Slant Shear Test Research Articles

Effect of thermal exposure on the mechanical properties of polymer adhesives

An experimental research programme was carried out to study the effect of thermal exposure on mechanical properties of three different types of polymer adhesives widely used in the construction industry. All specimens were subjected to 4 different degrees of elevated temperature applied for 4 different exposure times. The compression and tensile strengths, carried out as per ASTM C579 and ASTM C307 respectively, were compared before and after thermal exposure. The majority of deteriorating strengths is due to higher temperature level while most of the deterioration took place after 1h of exposure time. The decrease of residual compressive and tensile strengths, depends on the type of polymer adhesive, level of elevated temperature, type of applied stress and to a lesser effect on exposure time. The effect of elevated temperature on bond strength using concrete/polymer adhesive/FRP specimens was evaluated using four different test methods namely; slant shear test as per BS 6319 Part 4, tensile bond strength test as per ASTM C952, shear bond strength test as per ASTM D905 and double-face shear bond strength. The residual bond strength was reduced and the mode of failure changed due to the high temperature, prolonged exposure time, type of polymer adhesive and the increase in the surface area of bond.

The significance of nanoparticles on bond strength of polymer concrete to steel

Polymer concrete (PC) is a commonly used material in construction due to its improved durability and good bond strength to steel substrate. PC has been suggested as a repair and seal material to restore the bond between the cement annulus and the steel casing in wells that penetrate formations under consideration for CO2 sequestration. Nanoparticles including Multi-Walled Carbon Nano Tubes (MWCNTs), Aluminum Nanoparticles (ANPs) and Silica Nano particles (SNPs) were added to an epoxy-based PC to examine how the nanoparticles affect the bond strength of PC to a steel substrate. Slant shear tests were used to determine the bond strength of PC incorporating nanomaterials to steel; results reveal that PC incorporating nanomaterials has an improved bond strength to steel substrate compared with neat PC. In particular, ANPs improve the bond strength by 51% over neat PC. Local shear stresses, extracted from Finite Element (FE) analysis of the slant shear test, were found to be as much as twice the apparent/average shear/bond strength. These results suggest that the impact of nanomaterials is higher than that shown by the apparent strength. Fourier Transform Infrared (FTIR) measurements of epoxy with and without nanomaterials showed ANPs to influence curing of epoxy, which might explain the improved bond strength of PC incorporating ANPs.

초고성능 섬유보강 콘크리트로 보강된 콘크리트의 계면 전단강도 결정을 위한 경사전단 실험

이 연구에서는 강섬유 보강 초고성능 콘크리트(Ultra-high performance fiber reinforced concrete, 이하 UHPFRC)로 보강된 콘크리트 계면에서의 전단강도 평가를 위한 경사전단실험을 수행하였다. 실험변수는 면처리 유무와 콘크리트 강도, 그리고 UHPFRC의 강섬유 혼입률이다. 콘크리트의 계면은 숏블라스팅으로 면처리되었다. 실험결과, 숏블라스팅으로 면처리된 실험체의 계면 전단강도는 매끄러운 표면을 가진 실험체의 부착강도에 비해 매우 크게 나타났으며, 거친면을 만들기 위한 숏블라스팅 방법은 매우 효과적인 방법인 것으로 나타났다. 숏블라스팅으로 표면처리를 할 경우, 전단마찰 철근이 없더라도 콘크리트 계면에서 저항하는 전단강도는 현행 기준에서 제시하고 전단강도 상한값을 초과하는 것으로 나타났다. 기존의 콘크리트와 UHPFRC 사이의 전단마찰 설계는 전단마찰 철근의 유무와 상관없이 현행 콘크리트 구조기준을 사용해도 무방할 것으로 판단된다. 다만, 면처리를 하지 않은 경우에는 적절한 전단 보강재가 추가 설치하여야 할 것이다.

