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Islamic Relief Centre
DEFECT SURVEY & CONCRETE INVESTIGATION
12B/1394
for TIC International Ltd
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
Your Ref: TIC International Ltd 49 Landor Street Birmingham B8 1AG For the attention of Mr N HagMamed
Contents Pages
1 Introduction 1
2 Objectives 1
3 Methodology 1 to 3
4 Defect/Hammer Survey Results 3
5 Concrete Investigation Results 4
6 Construction Detail Results 4
7 Petrographic Examination Results 5
8 Discussion 6 & 7
9 Conclusions 7 & 8
10 Recommendations 8 & 9
Attachments No. of Pages
Sample & Defect Location Sketches 2
Appended Results & Photographs 25
Petrographic Examination Report, Reference: BCL/PR/020113 14
Electronic copy to Mr C Perry, Structural Design Partnership Ltd
Our Ref: 12B/1394
Date of Report: 4th January 2013
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 1 - REPORT REFERENCE: 12B/1394
ISLAMIC RELIEF CENTRE
DEFECT SURVEY & CONCRETE INVESTIGATION
1.0 INTRODUCTION As requested, we have undertaken investigative works to the external elevations of the Islamic Relief Centre, 49 Landor Street, Birmingham, B8 1AG. The building, age unknown possibly constructed 1920’s or 1930’s, appears originally designed for an industrial purpose, but now serves as offices. The construction method comprises of beam and column reinforced concrete frame, with masonry cladding infill panels. Toward the front entrance recent refurbishment has been conducted. The remaining more historical elements show significant deterioration. The BCL site works were conducted 15th and 16th November 2012. 2.0 OBJECTIVES The objectives of the survey, as instructed by Chris Perry of the Structural Design Partnership Ltd, are as follows.
Perform a defect survey of the external elevations From selective concrete elements obtain dust samples for chloride ion and
cement content determinations Determine concrete cover to reinforcement Determine depth of carbonation Determine the extent of cracking occurring centrally to main beams and
ascertain the extent of reinforcement corrosion Remove samples for petrographic examination Conduct a photographic log throughout the investigative works
3.0 METHODOLOGY 3.1 Defect Survey A defect/hammer/soundness survey was conducted to the external elevations. This comprised of;-
Tapping the external elements with a hammer Removing spalled/loose material Recording defects
This work was conducted from either ground level or a mobile tower scaffold. 3.2 Concrete Sampling The concrete dust samples were taken by percussive drilling, in accordance with BS EN 14629: 2007. Concrete dust samples were taken either to a depth of 80mm in 25mm increments or to just 30mm. In both cases, the first 5mm was discarded.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 2 - REPORT REFERENCE: 12B/1394
3.0 METHODOLOGY 3.3 Covermeter Survey Site determinations of concrete cover to reinforcement were made using an Elcometer 331 covermeter, in accordance with British Standard 1881: Part 204: 1988. The particular model of covermeter employed is designed to locate steel within 100mm of the concrete surface. Minimum concrete cover to primary and secondary reinforcement was determined at sample locations. Readings were verified by the removal of sections of concrete to allow for the reinforcement cover to be physically measured. 3.4 Carbonation Survey Depth of carbonation was determined using phenolphthalein indicator in accordance, with BS EN 14630: 2006. The mean and maximum depth of the carbonation was measured to an accuracy of 1mm, using a depth gauge. 3.5 Cement Content A beam and a column concrete dust sample have been subjected to cement content determination, in accordance with British Standard 1881: Part 204: 1988. 3.6 Chloride Ion Content Samples have been analysed to determine the chloride ion content in accordance with BS EN 14629: 2007. Results are presented by weight of sample and by weight of cement. The results of the cement content analysis have been used to categorise the estimated risk of steel reinforcement corrosion associated with carbonation, cast-in chloride content and environmental conditions. The chloride risk levels have been classified in accordance with criteria given in Building Research Establishment Digest 444: Part 2 table 4b. The chlorides have been considered as cast in-situation and are based on circa sixty year old concrete, within a damp environment as all the elements investigated are external. 3.7 Construction Detail Investigation At two positions the extent of vertical cracking occurring centrally to main beams has been investigated. This has been achieved by using percussive equipment to remove sections of concrete in order to ascertain the full penetration of the cracks. At various locations, areas of significant spalling concrete with exposed corroding reinforcement were examined in order to ascertain the extent of corrosion occurring. The reinforcement bars were physically measured for loss of section. 3.8 Petrographic Examination Concrete core samples were removed from a beam and column using diamond drilling apparatus.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 3 - REPORT REFERENCE: 12B/1394
3.0 METHODOLOGY 3.8 Petrographic Examination (Continued) The core positions were reinstated using a proprietary concrete repair material. The core samples have been examined petrographically in order to ascertain the material quality, composition and the presence of any latent defects, such as fire damage or sulphate attack. This petrographic work has been conducted on our behalf by Aston University. 4.0 DEFECT RESULTS The results of the limited defect survey are presented as follows.
