slab-placement - EVALUATION OF EARLY STRENGTH REQUIREMENT...

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1 EVALUATION OF EARLY STRENGTH REQUIREMENT OF CONCRETE FOR SLAB REPLACEMENT USING APT – PHASE II Mang Tia Kitti Manokhoon Department of Civil and Coastal Engineering University Florida February 26, 2008 Acknowledgment Project Managers: Bouzid Choubane Mike Bergin Key FDOT Personnel: Steve Ross Tom Byron Abdenour Nazef Charles Ishee Richard DeLorenzo Content Content • Research Need • Instrumentation & Construction of Test Slabs • Characterization of Concrete Mixes & Test Slabs • HVS Testing & Observed Performance of Test Slabs •Model Calibration & Verification • Evaluation of Potential Performance • Findings & Recommendations Research Need -- Slab Replacement Slab Replacement Current FDOT Specification Minimum 6-hour compressive strength of 2,200 psi. Minimum 24-hour compressive strength of 3,000 psi. Problem statement Problem statement • Is the present FDOT specification for replacement slab sufficient to ensure performance ? • There is a need to better understand the behavior of concrete replacement slabs at early age, and to develop an effective methodology to evaluate and control of concrete mixes to ensure good performance in concrete replacement slabs. Objectives of Research Objectives of Research • To calibrate and verify an analytical model for calculating load and temperature induced stresses in a concrete replacement slab. The applicability of the model was validated by comparing the predicted results to the experimental results. • To determine the required properties for replacement slab concrete to ensure adequate performance. • To develop a rational methodology for evaluation of concrete mixes to ensure adequate performance in replacement slabs
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2 Construction of Test Slabs Construction of Test Slabs Test Slabs 1 - 4 Lime Rock Base Test Slab 5 Typical Test Slab Layout Typical Test Slab Layout Parameters considered: •Concrete elastic modulus •Concrete thickness •Mod. of subgrade reaction •Joint shear stiffness •Joint torsional stiffness •Edge stiffness •Poison’s ratio •Temperature differentials •Coefficient of thermal expansion Edge Spring Winkler Foundation Spring Shear Spring Torsional Spring Concrete Slab Adjacent Slab Test Slab Finite Element Analysis of CONcrete Slabs version IV (FEACONS IV) Analytical Model Used: Loading Positions Used to Determine Critical Loading Positions Used to Determine Critical Stress Locations Plots of σ xx Contours Caused by Load at Slab Corner joint joint
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3 Plots of σ yy Contours Caused by Load at Slab Corner Joint Joint Plots of σ xx Contours Caused by Load at Mid Edge Joint Joint Plots of σ yy Contours Caused by Load at Mid Edge Joint Joint Instrumentation Layout Preparation for Placement of Test Slab Preparation for Placement of Test Slab Concrete Mix Design for Slabs 1 & 2 Concrete Mix Design for Slabs 1 & 2 142.1 pcf (2% Air) 139 pcf (3% Air) 140 pcf (2% Air) Theoretical unit weight 0.35 0.34 0.36 W/C 195 lb 185 lb 283 lb Water 25.04 lb 25.04 lb 384 oz (25 lb) Accelerator (Daraccel) 4.017 lb 2.125 lb 50 oz (3.26 lb) Superplasticizer (Adva-540) 0.0625 lb 0.0625 lb 1 oz (0.065 lb)
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This note was uploaded on 05/26/2011 for the course CGN 6505 taught by Professor Mang during the Spring '11 term at University of Florida.

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slab-placement - EVALUATION OF EARLY STRENGTH REQUIREMENT...

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