The influence of physico-chemical properties of fly ash and CKD on strength generation of high-volume fly ash concrete

This paper presents a laboratory study on the use of cement kiln dust (CKD) as an activator of fly ash when used in high volumes within concrete. Two separate batches of fly ash and CKD were tested to assess the effect of material variability on binder properties and compressive strength gain. Ternary blends of fly ash (55-65%), CEM 1 (30%) and CKD (5-15%) and quaternary blends that included moderate amounts (15-18•5%) of ground granulated blast-furnace slag (GGBS) were prepared. Physico-chemical properties of individual binder materials were compared and concrete compressive strength was measured at 2 d, 7 d and 28 d. Ternary blends of 60% fly ash, 30% cement and 10% CKD resulted in moderate early age and 28 d strength and addition of GGBS enhanced strength significantly due to increased ettringite formation. Particle fineness, water demand and loss on ignition content of fly ash, and calcium oxide and sulfur trioxide content of CKD were found to be the main physico-chemical factors that influence compressive strength gain

Carbon dioxide reduction in the building life cycle: a critical review

The construction industry is known to be a major contributor to environmental pressures due to its high energy consumption and carbon dioxide generation. The growing amount of carbon dioxide emissions over buildings’ life cycles has prompted academics and professionals to initiate various studies relating to this problem. Researchers have been exploring carbon dioxide reduction methods for each phase of the building life cycle – from planning and design, materials production, materials distribution and construction process, maintenance and renovation, deconstruction and disposal, to the material reuse and recycle phase. This paper aims to present the state of the art in carbon dioxide reduction studies relating to the construction industry. Studies of carbon dioxide reduction throughout the building life cycle are reviewed and discussed, including those relating to green building design, innovative low carbon dioxide materials, green construction methods, energy efficiency schemes, life cycle energy analysis, construction waste management, reuse and recycling of materials and the cradle-to-cradle concept. The review provides building practitioners and researchers with a better understanding of carbon dioxide reduction potential and approaches worldwide. Opportunities for carbon dioxide reduction can thereby be maximised over the building life cycle by creating environmentally benign designs and using low carbon dioxide materials

Measuring the Environmental Sustainability Performance of Global Supply Chains: a Multi-Regional Input-Output analysis for Carbon, Sulphur Oxide and Water Footprints

Measuring the performance of what an environmentally sustainable supply chain has become a challenge despite the convergence of the underlining principles of sustainable supply chain management. This challenge is exacerbated by the fact that supply chains are inherently dynamic and complex and also because multiple measures can be used to characterize performances. By identifying some of the critical issues in the literature regarding performance measurements, this paper contributes to the existing body of literature by adopting an environmental performance measurement approach for economic sectors (primary, secondary and tertiary sectors). It uses economic sectors and evaluates them on a sectoral level in specific countries as well as part of the Global Value Chain based on the established multi-regional input-output (MRIO) modelling framework. The MRIO model has been used to calculate direct and indirect (that is supply chain or upstream) environmental effects such as CO2, SO2, biodiversity, water consumption and pollution to name just a few of the applications. In this paper we use MRIO to calculate emissions and resource consumption intensities and footprints, direct and indirect impacts, and net emission flows between countries. These are exemplified by using carbon emissions, sulphur oxide emissions and water use in two highly polluting industries; Electricity production and Chemical industry in 33 countries, including the EU-27, Brazil, India and China, the USA, Canada and Japan from 1995 to 2009. Some of the results highlights include: On average, direct carbon emissions in the electricity sector across all 27 member states of the EU was estimated to be 1368 million tonnes and indirect carbon emissions to be 470.7 million tonnes per year representing 25.6% of the EU-27 total carbon emissions related to this sector. It was also observed that from 2004, sulphur oxide emissions intensities in electricity production in India and China have remained relatively constant at about 62.8 gSOx/$and 84.4 gSOx/$ although being higher than in other countries. In terms of water use, the high water use intensity in China (1040.27 litres/$) and India (961.63 litres/$), which are among the highest in the sector in the electricity sector is exacerbated by both countries being ranked as High Water Stress Risk countries. The paper also highlights many merits of the MRIO including: a 15-year time series study (which provides a measurement of environmental performance of key industries and an opportunity to assess technical and technological change during the investigated time period), a supply chain approach that provides a consistent methodological framework and accounts for all upstream supply chain environmental impacts throughout entire global supply chains. The paper also discusses the implications of the study to environmental sustainability performance measurement in terms of the level of analysis from a value chain hierarchy perspective, methodological issues, performance indicators, environmental exchanges and policy relevance

Modelling the transportation of primary aggregates in England and Wales: exploring initiatives to reduce CO2 emissions

Millions of tonnes of aggregates are transported across England and Wales each year, which causes constant concerns in regard to CO2 emissions. Much of that concern arises out of the long journeys from quarries to construction sites, and the fact that the main mode of transfer is by road. The aim of this paper is to describe the construction of a spatial decision support system (SDSS) to examine the impacts of scenarios to reduce the level of CO2 emissions. The SDSS is made up of a GIS containing a set of spatial models (including a spatial interaction model and a microsimulation model) underpinned by a detailed transport network of road and rail routes across England and Wales. The spatial interaction models are first calibrated to reproduce the existing set of flows of aggregates between quarries and local authority districts. The distance decay component is the travel distance equivalent across the road and rail networks. Based on these flows, linear models can be set up to estimate the amount of CO2 emissions associated with the existing set of flows. Then a series of what-if scenarios are set up which look at how changes in any part of the geography of production, the level of demand in certain areas or the transport process will impact the CO2 emissions. The paper demonstrates the capability of the SDSS in responding to the various spatial policies applied in different stages of the supply chain of the aggregates markets