Locations – sketches 12B/1394-1 and 2 Results – appendices 1 to 11 Photographs – appendices 12 to 20 Tables 1 and 2 below
A total of 162 defects were highlighted. The total number of individual defects comprises of the following.
Defect Details No. of Defects
Concrete cracking 61
Spalling concrete & exposed reinforcement 51
Spalling concrete 21
Render cracking 20
Masonry cracking 3
Delaminating concrete 2
Previous investigation locations 2
Hollow render 1
Mortar eroding 1 Table 1: Summary by defect frequency The hollow render defects affect approximately 50% of all render to the left gable elevation. The 162 defects are affecting the following number of elements.
Element Affected No. of Defects
Beams 80
Columns 56
Render 21
Masonry 5 Table 2: Defect summary by element
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 4 - REPORT REFERENCE: 12B/1394
5.0 CONCRETE INVESTIGATION RESULTS A total of six separate elements were investigated for concrete cover to reinforcement and carbonation depths, with samples for chloride ion content removed from each location. Two samples have been analysed for cement content. The site test and laboratory analysis results can be found in appendices 21 to 25, with the sample locations shown on the attached sketches 12B/1394 – 1 and 2. A summary of concrete cover to reinforcement, carbonation depths and chloride results are presented below in Table 3.
Min Max Ave Min Max Ave Min Max Ave
23 76 51 12 >50 31 0.07% 0.07% 0.07%
28 58 41 7 35 23 0.07% 0.13% 0.11%
Corrosion risk levels = 2 low & 1 moderate areas
Areas where reinforcement is located
within carbonated concrete = 2 (67%)
Corrosion risk levels = 1 low & 2 moderate areas
Beams Areas where concrete cover is less than
20mm = 0
Areas where reinforcement is located
within carbonated concrete = 1 (33%)
ElementChloride LevelsConcrete Cover (mm) Carbonation (mm)
Columns Areas where concrete cover is less than
20mm = 0
Table 3: Summary of concrete cover to reinforcement, carbonation depths and chloride results 6.0 CONSTRUCTIONAL DETAIL RESULTS 6.1 Exposed Corroding Reinforcement During the investigation, areas of significant spalling concrete with exposed corroding reinforcement were examined in order to ascertain the extent of corrosion occurring. The results of this examination are presented in appendix 23 and 24. As can be seen, all exposed reinforcement is in a corroding condition, with some areas exhibiting scaling and loss of section up to 2mm. 6.2 Beam Mid-Span Cracking Investigation At two positions, denoted as A and B on drawing 1, the vertical cracking occurring mid span to beams was investigated. The results of the crack investigation are presented below.
At position A, concrete was removed around the crack which was found to penetrate to a depth of 30mm.
At position B, concrete was removed around the crack which was found to penetrate to in excess of a depth of 100mm. To try and preserve the integrity of the beam the investigation was halted at a depth of 100mm.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 5 - REPORT REFERENCE: 12B/1394
7.0 PETROGRAPHIC EXAMINATION Initially, a concrete core sample was removed from a column and a beam for petrographic examination. However, during the defect survey large sections of concrete were readily removed from the roof beam. It was therefore decided that one of these pieces would be more representative for petrographic examination, as the failure/spalling mechanism could be investigated. The petrographic examination was conducted on our behalf by Aston University and the report, reference: BCL/PR/020113 is attached and should be read in full. Salient points taken from the report are presented below. Both samples are from the same type of concrete. The concrete is made with crushed epidosite (coarse aggregate),
quartz‐dominated sand and Portland Cement, probably OPC. There is no petrographic evidence of in situ aggregate instability or of
abnormal set. There is no excessive voidage. The mix design is within normal limits though the water: cement ratio, and
hence the capillary porosity of the paste, is high for concrete with ferrous reinforcement.