Slant shear bond strength between self compacting concrete and old concrete

This experimental investigation aims to study the bond strength between old and new self-compacting concrete (SCC). The first part presents the factors affecting slant shear bond strength between old concrete and new self-compacting concrete. The studied parameters are compatibility between old concrete and new SCC through variation of concrete compressive strength and concrete stiffness, type of bonding agent, roughness of old concrete, and the effect of adding latex and polypropylene fiber to self-compacting concrete. In the second part, the proper specimen of slant shear test is studied. From the test results, cylindrical specimens with 150mm diameter and 300mm height have a minimum coefficient of variation compared with other studied shapes. The concrete compressive strength overlay self-compacting concrete, roughness of old concrete configuration, adding latex and using polypropylene fiber have a significant effect on slant shear bond strength. In addition, the prism specimen represents more reliable value of slant shear strength than cylinder specimen.

Evaluation of bond strength between fire-damaged normal concrete substance and ultra-high-performance fiber-reinforced concrete as a repair material

Purpose This study aims to investigate and compare the interfacial bond characteristics between fire-damaged normal concrete substrate and ultra-high-performance fiber-reinforced concrete (UHPFRC) as a repair material. Design/methodology/approach First, fire-damaged normal concrete was prepared. Then, with a cast surface, the substrate was subjected to different surface moisture conditions. Three types of moisture conditions were set, namely, air dry, saturated surface dry (SSD) and wet. Slant shear and splitting cylinder tests were conducted to determine the interfacial bond strength of the composite. Findings In general, results indicate that surface moisture conditions significantly influence bond strength. The substrate under SSD condition exhibited the highest bond strength. The findings suggest that UHPFRC is a promising material for the repair and reuse of fire-damaged concrete structures. Originality/value This study compares the bond strength between fire-damaged normal concrete and UHPRC.

Comparison and Review of Concrete-to-Concrete Interface Shear Resistance According to Major Design Codes

The paper focuses on interface shear behavior, more precisely on shear resistance of the interface between lightweight and regular concrete layers cast at different times without shear reinforcement crossing the interface. Different approaches according to most of major design codes (Eurocode, ACI and Model Code 2010 among other) are briefly reviewed, with emphasis on difference between variables resp. material and cross-section characteristics, on which interface resistance depends. Furthermore, two sets of experiments were carried out: direct shear test on Z-type specimens and slant shear test slightly modified to enforce adhesive failure. Obtained results are compared with theoretical values.

Shear strength of recycled aggregate concrete to natural aggregate concrete interfaces

The main goal of this study was to characterize, using the slant shear test, the bond strength of the interface between recycled aggregates concrete (RAC) and natural aggregates concrete (NAC). This can be relevant in the case of new construction, if precast NAC members with cast-in-place RAC parts are adopted, as well as in the case of rehabilitation of existing NAC structures if strengthened using an RAC overlay.Four replacement rates of natural coarse aggregates by recycled coarse aggregates obtained from concrete blocks, 0% (NAC, to serve as reference), 20%, 50% and 100%, were considered. The following substrate roughness conditions were produced: smooth interface – cast against wood formwork (CAW) without any further treatment; slightly rough interface – produced with a steel brush (SB); and rough surface – treated with a needle gun (NG). A total of 12 tests were performed regarding the four replacement rates and the three substrate roughness conditions. The assessment of the roughness parameters was performed using the 2D-LRA method.It was concluded that RAC exhibits adequate mechanical properties for structural use, although declining with the increase of the replacement rate. Regarding roughness, results corroborated previous studies, since an increase of strength for rougher substrates was observed.Finally, it is found that the values obtained by the codes are very conservative for all types of tested concrete, including for RAC100 despite their low concrete strengths.

Effect of Surface Roughness on the Bond Between Ultrahigh-Performance and Precast Concrete in Bridge Deck Connections

This study investigated the performance of the bond between ultrahigh-performance concrete (UHPC) and precast concrete by the use of three bond test methods: the slant shear test, the third-point flexural bond test, and the pull-off test. The influence of the degree of surface roughness—prepared by sandblasting—on the bond between UHPC and the precast concrete was also studied. The test results showed that the third-point flexural bond test was a convenient and a more realistic test of the bond. The increase in the duration of sandblasting increased the roughness of the precast concrete surface, which was quantified by the sand-spread test. A duration of sandblasting of as short as 10 s was enough to achieve an adequate bond between UHPC and precast concrete at 7 days of age after casting of the UHPC, which was indicated by a failure in the precast concrete part. The ultimate flexural load of those specimens was about the same as the ultimate flexural load of a monolithic precast concrete specimen. Specimens that did not receive any surface roughening (i.e., specimens that were not sandblasted) failed at the bond between UHPC and precast concrete, regardless of the type of precast concrete surface: a sawed surface or a molded surface. The ultimate load carried by these specimens was lower than that carried by monolithic precast concrete specimens. Moreover, the strength of the bond between UHPC and precast concrete cast on an unroughened sawed surface was higher than that between UHPC and precast concrete cast on an unroughened molded surface.

