Effect of accelerated carbonation on cementitious roofing tiles reinforced with lignocellulosic fibre

The present work evaluated the effects of accelerated carbonation on mechanical and physical characteristics of cementitious roofing tiles reinforced with vegetable fibre. The maximum load and toughness of the tiles have increased approximately 25% and 80% respectively as a consequence of the accelerated carbonation. Water absorption and apparent porosity decreased with carbonation while bulk density increased as a clear indication of the densification of the composite. The improvement on the mechanical performance suggests that the fibres retained their tensile strength in the inorganic matrix. Results of specimens extracted from the tested tiles after approximately 480 days in laboratory environment and further aged indicate that soak and dry cycles promoted some leaching of hydration products and more voids and lower density when performed before carbonation. The results indicate the utilization of accelerated carbonation as an effective procedure to mitigate the degradation suffered by the cellulose fibres in the less aggressive medium. (C) 2009 Elsevier Ltd. All rights reserved.

Fracture and fatigue of natural fiber-reinforced cementitious composites

This paper presents the results of an experimental study of resistance-curve behavior and fatigue crack growth in cementitious matrices reinforced with eco-friendly natural fibers obtained from agricultural by-products. The composites include: blast furnace slag cement reinforced with pulped fibers of sisal, banana and bleached eucalyptus pulp, and ordinary Portland cement composites reinforced with bleached eucalyptus pulp. Fracture resistance (R-curve) and fatigue crack growth behavior were studied using single-edge notched bend specimens. The observed stable crack growth behavior was then related to crack/microstructure interactions that were elucidated via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Fracture mechanics models were used to quantify the observed crack-tip shielding due to crack-bridging. The implications of the results are also discussed for the design of natural fiber-reinforced composite materials for affordable housing. (C) 2009 Elsevier Ltd. All rights reserved.

Star products made (somewhat) easier

We develop an approach to the deformation quantization on the real plane with an arbitrary Poisson structure which is based on Weyl symmetrically ordered operator products. By using a polydifferential representation for the deformed coordinates, xj we are able to formulate a simple and effective iterative procedure which allowed us to calculate the fourth-order star product (and may be extended to the fifth order at the expense of tedious but otherwise straightforward calculations). Modulo some cohomology issues which we do not consider here, the method gives an explicit and physics-friendly description of the star products.

Microgranitic Enclaves as Products of Self-mixing Events: a Study of Open-system Processes in the Maua Granite, Sao Paulo, Brazil, Based on in situ Isotopic and Trace Elements in Plagioclase

Felsic microgranular enclaves with structures indicating that they interacted in a plastic state with their chemically similar host granite are abundant in the Maua Pluton, SE Brazil. Larger plagioclase xenocrysts are in textural disequilibrium with the enclave groundmass and show complex zoning patterns with partially resorbed An-rich cores (locally with patchy textures) surrounded by more sodic rims. In situ laser ablation-(multi-collector) inductively coupled plasma mass spectrometry trace element and Sr isotopic analyses performed on the plagioclase xenocrysts indicate open-system crystallization; however, no evidence of derivation from more primitive basic melts is observed. The An-rich cores have more radiogenic initial Sr isotopic ratios that decrease towards the outermost part of the rims, which are in isotopic equilibrium with the matrix plagioclase. These profiles may have been produced by either (1) diffusional re-equilibration after rim crystallization from the enclave-forming magma, as indicated by relatively short calculated residence times, or (2) episodic contamination with a decrease of the contaminant ratio proportional to the extent to which the country rocks were isolated by the crystallization front. Profiles of trace elements with high diffusion coefficients would require unrealistically long residence times, and can be modeled in terms of fractional crystallization. A combination of trace element and Sr isotope data suggests that the felsic microgranular enclaves from the Maua Pluton are the products of interaction between end-member magmas that had similar compositions, thus recording `self-mixing` events.

Supramolecular Approach to Gold Nanoparticle/Triruthenium Cluster Hybrid Materials and Interfaces

