A 7.8 Excessive Water Jet Pressure Description: During hydro-blasting, a high-pressure water jet impacts the concrete to be removed (FM 7.8 Exhibit 1 is a September 2004 International Concrete Repair Institute.(ICRI) Technical Guideline "Guide for the Preparation of Concrete Surfaces for Repair Using Hydro-demolition Methods" and FM 7.8 Exhibit 2 is the ACI 546R-04 Concrete Repair Guide). The water jet pressure that is used is nominally 20,000 psi (FM 7.8 Exhibit 3 is the Work Plan agreed by Mac & Mac, the hydro-blasting company used for this project, and Progress Energy, the owner) although in practice it can vary somewhat (FM 7.8 Exhibit 4 is an interview with Dave McNeill, co-owner of Mac & Mac and FM 7.8 Exhibit 5 is an interview of Robert Nittinger, President of American Hydro). The pressure is obtained by means of a plunger positive displacement pump. The water nozzles rotate at 500 rpm. The jet flow rate per nozzle is around 50 gallons per minute. The intent of hydro-demolition as applied here is to damage and remove the concrete section of interest. This is indeed the point of using this technology in this particular application where concrete HAS to be removed. This FM is looking at if and how the hydro pressure might cause damage beyond the application area via force or pressure buildup. Damage to underlying or surrounding concrete (outside the targeted removal area) may occur if water jet pressure and flow is not maintained within a controllable range. Note that issues associated with resonant frequency are analyzed separately in FM 7.2. Data to be collected and Analyzed: 1. Determine impulse force associated with the hydro-blasting technology (FM 7.8 Exhibit 7 is a vibration analysis performed by P11, and FM 7.8 Exhibit 8 is a calculation performed by American Hydro); 2. Observations of phenomena that may be related to impact from the water jets (FM 7.8 Exhibit 9 describes observations made at 2/18/10 P1 , fidential, 2u09 Page 1 of 3 Dr asston the CR3 containment near the liner); 3. Review of the Turkey Point liner issues during its concrete containment opening (FM 7.8 Exhibit 10 is a report summary of the issues observed at Turkey Point during concrete containment hydro-blasting). Verified Supporting Evidence: I a. The hydro-blasting water jets appear to be responsible for some damage to the surrounding concrete close to the liner plate (FM 7.8 Exhibit 9). This occurred late in the hydro-blasting process when the thickness of concrete left in front of the liner plate was low; Verified Refuting Evidence: a. The force and pressure applied by the hydro-blasting water jet were within the expected range for the intended operation, and within a controllable range to prevent/limit unintended concrete removal or damage to surrounding concrete or structures (FM 7.8 Exhibit 7); b. The PII calculation (FM 7.8 Exhibit 7) agrees with a calculation done by American Hydro (FM 7.8 Exhibit 8). They also conclude that the force from the water jet to the containment is minimal; c. There are no indication that Mac & Mac operated the equipment at a higher pressure than expected (FM 7.8 Exhibit 3 and FM 7.8 Exhibit 4); d. The first time the hydro-blasting equipment was turned on, a mock-up operation was performed. This consisted of a small 8ft wide by 6ft high area to be hydro-blasted about 10 inches deep. There are strong indications that the crack was present very early while this mock-up was being performed (FM 7.8 Exhibit 11 is a summary of observation of cracks very early in the hydro-blasting process). This would indicate that the delamination may have been present before the hydro-blasting operation started; Discussion: Interviews with engineers at Mac & Mac and at American Hydro demonstrated that the two systems are mostly similar. PII calculations and American Hydro calculation confirm that in both cases the force from the water jet tothe concrete is not sufficiently high to 2/18/10 P -rtryr Cui •-fi•I, Page 2 of 3 Draft 1 generate damage by itself. The principle of hydro-blasting confirms that hydro-blasting takes advantage of pre-existing cracks (FM 7.8 Exhibit 12 is chapter 5 "Waterjets in Civil Engineering Applications" from Professor David Summers book on water jets and their applications). American Hydro has performed eight SGR openings into post-tensioned reactor building containments (seven were performed when we started this investigation in October 2009 and one more was done since at TMI). All were successful, demonstrating capability and process effectiveness for hydro-blasting SGR openings without unacceptable collateral damage to surrounding concrete or structures. Additionally, all the literature we found on comparing the various means to perform concrete removal agree that hydro-blasting is the least damaging to the underlying structure. Pressures and forces generated during hydro-blasting are limited by the equipment and water requirements. When providing sufficient control for confining concrete removal to the desired area and depth, no damage is