Development Of Self Consolidating Hybrid Fiber Reinforced Concrete And Assessment Of Its Durability Performance
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Development Of Self Consolidating Hybrid Fiber Reinforced Concrete And Assessment Of Its Durability Performance
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Author : Gabriel Jen
language : en
Publisher:
Release Date : 2014
Development Of Self Consolidating Hybrid Fiber Reinforced Concrete And Assessment Of Its Durability Performance written by Gabriel Jen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Conventional concrete used for construction has neither the inherent ductility nor durability to meet the requirements of modern infrastructure construction. With ageing highway and bridge infrastructure requiring a significant expenditure of capital, it is prudent to explore utilization of so-called high performance materials that have the potential to outperform and outlast their conventional counterparts. This research program is built around the concept of creating a sustainable material that exceeds the performance of conventional concrete through a characteristic enhanced cracking resistance achieved by the introduction of discrete fiber reinforcement combined with an optimized level of workability. In an effort to meet the existing demand for high performance materials suitable for modern construction practice, self-consolidating features have been developed for a preexisting high performance hybrid fiber reinforced concrete. A parametric study was employed to maximize the fresh state performance benefits of chemical and supplementary cementitious material additives in conjunction with optimization of the fiber reinforcement to meet the flow criteria of self-consolidating type concrete. The resulting composite, Self-Consolidating Hybrid Fiber Reinforced Concrete (SC-HyFRC), is tested under compression, tension and flexure loading independently and in combination with conventional steel reinforcement to illustrate the mechanical performance gains that can be achieved with such composites. The performance enhancements gained in each manner of loading are then combined in the material's application to a structural element that must be designed to undergo a substantial inelastic (cracked) response. The intrinsic durability of the SC-HyFRC material is tested against two environmental deterioration mechanisms which plague modern concrete. Due to the enhanced crack resistance present in SC-HyFRC, chloride-induced steel reinforcement corrosion is mitigated during both the initiation and the propagation phases. This mitigation is qualitatively and quantifiably measured by suppression of observable cracking and direct electrochemical measurements of the reinforcing steel surface. Similarly, the cracking resistance feature of SC-HyFRC and similar fiber reinforced cementitious composites is judged for mitigation capacity of alkali-silica reaction. The magnitude of internal cracking accompanying the swelling-induced expansion is measured by relative changes in structurally relevant concrete mechanical properties, compressive strength and elastic modulus, with fiber reinforced restraint of expansion observed to correlate well with mechanical property retention. As reinforcement corrosion and alkali-silica reaction are but two of many deterioration mechanisms that induce damage by way of internal expansion, the positive outcomes of SC-HyFRC testing are expected to be transferable to concrete durability in a holistic sense. The potential benefit of constructing critical infrastructure elements with such high performance materials is a two-fold gain in overall structural life cycle assessment, being better equipped to deal with multiple facets of loading placed on modern structures. This and similar research of SC-HyFRC and other such materials will hopefully validate the upfront costs necessary to build with materials that can generate outsized long term fiscal savings.