Potential of Carbon Nanotube Reinforced Cement Composites as Concrete Repair Material

Carbon nanotubes (CNTs) are a virtually ideal reinforcing agent due to extremely high aspect ratios and ultra high strengths. It is evident from contemporary research that utilization of CNT in producing new cement-based composite materials has a great potential. Consequently, possible practical application of CNT reinforced cementitious composites has immense prospect in the field of applied nanotechnology within construction industry. Several repair, retrofit, and strengthening techniques are currently available to enhance the integrity and durability of concrete structures with cracks and spalling, but applicability and/or reliability is/are often limited. Therefore, there is always a need for innovative high performing concrete repair materials with good mechanical, rheological, and durability properties. Considering the mechanical properties of carbon nanotubes (CNTs) and the test results of CNT reinforced cement composites, it is apparent that such composites could be used conveniently as concrete repair material. With this end in view, the applicability of multiwalled carbon nanotube (MWNT) reinforced cement composites as concrete repair material has been evaluated in this study in terms of setting time, bleeding, and bonding strength (slant shear) tests. It has been found that MWNT reinforced cement mortar has good prospective as concrete repair material since such composites exhibited desirable behavior in setting time, bleeding, and slant shear.

Bond strength of PCC pavement repairs using metakaolin-based geopolymer mortar

In order to use geopolymer mortar as a pavement repair material, a splitting test and a slant shear test are performed to characterize the bond strength of the geopolymer and conventional cement mortar interfaces. Effect of curing time, degradation of the cement mortar under different acid conditions on the bond strength of geopolymer with conventional cement mortar, and comparison of the metakaolin geopolymer with other pavement repair materials are analyzed. It was found that curing time affects the interface bond strength greatly. Metakaolin geopolymer reaches 80% of its 28 day strength in 3 days curing, but shows low strength in 24 h curing. Curing temperature affects the strength of metakaolin geopolymer, however metakaolin geopolymer cured in ambient temperature and the bond strength of 3 days curing through splitting and slant shear tests reaches 3.63 MPa and 16.32 MPa, respectively. Degradation of cement mortar negatively affects the bond strength of geopolymer and conventional cement mortar. Possibility of using metakaolin geopolymer as a repair material is discussed by comparison of this experimental result with these of other repair materials.

Apparent vs. True Bond Strength of Steel and PC with Nanoalumina

The bond of polymer concrete (PC) to a steel surface is a critical aspect in many infrastructure applications. Bond strength can be evaluated through several means including pull-off, flexural, twist-off, and slant shear tests. While pull-off strength tests are the most common method for evaluating bond for PC overlays in bridge and parking structures, slant shear tests are more suitable when vertical rather than horizontal bond lines are used. In this paper, we discuss the use of slant shear tests to examine bond of polymer concrete repair material to steel pipes used to ensure wellbore integrity of abandoned oil wells used for CO2sequestration.Bond strength of Novolac PC incorporating nanoalumina particles to a steel surface was measured using slant shear tests. Different amounts of nanoalumina were used in the PC to improve bond strength without significantly reducing PC flowability. Slant shear testing confirmed the ability of nanoalumina to improve the steel-PC bond strength. A finite element (FE) model using the ABAQUS simulation environment was developed to compare the apparent versus the true bond strength. A cohesive contact element surface was used to simulate bond along the interface line. The FE model showed that the stiffness mismatch between the PC and steel controls the maximum shear stress developed at the interface surface. The true bond strength extracted from the FE model appears to be about twice that of the apparent bond strength.

