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With much of the world's infrastructure needing rehabilitation, new and more effective methods of repair are required to ensure that concrete structures can continue to perform adequately. This work investigates the potential for using locally produced ultra-high performance concrete (UHPC) as an overlay material to rehabilitate existing normal str...
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... The rebound and in-place properties of concrete are influenced by the placement process [22] for pneumatic spray applications. The rebound of UHPC is less than conventional concrete as it does not have large aggregates. ...
... With the use of the gravel patterns, the bond strength was increased by 60.3% as compared to the chipped surface (30). Bond strength testing of split prism specimens was performed using a modified version of ASTM C496, with results of 1.5 MPa for the 0.05 mm texture and the bond strength was nearly 3.7 MPa for the rough texture (31). ...
... This paper presents an assessment of the effects of substrate surface preparation (surface moisture condition and surface texture) on ultra-high performance concrete (UHPC) overlay bond strength. UHPC has exceptional durability, excellent mechanical properties, and has the potential to be an excellent overlay material (Graybeal 2007, Newtson et al. 2018, and Flores et al. 2020. Overlay bond strength was assessed for UHPC-normal strength concrete (NSC) composite specimens using direct shear and direct tension bond tests. ...
This study assesses the effects of substrate surface preparation on ultra-high performance concrete (UHPC) overlay bond. Bond assessment is important because effectiveness of an overlay greatly depends on overlay-substrate bond. Bond was assessed by subjecting overlaid specimens with five substrate surface moisture conditions (excess free moisture, a thin layer of free moisture, air-dried saturated surface-dry (SSD), towel dried SSD, or dry) and five substrate surface textures (smooth and brush, light, medium, and heavy sandblasted) to direct tension and direct shear tests. All surface textures facilitated adequate shear strengths when there was free moisture on the surface. In general, bond strength improved with aggregate exposure as long as the substrate was visibly moist (SSD or wetter) at UHPC overlay placement. The primary conclusion was that visibly moist exposed aggregate surfaces facilitated acceptable bond [greater than 1.03 MPa (150 psi) for tension and 1.00 MPa (145 psi) for shear].
... In Fig. 11, at any location of the overlay, the shrinkage strain in UIC-R with reinforcement is always lower than that in UIC-N without reinforcement, especially at corner and ¼ edge where less restraint occurs. In later ages, the shrinkage strain in overlay UIC-R could be approximately 16% (40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50) μm/m) lower than that in UIC-N at center and ¼ edge. Their strain difference is relatively small at the two sensors (3 and 4) both at midspan since these areas have higher restraint degrees. ...
... Teng et al. [20] reported that the bond strength between UHPC and concrete could be 2.0-2.8 MPa by pull-off test, and Craig et al. [40] reported that their bond strength by slant-shear tests could be 7.1-19.8 MPa depending on the interface texture type (groove, ground, rough, etc.). ...
Ultra-high performance concrete (UHPC) can be a good candidate for bridge deck overlay or repair materials of structural members due to its superior mechanical properties or durability. However, large autogenous shrinkage characterized by UHPC may be an obstacle to extending its applications. A novel internal curing (IC) agent, calcined bauxite (CB) aggregate, has been developed to effectively reduce the autogenous shrinkage of UHPC and meantime enhance its mechanical properties. This study further examines its efficiencies in solving shrinkage issues by restrained ring test and large-scale UHPC-concrete composite slabs. In restrained ring tests, when both no fibers, the IC UHPC matrix with CB aggregate shows smaller crack width (0.25 versus 1.0 mm at 9 d) and delayed (5.2 d versus 3.6 d) onset of cracking than the normal UHPC matrix; when having fibers, the normal UHPC shows micro-cracking while no cracking was detected in IC UHPC even observed at one year. Normal UHPC overlay shows more serious delamination and curling than the IC UHPC overlay, and it also shows a hairline crack on the side surface at midspan. Early-age exposure to drying at 1 d has a detrimental effect by exhibiting the most severe delamination and curling of the UHPC overlay, and reinforcement in UHPC layer is effective in reducing its shrinkage strain.
