George V. Voinovich Bridge Project

Transcription

1 George V. Voinovich Bridge Project

2 CCG2 Mass Concrete ODOT Background In larger concrete structural elements, the exterior surfaces exposed to air or water cool faster versus the interior core of the element s. This differential cooling can result in internal concrete stresses where the concrete prematurely cracks which can reduce the overall service life of the structure element.

3 CCG2 Mass Concrete ODOT Background Theoretical computer models have been developed which use dimensional, material, and environmental factors to estimate the elements concrete temperatures to be experienced during its concrete placement and cure period.

4 CCG2 Mass Concrete ODOT Background ODOT s 2013 Specification Item 511 includes requirements to control thermal cracking in larger structural elements. (i.e.: Mass Concrete) These concrete requirements also reference and utilize the Item 455 QC/QA Concrete Quality Control plans.

5 District 12 Mass Concrete History ODOT District 12 has implemented Mass Concrete requirements previously on four separate Construction Projects: o Fulton Road Bridge over the Zoo in 2006 o LAK 90 Bridge over the Grand River in 2007 o Innerbelt CCG1 in 2010 o Innerbelt CCG2 in 2013 o Statewide, there is a much broader sample.

6 District 12 Mass Concrete History Fulton Road Bridge Mass Concrete Thrust Block

7 District 12 Mass Concrete History CCG1 Mass Concrete Typical Element

8 District 12 Mass Concrete History CCG2 Mass Concrete Typical Element

9 District 12 Mass Concrete History District 12 has progressively moved from Special Provisions, initially in 2006, to the current ODOT Item 511 Specifications in 2013 for mass concrete. The District made adjustments to these Provisions from the earlier Projects to improve the service life and constructability of the structures.

10 District 12 Mass Concrete History An example of these progressive changes are: In 2006, the mass concrete dimensional minimum was 6 feet. In 2010, it was revised to 4 feet and now with the 2013 ODOT Specifications, it is set at 5 feet minimum. Coincidentally, on current Design Builds, ODOT strives for a 4 11 minimum design dimension for structural elements to minimize the need for mass concrete pours.

11 Innerbelt Mass Concrete Comparison CCG1 Contractual 4 or greater dimension 160F Max Concrete Temp. 35F or less differential Temp. 28 Days cure Project Scope Provisions and Appendix with Supplemental Spec. requirements Maturity Curve was not allowed, added by Change Order CCG2 Contractual 5 or greater dimension 160F Max Concrete Temp. 36F or less differential Temp. 28 Days cure ODOT Item 511 and Item 455 Specification Maturity curve is allowed by Spec.

12 Innerbelt Mass Concrete Comparison CCG1 Materials 500 lbs. cement min. 50% Max. slag content 25% Max. Fly ash content <50% Pozzolan Materials CCG2 Materials 470 lbs. cement min. 30% Max. slag content 15% Max. Fly ash content <40% Pozzolan Materials *** CCG1 had some material correlation testing issues trying to achieve a consistent air content. The Project made these concrete material mix changes to address these inconsistent testing results. Achieving better quality results on CCG2.

13 Innerbelt Mass Concrete TCP Per Spec. Item A. Mass Concrete Requirements: For concrete components with a minimum dimension of 5 ft (1.5 m) or greater, develop a concrete mix design QC 4 for mass concrete according to Develop a Thermal Control Plan (TCP) to control placement of the mass concrete so that the highest maximum internal temperature of the placed concrete is not greater than 160⁰ F (71⁰ C) and the maximum differential concrete temperature does not exceed 36⁰F (20⁰C) over 28 days ODOT was aware of two consultant firms which specialize in this TCP work. Each firm has their own proprietary thermal computer model and assumptions to develop such Plans. CCG1 and CCG2, each had different firms develop their TCP s.

14 CCG2 Mass Concrete Overview 10 Pier Caps approx. 600 cy each

15 CCG2 Mass Concrete Overview 20 Individual Pier Footers approx. 250 cy each

16 CCG2 Mass Concrete Overview 2 semi integral Abutment diaphragms 100 cy each ***** The Drilled Shafts were not required to be Mass Concrete on CCG2 as their designed dimension was < 7. The Department had specifically excluded Drilled Shafts for Mass Concrete on CCG1 in the Bid Provisions.

17 Mass Concrete Thermal Control Plan Thermal Control Plan (TCP) Requirements: Mix Design Analysis Procedures to Control Temps Sensor Monitoring Plan

18 Mass Concrete Thermal Control Plan

19 Mass Concrete Thermal Control Plan

20 Mass Concrete Thermal Control Plan

21 Mass Concrete Plan Execution

22 Mass Concrete Plan Execution

23 Mass Concrete Plan Execution

24 Mass Concrete Plan Execution

25 Mass Concrete Plan Execution

26 Mass Concrete Plan Execution Temperature(⁰F) Mass Concrete Footer Example Temperature v. Time Core Bottom Top Differential Allowable Time(hrs)

27 Mass Concrete Best Practices 1. Plan Implementation 2. Schedule/Resource Constraints

28 Mass Concrete Best Practices Plan Implementation Integrate thermal system Sensor installation and access

29 Mass Concrete Best Practices

30 Mass Concrete Best Practices Schedule and Resource Constraints Cold/Cool weather impacts Formwork / Insulation System

31 Mass Concrete Acknowledgements Concrete Supplier Cuyahoga Concrete Co. Mass Concrete Consultant W. S. Langley, Inc. Material Testing Solar Testing Laboratories, Inc. Concrete Monitoring Equipment FLIR Systems, Inc.