Environmental effects on the adhesion properties of nanostructured epoxy‐silica hybrids

ABSTRACTA nanostructured epoxy‐silica hybrid based on epoxy systems with interpenetrating silica domains was designed for a possible use as a structural adhesive for civil engineering applications. Silica domains were obtained in situ during the curing of the thermosetting matrix by means of the sol‐gel process, which was able to chemically bind the organic phase with the inorganic one. To assess the ability of the developed epoxy‐silica hybrid system of overcoming some of the well known deficiencies of conventional epoxy adhesives used in civil engineering field, the environmental effects on the adhesion properties of these novel systems were investigated. First, flexural tests were undertaken on cast epoxy‐silica specimens to determine the mechanical properties of the nanostructured adhesive when exposed to different environmental conditions, that is, moderate temperature or immersion in water. For comparison purposes, a control sample of epoxy resin, representative of a commercially available adhesive, was tested after the same exposure regimes. In order to assess their durability in service, concrete/concrete joints, bonded or with the hybrid epoxy‐silica or with the control epoxy adhesive, were exposed to the same environmental conditions and subjected to adhesion tests according to the “slant shear test.” The results obtained on both cast specimens and concrete/concrete adhesive joints proved the significantly better retention of properties of the nanostructured organic–inorganic adhesive compared to the control resin after exposure to moderate temperature or immersion in water. This constitutes a distinct advantage of the hybrid system over the corresponding conventional epoxy resins cured at ambient temperature for civil engineering applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42514.

Effects of Compressive Strength, Autogenous Shrinkage, and Testing Methods on Bond Behavior of High-Early-Strength Engineered Cementitious Composites

An experimental study was undertaken to assess the bond characteristics of high-early-strength engineered cementitious composites (HES-ECC) with characteristics of high ductility and low early-age shrinkage. For comparison purposes, a mixture of repair material (REP), which is commercially available and extensively used for fast and durable repair of infrastructures, was used to compare the bonding performance. For the evaluation of bond characteristics, slant shear and tensile pulloff tests were performed. In this study, the influence of compressive strength and autogenous shrinkage on individual bond strength results is also discussed, along with the basic mechanical properties of the proposed materials. Experimental results indicate that the influence of compressive strength and autogenous shrinkage on bond strength results varies significantly depending on the test method. It was also shown that the use of HES-ECC mixtures significantly improves the bond characteristics of a repair assembly in comparison to REP. Enhanced bond performance of HES-ECC mixtures over REP is more evident in the case of direct pulloff tests than in slant shear tests, both in terms of bond strength results and failure type.

Bond Strength Characteristic of Concrete Patch Repair Material Made from Unsaturated Polyester Resin (UPR)-Mortar

Patch repair materials made from unsaturated polyester resin (UPR)-mortar have been investigated to determine their bond strength characteristic by slant shear test method. The relative mechanical properties of UPR-mortar and substrate concrete for composing the specimens are: lower modular and high strength ratio. The experimental results show that the combination of materials causes the observed bond strength are dictated by failure of substrate concrete. The actual bond strength could be higher as most of the specimens fail without separation of the UPR-mortar and substrate concrete at the bond plane.

Interfacial strength study between a concrete substrate and an innovative sprayed coating

This paper investigates the mechanical behaviour, at a local scale, of a solution of a thick thermal insulation pneumatically placed from the outside for refurbishment. In particular, this study shows the strength of the critical area: the interface with its concrete substrate. It is possible to define the failure criterion of this interface using the slant-shear test. However, due to a difference in rigidity between the concrete substrate and the insulating coating, a numerical study is necessary to better understand the experimental results and to assess the possible stress concentrations at this interface, which could distort the experimental results.

A study of some factors affecting bond in cementitious fiber reinforced repairs

Concrete infrastructure repair remains a formidable challenge. We need to understand the repair performance and develop innovative materials and placement processes that lead to durable, cost-effective and esthetically pleasing repairs. In this context, fiber reinforced concrete is considered promising.The influence of fibers on the properties of the interface between old concrete and fiber reinforced repair remains poorly understood. This paper describes an experimental study on the influence of fibers on the mechanical properties of the interface. Bond strength was assessed by means of slant shear tests with different slants. Shear-normal stress interaction diagrams, adhesion strength and internal friction were obtained. Repair mortars with different contents of Polyvinyl Alcohol (PVA) fibers and the influence of wet–dry cycles were investigated.Results show that PVA fibers added to the repair can significantly enhance interfacial adhesion. Once the repair interface is fully developed, fibers, however, do not mitigate damage from wetting and drying.

