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The work presented in this paper includes the construction methods and lessons learned from the placement of a non-proprietary ultra-high performance concrete (UHPC) overlay through the rehabilitation of a concrete bridge deck located in Socorro, New Mexico, USA. The selected bridge is a multi-cell, box girder bridge with four spans and a total length of 91.4 m and a width of 16.5 m with two traffic lanes. Rehabilitation of the bridge involved removing the top surface of the existing deck (deteriorated concrete), installing a high-performance deck (HPD) leveling course, and placing a 25 mm UHPC overlay. Sensors were installed in the bridge superstructure (multi-cell box girders, HPD, and overlay) for long-term monitoring. Overlay assessment included physical testing to evaluate the condition of the overlay–substrate bond by chain dragging and direct tension pull-off testing. Conclusions and lessons learned from this investigation serve as a fundamental list of best practices and recommendations for field construction of a non-proprietary UHPC overlay. Recommendations for preparatory tasks including material selection, substrate surface preparation, placement preparation, handling of materials, and UHPC mixing are provided. The recommendations also list best practices concerning the placement of the overlay, curing procedures, and quality assurance testing. Lastly, suggestions are presented for contracts pertaining to UHPC overlay projects. [ABSTRACT FROM AUTHOR]

The work presented in this paper includes the construction methods and lessons learned from the placement of a non-proprietary ultra-high performance concrete (UHPC) overlay through the rehabilitation of a concrete bridge deck located in Socorro, New Mexico, USA. The selected bridge is a multi-cell, box girder bridge with four spans and a total length of 91.4 m and a width of 16.5 m with two traffic lanes. Rehabilitation of the bridge involved removing the top surface of the existing deck (deteriorated concrete), installing a high-performance deck (HPD) leveling course, and placing a 25 mm UHPC overlay. Sensors were installed in the bridge superstructure (multi-cell box girders, HPD, and overlay) for long-term monitoring. Overlay assessment included physical testing to evaluate the condition of the overlay–substrate bond by chain dragging and direct tension pull-off testing. Conclusions and lessons learned from this investigation serve as a fundamental list of best practices and recommendations for field construction of a non-proprietary UHPC overlay. Recommendations for preparatory tasks including material selection, substrate surface preparation, placement preparation, handling of materials, and UHPC mixing are provided. The recommendations also list best practices concerning the placement of the overlay, curing procedures, and quality assurance testing. Lastly, suggestions are presented for contracts pertaining to UHPC overlay projects.

Repair is a common method for restoring deteriorated structures. A strong bond between the substrate-overlay is critical to concrete restorations. The interface layer between substrate-overlay effects the strength and durability of a composite system. This interface layer is influenced by the mechanical load and chemical properties of the composition of the substrate and repair material. Because of these interactions, the bond strength between the substrate- overlay concrete is critical. Factors influencing bond strength are surface roughness, micro fractures, compaction, curing, workability, and other environmental factors. Several tests are available to examine the bonding behaviour of substrate-overlay concrete. However, there is no specific way to determine bond strength. This paper outlines the various approaches and strategies by researchers to assess bond strength. Due to its simplicity, most researchers utilised slant shear test, split tensile test, and pull off test and avoided the mixed test method due to its complexity. According to literature, concrete repair is the best method, and higher strength concrete is used to produce better shear outcomes; conventional concrete is more cost-effective than higher strength concrete. [ABSTRACT FROM AUTHOR]

This work investigated the effects of substrate surface moisture condition and texture on ultra-high-performance concrete overlay bond strength. This investigation was performed in three parts that studied extreme substrate moisture conditions, partially dried substrate moisture conditions, and surface texture. These studies investigated the effects of substrate surface moisture conditions, from dry to a surface with a thin layer of free moisture, and surface textures that provided various aggregate exposure conditions on overlay bond strength. Direct tension pulloff tests were conducted to assess overlay bond strength. Results for specimens with exposed fine aggregate surface textures showed that visibly moist substrate surfaces facilitated development of excellent bond strengths, and adequate bond was achieved for conditions with a thin layer of free moisture. For specimens with saturated surface-dry conditions, acceptable bond was achieved with a slightly exposed fine aggregate texture and increasing bond strength was observed with increasing aggregate exposure. [ABSTRACT FROM AUTHOR]

