ML102870210
| ML102870210 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 11/02/2009 |
| From: | David Brown CTL Group |
| To: | Office of Information Services |
| References | |
| FOIA/PA-2010-0116, 059169 | |
| Download: ML102870210 (4) | |
Text
- FM 5.8 Exhibit 7 Page 1 of 4 CiGROUp Building Knowledge; Delivering Results.
www.CTLGroup.com REPORT OF PETROGRAPHIC EXAMINATION Date: November 2, 2009 CTLGroup Project No.: 059169 Petrographic Examination of Concrete Half Core from Delaminated Containment Wall, Crystal River, Florida One saw cut half concrete core labeled Core #5 (Figs. 1 and 2) was received on October 27, 2009 from Mr. Jerzy Zemajtis, Project Manager, CTLGroup on behalf of Mr. Paul Fagan of Progress Energy, Crystal River, Florida. According to Mr. Zemajtis, the core represents the outer portion of concrete from a containment wall and the core is fractured at its inner surface at a delamination that was found to be present when, access was gained to the Wall interior. The delamination is approximately at a depth of 200 mm (8.0 in.) where horizontal post tensioning ducts are present.
Petrographic examination (ASTM C856-04) of the core was requested in order to determine, if possible, if the delamination is a recent feature, or alternatively if it occurred at some earlier time in the age of the structure.
FINDINGS AND CONCLUSIONS The following findings result from the petrographic examination.
Based on the general appearance, and both the physical and microstructural properties, the fracture at the point of delamination is most likely a fairly recent event. However, it is not possible to be completely definitive about the time frame since an older fracture, if subsequently well protected from air and moisture ingress, may also have similar characteristics.
The fracture surface passes through, not around the aggregates particles, is moderately hard, and does not exhibit loose surface debris. There is an absence of significant microcracking in the general vicinity of the fracture, and only limited evidence of surface deposits (slight efflorescence).
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- FIM 5.8 Exhibit 7 Page 2 of 4 Progress Energy Page 2 of 10 Crystal River November 2, 2009 CTLGroup Project No. 059169 Carbonation to any significant depth from the fracture surface into the outer concrete is not observed (Fig. 3). Incipient carbonation is exhibited in thin section at the immediate fracture surface (Fig. 6a). However, an older delamination surface that was not exposed to air due to the depth of outer concrete, and other possible wall coverings, may also have such an absence of carbonation.
The cement hydration adjacent to the fracture is well advanced and comparable to that of the body of the core (Figs. 6b and 6c). This suggests that there was no moisture ingress to the fracture surface, over a period of time long enough, to change the general degree of hydration.
This is supported by an absence of secondary deposits within air voids adjacent to the fracture surface.
Additional Comments The concrete represented by Core #5 is well consolidated and free of any cracks or excessive microcracks (Fig. 4). The concrete consists of crushed carbonate rock coarse aggregate and natural sand fine aggregate, well distributed in a portland cement-paste. No evidence is exhibited of any deleterious chemical reactions involving the cement paste and / or aggregates.
The concrete could be considered marginally air entrained based on an approximate volume of 1 to 2% of small, spherical entrained air voids in the hardened cement paste (Fig. 5).
Based on the physical properties and microstructure of the hydrated cement paste, and the tight aggregate to paste bond, lack of major cracks and microcracks, and absence of a materials-related distress mechanism, the concrete is considered to be in good condition.
Further details of the petrographic examination are given in the following image and data sheets.
METHODS OF TEST Petrographic examination of the provided sample was performed in accordance with ASTM C 856-04, "Standard Practice for Petrographic Examination of Hardened Concrete." The core was visually inspected and photographed as received. The core half was ground (lapped) on the saw cut surface to produce a smooth, flat, semi-polished surface. Lapped and freshly broken surfaces of the concrete were examined using a stereomicroscope at magnifications up to 45X.
