1、An ACI Technical Publication SYMPOSIUM VOLUMESP-319Reduction of Crack Width with FiberEditors:Corina-Maria Aldea and Mahmut EkenelPhoto courtesy of Dr. Alessandro P. FantilliReduction of Crack Width with FiberSP-319Editors:Corina-Maria Aldea and Mahmut Ekenel Discussion is welcomed for all materials
2、 published in this issue and will appear ten months from this journals date if the discussion is received within four months of the papers print publication. Discussion of material received after specified dates will be considered individually for publication or private response. ACI Standards publi
3、shed in ACI Journals for public comment have discussion due dates printed with the Standard.The Institute is not responsible for the statements or opinions expressed in its publications. Institute publications are not able to, nor intended to, supplant individual training, responsibility, or judgmen
4、t of the user, or the supplier, of the information presented.The papers in this volume have been reviewed under Institute publication procedures by individuals expert in the subject areas of the papers.Copyright 2017AMERICAN CONCRETE INSTITUTE38800 Country Club Dr.Farmington Hills, Michigan 48331All
5、 rights reserved, including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval s
6、ystem or device, unless permission in writing is obtained from the copyright proprietors.Printed in the United States of AmericaEditorial production: Gail TatumISBN-13: 978-1-945487-68-2First printing, June 2017PrefaceFiber reinforcement is the most effective way of improving the resistance of concr
7、ete to cracking, but little is known of the extent of the reduction of crack width with fiber. The papers included in this special publication discuss the role of fiber reinforcement in reduction of crack width and lay the foundation for Life Cycle Engineering Analysis with fiber reinforced concrete
8、.Recognizing the reduction of crack width with fibers in cement-based materials, ACI Committee 544 Fiber Reinforced Concrete, together with 544F Fiber Reinforced Concrete Durability and Physical Properties sponsored two technical sessions entitled Reduction of crack width with fiber at the Fall 2016
9、 ACI Convention in Philadelphia. Papers were presented by invited international experts from Belgium, France, Germany, Italy, Portugal, United Arab Emirates and the United States of America.This Symposium Publication (SP) contains eleven papers which provide insight on the state of the art of the to
10、pic in the academia, in the industry and in real life applications. The topics of the papers cover the reduction of crack widths in steel reinforced concrete bridge decks with fiber, 15 years of applying SFRC for crack control in design from theory to practice, the effectiveness of macro synthetic f
11、ibers to control cracking in composite metal decks, conventional and unconventional approaches for the evaluation of crack width in fiber reinforced concrete (FRC) structures, reduction of water inflow by controlling cracks in tunnel linings using fiber reinforcement, a review of Engineering Cementi
12、tious Composites (ECC) for improved crack-width control of FRC beams, tailoring a new restrained shrinkage test for fiber reinforced concrete, a model to predict the crack width of FRC members reinforced with longitudinal bars, a probabilistic explicit cracking model for analyzing the cracking proce
13、ss of FRC structures, toughening of cement composites with wollastonite sub micro-fibers and self healing of FRC: a new value of “crack width” based design. The papers included in this publication have been peer reviewed by international experts in the field according to the guidelines established b
14、y the American Concrete Institute.On behalf of ACI Committee 544 Fiber Reinforced Concrete and committee 544F Fiber Reinforced Concrete Durability and Physical Properties, the editors would like to thank all the authors for their contributions and the reviewers for their assistance, valuable suggest
15、ions and comments.Corina-Maria Aldea Mahmut EkenelAmec Foster Wheeler Environment continuous span structural slab bridges; crack widths; epoxy coated bars; fiber reinforced concrete; load testing; deck slabs; crack resistance Patnaik et al. 1.2 Author Biography Anil Patnaik is a Professor and the As
16、sociate Department Chair for Graduate Programs in Civil Engineering at The University of Akron in Ohio. His current interests include research on concrete and metallic materials and structures, FRP applications particularly using basalt fiber and MiniBar, and repair and rehabilitation. His current p
17、rojects are on corrosion of steel reinforced structural concrete and steel structures, impact behavior of reinforced concrete members, structural slab bridge decks, and adjacent box beam bridges. Prince Baah is a Transportation Engineer/Structural and Durability Engineer at Michigan Department of Tr
