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Graphical abstract Highlights • Dynamic infrared heating aims to improve pothole repair interface bonding. • Shallow and deep pothole excavations were subjected to dynamic infrared heating. • Temperatures were measured on the excavation wall and inside the slab during heating. • Temperatures in the excavations were significantly higher than inside the slab mixture. • Temperatures inside the slab mixture had a lowering trend from the top to the bottom of the slab. Abstract In hot mix asphalt patch repair, inadequate temperature at the interfaces is one of the influencing factors for inferior compaction and poor interface bonding. To enhance repair performance, a precisely controlled infrared pre-heating method for patch repair has been investigated. Asphalt slabs with 45 mm, 75 mm and 100 mm deep pothole excavations were subjected to dynamic heating with infrared heater operating power from 6.6 kW to 7.7 kW. The heater was kept either stationary or moving slowly across the excavations at 130 mm and 230 mm offsets. The tests included evaluating temperature increase throughout the excavations and inside the slab, recording heat power of infrared heater and heating time to avoid burning the asphalt. Irrespective of excavation depth, heating power and offset, the temperature distribution was found non-uniform in the pothole excavations and into the asphalt slab. The temperatures were higher at the faces of the excavation than inside the slab. Dynamic heating for approximately 10 min yielded better heat distribution while minimising the possibility of asphalt overheating and long pre-heating time. It has been concluded that 45 mm and 100 mm deep pothole excavations can be pre-heated with 6.6 kW and stationary heater or 7.5 kW and moving heater at 230 mm and 130 mm offset respectively. 75 mm deep excavation can be pre-heated with 7.1 kW and stationary heater at 230 mm offset. [ABSTRACT FROM AUTHOR]

Highlight • Combined effects of surface roughness, bonding agents and curing age were investigated through orthogonal experiments. • Bond strength was evaluated using a self-designed test device (Patent Number: ZL 2017 2 1680364.4). • Freeze-thaw cycle test was conducted to validate the results of orthogonal experiments. • RRM concrete appears to be a promising material for rapid repair of concrete pavements. Abstract Patch repair is an important category in the repair or restoration of pavements. The effectiveness of the repair largely depends on the bond strength between the repair material and the concrete substrate. In the present work, surface roughness, bonding agents and curing age of the repair materials have been taken into consideration to evaluate the applicability and serviceability of a novel rapid repair material for concrete pavement. A three-factor and four-level orthogonal experiment was designed for systematic investigation. The bond strength of the combined specimens was measured using splitting tensile test and direct shear test. It is found that the splitting tensile strength varied from 1.21 MPa to 2.43 MPa and the direct shear strength varied from 2.84 MPa to 5.92 MPa and the bond strength has a good correlation with surface roughness and curing age. Different failure modes and the shear-slip characteristics were analyzed to understand the actual bond performance of combined specimens. It can be concluded that the slip distance of high surface roughness concrete was almost three times that of low surface roughness. In addition, the freeze-thaw cycle test of the combined specimen was conducted to validate the compatibility of the designed repair material with the concrete substrate. It is found that the he splitting tensile strength and direct shear strength of high surface roughness specimens reduced to 74.5% and 66.3% of its original bond strength after 100 times of freeze-thaw cycles, respectively. The rapid repair material studied in this study can act as a promising alternative for rapid patch repair of concrete pavements. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Patch repairs are widely used for local damage in RC columns. • 15 patch-repaired RC columns were tested at the ICITECH. • The paper analyses the effectiveness of patch repairs on RC columns. • Patch repair is compared with: all-four-sides and one-side repair. Abstract This paper describes an experimental study on patch-repaired reinforced concrete columns subjected to axial loads until failure. The behaviour of four series of columns repaired with Class R3 and R4 cement-based mortar was analysed both with and without a bonding agent. The results obtained were compared with control series of undamaged and damaged but unrepaired columns to determine the effectiveness of the repairs and the subsequent improvement in the behaviour of the columns. The results of this study were compared with those of previous work by the authors on the analysis of all-four-side repairs and one-side repairs. The conclusion reached was that patch repairs are highly effective as compared to the other techniques studied and that using Class R3 mortar achieves better results on damaged columns made with low-quality concrete. It was also concluded that applying a bonding agent does not improve the results, although this element was found to be necessary to prevent the premature detachment of the repair when there is a substantial difference between the stiffness of the column concrete and that of the mortar used in the repairs. [ABSTRACT FROM AUTHOR]