... Interface layer bonding depends on various factors like, workability [8], [47][48][49], surface roughness [50][51][52][53], bonding agent [54], surface moisture condition [55], [56], overlay materials strength [4], [21], [47] [57], age of concrete [46], [58], specimen size [49], [59][60], micro-cracking [47], [61], shrinkage of concrete [62], [63], cohesion in the substrate concrete [64], [65], aggregate interlock [66], [67], and other time-dependent factors [19], [68]. Some factors have been shown in figure 2 that describes the relationship of bond strength and with its degree of influence. ...
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.
... Recent research has demonstrated that UHPC may have the ability to increase service lives of bridge deck overlays and reduce maintenance costs (Newtson et al. 2018, Haber et al. 2017, Graybeal 2007, Graybeal and Davis 2008, and Graybeal and Hartmann 2003. A 2017-2018 research project at New Mexico State University (NMSU), funded by the Transportation Consortium of South-Central States (Tran-SET), demonstrated that UHPC produced with local materials was able to achieve adequate bond strength when proper surface preparation of the substrate was provided (Newtson et al. 2018). ...
... Recent research has demonstrated that UHPC may have the ability to increase service lives of bridge deck overlays and reduce maintenance costs (Newtson et al. 2018, Haber et al. 2017, Graybeal 2007, Graybeal and Davis 2008, and Graybeal and Hartmann 2003. A 2017-2018 research project at New Mexico State University (NMSU), funded by the Transportation Consortium of South-Central States (Tran-SET), demonstrated that UHPC produced with local materials was able to achieve adequate bond strength when proper surface preparation of the substrate was provided (Newtson et al. 2018). ...
... Recent research has demonstrated that UHPC may have the ability to increase service lives of bridge decks and reduce maintenance costs when used as an overlay [2][3][4][5][6]. A 2017-2018 research project at New Mexico State University (NMSU), funded by the Transportation Consortium of South-Central States (Tran-SET), demonstrated that UHPC produced with local materials was able to achieve adequate bond strength when proper surface preparation of the substrate was provided [2]. ...
... Recent research has demonstrated that UHPC may have the ability to increase service lives of bridge decks and reduce maintenance costs when used as an overlay [2][3][4][5][6]. A 2017-2018 research project at New Mexico State University (NMSU), funded by the Transportation Consortium of South-Central States (Tran-SET), demonstrated that UHPC produced with local materials was able to achieve adequate bond strength when proper surface preparation of the substrate was provided [2]. Consequently, the New Mexico Department of Transportation implemented the UHPC overlay technology by specifying UHPC as the overlay material for a bridge in Socorro, NM, USA. ...
Direct tension tests were conducted to investigate the effects of substrate moisture conditions and texture on ultra-high performance concrete (UHPC) overlay bond strengths. Improper substrate surface preparation can result in inadequate bond strengths and, in severe cases, lack of bond. To demonstrate the importance of surface preparation, pull-off tests were performed on overlaid slabs that had two extreme substrate surface moisture conditions (saturated and dried) prior to overlay application. Saturated slabs had a tined, tined-light sand blasted, or tined-medium sand blasted substrate surface texture. Dried slabs had either a tined or an exposed aggregate surface texture. Saturated specimens with tined, tined-light sand blasted, and tined-medium sand blasted surface textures achieved average bond strengths of 0.924, 1.45, and 1.95 MPa, respectively. Dried substrate surfaced specimens had zero bond strength. Surface moisture conditions that ranged from saturated to dry were also investigated by allowing the substrate surfaces to dry for 15, 30, 45, and 60 minutes prior to application of an UHPC overlay. Tined-light sand blasted specimens with surfaces that dried for 15, 30, 45, and 60 minutes achieved average bond strengths of 2.86, 2.01, 1.59, and 0.165 MPa, respectively. Results showed tined-light sand blasted specimens with proper saturating achieved adequate bond strengths, and properly saturated, tined-medium sand blasted specimens produced excellent bond strengths. Results also exposed the drastic consequences of not maintaining a saturated substrate surface prior to overlay application and delaying overlay application up to 60 minutes can drastically reduce bond strength.
... This study focused on investigating the potential for using locally produced ultra-high-performance concrete (UHPC) as a grouting material to rehabilitate shear keys in adjacent pre-stressed girder bridges in New Mexico, U.S. Previous research at New Mexico State University (NMSU) has shown that locally produced UHPC has excellent mechanical and durability properties (2). UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material (3,4). Additionally, the use of non-proprietary UHPC mixtures provides an economical and sustainable alternative to proprietary products. ...
