scholarly journals Alkali-Aggregate Reactions in Concrete: Methodologies Applied in the Evaluation of Alkali Reactivity of Aggregates for Concrete

2012 ◽  
Vol 730-732 ◽  
pp. 409-414
Author(s):  
António Santos Silva ◽  
Dora Soares ◽  
Lina Matos ◽  
Isabel Fernandes ◽  
Maria Manuela Salta
Keyword(s):  
Field Performance ◽  
Test Methods ◽  
Mitigation Measures ◽  
Internal Stresses ◽  
Interstitial Solution ◽  
Expansion Test ◽  
Rock Types ◽  
Natural Exposure ◽  
Alkali Aggregate Reaction

The alkali-aggregate reaction (AAR) in concrete is a group of chemical reactions that involves the reaction of certain minerals present in the aggregates with alkali and hydroxyl ions in the interstitial solution of cement paste in concrete. These reactions form an alkaline hygroscopic gel that absorbs water and expands causing internal stresses with cracking [1]. The AAR mitigation measures oblige the correct evaluation of the alkali reactivity of the aggregates. This is normally assessed by petrographic, chemical or expansion test methods. Several studies regarding alkali reactivity of aggregates for concrete structures in Portugal, including bridges and dams, indicated that their field performance does not correspond to the previously performed evaluation. Presently, Portuguese methodology is based on the LNEC Specification E461-2007, which shows some limitations regarding rock types such as granitoids [2]. This situation motivated the development of a research project, involving medium and long term expansion tests in different conditions, under accelerated and natural exposure conditions, as well as petrographic evaluation of the main Portuguese aggregates used/to be used in concrete. This paper presents the preliminary results of this research.

Demonstration of Biofouling Mitigation Methods for Long-Term Deployments of Optical Cameras

2015 ◽  
Vol 49 (1) ◽  
pp. 88-96 ◽  
Author(s):  
James Joslin ◽  
Brian Polagye
Keyword(s):  
Field Performance ◽  
Mitigation Measures ◽  
Camera System ◽  
Antifouling Coating ◽  
Tidal Turbines ◽  
Quantitative Studies ◽  
Performance Results ◽  
Mitigation Methods

AbstractBiofouling mitigation measures for optical ports can extend the duration of oceanographic deployments, but there have been few quantitative studies of field performance. Results are presented from a 4-month field test of a stereo-optical camera system intended for long-term environmental monitoring of tidal turbines. A combination of passive (copper rings and ClearSignal antifouling coating) and active (mechanical wipers) biofouling mitigation measures are implemented on the optical ports of the two cameras and four strobe illuminators. Biofouling on the optical ports is monitored qualitatively by periodic diver inspections and quantitatively by metrics describing the quality of the images captured by cameras with different antifouling treatments. During deployment, barnacles colonized almost every surface of the camera system, except the optical ports with fouling mitigation measures. The effectiveness of the biofouling mitigation measures suggests that 4-month deployment durations are possible, even during conditions that would otherwise lead to severe fouling and occlusion of optical ports.

Development of a Performance-Related Framework for Asphalt Mixture Design for the Illinois Tollway

2021 ◽  
pp. 036119812110148
Author(s):  
Behnam Jahangiri ◽  
Punyaslok Rath ◽  
Hamed Majidifard ◽  
William G. Buttlar
Keyword(s):  
Asphalt Mixture ◽  
Field Performance ◽  
Compact Tension ◽  
T Test ◽  
Novel Approach ◽  
Final Adjustment ◽  
Development And Validation ◽  
High Degree ◽  
Selection Of

Various agencies have begun to research and introduce performance-related specifications (PRS) for the design of modern asphalt paving mixtures. The focus of most recent studies has been directed toward simplified cracking test development and evaluation. In some cases, development and validation of PRS has been performed, building on these new tests, often by comparison of test values to accelerated pavement test studies and/or to limited field data. This study describes the findings of a comprehensive research project conducted at Illinois Tollway, leading to a PRS for the design of mainline and shoulder asphalt mixtures. A novel approach was developed, involving the systematic establishment of specification requirements based on: 1) selection of baseline values based on minimally acceptable field performance thresholds; 2) elevation of thresholds to account for differences between short-term lab aging and expected long-term field aging; 3) further elevation of thresholds to account for variability in lab testing, plus variability in the testing of field cores; and 4) final adjustment and rounding of thresholds based on a consensus process. After a thorough evaluation of different candidate cracking tests in the course of the project, the Disk-shaped Compact Tension—DC(T)—test was chosen to be retained in the Illinois Tollway PRS and to be presented in this study for the design of crack-resistant mixtures. The DC(T) test was selected because of its high degree of correlation with field results and its excellent repeatability. Tailored Hamburg rut depth and stripping inflection point thresholds were also established for mainline and shoulder mixes.

