Editors: Corina-Maria Aldea and Mahmut Ekenel

Fiber reinforcement is the most effective way of improving the resistance of concrete 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.

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 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 topic 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 fibers 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 Cementitious 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 process 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 by the American Concrete Institute.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-319

SFRC (Steel Fibre Reinforced Concrete) is increasingly used for structural applications. Existing national and international recommendations are efficient for designing simple statically determinate structures (beams and slabs) loaded in bending. However, they do not possess a sufficient physical base to propose relevant solutions for more complex structures such as statically indeterminate structures. Moreover, the control of cracking in the serviceability limit state is one of the main interests of using SFRC (for durability aspects) compared with using traditional reinforcement bars. Nowadays, existing design recommendations are not able to provide sufficient relevant information regarding cracking in the serviceability limit state. In this way, the best approach for designing structures with respect to both safety and sustainable development is the use of finite element analysis. The present paper is devoted to a probabilistic explicit cracking model developed since 1985. It is used to analyze the cracking behaviour of different SFRC beams submitted to different loading conditions: bending, shear, statically indeterminate situation. It is demonstrated that this numerical model is fully capable to provide precise information about the cracking process related to this types of structural behaviour, especially concerning the cracks opening evolution.

The progress of concrete research during the last three decades has highlighted the possibility of enhancing the properties of cement-based materials, such as compressive strength or workability of the fresh mixes, as well as for other important properties like toughness, durability or volumetric stability. Among these, the resistance to shrinkage cracking is gaining an increasing attention, due to its strict relation to durability. In fact, shrinkage cracking occurs in all concrete structures when the free deformation of concrete is restrained. The higher the shrinkage deformation and the degree of restraint, the higher the risk of cracking, for the same concrete strength. Fiber Reinforced Concrete (FRC), now widely available into the market, allows for a better crack control due to the higher post-cracking strength; the latter is related to the links provided by fibers between the crack faces. However, shrinkage-cracking resistance should be determined with tailored methodologies measuring the crack development under restrained shrinkage conditions. The aim of this paper is a critical discussion on the current standard test procedures and, eventually, a proposal for a novel and enhanced testing set-up for measuring the shrinkage-cracking resistance of FRC. The effects of polymer fibers and Shrinkage Reducing Admixture (SRA) are discussed with reference to the time-to-cracking and the crack width development. Keywords:

To evaluate crack patterns accurately, a conventional tension-stiffening approach has to be used. Accordingly, both the bridging of fibers and the bond-slip mechanisms of rebars are taken into account in a new block model. At one time, the model predicts the values of crack width, crack spacing, and crack depth. Moreover, it also leads to the definition of the so-called Golden Scaling Law. The practical interest of this unconventional approach lies in the possibility of predicting the crack pattern of large FRC structures without knowing the material performances, and testing prototypes of small size.

A hybrid analytical/numerical approach for the evaluation of the moment-rotation behavior of a cross section of fiber reinforced concrete (FRC) elements flexurally reinforced with longitudinal bars is briefly described. This model is applied to FRC elements failing in bending, and considers the constitutive laws of the constituent materials, where a special focus on the simulation of the post-cracking tensile behavior of FRC was given, as well as the bond behavior between flexural reinforcement and surrounding FRC. The predictive performance of the proposed model is assessed by simulating experimentally tested FRC beams of different geometry, fiber content, and longitudinal reinforcement ratio. Furthermore, the predictive performance of RILEM TC 162 TDF and fib Model Code 2010 design guidelines for the prediction of the crack width in FRC elements failing in bending is also discussed in the present work. The potentiality of the developed model is then explored for the assessment of the influence of toughness classes of FRC and the bond stiffness between flexural reinforcement and surrounding FRC on the moment-crack opening response of FRC flexural members.