en-us Tue, 5 Jun 2012 00:24:07 UTC Inmagic DB/Text WebPublisher http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR148E Mon, 14 May 2012 14:00:00 UTCBecause of the unique combination of strength and versatility of reinforced concrete, it forms the most common part of our infrastructures (roads, bridges, buildings, airports and wharfs). It is a composite material comprised of steel reinforcing bars encased in a porous matrix of relatively inert aggregates bound together by a cementitious network. The successful performance of reinforced concrete mix depends on the integrity of both these components. While past study has shown that reinforced geopolymer concrete is a desirable construction material that stems from its unique combination of strength, low creep, better resistance to acid and heat but long term durability properties of its composite materials - reinforcing steel bars, encasing matrix of cementitious and inert aggregate material are yet to be understood fully. The research paper aims to develop an understanding of potential passivation mechanism of embedded steel in geopolymer concrete, its durable performance and avenues of further research needs. Preliminary research study has shown that alkaline sodium silicate solution during the initial stages of geopolymer concrete mix synthesisation has the potential to passivate the embedded steel against corrosion processes and opens up further research avenues of optimising it. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR149E Mon, 14 May 2012 14:00:00 UTCThe progression of corrosion loss and maximum pit depth, once initiated, is of much interest for predicting the future or remaining long-term life of infrastructure systems. Their failure can have substantial economic and environmental consequences. The model most widely used for the prediction of long-term corrosion is a strictly concave function such as the power law. However, as now shown repeatedly and for immersion, tidal, coastal atmospheric and for different steel, including chromium steels and also for freshwater and brackish water immersion, this model is inconsistent with longer-term empirical observations. These mostly exhibit a bi-modal trend, even for sterile seawaters and triply distilled freshwaters. Herein it is proposed that the bi-modal behaviour arises from changes in the nature of the corrosion reactions as the rust layers deposited on the exterior surface of the steel become increasingly less permeable, particularly to oxygen. The mechanisms and chemistry involved are described. It is shown that the bi-modal characteristic primarily is the result of a change from corrosion rate controlled by the rate of oxygen diffusion with oxygen as the electron acceptor in the corrosion process, to one involving hydrogen reduction and associated diffusion for a short period followed by other possible rate-controlling mechanisms. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR150E Mon, 14 May 2012 14:00:00 UTCIn the construction and building industries it has become increasingly frequent for infrastructure asset owners and operators to specify design life requirements for both capital and remediation works. This trend supports the development of more sustainable design and construction practices that take a life-cycle approach, such as including operational and maintenance considerations in the design solution process, and don’t just focus on minimisation of initial capital cost. Whenever design lives are specified there is a clear need to adopt and implement uniform durability design practices throughout the project so that consistency of approach is achieved through: Developing a durability management plan outlining the approach needed to achieve the design life requirements; Providing technical support to the design team so that durability is embedded in the design process; Supporting the construction team to manage issues that impact on the design life of the facility or structure; Providing input to handover documentation such as the asset register, inspection and maintenance plans etc. so that the integrity of the key design inputs and assumptions required to achieve the specified service life are captured prior to commissioning and embedded in the operation phase. This paper presents the findings of a literature survey of various documents that deal with durability design, especially ISO 13823 - “General principles on the design of structures for durability” which is discussed in detail. Of particular interest is the potential for ISO 13823 and the associated standard ISO 15686 - “Buildings and constructed assets - Service life planning” to be used more extensively in Australia. Furthermore, this paper discusses and proposes the terminology and template that could be used when designing for durability in an effort to standardise this important design practice. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR151E Mon, 14 May 2012 14:00:00 UTCSelective use of stainless steel reinforcing bars (SSR) in parts of reinforced concrete (RC) structures that will be subject to chloride exposure is becoming more scientific in its application. Two years ago Outokumpu began a testing regime to determine the Critical Chloride Threshold Level (CCTL) for various alloy designations. A literature review and early results were published at the ACA in 2009. Since then, this testing program has revealed reproducibility, surface condition and temperature to be important parameters to consider and has also begun to correlate in-solution testing with cast-in testing using similar measures. This paper discusses the consequence of scatter within corrosion resistance results for stainless rebar in a similar way as for carbon steel, the impact of surface finish on stainless rebar on corrosion resistance and the need for quality assurance to include corrosion resistance, and thirdly the first set of results at 40 degrees C with the same sample as for those at room temperature. Finally, this paper includes an early comparison of cast-in results with in-solution testing. