United States Department of Transportation
i
Performance Improvement of High Early Strength (HES) Concrete for Pavement Replacement Slabs
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2018-09-01
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[PDF-9.58 MB]
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Edition:Final report 11/25/2015-12/1/2018
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Abstract:The objectives of this study were to identify concrete mixture combinations, slab base-restraint, and placement conditions that can reduce the risk of early-age cracking potential of concrete pavement repair slabs and to provide recommendations for specifications changes. Towards satisfying the objectives, a battery of laboratory tests as well as field slab placements were conducted to assess several mitigating strategies adopted here to reduce incidents of cracking in pavement concrete slabs. Field slabs were instrumented with stressmeters and thermocouples. Cracking mitigating strategies studied here were reduction of cementitious paste volume through aggregate grading optimization, internal curing using saturated lightweight aggregates, fiber reinforcement to inhibit plastic cracking, use of shrinkage-reducing admixtures, reduction of base restraint using geotextile and plastic sheeting. DIANA and HIPERPAV software programs were used to identify the main factors affecting cracking potential in pavement slabs. The findings indicate that the initial stress development in most of the field-placed slabs was affected by moisture migration to the base; tensile stresses were observed due to an increased autogenous shrinkage within the slab. DIANA finite element analysis indicated that the initial temperature gradient within the slab would not contribute to the development of tensile stresses at early age. The cracking risks of HES concrete can be greatly reduced by increasing the aggregate packing density and lowering the paste content. The cracking probability of HES concrete slabs can be minimized by incorporating LWA as a means of internal curing to extend hydration and reduce autogenous shrinkage effects. The base friction-reducing mediums showed more pronounced effects on early-age stress development by affecting moisture absorption than by reducing friction. The geotextile augmented the absorption of moisture from concrete, which increased cracking risks during early age.
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