This research investigated the use of locally produced ultra-high-performance concrete (UHPC) as a grouting material to repair deteriorated shear keys. Shear keys are used in adjacent girder superstructures to produce monolithic behavior and load transfer across the structure. Shear key degradation can jeopardize the integrity of the structure. Transportation agencies have reported that 75% of distress in adjacent girder bridges is due to cracking and de-bonding along shear keys. Previous research has shown that locally produced UHPC has excellent mechanical and durability properties. UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material. Full-scale testing was used to evaluate load-deflection behavior of channel girder assemblages with grouted shear keys. Results showed that while UHPC grout and non-shrink grout had similar mechanical performance, the non-shrink grout began to deteriorate faster under cyclic loading. Excellent bond was achieved with all grouts, even with minimal surface preparation.
... This study focused on investigating the potential for using locally produced ultra-high-performance concrete (UHPC) as a grouting material to rehabilitate shear keys in adjacent pre-stressed girder bridges in New Mexico, U.S. Previous research at New Mexico State University (NMSU) has shown that locally produced UHPC has excellent mechanical and durability properties (2). UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material (3,4). Additionally, the use of non-proprietary UHPC mixtures provides an economical and sustainable alternative to proprietary products. ...
This research investigated the use of locally produced, non-proprietary ultra-high-performance concrete (UHPC) as a grouting material to repair deteriorated shear keys. Shear keys are used in adjacent girder superstructures to produce monolithic behavior and load transfer across the structure. Shear key degradation can jeopardize the integrity of the structure. Transportation agencies have reported that 75% of distress in adjacent girder bridges is because of cracking and de-bonding along shear keys. Previous research has shown that locally produced UHPC has excellent mechanical and durability properties. UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material. Bond strength between UHPC grout and substrate concrete was evaluated using slant-shear and direct tension tests. Results showed that adequate bond was achieved at 7 days. Low strengths at 28 days were observed because of low strength of the substrate concrete. Shrinkage of UHPC grout was also investigated. Shrinkage at 28 days was less than 600 µstrain which is acceptable for repair practices. Full-scale testing was used to evaluate load-deflection behavior of channel girder assemblages with grouted shear keys. Results showed that UHPC grout and non-shrink grout had similar mechanical performance. Excellent bond was achieved with all grouts, even with minimal surface preparation. The similar performances of the non-shrink grout and the UHPC grout indicates that UHPC grout does not provide a mechanical benefit over the non-shrink grout.
... The reason for this is the use of test methods for conventional concretes, which do not take into account the structural features of the composite, the nature and degree of interaction of the concrete matrix with reinforcing fibres, and therefore in some cases are not applicable to the UHPFC tests [42,43]. This is especially noticeable in the study of crack resistance, energy characteristics, indicating a high fracture toughness of the composite, that is, those indicators for which, in the first place, new compositions of fibre reinforced concrete are being developed [44][45][46]. Given this, the issues of improving existing ones, as well as the creation of special methods and means of testing fibre-reinforced concrete as a composite material are relevance. ...
The present work emphasized on identifying and optimizing mix proportions for ultra-high-performance polypropylene
cementitious composites (UHPPFCC) made with lime sludge, micro silica and polypropylene fibre. In
this connection, UHPPFCC was prepared by replacing the cement with lime sludge by 0%, 15%, 30% and 45%;
micro silica as replacement of cement by 0%, 2%, 4% and 6%. In addition the polypropylene fibres were
incorporated to the mix at a dosage of 0%, 0.2%, 0.4% and 0.6%. The UHPPFCC was optimized by Taguchi
design approach with L16 orthogonal array. The number of trials were configured with three varying factors at
four levels each. Besides that, the contribution of lime sludge, micro silica and polypropylene fibre were analysed
using mean response data and ANOVA technique. The optimized mix proportions attained from the Taguchi
design approach is verified with the experimental and modeling results of impact energy. It was found that the
optimized compressive strength and impact energy using Taguchi method was higher than those of proposed in
initial 16 series. Findings revealed that the highest compression strength and impact energy of UHPPFCC were
found in the mix comprising 30% of lime sludge, 6% of micro silica and 0.6% of polypropylene fibre.