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR153E Mon, 14 May 2012 14:00:00 UTCA durability plan with an ‘exposure environment domain’ approach was developed during the tender design phase of a transport infrastructure project near the Queensland coast. An exposure environment domain approach consists of understanding the deteriorating loading of each exposure environment and the anticipated response of each material to such loading. Subsequently, the appropriate durability requirements can be identified and the required design life of the structure modelled. For this project, three exposure environments were identified - saline river water exposure, in ground exposure and atmospheric exposure. In the saline river water exposure with tidal and submerging zones, the greatest durability risk to the reinforced concrete was considered to be chloride ion induced reinforcement corrosion. For in ground exposure, the reinforced concrete was expected to deteriorate as a result of acid sulfate attack of concrete and chloride ion induced reinforcement corrosion. In atmospheric exposure, deterioration of reinforced concrete was expected due to carbonation and airborne chloride penetration induced reinforcement corrosion. Following identification of the different environments and subsequent deterioration mechanisms, appropriate durability requirements were determined in accordance with relevant Australian standards, project technical specifications and appropriate mathematical modelling. This allowed development of appropriate durability requirements for the required design life of different materials. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR155E Mon, 14 May 2012 14:00:00 UTCThis paper presents failure investigation and analysis of corrosion of elements of a tunnel wall panel system containing galvanized steel frames supporting the architectural wall panels on the sides of a tunnel. These wall panels were installed in around year 2001. The panels were mounted on galvanized steel frames using stainless steel screws through Aluminium strips. The specification for the wall panel system was based on performance and required the system to have 25 years design life. However, the elements of the wall panel system started showing sign of corrosion within ten years of installation. An investigation into the root cause of the problem was carried out. This involved inspection and visual examination of the elements of the wall panel and sampling of water that was present due to seepage from the tunnel walls. The failure analysis identified presence of Chloride in water around the support frames and the contact of dissimilar metals resulting in galvanic corrosion of the elements. The corrosion was apparent in the elements of the wall panel system only at the locations where there was ponding of water. The paper examines the provisions in the performance specification, describes the corrosion mechanism and reviews the proposed remedial measures. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR156E Mon, 14 May 2012 14:00:00 UTCAlkali Silica Reaction (ASR) and Delayed Ettringite Formation (DEF) are by definition two forms of concrete “corrosion”, in that they are forms of deterioration related to the chemistry of a nonmetallic material and its exposure environment. They have chemically different mechanisms, but physically similar manifestation in the form of slow concrete expansion in the presence of moisture. Both mechanisms are characterised by the occurrence of extensive concrete craze cracking, which can in turn promote corrosion of embedded reinforcement. Deleterious ASR and DEF have been reported mostly in concrete structures constructed prior to the early 1980's when these deterioration mechanisms were less fully recognised and thus less controlled by design, materials selection, and construction practice. Unlike reinforcement corrosion, the assessment and differentiation of ASR and DEF is not always a clear-cut exercise without sufficient invasive investigation. These mechanisms can associate directly or indirectly with other forms of deterioration, such as reinforcement corrosion and early age cracking, which adds to the difficulty and complexity to the investigation. This paper presents a case study review of investigation work on a 37 year old concrete dam spillway structure in Western Australia suffering from apparent damage due to ASR/DEF. A holistic approach involving site investigation and laboratory testing was adopted to examine the likely deterioration mechanisms and factors affecting the severity of the damage. Although the primary deterioration mechanism could not be confirmed with confidence, evidence suggested that both ASR and DEF have occurred, facilitated by early age thermal restraint/shrinkage cracking. Other factors such as solar heating of the concrete also appear to contribute to the local extent of the damage. The findings revealed that typical ASR detection techniques based on macroscopic visual evidence and the uranyl acetate UV-fluorescence staining test do not adequately address the likelihood of DEF occurrence. