Now showing 1 - 10 of 47
  • Publication
    Use of post-installed screws in the compressive strength assessment of in-situ concrete
    In the structural evaluation of existing concrete structures, concrete strength is an important parameter that influences the quality of the overall assessment. Non-destructive tests (NDTs) allows the inspection of larger areas of concrete at lesser cost and time than coring and provides more reliable information than visual inspection. The low reliability of common NDTs in the assessment of compressive strength of concrete limits the use of NDTs in the practical field. A new technique, post-installed screw pullout (PSP) test, based on the modified pullout of post-installed screw, is presented in this paper. The screw transfers the load to the concrete through bearing on the threads. During the complete pullout failure mode, the failure pattern involves local crushing of concrete under the threads. The PSP test was investigated in mortar and concrete to study different factors; compressive strength, presence of aggregates, and the types of aggregate. Mortar was considered to be a homogenous material and thus taken as a baseline for comparing the effect of aggregate type. Experimental studies showed that aggregates play a significant role in the assessment of compressive strength by PSP test, and a better correlation with compressive strength was observed when concretes with different aggregates were analysed separately. In the strength assessment, the degree of variability of the PSP test in terms of R-squared value, standard deviation, coefficient of variation, and RMSE for mortar and concrete with brick chips and lightweight aggregates was found to be low; however concrete with limestone aggregate showed higher variability in the test results. The study confirms that the PSP test is a viable test method with the potential to be reliable and reasonably accurate, yet cost effective; it can also contribute to the reduction of the uncertainty in the assessment of compressive strength of in-situ concrete.
  • Publication
    A concrete home for marine micro inhabitants
    (RILEM Publications S.A.R.L., 2018-10-24) ;
    In the last decades, the prevalence of artificial marine structures along natural shorelines has increased significantly. In some parts of the world, more than half of the available natural shoreline has been covered by these structures. Epibiotic diversity has been shown to decrease significantly on submerged artificial structures due to the reduced environmental heterogeneity of artificial environments. Natural rocky shores provide microhabitants through their rough surfaces, pits, rock pools and crevices. In contrast, modern building materials typically fail to provide many of these features. The ecological value of artificial coastal infrastructure could be increased through careful design of pre–fabricated ecological engineering units. Material selection is a crucial parameter in the design of these units. Reinforced concrete plays an important role in the design process due to its ease of production, relatively low cost and its suitability for mass construction. To maximise the potential of concrete to support biodiversity and natural capital, binder composition, aggregate type, and texture are considered to be important parameters. To investigate these parameters, an experimental programme has been developed which is focusing on a number of different concrete designs. Key engineering parameters, such as strength, chloride diffusion coefficient, and their ecological colonisation performance are evaluated.
  • Publication
    Chloride diffusion coeficient determination for specifications
    The chloride diffusion resistance of reinforced concrete can have a major influence on durability. A move to performance-based specifications is therefore to be encouraged in the case of highway structures, where the client expects a long trouble-free service life. The introduction to practice of service life modelling and performance-based specifications requires a parallel development in user-friendly test methods. This paper reports on experience with three techniques used to determine apparent chloride diffusion coefficients: long-term immersion tests with chloride analysis by Volhard titration, tests of medium duration with chloride analysis by an internal-calibration potentiometric method and short-term Nordtest rapid migration tests. Concrete compositions tested included Portland cement, pfa and ggbs mixes. It was found that medium and long-term tests were consistent, but care is needed with early age tests.
  • Publication
    Reactivity assessment of aggregates : the role of chert crystallinity
    A systematic assessment scheme for determining the alkali reactivity of aggregates has been developed for international use. Expansion tests were conducted on Irish aggregates. Aggregates were subjected to a sequence of tests for alkali reactivity: petrographic examination and mortar bar and concrete prism expansion testing. No cases of damaging alkali-silica reaction have been identified to date in Ireland despite the presence of chert in significant commercial sources. Chert-bearing Irish aggregates performed poorly in expansion tests despite an exemplary service record. Chert crystallinity was examined through domain size and quartz crystallinity index. The crystallinity study helped explain the apparently anomalous behavior of the aggregates in tests. A preliminary study of the effect of alkali loading provided confirming evidence. It is suggested that enhanced crystallinity raises the alkali threshold value for reaction to one intermediate between that experienced in practice and in tests.
  • Publication
    Significance of the concentration of chloride in the repair of concrete highway structures using surface applied corrosion inhibitors
    Advances in surface-applied corrosion inhibitors suggest that they have the potential to prevent or significantly retard corrosion of steel in reinforced concrete structures. It is thought that the effectiveness of the inhibitor depends on both the chloride concentration at the steel reinforcement and the inhibitor concentration. This paper presents the preliminary findings of a laboratory study into this assumption. Concrete specimens were ponded with chloride solutions to initiate corrosion. Inhibitor was applied to one face and the influence on corrosion activity was monitored by linear polarisation resistance measurement. The preliminary results of this continuing study showed that the surface-applied inhibitors could reduce the corrosion rate and this reduction depends on the chloride concentration. The practical implication is that there exists a chloride concentration range within which inhibitor use is most effective.