Performance evaluation of jointed plain concrete pavements with sealed and unsealed joints in North Texas

2019 ◽  
Vol 46 (7) ◽  
pp. 601-608
Author(s):  
Mena I. Souliman ◽  
Ashish Tripathi ◽  
Lubinda F. Walubita ◽  
Mayzan M. Isied
Keyword(s):  
Field Performance ◽  
Plain Concrete ◽  
Water Infiltration ◽  
Concrete Pavements ◽  
North Texas ◽  
Pavement Distress ◽  
Initial Cost ◽  
Additional Costs ◽  
Cost Of Construction

Joint sealing in jointed plain concrete pavement (JPCP) has been practiced throughout the world for many years as it improves the performance of concrete pavements. The infiltration of water is a common problem in concrete pavements and often increases distresses, such as faulting and pumping. For this reason, sealing the joints can help reduce water infiltration. Additionally, the infiltration of sand and small stones, aggregates, or debris into the joints can also be prevented, consequently reducing joint spalling in concrete pavements. However, it is also reported that joint sealing increases the initial cost of construction, especially if the joints need to be resealed, which leads to some additional costs. In this study, the pavement distress data was collected from the long-term pavement performance (LTPP) database for all the JPCPs sections in North Texas. The study illustrates the relative field performance in terms of spalling, faulting, roughness, and deflections of JPCP sections for both sealed and unsealed LTPP sections of North Texas.

Predicting the Long-Term Field Performance of Coating Systems on Steel Using a Rapid Electrochemical Test: The Damage Tolerance Test

CORROSION ◽  
2012 ◽  
Vol 68 (3) ◽  
pp. 035007-1-035007-13 ◽  
Author(s):  
S.R. Taylor ◽  
F. Contu ◽  
L.M. Calle ◽  
J.P. Curran ◽  
W. Li
Keyword(s):  
Damage Tolerance ◽  
Field Performance ◽  
Tolerance Test ◽  
Electrochemical Test ◽  
Term Field

Projecting conflict risk following the Shared Socioeconomic pathways: what role for water stress and climate?

2021 ◽  
Author(s):  
Sophie de Bruin ◽  
Jannis Hoch ◽  
Nina von Uexkull ◽  
Halvard Buhaug ◽  
Nico Wanders
Keyword(s):  
Climate Change ◽  
At Risk ◽  
Machine Learning Techniques ◽  
Mitigation Measures ◽  
Related Factors ◽  
Socioeconomic Impacts ◽  
Learning Techniques ◽  
The Future ◽  
Conflict Risk

<p>The socioeconomic impacts of changes in climate-related and hydrology-related factors are increasingly acknowledged to affect the on-set of violent conflict. Full consensus upon the general mechanisms linking these factors with conflict is, however, still limited. The absence of full understanding of the non-linearities between all components and the lack of sufficient data make it therefore hard to address violent conflict risk on the long-term. </p><p>Although it is neither desirable nor feasible to make exact predictions, projections are a viable means to provide insights into potential future conflict risks and uncertainties thereof. Hence, making different projections is a legitimate way to deal with and understand these uncertainties, since the construction of diverse scenarios delivers insights into possible realizations of the future.  </p><p>Through machine learning techniques, we (re)assess the major drivers of conflict for the current situation in Africa, which are then applied to project the regions-at-risk following different scenarios. The model shows to accurately reproduce observed historic patterns leading to a high ROC score of 0.91. We show that socio-economic factors are most dominant when projecting conflicts over the African continent. The projections show that there is an overall reduction in conflict risk as a result of increased economic welfare that offsets the adverse impacts of climate change and hydrologic variables. It must be noted, however, that these projections are based on current relations. In case the relations of drivers and conflict change in the future, the resulting regions-at-risk may change too.   By identifying the most prominent drivers, conflict risk mitigation measures can be tuned more accurately to reduce the direct and indirect consequences of climate change on the population in Africa. As new and improved data becomes available, the model can be updated for more robust projections of conflict risk in Africa under climate change.</p>

GEOLOGICAL STUDY AND MINING PLAN IMPORTANCE FOR MITIGATING ALKALI SILICA REACTION IN AGGREGATE QUARRY OPERATION

2016 ◽  
Vol 78 (7-3) ◽  
Author(s):  
Edy Tonnizam Mohamad ◽  
Bhatawdekar Ramesh Murlidhara ◽  
Mohd Nur Asmawisham Bin Alel ◽  
Danial Jahed Armaghani
Keyword(s):  
Aggregate Demand ◽  
Peninsular Malaysia ◽  
Alkali Silica Reaction ◽  
Petrographic Analysis ◽  
Kuala Lumpur ◽  
Developing Regions ◽  
Geological Structures ◽  
Rock Types ◽  
Mine Plan

