Strength of lime-fly ash compacts using different curing techniques and gypsum additive

Lime-fly ash mixtures are exploited for the manufacture of fly ash bricks finding applications in load bearing masonry. Lime-pozzolana reactions take place at a slow pace under ambient temperature conditions and hence very long curing durations are required to achieve meaningful strength values. The present investigation examines the improvements in strength development in lime-fly ash compacts through low temperature steam curing and use of additives like gypsum. Results of density-strength-moulding water content relationships, influence of lime-fly ash ratio, steam curing and role of gypsum on strength development, and characteristics of compacted lime-fly ash-gypsum bricks have been discussed. The test results reveal that (a) strength increases with increase in density irrespective of lime content, type of curing and moulding water content, (b) optimum lime-fly ash ratio yielding maximum strength is about 0.75 in the normal curing conditions, (c) 24 h of steam curing (at 80A degrees C) is sufficient to achieve nearly possible maximum strength, (d) optimum gypsum content yielding maximum compressive strength is at 2%, (e) with gypsum additive it is possible to obtain lime-fly ash bricks or blocks having sufficient strength (> 10 MPa) at 28 days of normal wet burlap curing.

When should fig fruit produce volatiles? Pattern in a ripening process

Ripe fruit need to signal their presence to attract dispersal agents. Plants may employ visual and/or olfactory sensory channels to signal the presence of ripe fruit. Visual signals of ripe fruit have been extensively investigated. However, the volatile signatures of ripe fruit that use olfactorily-oriented dispersers have been scarcely investigated. Moreover, as in flowers, where floral scents are produced at times when pollinators are active (diurnal versus nocturnal), whether plants can modulate the olfactory signal to produce fruit odours when dispersers are active in the diel cycle is completely unknown. We investigated day night differences in fruit odours in two species of figs, Ficus racemosa and Ficus benghalensis. The volatile bouquet of fruit of F.racemosa that are largely dispersed by bats and other mammals was dominated by fatty acid derivatives such as esters. In this species in which the ripe fig phase is very short, and where the figs drop off soon after ripening, there were no differences between day and night in fruit volatile signature. The volatile bouquet of fruit of F. benghalensis that has a long ripening period, however, and that remain attached to the tree for extended periods when ripe, showed an increase in fatty acid derivatives such as esters and of benzenoids such as benzaldehyde at night when they are dispersed by bats, and an elevation of sesquiterpenes during the day when they are dispersed by birds. For the first time we provide data that suggest that the volatile signal produced by fruit can show did l differences based on the activity period of the dispersal agent. (C) 2011 Elsevier Masson SAS. All rights reserved.

Geotechnical properties of some Indian fly ashes

To reduce the cost of disposal of large quantities of fly ash generated and environmental problems associated with it, efforts are made to utilize fly ash for geotechnical applications. Geotechnical properties of fly ash play a key role in enhancing their application. Physical properties and chemical composition control the index properties arid engineering behaviour. The paper brings out the rob of surface area, surface characteristics, reactive silica and lime content of fly ashes on index, compaction, consolidation and strength properties of fly ashes.

Degradation studies of organic acids in commercially packed fruit juices: A reverse phase high performance liquid chromatographic approach

Organic acids are important constituents of fruit juices. They render tartness, flavour and specific taste to fruit juices. Shelf life and stability of fruit juices are important factors, which determine their nutritional quality and freshness. In this view, the effect of storage on the concentration of organic acids in commercially packed fruit juices is studied by reverse phase high performance liquid chromatography (RP-HPLC). Ten packed fruit juices from two different brands are stored at 30 C for 24, 48 and 72 hours. A reverse phase high performance liquid chromatographic method is used to determine the concentration of oxalic, tartaric, malic, ascorbic and citric acid in the fruit juices during storage. The chromatographic analysis of organic acids is carried out using mobile phase 0.5% (w/v) ammonium dihydrogen orthophosphate buffer (pH 2.8) on C18 column with UV-Vis detector. The results show that the concentration of organic acids generally decreases in juices under study with the increase in storage time. All the fruit juices belonging to tropicana brand underwent less organic acid degradation in comparison to juices of real brand. Orange fruit juice is found to be least stable among the juices under study, after the span of 72 hours. Amongst all the organic acids under investigation minimum stability is shown by ascorbic acid followed by malic and citric acid.