  • Publication
    Developing braided FRP reinforcement for concrete structures
    (Civil Engineering Research Association of Ireland, 2016-08-30) ; ;
    In recent years, significant research has been conducted, by both industry and academia, into the optimum development and use of Fibre Reinforced Polymer composite materials in infrastructure. In particular, it is widely recognised that FRPs have the potential to replace conventional internal steel rebars in concrete reinforcement and offer performance benefits related to their advanced properties, such as corrosion resistance, high tensile strength etc.A review of the available literature indicates that brittle behaviour of FRP can significantly decrease the expected ultimate load capacity and, thus have a negative effect on structure¿s long term durability. However, selecting braiding as manufacture technique and enhancing flexural capacity and shear strength through additional helical reinforcement, could provide structure with the additional ductility needed to prevent a brittle failure. Furthermore, the impact of deterioration mechanisms, focusing on the interaction between FRP and concrete in a structure, is an aspect for further investigation via laboratory testing and advanced analysis.This study summarises the results of research on structural design and manufacture methods of FRP composite materials by presenting new configuration and types of FRP reinforcement in order to encourage the use of these promising materials in construction industry.
  • Publication
    Development of Braided Basalt FRP Rebar for Reinforcement of Concrete Structures
    (The Hong Kong Polytechnic University, 2016-12-16) ; ;
    In recent years, the development and use of Fibre Reinforced Polymer composite materials in infrastructure have gained increasing attention worldwide. More specifically, natural mineral fibres such as basalt are currently being developed and are showing promising properties. Within an appropriate polymer matrix, their use as reinforcement in concrete structures offers performance benefits related to their environmentally friendly and non-corrodible nature. In particular, BFRPs have the potential to replace conventional internal steel rebar and thus, to be the next generation material in concrete reinforcement applications. A detailed literature review indicates that a careful selection of the appropriate manufacture technique and design methodology are required in order to prevent brittle failure on a concrete structure reinforced with FRP composite material. This paper reports on how to use the additional helical reinforcement and the braid configuration in order to increase strength, structural ductility and long term durability. Moreover, this study outlines the development of an analytical numerical model to predict the longitudinal elastic modulus of braided composites, as well as its validation by comparison of the results with available data from the literature.
  • Publication
    TRUSS, a European innovative training network dealing with the challenges of an aging infrastructure network
    Inspections and maintenance of infrastructure are expensive. In some cases, overdue or insufficient maintenance/monitoring can lead to an unacceptable risk of collapse and to a tragic failure as the Morandi bridge in Genoa, Italy, on 14th August 2018. An accurate assessment of the safety of a structure is a difficult task due to uncertainties associated with the aging and response of the structure, with the operational and environmental loads, and with their interaction. During the period from 2015 to 2019, the project TRUSS (Training in Reducing Uncertainty in Structural Safety) ITN (Innovative Training Network), funded by the EU H2020 Marie Curie-Skłodowska Action (MSCA) programme, has worked towards improving the structural assessment of buildings, energy, marine, and transport infrastructure. Fourteen Early Stage Researchers (ESRs) have been recruited to carry out related research on new materials, testing methods, improved and more efficient modelling methods and management strategies, and sensor and algorithm development for Structural Health Monitoring (SHM) purposes. This research has been enhanced by an advanced program of scientific and professional training delivered via a collaboration between 6 Universities, 1 research institute and 11 companies from 5 European countries. The high proportion of companies participating in TRUSS ITN has ensured significant industry expertise and has introduced a diverse range of perspectives to the consortium on the activities necessary to do business in the structural safety sector.
  • Publication
    The structural reliability of bridges subject to time-dependent deterioration
    The reliability of the structural performance of any given structure is affected by both in-service loading and material deterioration due to environmental attack. They must be evaluated at any given time in order to compute lifetime probability of failure. This paper presents an innovative methodology to derive the structure lifetime load effect due to existing traffic using a statistical tool known as Predictive Likelihood. Loss of resistance due to corrosion originated by chloride ingression is also taken into account. Finally the lifetime probability of failure is evaluated via the application of a time-discretization strategy
  • Publication
    Ecostructure: Concrete design for improved marine biodiversity
    In some parts of the world artificial marine structures now cover more than half of the available natural shoreline. Due to the impact of climate change and the need for improved coastal defences this number is set to increase, and these will inevitably have a significant impact on the local marine ecosystem. As an indicator of this impact, research in the UK has shown the epibiotic diversity to be significantly reduced on submerged artificial structures. The Ecostructure project is part funded by the Ireland Wales Cooperation Programme and has the objective of addressing climate change adaptation through ecologically sensitive coastal infrastructure. The approach under development is to increase the ecological value of artificial coastal infrastructure in the Irish Sea through careful design of pre–fabricated ecological engineering units. A key parameter in the design of these units is material selection. Reinforced concrete plays an important role in the design of these units, due to its ease of production, relatively low cost and its suitability for mass construction. However when assessing concrete mixes for use in this application, a key issue is how easily the local marine organisms can colonise the hard concrete substrate. It is considered that key parameters can include binder composition, aggregate type, texture, colour etc. To assess these parameters, a testing programme has been developed that is focusing on 9 different concrete designs. These are assessed for key engineering parameters (strength, chloride diffusion coefficient etc.), as well their ecological colonisation performance. This is determined by placing concrete samples in marine environments in Ireland and measuring the ecological diversity through quadrat sampling at a number of time intervals. This testing is taking place in Dublin and initial results are presented.