A systematic and comprehensive study of the interaction of citrate-stabilized gold nanoparticles with triruthenium cluster complexes of general formula [Ru(3)(CH(3)COO)(6)(L)](+) [L = 4-cyanopyridine (4-CNpy), 4,4`-bipyridine (4,4`-bpy) or 4,4`-bis(pyridyl)ethylene (bpe)] has been carried out. The cluster-nanoparticle interaction in solution and the construction of thin films of the hybrid materials were investigated in detail by electronic and surface plasmon resonance (SPR) spectroscopy, Raman scattering spectroscopy and scanning electron microscopy (SEM). Citrate-stabilized gold nanoparticles readily interacted with [Ru(3)O(CH(3)COO)(6)(L)(3)](+) complexes to generate functionalized nanoparticles that tend to aggregate according to rates and extents that depend on the bond strength defined by the characteristics of the cluster L ligands following the sequence bpe > 4,4`-bpy >> 4-CNpy. The formation of compact thin films of hybrid AuNP/[Ru(3)O(CH(3)COO)(6)(L)(3)](+) derivatives with L = bpe and 4,4`-bpy indicated that the stability/lability of AuNP-cluster bonds as well as their solubility are important parameters that influence the film contruction process. Fluorine-doped tin oxide electrodes modified with thin films of these nanomaterials exhibited similar electrocatalytic activity but much higher sensitivity than a conventional gold electrode in the oxidation of nitrite ion to nitrate depending on the bridging cluster complex, demonstrating the high potential for the development of amperometric sensors.

An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling

The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on the material microstructure and especially the presence and distribution of microstructural constituents, such as the different carbide phases and graphite (in the case of Indefinite Chill Iron). Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.

Environmental Assessment of Rammed Earth Construction Systems

Present concerns for sustainable development have led to a revival of traditional building practices using natural or recycled resources. There is a perception that buildings constructed from such materials are environmentally benign. This perception is questionable, as often no evaluation is undertaken to assess the associated environmental impacts. Rammed earth is one such construction technology that has seen renewed interest in recent years. The energy required to manufacture materials (i.e. embodied energy) is a significant component of the life cycle energy associated with buildings. This paper assesses the embodied energy of rammed earth construction relative to brick veneer and cavity brick construction. Rammed earth was found to have significantly less embodied energy than cavity brick construction (to which it is closer in thermal performance), but was approximately equivalent to brick veneer construction. Topics of further research identified include thermal performance and strategies for reducing the embodied energy of cement used for earth stabilisation.

Multifactor productivity measures of construction sectors using OECD input-output database

This research develops a new productivity measurement framework for the construction sector in the light of an input-output table. Three group multifactor productivity indicators are formulated based on the multiplier concepts in the input-output analysis. This measurement framework focuses on the intro-industry flows of products and considers the direct and indirect effects of input and output. Moreover, this framework enables us to measure the multifactor productivity of a specific sector systematically. Historical analyses and international comparisons are carried out to indicate the differences of the productivity of the construction sectors in seven selected countries, using the newly published OECD input-output database. Research findings are expected to clarify how technological, organizational and political factors affect the productivity growth, enabling the policy makers, construction businesses and researchers to quantify the competitive ability of the construction sector.

Promoting the reuse and recycling of building demolition materials

The demolition of constructed structures has earned a negative reputation for the construction industry due to the enormous amount of waste that is sent to landfills. Demolition waste reuse and recycling is, therefore, significant; it is a new and illustrative perspective on demolition waste management from the viewpoint of the building material lifecycle. It is discovered that demolition waste reuse and recycling plays important roles in value transformation for building material lifecycle, local economics,
sustainable environment and nature resource conservation. In this research article, the authors aim to pinpoint demolition waste management in the lifecycle of building materials, and to examine various economic and environmental aspects of demolition waste reuse and recycling. In addition, the barriers, limitations and solutions for improving the implementation of demolition waste reuse and recycling are discussed in the article.

Value analysis of just-in-time demolition approach

The recent deconstruction approach for demolition projects promotes reusing and recycling materials. However, the demolition project is interrupted and slowed down while the project team wait for the waste exchange process. Wasted materials generated from the demolition project have to be stored on demolition site or extra depository. Cost and time might be lost for the inventory of wasted materials and products. Just-in-Time (JIT) is a matured method widely used in manufacture industry as well as construction industry. It is utilised to reduce the inventory of both raw materials and final products. It is also used to shorten production cycle and improve the quality of the products. The JIT philosophy can be applied into demolition project so that the inventory of wasted materials can be eliminated and the project time can be shortened. To implement JIT demolition, the waste exchange process can be performed before the wasted materials are generated from the project. Material owners and demanders can virtually plan for waste handling before the demolition project is physically implemented. As a result, waste materials can be sent to demanders through transportation right after they are produced from the project. Applying JIT philosophy in demolition projects can effectively reduce the inventory of wasted materials and the amount of demolition waste to be sent to landfills. Therefore the cost and time of the project are reduced, and the quality of final delivered materials is improved.

