire rubber particles as a partial substitute for fine aggregates in normal strength and high strength cement concrete and the resistance to abrasion has been measured. Statistical Analysis was carried out to strengthen the results obtained from experiments. The results show that the use of tire rubber particles can improve the abrasion resistance of concrete, and this can ensure its applications in pavements, floors and concrete highways, or in places where there are abrasive forces between surfaces and moving objects. (C) 2016 Elsevier Ltd. All rights reserved

Biotransformation of lanthanum by Aspergillus niger

Lanthanum is an important rare earth element and has many applications in modern electronics and catalyst manufacturing. However, there exist several obstacles in the recovery and cycling of this element due to a low average grade in exploitable deposits and low recovery rates by energy-intensive extraction procedures. In this work, a novel method to transform and recover La has been proposed using the geoactive properties of Aspergillus niger. La-containing crystals were formed and collected after A. niger was grown on Czapek-Dox agar medium amended with LaCl 3. Energy-dispersive X-ray analysis (EDXA) showed the crystals contained C, O, and La; scanning electron microscopy revealed that the crystals were of a tabular structure with terraced surfaces. X-ray diffraction identified the mineral phase of the sample as La 2(C 2O 4) 3·10H 2O. Thermogravimetric analysis transformed the oxalate crystals into La 2O 3 with the kinetics of thermal decomposition corresponding well with theoretical calculations. Geochemical modelling further confirmed that the crystals were lanthanum decahydrate and identified optimal conditions for their precipitation. To quantify crystal production, biomass-free fungal culture supernatants were used to precipitate La. The results showed that the precipitated lanthanum decahydrate achieved optimal yields when the concentration of La was above 15 mM and that 100% La was removed from the system at 5 mM La. Our findings provide a new aspect in the biotransformation and biorecovery of rare earth elements from solution using biomass-free fungal culture systems. </p