Reinforcement is placed at a depth of circa 40 mm. Because of the high capillary porosity carbonation penetration commonly
exceeds the depth of placement of ferrous reinforcement. In concrete with uncarbonated paste ferrous reinforcement is rendered
passive and protected from corrosion by the high pH of pore fluids. When the binder is carbonated the pH of pore fluids falls from > 12 to about
8.5. The reinforcement is no longer protected and, in the presence of atmospheric oxygen and moisture, it begins to corrode with concomitant expansion and cracking of the enclosing concrete.
Cracking facilitates ingress of air and moisture so if no remedial action is taken the rate of deterioration may accelerate.
Degradation may be exacerbated in severe winter conditions by freeze – thaw action of water trapped in the fractures.
This concrete is in poor condition for the following reasons.
o The paste has high capillary porosity and this has permitted deep carbonation.
o Ferrous reinforcement is placed too close to the surface of the concrete (approx. 40 mm).
o Photographs of the structure suggest it has not always been well‐maintained.
This petrographic investigation suggests concrete from beams and columns
need immediate remedial treatment and local replacement.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 6 - REPORT REFERENCE: 12B/1394
8.0 DISCUSSION 8.1 Corrosion Mechanisms General corrosion of reinforcement is caused by the loss of protection afforded to steel in concrete. Steel in concrete is protected (passivated) by the high alkalinity of the concrete. Carbonation of the concrete, due to atmospheric carbon dioxide, causes a reduction in the concrete alkalinity. This results in the steel reinforcement being susceptible to corrosion in the presence of moisture and oxygen. Corrosion can also be caused by chlorides, either introduced into the concrete from an external source or cast in at the time of construction. Chlorides within the concrete result in the formation of an electrochemical cell, which can result in pitting corrosion. 8.2 Carbonation Induced Corrosion (General Corrosion) Carbonation of concrete cover occurs when atmospheric carbon dioxide dissolves in the concrete’s pore solution and forms carbonic acid, which reacts with the calcium hydroxide generated in cement hydration and with the sodium and potassium hydroxides generated from the alkalis in cement. This precipitates calcium carbonate and reduces the pH to below the level required for the steel to be passive. The relatively low concentrations of soluble sodium and potassium carbonate produced from the alkalis offset this reduction somewhat, but are not sufficient to passivate the steel. Carbonation takes place most rapidly in conditions of low to intermediate humidity (50-70% relative humidity). At high humidity carbon dioxide cannot penetrate the water filled pores to react with calcium hydroxide and other calcium silicate phases. In very dry concrete there is insufficient water for the carbon dioxide to dissolve and form carbonic acid. When the carbonation zone reaches the reinforcing steel, the steel becomes at risk of corrosion in the presence of moisture and oxygen. 8.3 Chloride Induced Corrosion Corrosion due to chloride ions can be a much greater problem as it can occur even when the surrounding concrete is alkaline. Chlorides are a common species but are generally present in concrete from marine contamination, from de-icing salts or from the use of chloride-based admixtures. Calcium chloride admixture was widely used well into the 1970’s as an accelerating and cold-weather admixture for reinforced concrete. Chloride admixtures, introduced during mixing, are mostly bound by the aluminate phase in ordinary Portland cement concrete. Carbonation releases the bound chlorides and can cause them to concentrate ahead of the carbonation front. The problems associated with chloride admixtures are closely linked to the extent of carbonation. Hence reinforcement, located within the carbonation zone, due to poor bar spacing, will be at a far greater risk of suffering chloride-induced corrosion.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 7 - REPORT REFERENCE: 12B/1394