Retention characteristics of Cu2+, Pb2+, and Zn2+ from aqueous solutions by two types of low lime fly ashes

The technical feasibility of utilization of fly ash as a low-cost adsorbent for the removal of metals from water has been studied. For two types of fly ashes, the retention capacities of copper, lead, and zinc metal ions have been studied. Contact time, initial concentration, and pH have been varied and their effect on retention mechanism has been studied. The dominant mechanisms responsible for retention are found to be precipitation due to the presence of calcium hydroxide, and adsorption due to the presence of silica and alumina oxide surfaces in the fly ash. First-order kinetic plots have revealed that the rate constant increases with increase in the initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions considered under different conditions. X-ray diffraction studies revealed the formation of new peaks corresponding to respective metal ions precipitates under alkaline conditions.

Efficient Management of Fruit Pests by Pheromone Nanogels

Environment-friendly management of fruit flies involving pheromones is useful in reducing the undesirable pest populations responsible for decreasing the yield and the crop quality. A nanogel has been prepared from a pheromone, methyl eugenol (ME) using a low-molecular mass gelator. This was very stable at open ambient conditions and slowed down the evaporation of pheromone significantly. This enabled its easy handling and transportation without refrigeration, and reduction in the frequency of pheromone recharging in the orchard. Notably the involvement of the nano-gelled pheromone brought about an effective management of Bactrocera dorsalis, a prevalent harmful pest for a number of fruits including guava. Thus a simple, practical and low cost green chemical approach is developed that has a significant potential for crop protection, long lasting residual activity, excellent efficacy and favorable safety profiles. This makes the present invention well-suited for pest management in a variety of crops.

``On-the-fly'' kinetics of enzymatic racemization using deuterium NMR in DNA-based chiral oriented media

We report the in situ and real-time monitoring of the interconversion of L- and D-alanine-d(3) by alanine racemase from Bacillus stearothermophilus directly observed by H-2 NMR spectroscopy in anisotropic phase. The enantiomers are distinguished by the difference of their H-2 quadrupolar splittings in a chiral liquid crystal containing short DNA fragments. The proof-of-principle, the reliability, and the robustness of this new method is demonstrated by the determination of the turnover rates of the enzyme using the Michaelis Menten model.

Role of Fly Ash Pozzolanic Reactions in Controlling Fluoride Release from Phosphogypsum

Phosphogypsum is added to building materials to accelerate fly ash pozzolanic reaction and contributes to early strength development of concrete. The release of unacceptable fluoride levels by phoshogypsum on contact with water is a major impediment in its usage to manufacture building products because excess fluoride consumption causes dental and skeletal fluorosis. This paper examines the efficacy of fly ash pozzolanic reactions in controlling fluoride release by phosphogypsum. Fly ash (FA), sand (S), lime (L), and phosphogypsum (G) (FA-S-L-G) slurries are cured for various periods, and the fluoride released by the mix is monitored as a function of time. A substantial reduction in fluoride release was observed and is attributed to entrapment of phosphogypsum particles in a cementious matrix formed by fly ash-lime pozzolanic reactions coupled with consumption of fluoride in formation of insoluble compounds. The compressive strength developed by compacted FA-S-L-G specimens with time was observed to be a three-stage process; maximum strength mobilization occurred during 14 and 28days of curing at room temperature. Exposure of the compacted FA-S-L-G specimens to acidic and alkaline environments for 9 days did not impact their compressive strengths. (C) 2013 American Society of Civil Engineers.

Rapid determination of main constituents of packed juices by reverse phase-high performance liquid chromatography: an insight in to commercial fruit drinks

The present work reports the compositional analysis of thirteen different packed fruit juices using high performance liquid chromatography (HPLC). Vitamin C, organic acids (citric and malic) and sugars (fructose, glucose and sucrose) were separated, analyzed and quantified using different reverse phase methods. A new rapid reverse phase HPLC method was developed for routine analysis of vitamin C in fruit juices. The precision results of the methods showed that the relative standard deviations of the repeatability and reproducibility were < 0.05 and < 0.1 respectively. Correlation coefficient of the calibration models developed was found to be higher than 0.99 in each case. It has been found that the content of Vitamin C was less variable amongst different varieties involved in the study. It is also observed that in comparison to fresh juices, the packed juices contain lesser amounts of vitamin C. Citric acid was found as the major organic acids present in packed juices while maximum portion of sugars was of sucrose. Comparison of the amount of vitamin C, organic acids and sugars in same fruit juice of different commercial brands is also reported.