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR158E Mon, 14 May 2012 14:00:00 UTCAn effective method of prevention of corrosion damage to chloride-contaminated reinforced concrete structures is the application of impressed current cathodic protection (CP) to the reinforcement steel, which makes it act as the cathode in an electrochemical cell. Electrons supplied to this cathode by the impressed current generate OH- ions through the cathodic reaction, and increases the OH- concentration in the concrete around the protected steel bars. When the concrete contains aggregates which are susceptible to alkali-aggregate reaction (AAR), the increased alkalinity can promote the AAR process, enhancing the reaction and causing further concrete cracking and deterioration. Evidence has accumulated through laboratory studies in the past two decades, using small concrete specimens and relatively high levels of CP current, confirming that expansion of concrete is enhanced as a result of increased CP currents. However, results obtained from such specimens and the high CP currents employed may not have much relevance to field structures. In this study, 300x300x1100 mm experimental reinforced columns, which had exhibited AAR-induced cracking, were protected using three levels of CP (5, 10 and 20 mA/m2), and their expansion behaviour monitored. Results show that the CP currents, particularly at higher level of CP, increase the AAR expansion. It is recommended that the AAR susceptibility of the aggregate contained in the concrete needs to be determined before an impressed current CP system is applied. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR159E Mon, 14 May 2012 14:00:00 UTCCulverts and tunnels assembled from ARMCO iron segments have been used for over a century with generally excellent results. However, in more recent years corrosion problems and failures have been encountered. The background to these structures and factors influencing corrosion are outlined together with an example of a recent disastrous failure. In the very small number of cases where significant corrosion has been encountered and where structures have sufficient residual strength they are being preserved by the application of cathodic protection to their external surfaces. Some of the considerations applying to cathodic protection are noted. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR160E Mon, 14 May 2012 14:00:00 UTCThis paper describes an experimental investigation to look at the underprotection of mild steel in sea water. Constant current and constant potential methods have been employed together with weight loss, impedance analysis and SEM/EDX, to look at calcareous film growth. Models explaining the behaviour in a variety of situations are presented. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR247E Mon, 14 May 2012 14:00:00 UTCWith a rise in virgin aggregate consumption, the use of recycled materials has become an attractive solution in earthwork and pavement construction. An understanding of the behavior and characteristics of recycled materials is necessary before they are used in practice. In this study, the behavior of recycled concrete aggregate (RCA) during compaction in a 3-ft-diameter cross-linked polyethylene bin was examined. The main objectives of this experiment were to (a) determine the applicability of the nuclear gauge and time domain reflectometry for measuring the dry density and moisture content of RCA, (b) measure the stiffness of the RCA with a portable falling weight deflectometer and GeoGauge, (c) estimate the compaction-induced lateral pressures of the RCA, and (d) assess the variation in moisture content, dry density, and stiffness of the RCA over a 2-month postcompaction period. Measurements were taken immediately after each lift was compacted and again over the postcompaction period. Highlights of the study findings include (a) the nuclear gauge provided higher moisture content values than the oven-measured values, which suggested a need for moisture offsets; (b) the zone of influence must be considered in the interpretation of portable falling weight deflectometer and GeoGauge moduli; and (c) compaction significantly increased the locked-in lateral stress from its normally consolidated at-rest value. In the postcompaction phase of the experiment, there was evidence that additional pozzolanic reaction occurred in the RCA, followed by shrinkage cracks. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR248E Mon, 14 May 2012 14:00:00 UTCThe pressure for pavement and geotechnical engineers to incorporate sustainability into engineering projects has led to a rise in the use of recycled concrete aggregate (RCA) as fill and in pavement sublayers. Although the use of RCA has many economical, environmental, and engineering advantages, an oversight in quality control can lead to the use of contaminated RCA in the unbound layers. This can lead to premature deterioration that is costly to repair but, more important, can slow down the market acceptance of RCA. The authors forensically investigated an asphalt concrete pavement supported on a base course containing RCA and that had experienced a significant number of eruptions. Significant amounts of a white substance were found within the base course below each eruption. Sampling and testing showed the primary constituent of the substance to be bayerite, an unstable form of gibbsite, which could form when aluminum metal corroded in an alkaline environment. The adjacent ground topography would have encouraged drainage through the pavement site and thereby rendered the base course moisture susceptible to high alkalinity, because RCA in an aqueous solution has a high pH. Exposing aluminum metal to alkali in the laboratory to duplicate the field reaction confirmed the formation of bayerite. Moreover, exposing aluminum powder to an alkaline environment in a Geonor H-200 apparatus attained a maximum swell pressure of 430 kPa. When the pavement was numerically subjected to this swell pressure, the calculated deflections were found to be consistent with the observed pavement deflections and thus corroborated the hypothesized cause of distress. Suggestions are offered to avoid this type of distress. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR249E Mon, 14 May 2012 14:00:00 UTCBetween 1986 and 1987, the Illinois Department of Transportation constructed a section of 10-in. continuously reinforced concrete pavement (CRCP) containing recycled concrete aggregate on I-57 near Effingham, Illinois. Functional and structural data, including falling weight deflectometer tests, visual distress surveys, surface profiles, and skid numbers were collected periodically throughout the service life of the pavement. Falling weight deflectometer results indicated that the pavement section exhibited excellent load carrying, with an average load transfer efficiency greater than 90 per cent across the transverse cracks. The prominent distress was longitudinal cracking, which appeared over the reinforcement bars in all lanes. This abnormal cracking pattern had been noted for many years and had been attributed to problems with the original tube feeding process. The section developed a significant amount of localized distresses and patches over its last 5 years as a result of further deterioration of the longitudinal cracking. A petrographic examination concluded that no deleterious alkali-silica reaction had occurred in the pavement and that the air void system had been normal. The mean transverse crack spacing was approximately 1.5 ft, which was significantly shorter than normal CRCP and was attributed to the greater drying shrinkage potential of recycled concrete aggregate. Functionally, the pavement showed good skid resistance and fair-to-good ride quality. The overall performance of this CRCP section exceeded the performance of roughly 50 per cent of the 10-in. CRCP within Illinois in terms of age and 25 per cent in terms of traffic. In June 2010, this CRCP section was overlaid with 3.5 in. of asphalt concrete. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR250E Mon, 14 May 2012 14:00:00 UTCThe objectives of this research were to investigate the early-age structural properties of base materials stabilized with asphalt emulsion and to assess the rate at which emulsion-treated base (ETB) design properties are achieved. Three experimental sections were established along a pavement reconstruction project near Saratoga Springs, Utah. Field tests were performed to assess the structural properties of the ETB immediately after construction and at 2, 3, 7, and 14 days; 4 months; and 1 year. Measured values were plotted against time to determine trends in ETB strength development and to determine pavement capacity. Modulus values were consistently low in all three sections during the first 2 weeks after construction, increased dramatically by 4 months, and then decreased considerably by 1 year. In the first 2 weeks after construction, the average ETB structural coefficient was 0.04. Only two of the three sections reached the design structural coefficient of 0.25, which occurred after approximately 3 months; however, the average structural coefficient measured for all three sections after 1 year of curing, which included a winter, was only 47 per cent of the design strength. The results of this research showed that, while pavement capacity was sufficient at 4 months, it was severely reduced during the first 2 weeks and at 1 year. Trafficking under these reduced capacities would be expected to greatly compromise long-term pavement performance. For this reason, trafficking of materials similar to those investigated in this research is not recommended during at least the first 2 weeks after construction. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR251E Mon, 14 May 2012 14:00:00 UTCBefore incinerator bottom ash waste (IBAW) is used as a construction material, its environmental impacts should be thoroughly investigated. IBAW encompasses ferrous and nonferrous constituents that, in the presence of water, might be released into the groundwater and soil. The aim of this study was to find a treatment technique to improve the quality of IBAW and to reduce, to below regulatory limits, its potential to leach metals and salts. IBAW was mixed with limestone to achieve an environmentally and functionally acceptable blend to be used as a road foundation layer. The research studied the leaching characteristics of some constituents—including sulfate, chloride, sodium, copper, zinc, and lead—in IBAW blends under different conditions, such as initial pH value and the use of novel and traditional treatment agents. The experimental program was designed to recreate a realistic environment; a lysimeter was used as a large-scale leaching tool and a laboratory protocol was developed that simulated road foundation field conditions to evaluate the long-term release of heavy metals and salts from IBAW. In the lysimeter experiments, the concentrations of the leached elements were monitored through a sand substrate underneath the IBAW layer to study the potential element migration and sorption process. Mathematical modeling was then used to simulate the release of the aforementioned constituents from the IBAW on the basis of the initial measurement of intrinsic material properties and the sorption process concept. The experimental results showed that the additive treatment had a varied impact on the IBAW blends' leaching properties, as element release was reduced by a wide margin, ranging from 5 to 96 per cent. http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR009E Mon, 14 May 2012 14:00:00 UTC http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR010E Mon, 14 May 2012 14:00:00 UTC http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR060E Mon, 14 May 2012 14:00:00 UTC http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR106E Mon, 14 May 2012 14:00:00 UTC http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR110E Mon, 14 May 2012 14:00:00 UTC http://114.111.144.247/ics-wpd/exec/icswppro.dll?AC=QUERY&TN=inroads&QY=find+RC+=+1205AR111E Mon, 14 May 2012 14:00:00 UTC