Development of a multimedia data acquisition toolkit and its application for exchanging demolished materials

In the development of a web-based information system such as a demolition material management system, a great amount of diversified information on projects should be acquired from particular users located with various computer platforms. This issue is difficult to handle using the limited HTTP form submission, which could lead to inaccuracy of the information and inefficiency of the whole system. This paper describes a web-based graphical user interfaced, dynamic and distributed multimedia data acquisition mechanism, which accepts users' drawings and retrieval information from the canvas and stores the multimedia data on a server for further usages. Furthermore, techniques and principles needed to construct such a multimedia data acquisition tool are addressed in detail. The application of this distributed multimedia tool in developing a web-based demolition material management system is also described.

Assessment of embodied energy analysis methods for the Australian construction industry

Environmental assessment of buildings typically focuses on operational energy consumption in an attempt to minimise building energy consumption. Whilst the operation of Australian buildings accounts for around 20% of total energy consumption nationally, the energy embodied in these buildings represents up to 20 times their annual operational energy. Many previous studies, now shown to be incomplete in system boundary or unreliable, have provided much lower values for the embodied energy of buildings and their products. Many of these studies have used traditional embodied energy analysis methods, such as process analysis and input-output (1-0) analysis. More recently, hybrid embodied energy analysis methods have been developed, combining these two traditional methods. These hybrid methods need to be compared and validated, as these too have been considered to have several limitations. This paper aims to evaluate a recently developed hybrid method for the embodied energy analysis of the Australian construction industry, relative to traditional methods. Recent improvements to this hybrid method include the use of more recent 1-0 data and th.fl inclusion of capital energy data. These significant systemic changes mean that a previous assessment of the methods needs to be reviewed. It was found that the incompleteness associated with process analysis has increased from 49% to 87%. These findings suggest that current best-practice methods of embodied energy analysis are sufficiently accurate for most typical applications. This finding is strengthened by recent improvements to the 1-0 model.

Multi-scale rheological model for discontinuous phenomena in materials under deformation conditions

A study of possibilities given by the developed Cellular Automata–Finite Element (CAFE) multi-scale model for prediction of the initiation and propagation of micro-shear bands and shear bands in metallic materials subjected to plastic deformation is described in the paper. Particular emphasis in defining the criterion for initiation of micro-shear and shear bands, as well as in defining the transition rules for the cellular automata, is put on accounting for the physical aspects of those phenomena occurring in two different scales in the material. The proposed approach led to the creation of the real multi-scale model of strain localization. This model predicts material behavior in various thermo-mechanical processes. Selected examples of applications of the developed model to simulations of metal forming processes, which involve strain localization, are presented in the paper. An approach based on the Smoothed Particle Hydrodynamic, which allows to overcome difficulties with remeshing in the traditional CAFE method, is presented in the paper as well. In this approach remeshing becomes possible and mesh distortion, which limits application of the CAFE method to simple deformation processes, is eliminated.

Modelling direct and indirect water requirements of construction

Water consumed directly by the construction industry is known to be of little importance. However, water consumed in the manufacture of goods and services required by construction may be significant in the context of a building's life cycle water requirements and the national water budget. This paper evaluates the significance of water embodied in the construction of individual buildings. To do this, an input-output-based hybrid embodied water analysis was undertaken on 17 Australian non-residential case studies. It was found that there is a considerable amount of water embodied in construction. The highest value was 20.1 kilolitres (kL)/m2 gross floor area (GFA), representing many times the enclosed volume of the building, and many years worth of operational water. The water required by the main construction process is minimal. However, the water embodied in building materials is considerable. These findings suggest that the selection of elements and materials has a great impact on a building's embodied water. This research allows the construction industry to evaluate design and construction in broad environmental terms to select options that might be cost neutral or possibly cost positive while retaining their environmental integrity. The research suggests policies focused on operational water consumption alone are inadequate.

International comparisons of construction industry performance: further investigations

While there have been many attempts at comparisons of construction performance over the past 50 years, the results have generally been inconclusive and/or contradictory.

Such comparisons are of great interest to industry, governments and theorists alike but there is little agreement as to how they are best done. A variety of methodologies have been used, however, the lack of satisfactory outcomes has been due largely to one factor, the lack of a truly reliable method for comparing construction costs in different currencies

Exchange rates are recognised as being unsuitable, and while purchasing power parity (PPP) has a long history, the method still has many critics. In addition, the nature of the building industry and its products makes the establishment of reliable construction PPPs very difficult. Both the UN’s International Comparison Program (ICP) and the European Union gather data for the production of construction-specific PPP indices, but neither body publishes them, as there is too much doubt about their reliability.

New approaches are being developed and some are soon to be trialled. This paper looks at the problems, describes and discusses some new approaches, and assesses their potential.