Development Durability Studies And Application Of High Performance Green Hybrid Fiber Reinforced Concrete Hp G Hyfrc For Sustainable Infrastructure And Energy Efficient Buildings
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Author : Rotana Hay
language : en
Publisher:
Release Date : 2015
Development Durability Studies And Application Of High Performance Green Hybrid Fiber Reinforced Concrete Hp G Hyfrc For Sustainable Infrastructure And Energy Efficient Buildings written by Rotana Hay and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Concrete-related construction industry consumes considerable amount of energy, resulting in large CO2 release into the atmosphere. Cement which is used as the main binder in concrete is energy intensive to produce and contributes about 7% to total global anthropogenic carbon emission. Infrastructure across the globe suffers from durability problems and requires frequent repair and maintenance. This brings about high direct cost for rehabilitation and unaccounted indirect cost resulted from loss of productive time, traffic congestion and diversion, and in the process more CO2 emission. In the meantime, buildings which are part of the overall civil infrastructure system require extensive amount of energy to keep the internal environment comfortable to users. The sector accounts for about 40% of global primary energy consumption. With increasing population and demand, actions from various building disciplines are needed to build a more sustainable industry. This research addresses these issues through the development of a new high performance fiber-reinforced concrete, its durability studies and its application to reduce operational energy in buildings. Durability is critical for infrastructure systems whose frequent maintenance and rehabilitation pose adverse impacts to the environment and add considerable costs to the economy. By accounting for sustainability aspects from materials conception to usage and disposal, this study encompasses the concept of sustainability through life cycle consideration. This represents a deviation from conventional sustainable approach where a focus is usually spent on reducing embodied energy of concrete composites. The first area of focus was on the development of a new concrete composite called high performance green hybrid fiber-reinforced concrete (HP-G-HyFRC) reinforced with polyvinyl alcohol (PVA) micro- and hooked-end steel macrofibers. For easy construction and durability, the design criteria were defined to cover high workability, high strength and deflection hardening which is defined as an ability of the composite to carry increasing load after the first crack is formed. It was demonstrated that theoretical analysis could be used to limit the number of trials in determining the critical fiber volume fractions for the deflection hardening behavior in the composite. As compared to conventional self-consolidating concrete (SCC), fine aggregate over coarse aggregate ratio had to be increased in FRC for enhanced workability. Addition of supplementary cementitious materials (SCMs) in concrete especially fly ash helped to improve the composite's workability. This is attributed to fly ash's favorable fineness, size distribution and spherical shape which resulted in ball-bearing action provided to other concrete constituents. PVA microfibers controlled propagation of micro cracks inherent in concrete or formed during loading. They also provided toughening around steel fibers and ensured a gradual pullout of steel fibers. The synergy of PVA micro- and steel macrofibers led to a smooth deflection hardening behavior of the composite under flexure at a relatively low fiber volume fractions of 1.5% steel fibers and 0.15% PVA fibers. A study on corrosion performance of HP-G-HyFRC with accelerated corrosion test with an impressed current was then conducted. It was found that wide cracks ranging from 1.1 to 2 mm were observed in high performance concrete (HPC) without fibers. The presence of hybrid fibers in HP-G-HyFRC, on the other hand, reduced corrosion rates by half, attributable to crack bridging of fibers and the resulting formation of distributed cracks of small sizes. Also, under no applied current, all embedded steel rebars in HP-G-HyFRC were in the inactive corrosion zone even with the presence of 4% NaCl in the mixing water. Microscopic observation at steel-concrete interface showed a densification of corrosion products, which is postulated to limit iron dissolution and subsequently to reduce corrosion rates of the embedded bars. HP-G-HyFRC corrosion samples were also able to retain most of its strength after the accelerated corrosion tests. As corrosion resistance of HP-G-HyFRC was considered at a composite level, the effects of individual mix component such as slag and fibers on corrosion were yet unknown. The next area of focus was on the influence of high-volume slag as cement replacement, hybrid fibers and steel-concrete interface on corrosion of steel in concrete. The studies elaborated various phenomena observed in the corrosion study of HP-G-HyFRC and also provided a fundamental understanding of different concrete parameters on corrosion. It was found that due to shrinkage-induced cracking and possibly poor quality passive film due to the presence of reducing agents in concrete pore solutions, samples with 60% slag replacement and with no fiber reinforcement showed an early corrosion initiation and higher mass loss induced by the impressed current. Microstructural imaging showed that the samples with slag, despite having a higher gas permeability, showed a denser matrix but more continuous distributed microcracking in the matrix. This led to its poor ability to accommodate corrosion products at the interface and as a result the concrete experienced an early onset of cracking. Under the same regime of applied current, samples made of slag concrete also experienced higher gravimetric mass losses. This is attributed to a less stable passive film and more intense acidification at the interface due to a reduction in calcium hydroxide (CH) in the matrix. Also, an inclusion of hybrid fibers in concrete slightly increased concrete permeability although this did not adversely affect corrosion initiation performance of concrete. However, under propagation stage achieved by an induced current, hybrid fibers in concrete significantly reduced corrosion rates through confinement and densification of corrosion products at steel-concrete interface. The influence of interface qualities on corrosion of steel in concrete showed conflicting performance in corrosion initiation and propagation stages. It was found that higher porosity at the steel-concrete interface initiated an early corrosion. However, the porous interface could accommodate more corrosion products. This led to a smaller pressure buildup from the corrosion products and less damage to the surrounding concrete. As a result, smaller corrosion rates were observed in the samples with more porous interfaces after impressed current regimes. The finding helps to explain the more extensive damage in high performance concrete (HPC) as compared to normal strength concrete. This warrants the inclusion of fibers in HPC to extend the service life of structures constructed with the composite. The study ended with a proposed application of HP-G-HyFRC in an innovative double skin façade (DSF) system in place of a conventional solid façade system to enhance operational energy performance of buildings. It was found that although the DSF is more energy intensive and more costly to construct, it allowed for a full recovery of the additional embodied energy within the first year of operation and cost recovery within the first 6 years of operation. The overall study exemplifies a life-cycle consideration adopted for materials design, durability investigation and application to ensure more sustainable infrastructure and buildings for our society.