More than 80 million tonnes of construction aggregate are produced in Peninsular Malaysia. Majority of construction aggregate are produced from granite. Developing regions of Johor Bahru, Kuala Lumpur, Penang and Selangar utilize granite aggregates. Normally it is considered aggregates as non-alkali reactive. Geological study can identify various rock types, geological structures, and reactive minerals which contribute to Alkali Silica Reaction (ASR). Deformed granites formed through faulting results in reduction of quartz grain size. Microcrystalline quartz and phyllosilicates are found in granites in contact with country rocks. Secondary reactive minerals such as chalcedony and opal may be found in granite. Alkali Silica reaction is slow chemical reaction in concrete due to reactive silica minerals in aggregates, alkalis in cement and moisture. For long term durable concrete, it is essential to identify potential alkali silica reactive aggregates. Lack of identifying reactive aggregates may result spalling, cracking in concrete and ultimately ASR can result in hazard to concrete structure. This paper deals with geological study of any aggregate quarry to identify rock type and geological structures with laboratory test –petrographic analysis and bar mortar test can identify type of aggregates being produced. Mine plan with Surpac software can be developed for systematic working for aggregate quarry to meet construction aggregate demand.

scholarly journals Residual Capability of Alkali Binding by Hydrated Pozzolanic Cements in Long-Service Concrete Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Mario Berra ◽  
Teresa Mangialardi ◽  
Antonio Evangelista Paolini
Keyword(s):  
Concrete Structures ◽  
Test Results ◽  
Cement Pastes ◽  
Experimental Procedure ◽  
Accelerated Curing ◽  
Alkali Aggregate Reaction ◽  
Simple Mass ◽  
Pore Liquid ◽  
Pozzolanic Cement

An experimental procedure was developed and applied to cement pastes made with two different pozzolanic cements (CEM IV/B (P) and CEM IV/B (V)) in order to ascertain the existence of a residual capability of alkali binding by long-term hydrated pozzolanic cements and, at the same time, to evaluate the alkali retention capability and the concentration of OH− ions in the pore solution of such cementitious matrices. The developed procedure consisted of accelerated curing of cement paste specimens (150 days at 60°C and 100% RH), subsequent leaching tests at 60°C for 30 days by using deionized water or basic solutions (NaOH or KOH at different concentrations) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions. The developed procedure was found to be appropriate for evaluating both the pore liquid alkalinity and the alkali retention capability by long-term hydrated pozzolanic cement pastes. A residual capability of alkali binding was also identified for both tested pozzolanic cements, thus indicating their potential ability to prevent (CEM IV/B (V)) or minimize (CEM IV/B (P)) the risk of deleterious expansion associated with alkali-aggregate reaction in long-service concrete structures, like concrete dams.

scholarly journals Addressing fish-passage issues at hydropower and irrigation infrastructure projects in Indonesia

2018 ◽  
Vol 69 (12) ◽  
pp. 1805 ◽  
Author(s):  
Lee J. Baumgartner ◽  
Arif Wibowo
Keyword(s):  
Life History ◽  
Fish Passage ◽  
Mitigation Measures ◽  
Migratory Fish ◽  
Tropical Island ◽  
Life History Stages ◽  
Barrier Effects ◽  
Sumatra Island ◽  
Irrigation Infrastructure

Development activities threaten the long-term sustainability of tropical floodplain systems. The construction of dams, weirs, irrigation infrastructure and regulators affect connectivity among habitats and can facilitate rapid declines in riverine biota, especially fish. Indonesia is a tropical island country with an abundance of monsoonal rivers. Massive expansions in hydropower and irrigation infrastructure are planned over the next two decades and mitigation measures will be needed to protect migratory fish. Most Indonesian freshwater fish need to migrate among habitats to complete essential life-history stages. So, strategies are urgently needed to mitigate the barrier effects of river infrastructure to ensure the long-term sustainability of river fishes. A common tool used worldwide is the construction of upstream and downstream fish passes. Only two fish passes exist in Indonesia. One at Perjaya Irrigation Dam on the Komering River (Sumatra island) and another on Poso Dam on the Poso River (Sulawesi island). Neither of these structures has been assessed and many other projects are proceeding without considering potential impacts on fisheries. The proposed infrastructure upgrades over the next two decades provide a once-in-a-generation opportunity to ensure that migratory fish are adequately protected into the future.

Sign in / Sign up

Export Citation Format

Share Document