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  • 1.  Micro vs Macro Fiber Reinforced Concrete

    Posted 04-03-2018 10:37 AM
    Edited by Tirza Austin 04-03-2018 10:36 AM
    Is it better to use micro or macro fibers for concrete pavements, curbs and gutters?

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    Logan Mills B.S., A.M.ASCE
    Engineer
    Certified Engineering Design
    Wichita KS
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  • 2.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-04-2018 06:25 PM
    Edited by Tirza Austin 04-04-2018 06:24 PM
    I'm partial to microfibers myself.



    Original Message


  • 3.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-05-2018 11:06 AM
    I usually use Euclid's Tuf-Strand macrofiber and they have a slab design software that tells you how much to use depending on the application and whether you want to replace all steel rebars on slabs. Microfiber will basically help you with cracks but structurally they wont replace any steel rebars. You can maybe use microfibers in gutters and curves that have no critical vehicle load condition.

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    Alexander Stark C.Eng, Ing., M.ASCE
    Investigation and Development Director
    INATEC, S.R.L.
    Santo Domingo
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    Original Message


  • 4.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-07-2018 10:28 AM
    So now I know the purpose of macrofibers. I am familiar with the uses of microfibers. Until this thread I did not even know that they existed so I presumed that they served the same purpose microfibers do.



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  • 5.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-05-2018 11:07 AM
    Edited by Tirza Austin 04-05-2018 11:07 AM
    It depends on what structural purpose the <g class="gr_ gr_111 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling multiReplace" id="111" data-gr-id="111">fibers</g> are supposed to serve. 
    Simplified: <g class="gr_ gr_177 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling multiReplace" id="177" data-gr-id="177">micro-fibers</g> improve your early strength properties (i.e. help against shrinkage cracks); macro <g class="gr_ gr_265 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling multiReplace" id="265" data-gr-id="265">fibers</g> improve the properties of the hardened concrete (i.e. provide tensile strength and toughness primarily post-cracking).
    Refer to ACI 544 documents to learn more about properties.

    P.S. micro-synthetic fibers also improve the spalling resistance in case of a fire (i.e. in a tunnel), but that does not seem to apply in your case.

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    Axel Nitschke P.E., C.Eng, M.ASCE
    WSP USA
    Washington DC
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    Original Message


  • 6.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-05-2018 11:57 AM
    ​ACI's Guide for Design and Proportioning of Concrete Mixtures for Concrete Pavements ACI 325.14R-17 notes that fibers are mostly used in thin bonded overlays and very thin concrete pavements and have been recommended as a solution to plastic shrinkage cracking.  The guide also provides some information on fiber type and size to be used.  As noted by other commenters, fibers ARE NOT a replacement for reinforcing steel.  Most concrete pavements do not contain steel reinforcement.  Wire mesh, if used is intended to help control drying shrinkage cracking and proper control joint spacing can do this job very well on most pavement applications.  Also there are other effective ways to prevent plastic shrinkage cracking if the climate is hot and dry during concrete placement.

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    Jon Mullarky P.E., F.ASCE, F.ACI
    Chester MD
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    Original Message


  • 7.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-05-2018 02:50 PM
    Edited by Tirza Austin 04-05-2018 02:49 PM
    To my knowledge, I would prefer Microfibers (because shrinkage cracks will be less). 

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    Sundar T S.M.ASCE
    Student
    Chennai -600117 TN
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    Original Message


  • 8.  RE: Micro vs Macro Fiber Reinforced Concrete

    Posted 04-17-2018 10:20 AM
    ​Reinforced structural concrete is under-reinforced by safety code to provide slow ductile yielding of the steel reinforcing before sudden brittle crushing of the concrete. Consideration must be given to the failure mechanism when adding all types and proportions of fibers.

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    Michael Arpino P.E., M.ASCE
    Structural Engineer
    Federal Highway Adimistration
    Cambridge MA
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    Original Message


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