Performance Of Hybrid Fiber Reinforced Self Consolidating And Normal Concrete In The State Of Idaho
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Author : Bikash Sigdel
language : en
Publisher:
Release Date : 2017
Performance Of Hybrid Fiber Reinforced Self Consolidating And Normal Concrete In The State Of Idaho written by Bikash Sigdel and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Fiber-reinforced concrete categories.
The first part of this study aims at developing hybrid fiber reinforced self-consolidating concrete (HFRSCC) made with a very high volume of supplementary cementitious materials (SCMs). Self-consolidating concrete (SCC) is a highly workable concrete that can easily flow through heavily reinforced concrete sections without the need for mechanical vibration. The percentages (by volume) of fibers considered were 0.1% and 0.2% hybrid combinations of nylon (PVA) and steel fibers, respectively. Cement was replaced by various percentages of SCMs by up to 70%. The mechanical properties (compressive strength, modulus of elasticity and tensile strength) and unrestrained drying shrinkage of the developed mixtures were evaluated and compared to the standard specifications. The second part of this study aims at evaluating the mechanical properties (compressive strength, modulus of elasticity, tensile strength, and modulus of rupture), thermal properties and unrestrained drying shrinkage of the paving and structural concrete mixtures being used in the six districts of the State of Idaho. The focus of this evaluation was to develop a material database required for the implementation of the "AASHTOWare Pavement ME Design" (ME) Software which is used to design rigid Portland Cement Concrete (PCC) pavements. The data developed and examples of its implementation in the ME software were conducted, evaluated, and presented.
Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Of Bridge Sub Structures And Fiber Reinforced Super Workable Concrete For Infrastructure Construction
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Author : Kamal H. Khayat
language : en
Publisher:
Release Date : 2017
Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Of Bridge Sub Structures And Fiber Reinforced Super Workable Concrete For Infrastructure Construction written by Kamal H. Khayat and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Bridges categories.
The proposed research investigates the combined use of self-consolidating concrete (SCC) and fibers reinforcements to develop a novel repair material, fiber-reinforced self-consolidating concrete (FR-SCC) that can be used for the rehabilitation and strengthening of existing structures. Furthermore, the feasibility of using super workable concrete (SWC) reinforced with different types of fibers for new structural cast-in-place applications is investigated. The use of SCC matrix can greatly enhance the workability of fibrous mixtures along with incorporation of greater volume of fibers. SWC is a new type of flowable concrete with lower workability than SCC. Containing lower binder content can be more cost effective than SCC. SWC requires some mechanical consolidation energy to ensure proper filling of the formwork. Eight types of fibers, including a propylene synthetic fiber, five steel fibers and a hybrid steel and polypropylene synthetic fiber were investigated. Fibers were incorporated at a volume of 0.5% in FR-SCC and at 0.5% and 0.75% in FR-SWC. Two types of expansive agents (EA), Type G and Type K, were added to both concrete types to reduce shrinkage and enhance resistance to restrained shrinkage cracking. The optimized mixtures exhibited high workability, mechanical properties, and freeze/thaw durability. The incorporation of fibers with 4% Type-G EA in FR-SCC increased the 56-day flexural strength by up to 32%, and flexural toughness up to 23 times. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers (ST1) in FR-SCC made with 4% Type-G EA increased the elapsed time to cracking determined from restrained shrinkage ring test from 16 to 20 days compared to FR-SCC made with 0.5% ST1 fibers without EA. The use of ST1 steel fibers and 4% Type-G EA decreased the 1-year drying shrinkage by 48% compared to the reference SCC mixture without any fibers and expansive agent. In case of FR-SWC, the decrease in shrinkage was 37% compared to SWC. In addition, 20 monolithic full-scale beams were cast using different types of concrete, including conventional vibrated concrete (CVC), fiber-reinforced conventional vibrated concrete (FR-CVC), SCC, FR-SCC, SWC and FR-SWC. Twelve reinforced concrete beams were cast using CVC to fill two thirds of the beam height. They were then filled with five different types of FR-SCC and SCC to simulate beam repair in the tension zone. Findings indicated that macro fibers can be used with FR-SCC designated for repair with fiber length ≤ 2 in. (50 mm) up to 0.5% fiber volume. Macro fibers can be used with FR-SWC designated for construction with fiber length ≤ 2.6 in. (65 mm) up to 0.75% fiber volume. Fibers had great impact on structural performance of the full-scale monolithic beams. The incorporation of 0.5% of the 1.18 in. (30-mm) hooked end steel fibers combined with 0.5 in. (13-mm) straight steel fibers at ratio 4 to1 (STST) with 4% Type-G EA increased toughness of FR-SWC beams by 95% compared to SWC beams and by 86% in case of 0.75% 5D fibers. Repair using FR-SCC increased the flexural capacity of the beam by 6% and the toughness by 110% in case of using 0.5% ST1 fibers with 4% Type-G EA.
