The effects of higher strength and associated concrete properties on pavement performance.
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2001-06-01
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Edition:Final report; 1995-2000.
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Materials;NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance;NTL-HIGHWAY/ROAD TRANSPORTATION-Construction and Maintenance;
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Abstract:The major goal of this project was to develop recommendations for PCC properties and materials characteristics found
in higher strength JPCP's with improved long-term performance as determined by joint spalling and faulting, and
transverse slab cracking. Primary project variables were pavement age, climate, traffic (4 to 23 million ESALYs)d, istress
levels and types, joint spacing, and compressive strength. Fifteen PCP's were selected for detailed field and laboratory
investigation. The field compressive and tensile strengths (splitting) ranged from 33 to 75 MPa and from 3.1 to 4.5 MPa,
respectively.
Regular strength highway concrete with a design flexure strength of about 4.5 MPa can develop excellent long-term joint
spalling resistance provided that (1) good sub-surface drainage conditions are present, (2) the concrete reaches low
permeability level over time from additional curing (i.e. high resistance to physical and chemical deterioration from rapid '
chloride and water permeability test), (3) it has good entrained air void system (i.e. 6 to 8.5 percent), and (4) sound
aggregate are used in the concrete mix. Several different permeability tests were evaluated, and each showed a good
correlation with compressive strength. The compressive strength test is therefore a good indicator of the permeability
level. The range of low permeability can typically be achieved at a compressive strength range of 45 to50 MPa. Watercementitious
ratio was found to be the major mix feature controlling compressive strength. This requires a concrete mix
with a water-cementitious ratio of 0.42 to 0.45, a cement content of about 335 kg per m3 (6 sack mix typical for most
SHA's), and well-graded quality aggregate. Several aggregate characteristics of the concrete mix were found important to
achieve good long-term pavement performance. These included aggregate inertness with respect to AAR and F-T, and
strong and large sized coarse aggregate to ensure good cracking resistance and aggregate interlock. In addition, wellgraded
aggregate were beneficial in reducing the paste volume fraction. This results .in low coefficient of thermal
expansion and drymg shrinkage, which both are important properties for avoiding premature transverse cracking. Given
suflicient slab thickness, good long-term resistance to fatigue (transverse) cracking was found at any flexure strength level
of 4.5 to 6 MPa, provided that loss of slab support from pumping erosion was not a factor. Joint faulting was found to be a
consequence of factors causing pumping erosion and/or slab settlement and it was not affected by PCC strength level.
Prototype mix designs were developed for different climate regions.
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