8.0 DISCUSSION 8.3 Chloride Induced Corrosion (Continued) When steel is in a passive condition, its oxide film is believed to be in a state of dynamic equilibrium, constantly undergoing local, small breakdown and repair processes, more or less randomly over the surface. Chloride ions interfere with this process, the local environment inside the zone of film breakdown is transformed to an acidic, chloride-rich solution. This causes the anodic activity of the metal to increase locally so that the region develops into a pit, which grows in size leading to localised penetration of the metal. This localised degradation of embedded steel is known as pitting corrosion. It can lead to rapid loss of cross sectional area and load bearing capacity of the metal, as well as causing expansive forces which can cause spalling of the concrete. However, in some instances the volumetric expansion of the corrosion products is minimal compared with the section loss caused by the pit formation. This can lead to significant loss in section before obvious surface cracking or spalling is noticed. 9.0 CONCLUSIONS 9.1 Defect Survey The concrete is in a severely deteriorating condition, with a significant number of defects distributed across the elements surveyed. The greatest number of defects relates to spalling and cracked concrete. The masonry and render also exhibit significant cracking. 9.2 Concrete Investigation The results of the concrete condition survey indicate that concrete cover to reinforcement for the columns and beams is adequate as the likely specified minimum concrete cover of 20mm has generally been maintained. Carbonation depths can be considered as exceedingly variable and generally severely penetrating, with an average of 27mm across all elements. This indicates either a concrete of variable quality, with moderate level of porosity and/or the concrete is not being afforded adequate protection by applied finishes. Carbonation depth was found to exceed the level of reinforcement at fifty percent of locations investigated. This is as a result of excessively penetrating carbonation depths and not low concrete cover to reinforcement. The reinforcement at one column and two beam positions will now have lost passivity. For all remaining elements surveyed the reinforcement should still be in a passive condition, as regards carbonation. The chloride analysis results can also be considered low. This indicates that chlorides have not ingressed from an external source and/or have not been cast-in at the time of manufacture. A summary of the corrosion risk levels obtained for all samples is presented in the table overleaf.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 8 - REPORT REFERENCE: 12B/1394
9.0 CONCLUSIONS 9.2 Concrete Investigation (Continued)
Element
Neg
ligib
le
Lo
w
Mo
der
ate
Hig
h
Ver
y H
igh
Ext
rem
ely
Hig
h
Beams N.A. 1
(33%) 2
(67%)
Columns N.A. 2
(67%) 1
(33%)
Table 4: Corrosion risk summary 9.3 Petrographic Examination The petrographic examination report confirms the findings of the site investigative works in that:-
The concrete is in a severely deteriorating condition Deeply penetrating carbonation exists
The reason for the above relates to high original water: cement ratio for structural concrete with ferrous reinforcement. This has resulted in a high capillary porosity which allows carbonation penetration to exceed the depth of reinforcement. Due to loss of passivity, general corrosion of the reinforcement ensues, leading to concrete cracking and subsequent degradation. 10.0 RECOMMENDATIONS All concrete repairs should be specified and undertaken in accordance with methods and materials complying with BS EN 1504. As chloride levels within the concrete are low, repairs can be undertaken using standard concrete repair techniques and materials. Due to the level of deterioration the repairs are likely to be significant and classified as structural and temporary propping may have to be considered. In accordance with the above standard, class R3 and R4 repair mortars should be specified for any patch repairs undertaken. Where the concrete cover afforded to the reinforcement is inadequate additional protection should be considered. In some instances, this could be addressed by the application of an anti-carbonation coating. However, where concrete cover is very low, say <10mm, application of additional concrete cover could be achieved more economically by the use of a high specification proprietary polymer modified cementitious fairing coat. These types of coatings are typically applied in two layers with a minimum thickness of 2 to 3mm.