Development And Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Applications
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Author : Fodhil Kassimi
language : en
Publisher:
Release Date : 2013
Development And Performance Of Fiber Reinforced Self Consolidating Concrete For Repair Applications written by Fodhil Kassimi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
The use of self-consolidating concrete (SCC) in the concrete industry in cast-in-place applications, including repair applications, is growing given the various advantages offered in both fresh and hardened states. The present study deals with the design and performance of fiber-reinforced self-consolidating concrete (FR-SCC) as a repair material of concrete infrastructure. The study also considers the use of various steel and synthetic fibers (five fibers in total) that were used to produce FR-SCC and fiber-reinforced self-consolidating mortar (FR-SCM) that can be employed for structural and non-structural repair applications. The study evaluates the effect of material properties and mixture composition of the fibrous concrete and mortar on workability, mechanical, visco-elastic, durability, and structural behavior. The investigation that is presented in this thesis included the testing of 28 full-scale beams under four-point flexural loading. The majority of these beams were repaired by casting concrete to fill a relatively thin section along the tension zone of the beams. The repair technique was based on the FR-SCC characteristics including the maximum fiber volume and length. This technique required mixtures of high range of fluidity. The optimized FR-SCC and FR-SCM mixtures exhibited excellent flow characteristics along the 3.2-m long beams without blockage, segregation, nor debonding at the interface of repair-substrate concrete. Based on the structural characteristics of the composite beams, the overall performance of the beams repaired using the FR-SCC and FR-SCM was similar or higher (up to 2.6 times) than that of monolithic beams made with conventional vibrated concrete (CVC). The use of optimized FRSCC mixtures enabled the replacement of 50% of the tension steel reinforcement in repair sections; i.e., the number of bars in the tension zone decreased from three bars to two bars with the addition of fibers in the SCC without mitigating structural performance. The degree of prediction of crack width, cracking load/moment, ultimate loads, and deflection of various FR-SCC and FR-SCM mixture was evaluated using several design and code models. The results indicate that these code models can provide safe predictions for crack and ultimate loads, as well as crack width of FR-SCC. The deflection of FR-SCC is unsafe but predictable by these code models. In total, 18 large-scale beams were tested in four-point for flexural creep. FR-SCC incorporating steel fibers combined with expansive agent provided overall performance up to 10 times of that obtained with CVC with the same fiber type and volume. The cracking under constant load was reduced by 60% to 80% using self-consolidating fibrous mixtures made with or without expansion agents, compared to SCC without fibers. The best combination to reduce the cracking potential when the restrained shrinkage ring test was employed was obtained with SCC mixtures made with steel fibers and expansive agent. Models were elaborated to predict the time-to-cracking for FR-SCC and FR-SCM mixtures based on mixture modulus of elasticity and drying and autogenous shrinkages. The project involved extensive testing of highly flowable fibrous materials to determine drying shrinkage (nearly 260 prisms), modulus of rupture (nearly 180 prisms), as well as compressive and splitting tensile strengths and elastic modulus (nearly 2100 cylinders). Based on the results, models were proposed to predict these key material properties that affect the performance of FR-SCC and FR-SCM used in repair applications. In addition to FR-SCC, the investigation also was set to evaluate the feasibility of using fiber-reinforced superworkable concrete (FR-SWC) in construction and repair applications. Such highly flowable concrete that requires limited vibration consolidation can represent some advantages over FR-SCC (lower admixtures demand, lower risk of segregation, greater robustness, lower formwork pressure, etc.). The energy needed to ensure proper consolidation, using either vibration or rodding, applied on samples made with FR-SWC was determined. The energy requirement took into consideration the development of mechanical properties, the resistance to segregation, and the development of proper surface quality. The study also demonstrated the higher overall structural performance of optimized FR-SWC compared to the corresponding FR-SCC mixtures. The findings of the thesis on the design and performance of highly workable fiber-reinforced cementitious materials should facilitate the acceptance of such novel high-performance material in infrastructure construction and repair applications.