This paper deals with the numerical determination of potential and current distribution along the reinforcement when using patch repair applied to reinforced concrete elements. Numerical finite element models of the electrochemical phenomena demonstrate the useful contribution of Sacrificial Anode in improving the Cathodic Protection of the reinforcement by testing several configurations. The main result is that the Sacrificial Anode should be embedded in the substrate concrete area rather than in the patch area. Moreover, the influence of the resistivity of the repairing concrete is evaluated. [ABSTRACT FROM AUTHOR]

This research program examines the performance of different patch repair strategies for repairing concrete bridge deck slabs, damaged due to premature corrosion of embedded reinforcing steel bars (rebars). The electrochemical compatibility between the repaired patch concrete and the existing old concrete in fifteen (1000 mm × 1000 mm × 200 mm) specimens was examined using half-cell potential, chloride content, rebar mass loss and corrosion penetration rate tests. The experimental results showed that the potential difference between the repaired patch concrete and the existing old concrete local corrosion increased significantly at the periphery of the patch, and gradually progressed into the repaired zone. This effect varied from one repair technique to another. Different measures to increase the service life of the repair system are also proposed, such as incorporating a sacrificial embedded anode, an impressed current cathodic protection system, along with the use of surface coating or membrane as an additional line of defence. [ABSTRACT FROM AUTHOR]

Different proprietary repair materials and a CEM II mortar were used to characterise the relationship between the main parameters of microwave curing (power, curing time, temperature rise and volume). The time-temperature-power relationships are linear for normal, non-rapid setting repair materials cured within the recommended temperature range taking account of temperature variation and heat of hydration. A general relationship between the microwave curing parameters of power, temperature rise, curing time and repair volume has been derived. It has been used to design and operate a prototype system. Steel reinforcement in the repair remains free from arcing under microwave exposure. [ABSTRACT FROM AUTHOR]

Even after repairing a concrete structure, internal corrosion may continue in service state especially under a severe environment and this would deteriorate the newly applied repair material. In this regard, this study investigates the cracking and ultimate failure behavior of patch-repaired sections subjected to internal expansion pressures due to rebar corrosion. An experimental program was set up with major test variables being patch shape, patch depth, patch width, and bond strength of the patch material. The internal expansive pressure was applied through an expansive rubber at the location of a possible corroded rebar. While some patched sections were found to crack first directly above the expanding rebar, most of the patched sections eventually failed due to pop-out spalling along the patched edges. Patched sections deeper than the first layer of steel rebars were found to have higher load capacity until failure. The present study also indicates that the strength of patch material shows no sizable effects on ultimate load capacity of patched sections. [ABSTRACT FROM AUTHOR]

The application of fibre-reinforced polymer (FRP) composites for strengthening and rehabilitation of structural elements has become essential in recent years. However, most of the research and developments focused on using FRP strips or plates, which are limited in strengthening metallic structures with flat steel surfaces. In most cases, the damage due to corrosion are localised in the beam which requires more flexible composite repair system. In this study, a pre-impregnated carbon fibre reinforced epoxy repair system is evaluated through mechanical testing of tensile, double strap shear joint specimens, and structural testing of rehabilitated I-beams. The results showed that use of vacuum during laminate manufacture resulted in better mechanical properties due to the better consolidation of the fibre layers. A bond length of 120 mm provides a more consistent and reliable adhesively bonded joint and is representative of the bond strength of the rehabilitated steel beam. Finally, the patched carbon prepreg system successfully repaired the simulated crack and corrosion defects in steel I-beams, restoring them to their original load carrying capacity and stiffness. [ABSTRACT FROM AUTHOR]