The repair of existing reinforced concrete elements is mainly realized by overlaying them with a higher strength concrete layer strengthened with reinforcement, known as jacketing. The efficiency of the method is based on the stress transfer and strain compatibility at the interface. The common methods used on-site to enhance the concrete-to-concrete bond is roughening the surface and/or applying a bonding agent layer on the old concrete surface. The purpose of this research is to evaluate the contribution of roughness and bonding agent on the bonding strength and, additionally, to develop a general predictive model. Thus, three different levels of roughness were materialized: (i) left-as-cast, (ii) wire-brushed and, (iii) splitting-fractured while two modes of adhesion were tested: (i) substrate with repair cement paste and, (ii) use of a bonding agent. Bi-surface symmetrical shear tests were carried out to assess the ultimate bonding strength of specimens with properties usually found in situ. The experimental results showed that an increase of roughness leads to a better bond performance. The bonding agent effect, however, was notable only for the left-as-cast specimens. A physically-based model is proposed to predict the shear bonding strength concerning the surface roughness, as well as the old and repair concrete's properties. The model aims to offer to designers and researchers an accurate tool to evaluate the effectiveness of the interfacial bond in renovation jacketing procedures. [ABSTRACT FROM AUTHOR]

Objectives. The aim of the study isto assess the influence of concrete deformation properties during the restoration and (or) reinforcement of reinforced-concrete sections using repair compounds.Methods. In the study, a method of calculation of the load-carrying capacity of concrete sections is used according to a non-linear deformation model using diagrams of concrete deformation, taking into account the influence of the confinement effect and prescription factors on the deformation properties of concrete. Deformation diagrams are constructed for short-term loading of concrete of various classes, taking into account the possible change in its deformation properties due to its structural features (e.g. fine- grained) and the presence of modifying additives (repair concrete) in its the composition.Results. The increase in the load-bearing capacity of a section with its total area unchanged is not directly proportional to the area of the reinforced concrete. The increase in the loadbearing capacity of the section is not directly proportional to the increase in the class of concrete reinforcement. Increasing the confinement coefficient from 1.3 to 1.5 provides an increase in the loadbearing capacity of the section from 15.5% to 58%. An increase in the elastic modulus of repair concrete by 1.5 times leads to an increase in the load-bearing capacity of the section from 19% to 50%. While keeping sectional value and reinforcement factor constant, the use of repair concrete makes it possible to increase the bearing capacity of the section under consideration from 1.07 to 2.25.Conclusion. The calculation of the strength of reinforced concrete elements reinforced with repair compounds according to the nonlinear deformation model allows the stress-strain state (SSS) – and, consequently, the bearing capacity after the reinforcement – to be estimated more accurately, while the choice of the repair compound depends on the deformation properties of the “old” concrete.

In the present work, a great deal of importance is attached to sand concrete as a new repair material. An investigation was conducted to evaluate the bond strength and the type of failure in composite concrete bi-layers. The test specimens under study were made of an ordinary concrete substrate and sand concrete (repair material). The substrate was prepared from ordinary concrete of two different classes of strength, i.e. the first one contains a superplasticizer (OCS) and the other has no superplasticizer (OC). To this purpose, four different surfaces used as substrates, namely low roughness (LRG), high roughness (HRG), drilled holes (DH), and combination of high roughness with drilled holes (HRGDH) surfaces were prepared. For the repair materials, two mixes of sand concrete were selected, namely sand concrete with 100% of limestone filler (SCL), on one hand, and sand concrete with 50% of limestone filler and 50% of glass powder (SCG), on the other. Two adhesion tests (flexure test, and splitting test) were performed in order to evaluate the response of the composite test specimens under loading, by determining the mode of failure produced after the test. The results of splitting strength obtained showed that the sand concrete gives remarkable bond strength of 2.54 MPa for cylindrical specimens and 317 MPa for cubic specimens. These values present a good to excellent bond quality, depending on the strength level of ordinary concrete, reflecting a good adhesion to the substrate, which manifested a positive monolithic response. These performances allowed us to consider the sand concrete as a good cementitious repair material. [ABSTRACT FROM AUTHOR]