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES - 9 - REPORT REFERENCE: 12B/1394
10.0 RECOMMENDATIONS (continued) The control of further corrosion of the structure will rely on preventing additional carbonation and by reducing moisture levels to restrain corrosion rates. However, given the level of carbonation which has taken place and the general quality of the concrete used in the manufacture of the reinforced concrete elements, some continued deterioration is likely to occur and ongoing planned maintenance is likely to be considered necessary. We trust this report is to your satisfaction. If you require any further assistance please do not hesitate to make further contact. On behalf of: BIRMINGHAM CITY LABORATORIES
Prepared by: Verified by:
JOHN WALSH TREVOR BOX Senior Engineer Principal Engineer
TIC INTERNATIONAL LTD
APPENDIX 1DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
1 Front 1st Masonry Bottom centre Diagonal crack stepped through mortar 800 300 1 1
2 Front 1st Masonry Bottom left side Diagonal crack stepped through mortar 1200 420 1
3 Front Ground Masonry Top to bottom Vertical crack in mortar 3500 3 2
4 Front 1st Column Bottom right side Spalling concrete, exposed corroding reinforcement 500 130 50
5 Front 1st Column Top left side Spalling concrete, exposed corroding reinforcement 500 120 50
6 Front 1st Column Top right side Spalling concrete 150 50 10
7 Front Roof Beam Left side Previous investigation location 120 120 60
8 Front Roof Beam All Spalling concrete, exposed corroding reinforcement 1900 280 60
9 Front Roof Beam Right side Spalling concrete, exposed corroding reinforcement 290 150 25
10 Front 1st Masonry Right side Horizontal crack 1500 2
11 Front Ground Masonry Centre Eroding mortar joint 3000
12 Front 1st Column Top left side Spalling concrete, exposed corroding reinforcement 390 140 30
13 Front 1st Column Bottom left side Delaminating concrete 500 90
14 Front 1st Column Top right side Spalling concrete, exposed corroding reinforcement 600 180 35
15 Front 1st Column Bottom right side Spalling concrete, exposed corroding reinforcement 180 180 30
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 2DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
16 Front Roof Beam Centre Spalling concrete, exposed corroding reinforcement 3
17 Front 1st Beam Left side Multi directional cracking 400 300 1
18 Front 1st Beam Centre Vertical crack 400 1
19 Front Roof Beam Right side Spalling concrete, exposed corroding reinforcement 310 120 30
20 Front 1st Column Left side centre Spalling concrete, exposed corroding reinforcement 600 210 40
21 Front 1st Column Bottom left side Vertical crack (hollow) 290 2
22 Front 1st Column Right side centre Spalling concrete, exposed corroding reinforcement 390 200 50 4
23 Front Roof Beam All Spalling concrete, exposed corroding reinforcement 3000 300 50
24 Front Ground Column Centre Horizontal crack 300 1
25 Front Ground Column Centre Horizontal crack 320 1
26 Front 1st Beam Centre Vertical crack 500 1
27 Front 1st Beam Top left side Spalling concrete, exposed corroding reinforcement 400 200 30
28 Front 1st Column Bottom Vertical crack (hollow) 1200 2
29 Front 1st Column Top Vertical crack (hollow) 1500 2
30 Front 1st Column Top right side Spalling concrete, exposed corroding reinforcement 450 210 30
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 3DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
31 Front 1st Column Right side centre Spalling concrete 300 90 25
32 Front 1st Column Bottom right side Spalling concrete (around vent) 280 180 30
33 Front 1st Beam All Delaminating concrete 2200 250 20
34 Front 1st Beam All Vertical crack 300 1
35 Front Ground Column Bottom Previous investigation location 150 130 60
36 Front Roof Beam Centre Spalling concrete, exposed corroding reinforcement 2500 190 30
37 Front 1st Column Top Spalling concrete, exposed corroding reinforcement 250 200 20
38 Front 1st Column Left side Spalling concrete, exposed corroding reinforcement 1800 200 40
39 Front 1st Column Right side Spalling concrete, exposed corroding reinforcement 1800 200 40 5
