2nd generation concrete construction: carbon footprint accounting

Purpose – Construction contractors and facility managers are being challenged to minimize the carbon footprint. Life cycle carbon‐equivalent (CO2‐e) accounting, whereby the potential emissions of greenhouse gases due to energy expenditure during construction and subsequent occupation of built infrastructure, generally ceases at the end of the service life. However, following demolition, recycling of demolition waste that becomes incorporated into 2nd generation construction is seldom considered within the management of the carbon footprint. This paper aims to focus on built concrete infrastructure, particularly the ability of recycled concrete to chemically react with airborne CO2, thereby significantly influencing CO2‐e estimates.

Design/methodology/approach – CO2‐e estimates were made in accordance with the methodology outlined in the Australian National Greenhouse Accounts (NGA) Factors and were based on the energy expended for each life cycle activity from audited records. Offsets to the CO2‐e estimates were based on the documented ability of concrete to chemically react with airborne carbon dioxide (“carbonation”) and predictions of CO2 uptake by concrete and recycled concrete was made using existing predictive diffusion models. The author's study focused on a built concrete bridge which was demolished and recycled at the end of the service life, and the recycled concrete was utilized towards 2nd generation construction. The sensitivity of CO2‐e and carbonation estimates were tested on several different types of source demolition waste as well as subsequent construction applications using recycled concrete (RCA). Whole‐of‐life CO2‐e estimates, including carbonation of RCA over the 1st and 2nd generations, were estimated and contrasted with conventional carbon footprints that end at the conclusion of the 1st generation.

Findings – Following demolition, CO2 capture by RCA is significant due to the more permeable nature of the crushed RCA compared with the original built infrastructure. RCA also has considerably greater exposed surface area, relative to volume, than a built concrete structure, and therefore more highly exposed surface to react with CO2: it therefore carbonates more comprehensively. CO2‐e estimates can be offset by as much as 55‐65 per cent when including the contribution of carbonation of RCA built within 2nd generation infrastructure. Further offsets are achievable using blended fly ash or slag cement binders; however, this study has focused on concrete composed of 100 per cent OPC binders and the effects of RCA.

Originality/value – Construction project estimates of life cycle CO2‐e emissions should include 2nd generation applications that follow the demolition of the 1st generation infrastructure. Life cycle estimates generally end at the time of demolition. However, by incorporating the recycled concrete demolition waste into the construction of 2nd generation infrastructure, the estimated CO2‐e is significantly offset during the 2nd generation life cycle by chemical uptake of CO2 (carbonation). This paper provides an approach towards inclusion of 2nd generation construction applications into whole‐of‐life estimates of CO2‐e.

Head morphology of 1st and 5th instar nymphs of Triatoma circummaculata and Triatoma rubrovaria (Hemiptera, Reduviidae)

Morphological structures of the head of 1st and 5th instar nymphs of Triatoma circummaculata and Triatoma rubrovaria were revealed by analysis using scanning electron microscopy (SEM). Differences between Ist and 5th instar nymphs of these two species were observed in the postocular callosity, the number of ommatidia and tapered hair, the small segment between antennal segments, the rostrum third segment and slit lines. These slit lines were different only in the 5th instar. Similarities observed were the presence of tapered hairs in the joints, and the type of sensilla in the antennal segments. Only the Ist instar shows anteclypeus and gena sensilla. The antennal segments comprise the following types of sensilla: basiconica, bristles type I, bristles type II, bristles type III, campaniformia, coeloconica, chemosensilla, placodea, trichobothria and trichoidea. We describe here for the first time six (3+3) sensilla basiconica on the dorsal portion of the first segment of the rostrum. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

THAUMATOMYRMEX STRIPS MILLIPEDES FOR PREY - A NOVEL PREDATORY BEHAVIOR IN ANTS, AND THE 1ST CASE OF SYMPATRY IN THE GENUS (HYMENOPTERA, FORMICIDAE)

We describe, for the first time, the predatory behaviour of Thaumatomyrmex ants on millipedes of the family Polyxenidae, based on field observations of T. atrox and a field and laboratory study of T. contumax. The capture of the prey and the removal process of its body-covering setae by the ants before they eat the millipede are described. This specialized behaviour in at least two species of the genus, belonging to two distinct groups of species, indicates a general trend in Thaumatomyrmex. We coupled this study with a comparative morphological analysis of the mouthparts and digestive tube of these and other Thaumatomyrmex species. Also, we report the first case of sympatry in the genus, which suggests that Thaumatomyrmex includes several species. and not only one highly variable taxon, as hypothesized earlier.

PREDATION OF COTTON LEAFWORM 1ST INSTAR LARVAE, ALABAMA-ARGILLACEA [LEP, NOCTUIDAE]

Natural predation first instar larvae of the cotton leafworm (CLW) A. argillacea was studied in cotton fields in Jaboticabal, São Paulo State, Brazil, during 1986. The presence of naturally occurring arthropod predators showed a first instar larvae predation rate of 78.6 and 88.9% after 24 h and 48 h of exposure, respectively. A predator prey ratio of 1 : 1 (1 CLW key predator per 1 prey/plant) maintained a level of no more than 1 CLW small larvae per plant. The most evident arthropod predators in the studied fields were: beetles (Coleoptera: Coccinellidae), ants Pheidole sp. and Conomyrma sp.; Dermaptera Doru lineare (Eschs); Hemiptera Geocoris sp., and Orius insidiosus Say; and the spiders Theridion volubile, Chrysso pulcherrima, Misumenops sp., Chiracanthium sp., and Oxyopes salticus Hentz.

Ticks (Acari: Ixodidae) within various phytophysiognomies of a Cerrado reserve in UberlA cent ndia, Minas Gerais, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Revista CEPAL: cent numéros, mille regards sur le développement de l'Amérique Latine et les Caraïbes

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Avaliação microbiológica e sensorial do guacamole conservado pelo frio: Juliana Wagner Simon. -

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Um ensaio sobre a racionalidade em economia: considerações acerca de concepções neoclássicas e Herbert Simon

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Os constituintes extrafrasais na Gramática Funcional de Simon Dik

Este trabalho tem por objetivo fazer algumas considerações sobre os elementos classificados por Dik (1989, 1997) como constituintes extrafrasais (ECCs). Procuramos especificar as propriedades comuns a todos os ECCs e levantar alguns problemas advindos da relação entre os constituintes extrafrasais e os elementos tradicionalmente conhecidos como satélites dentro da teoria da Gramática Funcional.