This paper presents the development of a new type of fiber reinforced polymer (FRP) composites jacket and the evaluation to demonstrate the application of this pre-fabricated composite repair system for rehabilitation of deteriorating concrete columns. The novelty of this fiber composite strengthening system is that it is quick and safe to install due to the easy-fit and self-locking mechanical joint. An intensive characterisation of the mechanical properties of the composite resin for the interlocking teeth and locking key of the jacket was conducted. Similarly, finite element (FE) simulation on the behaviour of the FRP jacket subjected to internal pressure was performed and verified through full-scale experimental testing. Finally, the behaviour of concrete columns with simulated steel corrosion defect and repaired with a composite jacket was investigated. The results showed that the provision of FRP jacket restored the axial capacity of concrete columns with 25% and 50% corrosion damage up to 99% and 95%, respectively.

A key concept of sustainability is the preservation of resources, thus adding life to existing concrete structures by means of durable strengthening and rehabilitation methods is a key objective. Composite materials, such as FRCM (Fabric-reinforced Cementitious Matrix), have proven to be a viable option for increasing durability of existing building stock. Experimental works show that the main failure mode of FRCM, applied to masonry or concrete substrates, is by debonding at the fabric/matrix interface. Here, the idea is to use an epoxy coating and a layer of quartz sand in order to increase the adhesion of the fabric with the matrix. The effectiveness of coating treatments was studied by means of tensile tests, as indicated in AC434 Annex A. Tests were carried out on seven different types of fabric, with different levels of pre-impregnation and with or without quartz sand applied to the fabric surface. Experimental evidence shows a promising enhancement of the bond between fabric and matrix and, therefore, of the entire strengthening system even with the use of low percentages of resin, depending on the type of mortar.

A method for screening the durability of FRP bars under bending stress andimmersion in high pH solution at elevated temperature is described. Discussion of theneed for such a test, process variables affecting durability, determination of theappropriate bending radius and a description of the test method are shown. Testresults from a series of eight production runs varying only one of the processes relatedvariables, glass fiber supplier, are shown. Fiber sizing chemistry for the fiber/resin/production system is key to better durability of GFRP rebar. The bending stressdurability test method helps reveal FRP bar system performance for differentconstituent materials and offers a more practical method for evaluating alkalinedurability of GFRP bars. The method is intended as an indicator of durabilityperformance and not a definitive evaluation.

Superplasticizers are key components to enhance greatly the workability of concrete. A new carboxylic acid-based copolymer was synthesized and evaluated as a superplasticizer. This copolymer was prepared from methacrylic acid and 2-acrylamido-2-methylpropane sulfonic acid through free radical polymerization. The test results on cement pastes indicate that this copolymer could uniformly disperse the cement particles and improve the fluidity of the system. Compared to the commercially available naphthalene-based superplasticizer, the polymer requires less amount to achieve the same mini-slump value, and provides longer slump retention time. Thus the synthesized resin has a potential to become a superplasticizer. Finally, the workability and compressive strength of concrete with this new admixture were also tested, and compared with that of the commercial superplasticizers.

A series of 16 reinforced concrete beams was tested to evaluate the flexural performance of RC beams strengthened by epoxy bonded plates after repair. The key parameters for this study were the repair materials, polymer, cementitious materials and strengthening materials, steel plates and carbon fiber sheets. The repaired specimens failed by a typical flexural mode with minor interfacial bond failure. The results show that the flexural performance of the strengthened beams is varied depending on the repaired material. Specimens with epoxy polyester resins and latex modified cementitious mortars are effective for repairing the concrete beams, compared to specimens repaired with cement mortar. The flexural capacity of specimen strengthened by epoxy bonded steel plates or carbon fiber sheets after repair are less than those of strengthened specimens without repair. The interfacial behavior between was the repair material and strengthening material observed as the major influencing factor for the composite structures.