Existing concrete textures: their effect on adhesion with fibre concrete overlay

This paper quantifies the roughness parameters of existing normal concrete substrate surfaces and evaluates their effect on adhesion strength with ultra-high-performance fibre concrete overlay. Three types of substrate surface textures are adopted: as-cast texture as control, wire-brushed texture and sand-blasted texture. The roughness profile of these substrate surfaces is assessed using an Alicona Infinite Focus device. Adhesion strength is quantified at 3, 7, 28 and 180 days based on the results of the pull-off test, splitting cylinder tensile test and slant shear test. The short- and long-term results of the splitting cylinder tensile and slant shear tests demonstrate that the surface texture profiles of the existing concrete substrate have an important effect on the adhesion strength between existing concrete and ultra-high-performance fibre concrete overlay. The behaviour of bonded ultra-high-performance fibre concrete/existing concrete with sand-blasted texture closely resembles that of monolithic normal samples under splitting cylinder and slant shear tests. The short- and long-term results of the pull-off test prove that failure occurs in the existing concrete, regardless of the type of existing concrete surface texture. A very good polynomial correlation (R2 > 80%) is observed between the average roughness parameter (Ra) of existing concrete textures and results of the splitting cylinder tensile and slant shear tests.

Influence of silica fume and metakaolin with two different types of interfacial adhesives on the bond strength of repaired concrete

In this article, the factors affecting the bond strength are studied through slant shear tests made on 168 samples in two phases. Effects of silica fume (SF) and two types of metakaolin (MA, MB) replacement with a portion of cement in concrete repair are studied as the first phase. The second phase consists of plain cement slurry (PCS) and bonding slurry (BS) as the interfacial adhesives. Only metakaolin type B could improve the bond strength, and best results were obtained in PCS applied specimens. Applying BS in concrete repairs exposed to the water was not suitable to be used as an interfacial adhesive. In applying pozzolan the sort of interfacial adhesive in addition to the chemical components of the pozzolan must be considered.

Comparison of Test Methods for High-Temperature Performance of Asphalt Mixtures

Through a comparative study of high-temperature asphalt mixture performance by three methods: the standard rutting test, uniaxial penetration test on cylindrical specimens, and slant shear test, this paper displays that the shear elastic modulus gained by both cylindrical uniaxial penetration test and slant shear test can reflect well the properties of shear deformation of asphalt mixture under high temperature. However, there are certain limitations in these test methods.

The relationship between substrate roughness parameters and bond strength of ultra high-performance fiber concrete

The bonding that exists between the old concrete and the new concrete depends largely on the quality of substrate surface preparation. The accurate representation of substrate surface roughness can help determine very precisely the correct bonding behavior. In this work, an experimental investigation was carried out to quantify the normal concrete (NC) substrate roughness parameters and evaluate their relationship with the bonding performance of ultra high-performance fiber concrete (UHPFC), used as a repair material. The bond strength was quantified based on the results of the pull-off test, splitting cylinder tensile test, and the slant shear test. Three types of NC substrate surface preparation were used: as-cast (without surface preparation) as reference, wire-brushed, and sand-blasted (SB); the roughness of which was determined using an optical three-dimensional (3D) surface metrology device (Alicona Infinite Focus). It was observed from the result of the pull-off test that failure occurred in the substrate, even though adequate substrate surface roughness was provided. Moreover, analysis of the splitting cylinder tensile and slant shear test results showed that the substrate surface preparation method had a significant influence in bonding strength between UHPFC and the NC substrate. The composite UHPFC/NC substrate having a SB surface behaved closely as a monolithic structure under splitting and slant shear tests. An excellent correlation (R 2 > 85%) was obtained between the substrate roughness parameters and the results of the splitting cylinder tensile and slant shear tests.