• The effectiveness of bio-based repair materials was presented and highlighted. • The resistance against ingress of water was enhanced by alginate-based healing agents. • Re-deterioration in patch repair method was prevented by the use of Bacillus subtilis (natto). • The use of Bacillus subtilis (natto) was proved to work as a cathodic inhibitor. This study explored the application of bio-based repair materials to concrete for crack repair and patch repair methods. First, the concept of crack repair using Bacillus subtilis (natto) under wet conditions is presented. In addition to the self-healing efficiency, enhancement of corrosion resistance owing to consumption of dissolved oxygen by bacteria which could work as a cathodic inhibitor is theoretically explained by electro-chemical reactions. And then, this study exemplified the application of the bio-based repair material to concrete with respect to crack repair and patch repair methods. First, alginate-based self-healing materials (in-situ encapsulation) are newly developed in this study to improve the resistance against ingress of water in cracked mortar specimens, which is demonstrated by the reduced absorption of water. This is adequately explained by the fact that the calcite precipitation in gel films formed in crack is highly effective in sealing crack in mortar specimen. In addition, the healing agents could reduce the concentration of dissolved oxygen in concrete, which is found to contribute to reduction of the macrocell corrosion current density in which the corrosion rate is determined by the cathodic reactions associated with diffusion of dissolved oxygen. The use of Bacillus subtilis (natto) is highly advantageous in preventing re-deterioration owing to macrocell corrosion taking place between patch repair region and surrounding concrete containing chloride. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a patch repair method that uses high performance fiber reinforced cement composites (HPFRCCs) to repair reinforced concrete members damaged by chloride attack. The beam specimens were deteriorated under chloride attack and then repaired using HPFRCC shotcreting, before they were loaded to investigate their mechanical performance. The experimental results indicates that even after formation of multiple fine cracks under applied load, the HPFRCC remains impermeable due to its very small crack width. With the proposed repair method, the HPFRCC patch layer allowed only very fine cracks to be formed in service conditions. The strength of a beam deteriorated by rebar corrosion could be recovered using HPFRCC patching if the amount of corrosion was less than 10%. It was also clarified that a combined use of a fiber net with HPFRCC patching improves the dispersibility of fine cracks in the HPFRCC layer. [Copyright &y& Elsevier]

Abstract: Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. In USA alone the rehabilitation needs are estimated to exceed 1.6 trillion dollars over the next 5years. Since the majority of the existent infrastructures are concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Besides the sooner concrete deterioration is tackled the lower are the rehabilitation costs. This paper provides a literature review on concrete repair materials, highlighting the current problems face by them. It covers concrete surface treatments, patch repair and FRP strengthening. The case of trenchless rehabilitation of concrete sewage pipelines is also discussed. The potential of geopolymers to overcome those limitations is analyzed. [Copyright &y& Elsevier]

Abstract: This paper presents results of an investigation on the variation of mass loss of deformed tensile steel bars in RC beams (153×254×3000mm) that were corroded whilst under a sustained load using an impressed current, constant wetting cycles with 5% NaCl solution and two different drying cycles. Following the corrosion test, selected beams were patch repaired whilst under a sustained load, but eventually all beams were tested to failure. The results indicated that the highest level of corrosion occurred where there were longer drying cycles, and that the level of sustained load had little effect on the rate of corrosion. Maximum mass loss of steel was found to occur at the centre of the corrosion region. The ultimate flexural capacity of beams was found to be best related to the maximum gravimetric mass loss compared to the average mass loss of steel. A maximum mass loss of steel of 1% was found to reduce the flexural capacity of beams by 0.7%. [Copyright &y& Elsevier]

Abstract: The properties of magnesium phosphate cement (MPC) mortars with different magnesium to phosphate (M/P) molar ratios and sand to binder (S/B) weight ratios have been investigated. The experimental results show that both M/P and S/B ratios have large influence on the setting time and mechanical properties of MPC mortars. Therefore, the formulation has to be optimized in terms of the workability, performance, as well as cost consideration. Besides, the bond strength is an important performance index for a patch repair material and hence received particular attention in this study. The test results demonstrate that MPC mortars have superior bond strength to ordinary Portland cement (OPC) mortar/concrete substrate. Finally, the volume stability measurements illustrate that the drying shrinkage of MPC based repair mortars is much less than that of OPC mortar. It is demonstrated that MPC mortar is promising to be utilized in patch repair and maintenance works of concrete. [Copyright &y& Elsevier]

Abstract: In repair works of reinforced concrete, patch repairs tend to crack in the interfacial zone between the mortar and the old concrete. This occurs basically due to the high degree of restriction that acts on a patch repair. For this reason, the technology of patch repair needs to be the subject of a discussion involving professionals who work with projects, construction maintenance and mix proportioning of repair mortars. In the present work, a study is presented on the benefits that the ethylene vinyl acetate copolymer (EVA) and acrylate polymers can provide in the mix proportioning of a repair mortar with respect to compressive, tensile and direct-shear bond strength. The results indicated that the increase in bond strength and the reduction in the influence of the deficiency in curing conditioning are the main contributions offered by the polymers studied here. [Copyright &y& Elsevier]