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The present work deals with engineering properties of high performance mortar (HPM) to be used as a repair material. The experimental study was conducted on HPM reinforced with mono steel fibers and hybrid fibers consist of steel and polypropylene fibers. The economical efficiency of the designed mono and hybrid fibers reinforced mortar were presen...
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An experimental study is achieved to investigate the polypropylene fibers potentials
on the mechanical performance of concrete constructions. It is found that an addition
of 1% and 2% of polypropylene fibers to concrete mixes produces a reduction of
concrete slump 20% and 28% respectively comparing with conventional mix (0% of
polymer) and an incre...
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Citations
... Angle of bonded interface with the horizontal plane Slant shear bond test specimen(Dawood et al., 2017). ...
This study evaluated the bond performance of overlays bonded to ultra-high performance concrete (UHPC) within the context of Delaware Department of Transportation (DelDOT) bridge applications. Polyester polymer concrete (PPC), latex modified concrete (LMC), and modified class D concrete (MCD) are applied as overlays on UHPC components to protect the bridge deck from deicing salts and provide a smooth riding surface. These overlays differ in composition, bonding agents used, mechanical and physical properties. The difference in properties between these materials results in distinct bond performance on the UHPC substrate. It is critical for an overlay to develop good bonding with the substrate to maximize overlay durability and minimize maintenance.
UHPC is a cementitious composite material with optimized particle packing, internal steel fiber reinforcement, and a low water-to-cement ratio, resulting in superior mechanical properties. UHPC has high compressive strength (at least 22 ksi) and sustained post-cracking tensile strength (of at least 0.72 ksi). Compared to conventional and high-performance concretes, UHPC is nearly impermeable (owing to its discontinuous pore structure), resulting in considerably improved durability. Transportation agencies are using UHPC in bridges for link slabs, connections between precast components, and entirely UHPC structural members. To ensure adequate bonding of overlays to the UHPC substrate, minimum pull-off bond strengths of 250 psi and 200 psi are recommended for PPC and LMC overlays by AASHTO T-34 and ACI 548.4M-11, respectively. In addition, DelDOT specifies a minimum pull-off bond strength of 250 psi for PPC and MCD overlays; the DelDOT specification does not have an explicit bond strength requirement for LMC.
Current literature addressed the bond performance of overlays bonded to conventional concrete substrates. However, when it comes to UHPC substrate, the literature is limited to investigating LMC and UHPC as overlay materials on UHPC, while considering only scarification and hydrodemolition as surface preparation methods. The lack of knowledge regarding the bond performance of other overlays (PPC and MCD) on UHPC as well as the influence of additional surface preparation methods was addressed in this work. The study evaluated the effects of cording depth, overlay age and substrate preparation method, specifically, grinding and sandblasting (GSB), hydrodemolition (HD), surface retarder (SR), and control “non-prepared” (NP) surface on the bond strength. Furthermore, the efficacy of different roughness measurement methods in quantifying the roughness of prepared UHPC substrate was investigated. The three roughness measuring techniques utilized include ICRI concrete surface profile (ICRI CSP) chips, sand patching, and surface profile gauge.
The sensitivity study looking at the effects of coring depth on bond strength concluded that the coring depth of 0.5 in. was the most appropriate for pull-off bond tests on UHPC. Results indicated that surface prepared by GSB performs better than NP substrate surface. However, HD and SR increased surface tortuosity beyond GSB and exposed steel fibers, which further promoted mechanical interlocking across the overlay-UHPC interface. For MCD overlays, it was determined that the substrate hygric state (dry versus saturated surface dry) does not have a statistically significant effect on the bond strength. Bond strength of PPC and LMC plateaued within 7 and 14 days of placement, respectively. Bond strength of MCD decreased by approximately 48% (from 338 to 175 psi) following 14-day moist curing. This reduction in bond strength of MCD was accredited to the effects of restrained drying shrinkage. Finally, in terms of roughness measuring methods, the surface profile gauge was deemed more effective in quantifying the roughness of prepared UHPC surfaces compared to sandpatch method (which could only be applied to NP and GSB surfaces because SR and HD exposed steel fibers in UHPC limiting the spread of sand). ICRI CSP chips could not be successfully used to qualitatively assess the texture of the UHPC substrate because they were created for normal concrete, which has significantly different microstructure compared to UHPC.