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FM 5.8 Exhibit 7 Page 3 of 4 Progress Energy Page 9 of 10 Crystal River November 2, 2009 CTLGroup Project No. 059169 PETROGRAPHIC EXAMINATION OF HARDENED CONCRETE, ASTM C 856 STRUCTURE: Containment wall DATE RECEIVED: October 27, 2009 LOCATION: Crystal River EXAMINED BY: Derek Brown SAMPLE Client Identification: Core #5.
CTLGroup Identification: 2452601.
Dimensions: Core diameter = 95 mm (3.75 in.). Core length = approximately 197 mm (7.75 in.); partial wall thickness.
Top End: Even, slightly rough formed surface.
Bottom End: Uneven and rough, fractured core end.
Cracks, Joints, Large Voids: Text.
Reinforcement: None observed in the core supplied.
AGGREGATES Coarse: Crushed rock composed of carbonate rock type.
Fine: Natural quartz sand.
Gradation & Top Size: Visually appears evenly graded to an observed top size of 18 mm (0.75 in.).
Shape, Texture, Distribution: Coarse-Sub rounded to angular, slightly irregular to rough, evenly distributed. Fine-Rounded to sub angular, slightly smooth to somewhat rough, evenly distributed PASTE Color: Medium gray, uniform coloration throughout the length of the core.
Hardness: Moderately hard at the outer surface and in the body of the core. At the fracture surface the paste is also moderately hard.
Luster: Subvitreous.
Paste-Aggregate Bond: Tight. Freshly fractured surfaces pass through aggregate particles.
Air Content: Estimated 2 to 4% total. Approximately 1 to 2% of the total air is larger entrapped air voids of up to 3 mm (0.12 in.) in size, plus a few large voids of 4 to 10 mm (0.16 CT C.ROUP' BuDng Knowledge DeflverfingResWts..
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FM 5.8 Exhibit 7 Page 4 of 4 Progress Energy Page 10 of 10 Crystal River November 2, 2009 CTLGroup Project No. 059169 to 0.4 in.). Somewhat uneven distribution of voids. Marginally air entrained based on the very low volume of moderate to small sized spherical air voids in the hardened cement paste.
Depth of Carbonation: 4 to 5 mm (0.16 to 0.20 in.) as measured from the outer surface.
Negligible when measured from the inner fractured core surface.
Calcium Hydroxide*: Estimated 6 to 12% of small to medium sized crystals evenly distributed throughout the paste, and around aggregate to paste interfaces. Estimation of the volume is difficult due to the presence of calcite fines in the cement paste.
Residual Portland Cement Clinker Particles*: Estimated 4 to 8%. Some large cement particles, particularly belite clusters, of up to 0.15 mm in size suggest a portland cement as produced more than 30 years ago.
Supplementary Cementitious Materials*: None observed by the core supplied.
Secondary Deposits: None observed either in the body of the core and or near the fracture surface.
MICROCRACKING: A small number of medium length (5 to 10 mm), randomly orientated microcracks are evenly distributed throughout the body of the core. At the fractured end of the core there was no observed increase in microcracking relative to the body of the core.
ESTIMATED WATER-CEMENT RATIO: Moderate to moderately high (0.50 to 0.60) but estimation may be biased upwards due to the well advanced degree of hydration / apparent old age of the concrete.
MISCELLANEOUS:
- 1. Water droplets applied to freshly fractured surfaces were somewhat slowly absorbed by the hardened cement paste.
- 2. Some small areas of the inner fractured surface of the core, as received, exhibit a thin white haze of efflorescence-like substance suggesting leaching of lime in solution from within the core, or alternatively, moisture on or flowing past the fractured surface at the delamination position within the wall.
- 3. A moderate volume of fine calcite particles is present within the hardened cement paste, most likely from coarse aggregate crusher fines.
percent by volume of paste C iGROUP Wid~gK~qnm,1edge; nMoPtvri, esu~tti. www.CTLGroup.com