40 Front Roof Beam Left side Spalling concrete, exposed corroding reinforcement 350 200 50 6
41 Front Ground Column Top Spalling concrete, exposed corroding reinforcement 400 350 40
42 Front 1st Beam Left side Spalling concrete 80 80 20
43 Front 1st Beam Centre Spalling concrete 80 80 20
44 Front 1st Beam Centre Spalling concrete 80 80 20
45 Front 1st Beam Right side Spalling concrete 80 80 20
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 4DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
46 Front 1st Beam Centre Vertical crack 500 1
47 Front Ground Column Top Spalling concrete, exposed corroding reinforcement 700 120 50
48 Front Ground Column Centre Spalling concrete, exposed corroding reinforcement 220 90 30
49 Front Roof Beam Left side Spalling concrete, exposed corroding reinforcement 250 80 20
50 Front Roof Beam Centre Spalling concrete, exposed corroding reinforcement 900 130 30
51 Front 1st Column Top Spalling concrete, exposed corroding reinforcement 300 100 20 7
52 Front 1st Column Centre Spalling concrete, exposed corroding reinforcement 550 180 50
53 Front Roof Beam All Spalling concrete 1700 200 30 8
54 Front 1st Beam Left side Vertical crack 500 1
55 Front 1st Beam Left side Vertical crack 500 1
56 Front 1st Beam Centre Vertical crack 500 1
57 Front 1st Beam Centre Vertical crack 500 1
58 Front 1st Beam Right side Vertical crack 500 1
59 Front 1st Beam Left side Spalling concrete 100 80 20
60 Front 1st Beam Centre Spalling concrete 100 80 20
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 5DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
61 Front Ground Column Right side centre Spalling concrete, exposed corroding reinforcement 310 100 30
62 Front 1st Beam Left side Spalling concrete, exposed corroding reinforcement 510 120 80
63 Front 1st Beam Centre Spalling concrete 1300 120 20
64 Front 1st Beam Centre Multi directional cracking 1300 120 20
65 Front Ground Column Right side centre Vertical crack 400 1
66 Front Ground Column Top Vertical crack over previous repair 450 1
67 Front Roof Beam All Spalling concrete, exposed corroding reinforcement 1700 200 40
68 Front Ground Column Top Spalling concrete, exposed corroding reinforcement 500 160 50
69 Front 1st Beam Left side Multi directional cracking 500 500 HL 9
70 Front 1st Beam All Spalling concrete, exposed corroding reinforcement 1100 400 40 10
71 Front Ground Column Bottom Spalling concrete, exposed corroding reinforcement 250 200 40
72 Front Ground Column Bottom Spalling concrete, exposed corroding reinforcement 250 200 40
73 Front 1st Column Top right side Vertical crack over previous repair (hollow) 320 1
74 Rear Ground Column Top Vertical crack 600 1
75 Rear Ground Column Top Spalling concrete 50 50 10
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 6DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
76 Rear 1st Beam Top left side Spalling concrete, exposed corroding reinforcement 310 100 40
77 Rear 1st Beam Top right side Spalling concrete 100 30 10
78 Rear 1st Beam Right side Vertical crack 500 1
79 Rear 1st Column Centre Vertical crack (hollow) 350 1
80 Rear 1st Column Centre Vertical crack (hollow) 350 1
81 Rear 1st Beam Bottom left side Spalling concrete, exposed corroding reinforcement 450 190 100 11
82 Rear 1st Beam Centre Spalling concrete 100 80 20
83 Rear 1st Beam Centre Spalling concrete 100 80 20
84 Rear Roof Beam Centre Vertical crack 250 HL
85 Rear Roof Beam Centre Vertical crack 250 HL
86 Rear 1st Column Top Vertical crack 310 HL
87 Rear 1st Column Centre Vertical crack (hollow) 340 1 12
88 Rear 1st Beam Left side Spalling concrete 50 50 20
89 Rear 1st Beam Centre Vertical crack 500 1
90 Rear 1st Beam Centre Vertical crack 500 1
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 7DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
91 Rear 1st Beam Centre Vertical crack 500 1
92 Rear 1st Beam Right side centre Spalling concrete, exposed corroding reinforcement 650 230 50 13
93 Rear Roof Beam Right side Vertical crack 250 1
94 Rear 1st Beam Centre Vertical crack 500 1
95 Rear 1st Beam Centre Vertical crack 500 1
96 Rear 1st Beam Centre Vertical crack 500 1
