Details:

Creators:
Sobanjo, John O. ; Tawfiq, Kamal S. ; Twumasi-Boakye, Richard ; Inkoom, Sylvester ; Gibbs, Sheldon
Sobanjo, John O. ; Tawfiq, Kamal S. ; Twumasi-Boakye, Richard ; Inkoom, Sylvester ; Gibbs, Sheldon Less -
Corporate Creators:
Florida State University. Dept. of Civil and Environmental Engineering ; Gibbs Group Engineers
Florida State University. Dept. of Civil and Environmental Engineering ; Gibbs Group Engineers Less -
Corporate Contributors:
United States. Federal Highway Administration
Subject/TRT Terms:
[+]
Compressive Strength Concrete Pavements Crumb Rubber Laboratory Tests Mechanical Properties Modulus Of Elasticity Ready Mixed Concrete Shrinkage Thermal Expansion Workability
Publication/ Report Number:
BDV30 977-08
Resource Type:
Tech Report
Geographical Coverage:
Florida
Corporate Publisher:
Florida. Dept. of Transportation. Research Center
Abstract:
This research was done to investigate if the problems associated with flexibility and temperature sensitivity (expansion and

contraction) in roadway concrete pavements can be addressed by replacing some of the fine or coarse aggregate component

with crumb rubber, specifically, Ground Tire Rubber (GTR). The research also intended to find out the general effects of

adding the GTR to the conventional pavement concrete, in terms of the mechanical properties and workability, requiring

several laboratory tests to be conducted as part of the study. Finally, the research was required to evaluate the practical

implementation at a ready mix plant, of the proposed use of GTR as a component in the concrete. It was found from the

study that the modulus of elasticity of concrete is reduced when GTR is used in concrete, thus the pavement concrete

becomes more flexible. Based on the results of the tests for the coefficient of thermal expansion (CTE), it was not

conclusive from this study, that adding GTR will significantly affect the expansion and contraction in the concrete

pavement.

Many valuable findings from this study include the following: the optimal content for GTR for use as a component in the

paving concrete mixture is 15% by weight of the fine aggregate; at a water/cementitious ratio of 0.44, concrete with GTR of

15% by weight of the fine aggregate, using water-reducing admixtures, can achieve a 28-Day compressive strength of about

3000 psi as well as reasonable values of the flexural strength and split tensile strength; slump was observed to typically

decrease with addition of GTR but use of the water-reducer will eliminate this problem; the unit weight of the GTR

concrete is less than that of the conventional concrete; air content will always increase with addition of GTR to the concrete

but the use of a defoaming agent will reduce the foam and air content; GTR concrete has a non-brittle mode of failure in

compression and flexure; examining GTR concrete under the Scanning Electron Microscope (SEM) indicated that there is

good bonding between the rubber particles and the cement matrix in the concrete; pretreatment of GTR by simple washing

and drying may improve the compressive strength of the GTR concrete; GTR concrete has very good plastic and dry

shrinkage attributes, with the ability to resist shrinkage cracking; the ready mix plant operations will require dry-safe

storage of the GTR, customized packaging (bag sizes or bag material) of the GTR for convenient batching, and a less

duration for mixing before placement (when compared to the 90 minutes mixing duration allowed for conventional

concrete); the GTR concrete can be used in the following applications: Class I pavement; sidewalks; curbs and inlets; or

applications where the compressive strength of 3000 psi or less is adequate and also where shrinkage may be a problem.


Format:
PDF
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:a3f85064a6adacfe5863145b6b9d46dac7ad7142a8b14cff4c4b97cfd1cc2b42
Download URL:
https://rosap.ntl.bts.gov/view/dot/28743/dot_28743_DS1.pdf
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