Hybrid Fiber Reinforced Concrete Incorporated With Phase Change Material
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Author : Chia-So Chuang
language : en
Publisher:
Release Date : 2015
Hybrid Fiber Reinforced Concrete Incorporated With Phase Change Material written by Chia-So Chuang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
To further efforts toward improvement, an innovative and durable High Performance Fiber Reinforced Cementitious Composites (HPFRCC) was developed, using hybrid steel macro-fibers with designed hook-ends, and polyvinyl alcohol micro-fibers for optimal fiber synergistic effects, crack width control, durability, and reduced maintenance and life-cycle costs for bridges. For functional performance improvements, an off-the-shelf phase change material (PCM) was utilized, optimized and incorporated into the HPFRCC as a bridge slab warmer, to improve freeze-thaw cycling durability, to reduce the use of de-icing salts, to provide improved skid resistance, and to improve safety in cold climates and to reduce traffic congestions. The goal for developing and deploying HPFRCC with controllable functional performance is to utilize new, durable cementitious composites resistant to stringent climate demands compromised of freeze-thaw cycles, de-icing salts, plastic shrinkage and drying shrinkage cracks, chloride and sulfate attacks, corrosion and scaling, and excessive abrasion/wear due to tire chains. This thesis utilized both numerical modeling and experimental. First, mechanical properties after incorporating PCM were discussed. Subsequently, destructive tests were performed in order to study the effect of adding PCM. In addition, thermal performance after incorporating PCM was also addressed as an important topic. As a result, freeze-thaw testing was performed in order to study PCM performance. Numerical modeling regarding material mechanical properties was proposed and compared with experimental data. Numerical modeling regarding concrete composite thermal performance was also studied. Lastly, concrete interior temperature, mechanical properties and concrete composite residual capacity were discussed. In chapter 3, several experimental tests were performed in order to study the behavior of hybrid fiber reinforced concrete with PCM and to verify the validity of the theoretical model. Experimental tests can be divided into two categories. One is a destructive test; where concrete composite compressive strength, tensile strength and ductile capacity can be determined. The other category is a freeze-thaw test where concrete composite freeze-thaw resistance can be studied. In chapter 4, a new crack bridging model accounting for slip-softening interfacial shear stress was proposed for randomly distributed and randomly oriented fibers after PCM were added, based on a micromechanics analysis of single fiber pull-out. The concrete composite bridging stress versus a crack mouth opening displacement (CMOP) curve and associated fracture energy were theoretically determined. In addition, a constant interfacial shear stress model was also proposed in order to compare this with a slip softening interfacial shear stress model. By applying the proposed model on various concrete composites, including 5% PCM and 7% PCM hybrid fiber reinforced concrete, the present model can well describe the slip-softening behavior during fiber pull-out. In chapter 5, the new proposed slip-softening model was used to predict the ultimate tensile stress of a single fiber. Maximum fiber debonding stress and fiber pull-out stress was determined based on slip softening interfacial shear stress. By applying the rule of mixture, maximum fiber debonding and pull-out stress, the maximum tensile stress of a concrete composite was able to be predicted when subjected to three point bending test. In chapter 6, PCM concrete composite interior temperature was modeled and compared with concrete without PCM after being subjected to freeze-thaw cycle. With PCM inside of concrete, interior temperature can be controlled. In preceding chapters, microcracks would be generated inside of the concrete and eventually become larger cracks by going through the freeze-thaw process. The aim of this chapter was to find a temperature gradient inside of concrete using an enthalpy method and specific heat capacity method to solve moving boundary problems. Numerical efficiency from both the enthalpy method and