Synthesis and Characterization of Fly Ash Geopolymer Sand

Geopolymers are an alternative binder to portland cement in the manufacture of mortars and concrete, as its three-dimensional aluminosilicate network imparts excellent mechanical properties. Use of geopolymers in place of ordinary portland cement is favored owing to the possible energy and carbon dioxide savings. River sand is another construction industry material that needs development of a sustainable alternate in India. Geopolymerization of fly ash amorphous silica mixtures is employed to produce fine aggregates as a possible replacement to river sand. Geopolymerization of fly ash amorphous silica mixtures in 10M NaOH solution at 100 degrees C for 7days produced fine aggregates termed fly ash geopolymer sand (FAPS)] that had comparable grain size distribution, specific gravity, and improved frictional resistance with river sand. The FAPS particles exhibited more alkaline pH (12.5) and higher total dissolved solids (TDS) concentration (TDS=747 mg/L) in comparison to the river sand specimen (pH=7.9 and TDS=32.5 mg/L). However, when used as fine aggregate in mortar, FAPS-mortar specimens develop similar pH, lower TDS, similar compressive strength, and modulus in relation to river sand-mortar specimens. The experimental results suggest that FAPS particles have the potential to replace river sand in the manufacture of mortar and concrete.

Activation of Fly Ash–Lime Reactions: Kinetic Approach

Lime–fly ash reactions play a key role in improving the mechanical strength and tailoring the permeability characteristics of compacted fly ash. Activation of fly ash–lime pozzolanic reactions should accelerate the rate of strength development and possibly mobilize higher compressive strengths, facilitating improved engineering performance of fly ash amended materials. This paper makes an assessment of activation of lime–fly ash reactions by curing compacted fly ash–lime specimens at ambient (25°C) and at elevated temperature (80°C). The kinetics of fly ash–lime reactions are examined by monitoring the reacted lime as a function of curing period and temperature. The influence of variations in fly ash/lime content and dry density on the compressive strength developed by specimens at both temperatures is evaluated. The thermodynamic parameters for the fly ash–lime reactions have also been examined. Experimental results showed that curing at 80°C for 24 h accelerated fly ash–lime reactions such that it caused the steam cured (SC) specimens to evelop 1.21–2.44 fold larger strengths than room-temperature cured (RTC) specimens cured at 25°C for 28 days. Analysis of thermodynamic parameters indicated that the fly ash–lime reactions are thermodynamically favored at fly ash contents of 50–70% and lime additions of 16–20%, and the reactions are endothermic in nature. DOI: 10.1061/(ASCE)MT.1943-5533.0000482. © 2012 American Society of Civil Engineers.

Strength and Deformation Characteristics of Fly Ash Mixed with Randomly Distributed Plastic Waste

In order to explore the potential use of fly ash and plastic waste in bulk quantities in civil engineering applications, it is necessary to understand the behavior of fly ash and fly ash mixed with plastic waste. These materials are considered as wastes and in this study, it is shown that combination of fly ash and plastic waste is very useful. In this regard, various tests such as classification tests, unconfined compressive strength and compressibility tests, consolidated undrained tests, and California bearing ratio tests were conducted. The results indicated that the inclusion of plastic waste in fly ash is effective in improving the engineering properties of fly ash in terms of compressive strength, shear strength parameters, and CBR values. In order to understand the effect of sample size on the shear strength parameters of fly ash and fly ash mixed with plastic waste, consolidated undrained tests were conducted with sample sizes of 38x76mm and 50x100mm. The results of the tests indicate that the shear strength increases with the increase in sample size. The implication of the use of fly ash mixed with plastic waste in unpaved roads is presented in terms of reduction of carbon print.

Fruit and Seed Volatiles: Multiple Stage Settings, Actors and Props in an Evolutionary Play

Plants emit volatile organic compounds (VOCs) from most parts of their anatomy. Conventionally, the volatiles of leaves, flowers, fruits and seeds have been investigated separately. This review presents an integrated perspective of volatiles produced by fruits and seeds in the context of selection on the whole plant. It suggests that fruit and seed volatiles may only be understood in the light of the chemistry of the whole plant. Fleshy fruit may be viewed as an ecological arena within which several evolutionary games are being played involving fruit VOCs. Fruit odour and colour may be correlated and interact via multimodal signalling in influencing visits by frugivores. The hypothesis of volatile crypsis in the evolution of hard seeds as protection against volatile diffusion and perception by seed predators is reviewed. Current views on the role of volatiles in ant dispersal of seeds or myrmecochory are summarised, especially the suggestion that ants are being manipulated by plants in the form of a sensory trap while providing this service. Plant VOC production is presented as an emergent phenotype that could result from multiple selection pressures acting on various plant parts; the ``plant'' phenotype and VOC profile may receive significant contributions from symbionts within the plant. Viewing the plant as a holobiont would benefit an understanding of the emergent plant phenotype.