... At 20% and 30% WGP, the cracks were occurred at the interface, the repair mortar separated completely from the support (cohesive failure). In order to ensure the mechanical anchoring of the repair mortar, i.e. a durable repair, the repair material must be workable enough to penetrate into the imperfections (cavities) of the surface support [40]. Indeed, from the slump flow results, it can be concluded that the mortar containing 10% WGP, is easy to flow than mortars containing 20% and 30% WGP. ...
This paper studies the effects of fine waste glass powder content (WGP) on fresh and hardened properties of self-compacting repair mortar mixes (SCRMs). For this purpose, mortar mixes were prepared to replace cement with waste glass powder ranging from 0 to 30% at 10% interval and tested. Fresh properties were assessed using mini-slump flow and mini V-funnel. Hardened properties assessed for all mixes were water absorption (at 28-days of age), compressive and flexural strengths (at 7, 28 and 56-days of age). In addition, the adhesion between the repair mortar mixes and substrate was conducted using a 3-point flexural test on a composite prism (half mortar/half substrate) at 28 and 56-days of age. The results showed that glass powder had a negative effect on the workability of mortars. However, in the hardened state, it had a good influence on the strength development after 28 days, durability and adhesion of mortars with the substrate for a waste glass powder content not exceeding 20%.
... Ultrahigh performance concrete or reactive powder concrete is one of the best cementitious composites which have been used in many applications such as highways and for repairing damaged structures [1,2] due to its good physical and mechanical properties. This type of building material has characterized by high compressive strength, tensile strength, flexural strength, flexural toughness, and high flowability which allow it to flow in congested reinforcement areas and fill complicated formwork segregating [3][4][5][6]. ...
The use of supplementary cementitious materials like crushed glass, steel slag, and silica fume at an acceptable level has resulted in many advantages such as reduction of the waste solid materials and production of eco-friendly material. Moreover, the inclusion of fibers for reinforcing cementitious matrix can improve its properties overall. Therefore, this research has been divided into two phases. The first phase has included the production of green reactive powder mortar and the investigation of its properties. The second phase has involved the incorporation of the micro steel fibers to green reactive powder mortar with different amounts. The results have indicated that the use of the crushed glass, steel slag, and silica fume by 8, 12, and 10% as a partial replacement of cement with suitable chemical admixture gives a great reduction of cement by 30% from the total cementitious amount used in reactive powder mortar and greater values of strengths for reactive powder mortar. The addition of micro steel fibers by 1, 1.5, 2, and 2.5% improves the dry bulk density, ultrasonic pulse velocity, compressive strength, flexural strength, and tensile strength of green mortar. The best increase has been observed at green reactive powder mortar (GRPC) containing 2 % of micro steel fibers.
... Adding fibers to the mortar or concrete can greatly enhance the mechanical properties of such materials [5]. Many studies [9][10][11][12][13][14] have reported significant advantages due to the use of different fibers in the cement mortar or/ and concrete. ...
Geopolymer has been presented as new evolution in the concrete technology world, where cementitious materials such as ceramic powder and Slag have been replaced by high percentages of cement used in construction. Thus, the activation of such materials was performed by highly alkaline solutions in order to be acted as a binder in the mix. Therefore, the selection of suitable ingredients proportion of geopolymer mortar to achieve desired strength at required workability has been intended in this study. The experimental Program has been implemented for the preparation of geopolymer mortar mixes. The concentration of sodium hydroxide solution was kept constant in the order of 12 M throughout the experiment. The ratio of Water to geopolymer binder ratio was 0.35, alkaline solution-to- cementitiuos materials ratio was 0.30 and sodium silicate-to-sodium hydroxide ratio was 1.85 by mass. Workability of geopolymer mortar was measured by flow table apparatus and cubes of 50 mm side were cast and tested for compressive strength after 28 days of normal water curing. The study concludes that the combination of ceramic powder and Slag up to 40% (by weight), in the total binder material, can be used for developing the geopolymer mortar. Continuously, the use of 1% steel fibers or 1% steel fiber with 0.5% sisal fibers promotes the level of cement replacement by such cementitous materials (slag and ceramic powder) up to 60%.
... In general, the premature deterioration of structures, especially those made of reinforced concrete is a comeback to many reasons like the exposure of structures to aggressive environmental conditions and significantly increased service loads [1][2]. The rehabilitating and repairing damaged structures instead of demolishing and rebuilding them have many advantages like saving in cement, reducing the use of raw materials, and reducing the waste materials which resulted from the destruction processes [3]. Many researchers have presented studies on the materials used for repairing damaged structures. ...
