Graduation Year

2014

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

MS in Civil Engineering (M.S.C.E.)

Department

Civil Engineering

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Abla Zayed, Ph.D.

Co-Major Professor

Kyle A. Riding, Ph.D.

Committee Member

Kyle A. Riding, Ph.D.

Committee Member

Rajan Sen, Ph.D.

Keywords

Autogenous shrinkage, Chemical admixtures, Free-shrinkage, Restraint, Stress relaxation

Abstract

Cracked pavement slabs lead to uncomfortable and eventual unsafe driving conditions for motorists. Replacement of cracked pavement slabs can interrupt traffic flow in the form of lane closures. In Florida, the traffic demands are high and pavement repairs need to be carried out swiftly typically using concrete with high cement contents and accelerators to create rapid setting and strength gain. The concrete used in these pavement replacements is usually accompanied by a high temperature rise, making the replaced slabs susceptible to cracking. Cracking is a result of developed tensile stresses in the concrete, which exceed the concrete's tensile strength capacity. This research is being conducted to determine the risk of cracking for pavement slabs with varying dosages of chloride based accelerator used to promote high early strength. To analyze the effect of the accelerator, five different concrete mixtures including a control were assessed in a series of tests with varying accelerator dosages. Experiments included: mortar cube testing, concrete cylinder testing, autogenous deformation measured with a free-shrinkage frame, and restrained stress analysis using a rigid cracking frame.

The findings indicate that accelerators are necessary to meet the strength requirements, and that the higher the accelerator dose, the higher the early shrinkage in the first 24 hours determined from the free shrinkage frame. Accidental overdose of the chloride-based accelerator results in the highest cracking potential and the highest shrinkage when tested under field generated temperature profiles.

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