97 Rear 1st Beam Bottom centre Spalling concrete, exposed corroding reinforcement 850 100 30
98 Rear Ground Column Top left side Spalling concrete, exposed corroding reinforcement 500 250 30 14
99 Rear 1st Column Right side Vertical crack (hollow) 400 1
100 Rear Roof Beam Centre Vertical crack 250 HL
101 Rear Roof Beam Centre Vertical crack 250 HL
102 Rear Roof Beam Centre Vertical crack 250 1
103 Rear 1st Beam Centre Spalling concrete 80 40 10
104 Rear 1st Beam Centre Spalling concrete 80 40 10
105 Rear 1st Beam Centre Spalling concrete 80 40 10
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 8DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
106 Rear Ground Column Top Spalling concrete, exposed corroding reinforcement 280 150 20
107 Rear Ground Column Centre Vertical crack (hollow) 750 1-2
108 Rear 1st Beam Centre Vertical crack over previous repair 150 HL
109 Rear Roof Beam Left side Vertical crack 250 HL
110 Rear Roof Beam Left side Vertical crack 250 HL
111 Rear 1st Beam Bottom right side Spalling concrete, exposed corroding reinforcement 380 250 50 15
112 Rear 1st Beam Bottom centre Vertical crack over previous repair 160 HL
113 Rear 1st Beam Bottom centre Vertical crack over previous repair 160 HL
114 Rear 1st Beam Bottom centre Vertical crack over previous repair 160 HL
115 Rear Ground Column Bottom right side Spalling concrete, exposed corroding reinforcement 350 130 30 16
116 Rear Ground Column Top Vertical crack (hollow ) 350 1
117 Rear Ground Column Top Vertical crack (hollow ) 350 1
118 Rear Ground Column Top Vertical crack (hollow ) 350 1
119 Rear 1st Column Bottom right side Spalling concrete 190 80 20
120 Rear 1st Column Right side centre Vertical crack (hollow ) 320 1
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 9DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
121 Rear 1st Column Left side centre Spalling concrete, exposed corroding reinforcement 350 120 30
122 Rear 1st Column Left side centre Vertical crack over previous repair (hollow) 550 1
123 Rear Roof Beam Centre Vertical crack 250 HL
124 Rear Roof Beam Centre Vertical crack 250 HL
125 Rear Roof Beam Centre Vertical crack 250 HL
126 Rear 1st Beam Right side Vertical crack 450 1 17
127 Rear Ground Column Centre Vertical crack 390 1
128 Rear Ground Column Centre Horizontal crack 390 1 18
129 Rear Ground Column Bottom Horizontal crack 230 1
130 Rear 1st Column Centre Horizontal crack 240 1
131 Rear Roof Beam Right side Spalling concrete, exposed corroding reinforcement 180 100 20
132 Right Roof Beam Top left side Spalling concrete, exposed corroding reinforcement 300 200 20
133 Right Roof Beam Top left side Spalling concrete, exposed corroding reinforcement 300 200 20
134 Right Roof Beam Top left side Spalling concrete, exposed corroding reinforcement 300 200 20
135 Right Roof Beam Centre Spalling concrete, exposed corroding reinforcement 250 200 20
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 10DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
136 Right Roof Beam Centre Spalling concrete, exposed corroding reinforcement 250 200 20
137 Right Roof Beam Centre Spalling concrete, exposed corroding reinforcement 250 200 20
138 Right Roof Beam Right side Spalling concrete 100 80 10
139 Right Roof Beam Right side Spalling concrete, exposed corroding reinforcement 350 250 20
140 Right 1st Beam Right side Spalling concrete, exposed corroding reinforcement 350 300 30
141 Right Ground Column Top right side Vertical crack (hollow) 450 1
142 Left 1st Render (beam) Left side Vertical crack 150 HL
143 Left 1st Render (beam) Left side Vertical crack 150 HL
144 Left 1st Render (beam) Left side Vertical crack 150 HL
145 Left 1st Render (beam) Left side Vertical crack 450 1
146 Left 1st Render (beam) Left side Vertical crack 450 1
147 Left Roof Render (beam) Left side Vertical crack 500 1
148 Left Roof Render (beam) Left side Vertical crack 500 1
149 Left Roof Render (beam) Centre Vertical crack 500 HL
150 Left Roof Render (beam) Centre Vertical crack 500 HL
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD
APPENDIX 11DEFECT RESULTS
ISLAMIC RELIEF CENTRE
W L D
Photo Ref.
Defect Ref.