18、ansportation. He received his B.Sc. in Civil Engineering from Kwame Nkrumah University of Science and Technology, Ghana; an M.S. in Civil Engineering from Lawrence Technological University, Michigan and his Ph.D. in Civil Engineering from The University of Akron, Ohio. Perry Ricciardi, PE is a Distr
19、ict Engineer of Tests at Ohio Department of Transportation District 3 in Ohio. He received his B.Sc. in Civil Engineering from The University of Akron. He also received his M.S. in Structural Engineering from The University of Akron, Ohio. Waseem Khalifa, PE is a Bridge Engineer and Program Manager
20、at Ohio Department of Transportation, Ohio. He is also an adjunct professor at The University of Akron, Ohio. He received his B.Sc. in Civil Engineering from the University of Engineering and Technology, Lahore, Pakistan, an MASc. in Structural Engineering from the University of Toronto, Canada, and
21、 his Ph.D. in Structural Engineering from The University of Glasgow, Scotland. INTRODUCTION Non-prestressed steel reinforced concrete solid structural slab bridges are commonly used by several Departments of Transportation (DOTs) in the United States. Structurally, a continuous deck slab runs parall
22、el to the longitudinal axis of the bridge, and is supported by the abutments at the ends and piers at intermediate locations. The decks typically are between 11 inch (280 mm) and 27 inch (685 mm) in thickness. One of the primary factors affecting concrete bridge durability is deck cracking. Cracks a
23、re caused primarily by low tensile strength of the concrete, volumetric instability, and/or deleterious chemical reactions. Crack openings and spacing are affected by bar size and the effective concrete area surrounding the bar (Soltani et al. 2013). Regardless of the causes, cracking on bridge deck
24、s is a serious concern, because cracks provide access to harmful, corrosive chemicals that deteriorate the reinforcing steel embedded within the concrete. Once chloride and other corrosive agents penetrate concrete, corrosion of the embedded steel can initiate and cause concrete spalling. Such deter
25、ioration can affect the shear and moment capacity of reinforced concrete bridge decks. Also, bridge deck cracks allow water and de-icing salts to flow down through the deck and can also damage to the substructure (Krauss and Rogalla 2003). According to a survey of 52 transportation agencies across N
26、orth America, more than 100,000 bridges were found to crack early (McDonald et al. 1995), and in some cases, typically when concrete is just one month old (Patnaik and Wehbe 2015). In 2002, corrosion of the reinforcing steel in concrete was estimated to have an annual direct cost to highway bridges
27、of $8.3 billion. However, the indirect cost to users due to traffic delays and lost productivity was estimated to be ten times as much (Yunivich et al. 2002). Replacement costs for bridge decks are a significant portion of that direct cost (Virmani and Clemena 1998). Cracks frequently form relativel
28、y early in the life of concrete bridge decks, at times well in advance of a bridge being open to traffic, and sometimes immediately following construction ( Schmitt and Darwin, 1995, Patnaik and Wehbe, 2015). Concrete bridge deck cracking is influenced by several conditions, including construction p
29、ractices, concrete mix proportions, material properties, structural design, and loading levels ( Ramakrishnan and Patnaik 2006; Cavaliero and Durham 2011). The addition of fiber to improve cracking behavior of reinforced concrete is gaining some recognition. One of the important features of fiber re
30、inforced concrete is the ability of the fiber to bridge across cracks. Fibers, when added to concrete, modify the cracking mechanism from macro cracking to micro cracking. The results are that crack widths are reduced, and the ultimate tensile cracking strain capacity of the concrete is increased. T
31、he mechanical bond between the embedded fiber and binder matrix redistributes the stresses. Additionally, the ability to modify the cracking mode results in quantifiable benefits. Reduced micro cracking leads to reduced permeability and increased surface abrasion resistance, impact resistance and fa
32、tigue strength (Adhikari and Patnaik 2012; Reduction of Crack Widths in Steel Reinforced Concrete Bridge Decks with Fiber 1.3 Patnaik et al. 2015). There are many different metallic and non-metallic micro or macro fiber available for use in fiber reinforced concrete. A new type of macro fiber known
33、as MiniBars was recently made from basalt fiber and is gaining acceptance in the industry. The addition of fiber to concrete will also improve the bond strength between the reinforcing bar and the surrounding concrete (Banibayat and Patnaik 2014; Grace et al. 2011; Grace et al. 2012, Baah 2012). Thi
34、s is particularly useful for epoxy-coated bars (ECB) because these are demonstrated in this study to have larger cracking potential, maybe due to inferior bond strength. Patnaik (2011) and Patnaik et al. (2013) performed a comprehensive study on the mechanical and structural characterization of conc