expected to occur in adjacent areas. Also, hydro-blasting does not result in mechanical impact per-se, but rather in rapid erosion/disintegration of the paste/aggregate sub-components (FM 7.8 Exhibit 12). The analysis of cracked features in the concrete on the outside of containment, close to the liner plate, concluded that the water jet had enough force to push the liner (FM 7.8 Exhibit 11). This can be explained because the water at that stage in the hydro-blasting is impacting on a thin (3/8 in) long (25 ft x 27 ft) plate of steel, loosely bonded on the four sides (mostly through mechanical locking due to the plate stiffeners). An important caveat to add is that although the forces generated by the water jet are not sufficient to initiate the delamination, it is possible they could have been instrumental in propagating it. Once the crack started in the plane of the tendon sleeves, it is "active" because it is in an area of local tensile stresses. Therefore it can be propagating with minimal forces serving as an "activation energy" force just pushing the local tensile stress above the tensile strength of the concrete. Conclusion: Excessive water jet pressure was not a factor in creating the delamination. It could have been a factor in the propagation of the delamination. -2/18/10 rI-P-r -5..~....TOO9 Page 3 of 3 Draft l-k- to th-d par1 wtho i FM 7.8 Exhibit 1 page 1 of 16 TECHNICAL GUIDELINES Prepared by the International Concrete Repair Institute September 2004 Guide for the Preparation of Concrete Surfaces for Repair Using Hydrodemolition Methods Guideline No. 03737 Copyright © 2004 International Concrete Repair Institute All rights reserved. International Concrete Repair Institute 3166 S. River Road, Suite 132, Des Plaines, IL 60018 Phone: 847-827-0830 Fax: 847-827-0832 Web: www.icri.org E-mail: [email protected] 925 926 FM 7.8 Exhibit 1 CONCRETE REPAIR MANUAL page 2 of 16 About ICRI Guidelines The InternationalConcrete Repair Institute (ICRI) literature on concrete repairmethods and materials was founded to improve the durability of concrete as they have been developed and refined. Neverthe- repairand enhance its valuefor structure owners. The less, it has been difficult to find critically reviewed identification,development, andpromotionof thenmost information on the state of the art condensed into promising methods and materials is aprimaryvehicle easy-to-use formats. for accelerating advances in repair technology. To that end, ICRI guidelines are prepared by Working through a variety offorums, ICRI members sanctioned task groups and approved by the ICRI have the opportunity to address these issues and Technical Activities Committee. Each guideline to directly contribute to improving the practice of is designed to address a specific area of practice concrete repair recognized as essential to the achievement of A principal component of this effort is to make durable repairs. All ICRI guideline documents carefully selected information on important repair are subject to continual review by the membership subjects readilyaccessible to decision makers. During and may be revised as approved by the Technical the past several decades, much has been reportedin Activities Committee. Technical Activities Committee Producers of this Guideline Rick Edelson, Chair Subcommittee Members David Akers Pat Winkler, Chair Paul Carter Don Caple Bruce Collins Bruce Collins William "Bud" Earley Eric Edelson Garth Fallis Ken Lozen Tim Gillespie Bob Nittinger Fred Goodwin Steve Toms Scott Greenhaus Robert Johnson Contributors Kevin Michols Allen Roth Scott Greenhaus Joe Solomon Rick Toman Mike Woodward Synopsis Keywords This guideline is intended to provide an Bond, bonding surface, bruising, chipping introduction to hydrodemolition for concrete hammer, coating, concrete, delamination, removal and surface preparation, the benefits deterioration, full depth repair, hand lance, and limitations of using hydrodemolition, high-pressure water, hydrodemolition, impact and an understanding of other aspects to be removal, mechanical removal, micro-fracture, addressed when incorporating hydrodemolition post-tensioning, rebar, reinforced concrete, into a repair project. This guideline provides reinforcing steel, robot, rotomill, safety, sound a description of the equipment, applications, concrete, surface preparation, surface profile, safety procedures, and methods of water surface repair, tendon, vibration, wastewater, control and cleanup. and water jet. This document is intended as a voluntary guideline for the owner, design professional, and concrete repair contractor. It is not intended to relieve the professional engineer or designer of any responsibility for the specification of concrete repair methods, materials, or practices. While we believe the information contained herein represents the proper means to achieve quality results, the International Concrete Repair Institute must disclaim any liability or responsibility to those who may choose to rely on all or any part of this guideline.