specific heat capacity method were also compared. Two different layouts of how PCM were incorporated into a concrete mix and were discussed in order to determine the efficiency of each design. In chapter 7, concrete mechanical properties after being subjected to freeze-thaw cycle were modeled. In addition, concrete composite residual capacity after freeze-thaw process was also determined based on a stress-strain relationship. With PCM inside of concrete, interior temperature can be controlled. However, the relationship between concrete structure mechanical properties, number of freeze-thaw cycles and freeze-thaw temperature differences also needs to be determined. After a correlation is found between concrete mechanical properties, number of freeze-thaw cycles and temperature difference, the stress-strain relationship can then be determined by using damaged concrete mechanical properties. A Constitutive relationship can be derived based on thermodynamic theory. Elastic damage and plastic damage were both evaluated. Once the stress-strain relationship is obtained, concrete residual life and residual durability can be stimated after going through a freeze-thaw action. Normal concrete was also compared with PCM concrete. The aim of this chapter was to develop a damage model that account for concrete structure strength, number of freeze-thaw cycles and freeze-thaw temperature differences. Concrete composite residual capacity was also estimated and derived from free energy potential function.
Towards Innovative And Sustainable Construction Of Architectural Structures By Employing Self Consolidating Concrete Reinforced With Polypropylene Fibers
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Author : Wael A. Zatar
language : en
Publisher:
Release Date : 2022
Towards Innovative And Sustainable Construction Of Architectural Structures By Employing Self Consolidating Concrete Reinforced With Polypropylene Fibers written by Wael A. Zatar and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with Science categories.
Self-consolidating concrete (SCC) has been successfully employed to reduce construction time and enhance the quality, performance, and esthetic appearance of concrete structures. This research aimed at developing environmentally friendly fiber-reinforced concrete (FRC) consisting of SCC and recycled polypropylene (PP) fibers for sustainable construction of city buildings and transportation infrastructure. The addition of the PP fibers to SCC helps reducing shrinkage cracks and providing enhanced mechanical properties, durability, and ductility of the concrete materials. Several mix designs of self-consolidating fiber-reinforced concrete (SCFRC) were experimentally examined. Material and esthetic properties of the SCFRC mixtures that include micro silica, fly ash, and PP fibers were evaluated. Trial-and-adjustment method was employed to obtain practically optimum SCFRC mixtures, mixtures that are affordable and easy to make possessing enhanced compressive strength and esthetic properties. Slump flow and air content testing methods were used to determine the fresh properties of the SCFRC mixtures, and the esthetic properties of the mixtures were also evaluated. The hardened properties of the SCFRC mixtures were examined using three- and seven-day compression tests. The amount of fine/coarse aggregate, water, and other admixtures were varied while the Portland cement content in all mixtures was maintained unchanged. The maximum three-day compressive strength was 43.17¬†MPa and the largest slump flow was 736.6¬†mm. Test results showed enhanced material properties such as slump flow, air content and compressive strength values of the SCFRC mixtures and their excellent esthetic appearance. The favorable seven-day compressive strength of the SCFRC mixture, with 4.8 percent air content and 660.4¬†mm slump flow, is 39.26¬†MPa. The mixtures,Äô in this study are proven to be advantageous for potential SCFRC applications in architectural structures including building fa√ßades and esthetically-pleasing bridges.
Investigation Of Fiber Reinforced Self Consolidating Concrete
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Author : Michael Carey Brown
language : en
Publisher:
Release Date : 2010
Investigation Of Fiber Reinforced Self Consolidating Concrete written by Michael Carey Brown and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Self-consolidating concrete categories.