35、rete reinforced with basalt MiniBars. Bagherzadeh et al. (2012) studied the influence of polypropylene fiber using different proportions and fiber lengths to improve the performance characteristics of the lightweight cement composites. This paper presents the results of a recent bridge investigation
36、 on twelve, three-span continuous reinforced concrete structural slab bridges in Ohio. These bridges were carefully selected from the bridge inventory in the state. These bridges vary in terms of span lengths, roadway width, skew angle, deck thickness, number of lanes, reinforcement ratio, and geogr
37、aphic location within the state. The study focused on the wide transverse cracks primarily in the direction parallel to the intermediate pier supports. Section and crack width analyses for select bridges were performed to compare the field-recorded crack widths to the theoretical crack widths determ
38、ined using the three most common equations for predicting crack widths. The Ohio Department of Transportation (ODOT) uses epoxy-coated bars (ECB) in bridge decks. An experimental program was set up, and tests were conducted to examine the flexural cracking behavior of laboratory-scale slabs represen
39、ting the intermediate support region of typical bridge decks using both ECB and conventional uncoated reinforcing bars, commonly referred to in the construction industry as “black bars”. The effects of addition of fiber on concrete cracking were also investigated. Variables studied in the experiment
40、al investigations included type of bar (ECB or black), bar size, with or without fiber, and specimen preparation (precut or non-precut). DIC (Digital Image Correlation) was used to obtain crack width measurements for one bridge included in this study. DIC was also used in the field investigation to
41、measure crack widening under both static and moving truck loads. Several DOTs routinely design, build, and maintain a large number of three-span continuous structural slab bridges. The sheer number of such bridges in the states necessitated a systematic study to determine the extent of the problem i
42、n structural slab bridge decks so that the causes of cracking can be identified and countermeasures established to minimize cracking in future bridge deck construction. Because several DOTs also use ECB in bridge decks, the need to investigate the effects of the ECB on cracking behavior of concrete
43、was identified as an immediate need. RESEARCH SIGNIFICANCE One of the primary factors affecting concrete bridge durability is deck cracking. Despite significant research specifically studying the problem, cracking in reinforced concrete bridge decks is still a widespread concern in old and newly-con
44、structed bridges. Previous research conducted by the authors focused mainly on shrinkage cracking of stringer supported bridge decks (Ganapuram et al. 2012; Patnaik and Wehbe 2015). However, limited research is available on the cracking behavior of structural slab bridge decks. This investigation ad
45、dresses the cracking problems identified in continuous structural slab bridge decks with an emphasis on “non-shrinkage” cracks. To investigate a preventive measure to deck cracking, this study examines the effects of the addition of basalt MiniBar and polypropylene fiber to reinforced concrete on de
46、ck cracking. Addition of fiber to concrete without changing any steel reinforcing details is expected to cost-effectively reduce the severity and extent of cracking in reinforced concrete bridge decks. Also, the effect of epoxy coating on bond and anchorage behavior of reinforcing bars has been stud
47、ied by several investigators (Treece and Jirsa 1989). However, little research has been done on the influence of ECB on crack control (Mitchell et al. 1996). This study also addresses the effect of epoxy-coating on deck cracking. The adequacy of merely satisfying the reinforcement spacing requiremen
48、ts given in AASHTO or ACI 318-14 to limit cracking below the ACI 224R-01 recommended maximum limit, even though all the relevant design requirements are otherwise met, is an important factor that remains to be fully understood. ALLOWABLE CRACK WIDTH LIMITS To minimize the adverse effects of cracks o
49、n reinforced concrete bridge decks, the design should ensure that the crack widths under normal service conditions are within recommended allowable limits. The cracking of a reinforced concrete slab at service loads should not impact the appearance of the structure or lead to corrosion of the embedded steel reinforcement. According to ACI Committee report 224, crack widths equal to or greater than 0.007 in. (0.18 mm) can reduce durability when bridge decks are exposed to de-icing chemicals (ACI 224R-01 2008). Similar limits are set for other exposure conditions (ACI 224R-01 2008). Crack wi
