Pervious Concrete and Rebar

Pervious Concrete and Rebar

David LiguoriPervious in Paradise 2014

Technical Services Division

Don’t you Love it when someone asks….

BAPC Technical Services Division

• You put rebar in pervious concrete, right?



• You can put rebar in pervious concrete, right?• Don’t All high quality slabs have rebar?



• You can put rebar in pervious concrete, right?• Don’t All high quality slabs have rebar?• What will stop the slab from falling apart

without rebar?



• You can put rebar in pervious concrete, right?• Don’t All high quality slabs have rebar?• What will stop the slab from falling apart

without rebar?• You need rebar to prevent vertical

displacement, don’t you?



Function of rebar in slabs on grade (SOG)

• Crack control• Minimize vertical displacement

Rebar in SOG is considered secondary reinforcement as it does not increase the compressive or flexural strength of the

slab




STRUCTURAL INTEGRITY OF EPOXY-COATED BARS

*Quality and consolidation of the surrounding concrete had an important influence on the corrosion of epoxy-coated bars. More corrosion was observed at surfaces surrounded by less dense, very porous concrete with more and larger voids.

*CORROSION PERFORMANCE OF EPOXY-COATED REINFORCEMENT–MACROCELL TESTS CORROSION PERFORMANCE OF EPOXY-COATED REINFORCEMENT–MACROCELL TESTS by Khaled Z. Kahhaleh, Enrique Vaca-Cortés, James O. Jirsa, Harovel G. Wheat, and Ramón L. Carrasquillo Texas Dept of Transportation Nov 1998



Will pervious concrete flow around rebar?


• Will pervious concrete flow around rebar?• No, it must be hand packed



• Is that possible?



• Is that possible? • If so is it practical?



70x70 ~ 5,000sqft ~ 6,500 lin ft rebar


• Is that possible? • If so is it practical? • Is it effective?



Air Pocket BAPC Technical Services Division

Air pockets due to lack of consolidation around the bars may actually weaken the slab,

Exactly the opposite of rebars intended purpose


Successful hand packing around rebar…

• Requires two lifts • Is highly Labor intensive and time consuming• Significantly increases the amount of time the

slab is exposed

All of which dramatically increase the cost of the installation as well as the risk of failure


Getting the concrete where you need it…

…how many chutes do you use?



Is Rebar Even Necessary in SOG ?

• Steel reinforcement actually increases the number of cracks by restraining shrinkage and creating additional stress forces within the slab.

• ACI 330R-08 Guide for the Design and Construction of Concrete Parking Lots: “Reinforcing steel is not required or recommended for rigid pavements”

• San Francisco prohibits the use of rebar in city sidewalks


For slabs on grade with a properly prepared subgrade and base, proper control joint design, proper mix design and section thickness, proper

placement, finishing, and curing… will do more to achieve good performance from the slab than rebar of any type .

Is Rebar Even Necessary in SOG ?


Is Rebar Necessary In Pervious Concrete ?

• Less water along with aggregate to aggregate contact means less shrinkage, and therefore less shrinkage cracks

• Adequate Sub base thickness is critical to performance of any SOG

• Pervious concrete typically has a better prepared, thicker sub base section, which results in more structural stability

• Aggregate interlock more effective due to course nature of pervious concrete


Alternative Reinforcement Method;Macro Fibers






Technical Services Division

Thanks!

Questions?


Engineering

Pervious Concrete and Rebar