... Several researchers have presented studies on the cementitious matrices used for repairing damaged structures. Dawood and Ganim [3] studied the performance of unreinforced and reinforced cement mortar in the repairing damaged concrete. The use of cement mortar instead of epoxy resins have given good results in bond strength of the repair material with damaged concrete. ...
... ormal N the composites samples composed of Results and discussion for . 3 . ...
Recently, there is an increased research awareness towards the use of high strength cementitious matrices like reactive powder concrete (RPC) for rehabilitation and repairing damaged structures in addition to their use in the maintenance of concrete structures. Therefore, this research has been conducted to present some RPC mixes prepared from various percentages of cement replacement, nanoparticles materials, and reinforced with three different types of fibers.
The green RPC mixes were prepared with a total 30% replacement of cement by silica fume, slag powder, and glass powder. Then, the addition of Nanoparticles combination as 2.5% Nano glass powder (NG) plus 2.5% Nano Iron slag powder (NS) was performed. Besides, the uses of mono micro steel fibers and hybridization of micro steel fibers (MSF), sisal fibers (SIF), and human hair fibers (HHF) were achieved. The combined systems of substrate concrete and such different green RPC mixes which were proposed here as repair materials besides epoxy were tested in bi-surface shear, oblique shear, flexural bond strength, splitting bond strength, and Pull-out.
The results showed that the reinforcing of green RPC with hybrid nanoparticles (2.5%NG + 2.5%NS) and hybrid fibers (1.5%MSF with 0.25%SIF and 0.25%HHF) boosted the best performances among green RPC mixes in bi-surface shear, oblique shear and Pull-out tests. Also, the said mix gives higher bond strengths between RPC with substrate concrete than that of epoxy by 2.273%, 3.663%, 6.168% and 10% through bi-surface shear, oblique shear, splitting strength and flexural strength, respectively.
... Round gravel with a maximum size of 14 mm was used in this study. The results showed that the coarse aggregate used in this study complies with the standard (IQS No. 45/1984) limits Size (5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Gravel must be washed to remove clay and salts and then stored in containers in a Saturated Surface Dry (SSD) condition before use it. ...
... Figure (4 -A) show effect of good flow on bond strength and Figure (4-B) show influence of little flow on bond strength. These results agreed with Marco (2014) and Dawood and Ganim (2017) studies [12,13]. From Figure 5 showing RPC with polypropylene fibre have lesser flow due to it reduced workability and make it more restricted thus reduced flowability, therefore it cannot inter to the groves easily without compaction. ...
... Figure (4 -A) show effect of good flow on bond strength and Figure (4-B) show influence of little flow on bond strength. These results agreed with Marco (2014) and Dawood and Ganim (2017) studies [12,13]. From Figure 5 showing RPC with polypropylene fibre have lesser flow due to it reduced workability and make it more restricted thus reduced flowability, therefore it cannot inter to the groves easily without compaction. ...
Repairing of reinforced concrete structures is currently a major challenge in the construction industry and is being put back into operation with a slight loss in load carrying capacity. Damage occurs due to many factors that reduce the strength of concrete structures and their durability. The aim of this paper is study the compatibility between three types of reactive powder concrete with (steel fibre, glass fibre and polypropylene fibre) as a repair materials and normal strength concrete as a substrate concrete. Compatibility was investigated in three steps. First: individual properties for substrate concrete were studied, these are (slump test, compressive strength, splitting strength, and flexural strength) also, for repair material these are (compressive strength and flexural strength) were determined by using standard ASTM test methods. Second: bond strength of composite cylinder for substrate concrete with different repair materials were evaluated by using slant shear test. Third: compatibility was investigated by using composite prisms of substrate concrete with different repair materials under two-point loading (flexural strength test). From the experimental results concluded, bond strength between reactive powder concrete with glass fibre as a repair material and normal strength concrete as a substrate layer is higher (17.38Mpa) compared with RPC with steel fibre (13.13Mpa) and polypropylene fibre (14.31MPa). Also, it is more compatible due to flexural strength for composite prisms (having higher flexural strength (8.13MPa). Compared with steel fibre (7.44MPa) and polypropylene fibre (6.47MPa). These results due to RPC with glass fibre have good workability with suitable flowability and glass fibre have higher tensile strength compare with other fibre.