The structural rehabilitation of reinforced lightweight aggregate concrete beams in shear was studied with resin injection. A series of model beams, reinforced in shear, were loaded in the laboratory until failure, repaired, and again loaded to failure.The variables in the test program were shear span-to-depth ratio 4.0,3.0,2.5,2.0,1.5 and 1.0 ; and shear reinforcement index ,ρvfy= 0.493,0.704 and 0.896 MPa .Experimental failure loads are compared with predictions using ACI 318M-02 code and the modified compression field theory by the program “Response 2000”.After testing, the beams failed due to new diagonal cracks. The ratio of ultimate load to crack load varies from 1.5 for a/d >2 to 2.27 for a/d ≤ 2 (deep beams) . Test results indicate the ACI 318M-02 is conservative.

Premature deterioration of civil infrastructure structures in the harsh environmental conditions of marine regions (high humidity, high thermal variation, acidic attacks, high reactivity chemical reactions, improper usage, and natural disasters) leads to the reduction of service life of these structures. Failures in the rehabilitation process have been observed are primarily attributable to insufficient rehabilitation treatment, improper selection of repair materials, and incorrect repair implementation on the structures themselves. To design a suitable repair solution, it is essential that the physical, mechanical, chemical, and electrochemical properties of the repair materials and base (substrate) concrete match properly. In this paper, a novel approach for selecting proper mix design for repairing and maintaining deteriorated concrete structures located in the marine regions of southern Iran has been proposed using multi criteria decision making (MCDM) methods. The technique of random generation (RG) has also been used for uncertainty analysis on the final results. The results of the case study showed that the proposed methodology can be used as a proper tool for the decision making process in similar repair projects. [ABSTRACT FROM AUTHOR]

Abstract: Hydraulic structures underlie extraordinary conditions due to their prominent function and exposure. Thus, high demands have to be made both on construction and maintenance or repair of the structures, respectively. In order to fulfill these demands new and special technologies have to be developed that ensure an effective construction and guarantee to meet the planned service life of the building required by the owner. Against this background two innovative methods for both construction and repair of hydraulic concrete structures are presented in the present paper. The methods are based on modern concrete technology and enable to either build concrete dams in flowing water or perform concrete repair below the water level. Both methods were developed at the Institute of Concrete Structures and Building Materials at the Karlsruhe Institute of Technology (KIT), Germany and were applied in practice for construction of the Bribin underground hydropower plant in Indonesia and for repair of the river hydropower plant of Albbruck-Dogern in Germany. [Copyright &y& Elsevier]

The experimental investigation on plastic shrinkage and plastic settlement for different self-consolidating concrete (SCC) mixtures as repairing materials is presented. The concrete mixtures were placed on the surface of the concrete substrate slabs at different restraint degrees. Four different types of repairing materials such as plain SCC, SCC with silica fume (SF), SCC with latex and SF, and SCC with latex, SF and fiber were evaluated. The slabs included both reinforcement and without reinforcing bars. The tests involved measurement of concrete bleeding and evaporation rates, steel bar strains and crack characteristics. The results indicated that bleeding rate is not the only controlling factor, but restraint condition, configuration of steel bars and the concrete strain capacity are also affect plastic shrinkage and settlement behaviors significantly. Latex and fiber were found to be effective in reduction of cracks and concrete strains. Cracks did not develop on the surface of concrete containing latex and fiber. The results showed that if a slab is reinforced by one single bar (in each direction of the slab), at relatively large diameter as used in this study, it would not improve the plastic shrinkage behavior, although it causes plastic settlement cracking. [ABSTRACT FROM AUTHOR]