The rising cost of materials and labor, as well as the demand for faster construction, has prompted development of cheaper, faster alternatives to conventional building techniques. Self-consolidating concrete (SCC), a high performance concrete characterized by its ability to flow without segregation under its own weight, promises to speed construction while reducing the need for skilled labor. However, experience has shown that SCC may be prone to shrinkage cracking, which may compromise its durability. In conventional concrete, fiber reinforcement has been used to control cracking and increase tensile and flexural strength. This study evaluated the feasibility of fiber-reinforced SCC (FR-SCC) for structural applications. Tests were conducted in the laboratory to assess the fresh and hardened properties of FR-SCC containing various types and concentrations of fibers. The results indicated that an SCC mixture can be prepared for use in transportation facilities that combines the properties of a high flow rate and some residual strength that would be beneficial for crack control. The residual strength is contributed by the internal fibers and provides load-carrying capacity after initial cracking of the concrete. At optimum fiber additions, FR-SCC mixtures can have the same fresh concrete properties as traditional SCC mixtures. FR-SCC also demonstrated a considerable improvement in the residual strength and toughness of a cracked section, which is expected to lead to the control of crack width and length. The improved performance of the FR-SCC cracked section indicated that it can be expected to have more durability in service conditions than would an identical SCC with no reinforcement. The study recommends that the Virginia Department of Transportation's Structure & Bridge Division evaluate FR-SCC in field applications such as link slabs and closure pours in continuous concrete decks; formed concrete substructure repairs; or prestressed beams where end zone cracking has been an issue. In such applications, construction with FR-SCC has the potential to be faster than with SCC, as traditional steel reinforcement may be reduced or eliminated, yielding reduced labor and materials costs for reinforcement placement. Enhanced public and worker safety may result from the reduction of overall construction time and required maintenance of traffic. The next step toward implementation of this technology would involve coordination with VDOT's Materials Division and Structure & Bridge Division to create special provisions or standard specifications regarding the use of FR-SCC and to identify candidate projects for field trials.
Development Of A Mix Design Adjustment Method For Fiber Reinforced Concrete And Super High Performance Concrete Based On Excess Paste
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Author : Joe Malloy
language : en
Publisher:
Release Date : 2019
Development Of A Mix Design Adjustment Method For Fiber Reinforced Concrete And Super High Performance Concrete Based On Excess Paste written by Joe Malloy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
The main objective of this study was to develop a mix design adjustment method for Fiber Reinforced Concrete (FRC) that would maintain appropriate workability while improving hardened concrete performance. A literature review was conducted to examine existing methods for adjusting mix designs to account for fiber introduction. It was found that while increasing fine aggregate and cement paste content can make up for lost workability with the addition of fibers, no rational mix design adjustment method is available. Reference mix designs from the Nevada Department of Transportation and the Nebraska Department of Transportation were used, and this study focused on tailoring the idea of increasing paste and fine aggregate to focus on the parameter of excess paste. Excess paste serves to coat the aggregate particles and is critical for workability. To apply this method of excess paste adjustment, a modified version of ASTM C29 was used to determine the void content of fiber-aggregate skeletons with varying fiber contents. Paste and fine aggregate content were then adjusted to maintain the excess paste quantity between reference mixes and mixes with fiber. A variety of tests including slump, vibrated L-box, compressive strength, splitting tensile strength, flexural strength, drying shrinkage, and restrained shrinkage were conducted to evaluate the overall concrete performance. Results indicated that, for each mix design, adjusting based on excess paste provided a workable FRC with improved hardened performance. Eight slabs were then prepared for a large-scale examination of constructability. Throughout the study of FRC, an alternative concrete to Ultra-High Performance Concrete (UHPC) that would considerably outperform High-Performance Concrete (HPC) was developed. This study delves into the development of a new type of concrete called Super High Performance Concrete (SHPC). SHPC is a high strength, self-consolidating FRC that would significantly cut back on cost and production limitations compared to UHPC as it can be produced with conventional drum-type mixers. Results indicate that SHPC outperforms HPC in matters of workability, compressive strength, flexural strength, and toughness and could potentially be a viable alternative of UHPC for applications such as bridge deck connections and overlays.
Pro 30 4th International Rilem Workshop On High Performance Fiber Reinforced Cement Composites Hpfrcc 4
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Author : Antoine E. Naaman
language : en
Publisher: RILEM Publications
Release Date : 2003
Pro 30 4th International Rilem Workshop On High Performance Fiber Reinforced Cement Composites Hpfrcc 4 written by Antoine E. Naaman and has been published by RILEM Publications this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Cement composites categories.