Size (mm)Elevation Floor Item Affected Approx Location Defect Details
151 Left 1st Render (beam) Centre Vertical crack 500 HL
152 Left 1st Render (beam) Centre Vertical crack 500 HL
153 Left 1st Render (beam) Centre Vertical crack 500 HL
154 Left 1st Render (beam) Centre Vertical crack 500 HL
155 Left 1st Render (beam) Centre Vertical crack 500 1
156 Left Roof Render (beam) Centre Vertical crack 500 HL
157 Left Roof Render (beam) Centre Vertical crack 500 HL
158 Left Roof Render (beam) Centre Vertical crack 500 HL
159 Left Roof Render (beam) Centre Vertical crack 500 HL
160 Left Roof Render (beam) Centre Vertical crack 500 HL
161 Left Roof Render (beam) Right side Diagonal crack (hollow) 650 1
162 General note; approx 50% left gable render hollow
BIRMINGHAM CITY LABORATORIESKEY
HL = Hairline Crack REPORT REFERENCE: 12B/1394
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 12 DEFECT PHOTOGRAPHS
Photograph 1 – Defect 1 masonry diagonal stepped crack
Photograph 2 – Defect 2 masonry vertical crack
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BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 13 DEFECT PHOTOGRAPHS
Photograph 3 – Defect 16 roof beam spalling concrete, exposed corroding reinforcement
Photograph 4 – Defect 22 column spalling concrete, exposed corroding reinforcement
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 14 DEFECT PHOTOGRAPHS
Photograph 5 – Defect 39 column spalling concrete, exposed corroding reinforcement
Photograph 6 – Defect 40 beam spalling concrete, exposed corroding reinforcement
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 15 DEFECT PHOTOGRAPHS
Photograph 7 – Defect 51 column spalling concrete, exposed corroding reinforcement
Photograph 8 – Defect 53 roof beam spalling concrete, exposed corroding reinforcement
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 16 DEFECT PHOTOGRAPHS
Photograph 9 – Defect 69 beam multi directional cracking
Photograph 10 – Defect 70 roof beam spalling, exposed corroding reinforcement
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 17 DEFECT PHOTOGRAPHS
Photograph 11 – Defect 81 beam spalling, exposed corroding reinforcement
Photograph 12 – Defect 87 column vertical crack
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 18 DEFECT PHOTOGRAPHS
Photograph 13 – Defect 92 beam spalling, exposed corroding reinforcement
Photograph 14 – Defect 98 column spalling, exposed corroding reinforcement
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 19 DEFECT PHOTOGRAPHS
Photograph 15 – Defect 111 beam spalling, exposed corroding reinforcement
Photograph 16 – Defect 115 column spalling, exposed corroding reinforcement
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE 12B/1394
APPENDIX 20 DEFECT PHOTOGRAPHS
Photograph 17 – Defect 126 beam vertical crack
Photograph 18 – Defect 128 vertical crack in column
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE: 12B/1394
APPENDIX 21
EXTERNAL BEAMS
CONCRETE COVER TO REINFORCEMENT, CARBONATION DEPTH & CHLORIDE RESULTS
Max Mean
4 44 52 60 23 35 23 9.7 0.01 0.10 LowHorizontal 10mm dia plain round bar with surface corrosion
6 48 55 45 74 76 45 9.7 0.01 0.10 ModerateVertical 30mm sq twist
bar with surface corrosion
9 53 49 45 50 45 9.7 0.01 0.10 ModerateReinforcement not
examined
Bold red type indicates reinforcement located within carbonated concreteSample 9 analysed for cement content.
Reinforcement Details
Sa
mp
le
Minimum Concrete Cover
to Vertical Reinforcement
(mm)
Minimum Concrete Cover
to Horizontal Reinforcement
(mm)
Minimum Concrete
Cover (mm)
Cement Content
by Weight of Sample
(%)
Depth of Carbonation
(mm)
Chloride Content
By Weight of Sample
(%)
Chloride Content
By Weight of Cement
(%)
Corrosion Risk Level
12
>50
>50
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE: 12B/1394
APPENDIX 22
EXTERNAL COLUMNS
CONCRETE COVER TO REINFORCEMENT, CARBONATION DEPTH & CHLORIDE RESULTS
Max Mean
5 52 58 51 50 48 48 10.8 0.01 0.09 LowVertical 16mm dia plain round bar with surface
corrosion
7 41 43 41 36 38 36 10.8 0.02 0.19 ModerateVertical 16mm dia plain round bar with surface
corrosion
8 35 28 30 35 34 28 10.8 0.02 0.19 LowVertical 30mm dia plain round bar with surface
corrosion
Bold red type indicates reinforcement located within carbonated concreteSample 7 analysed for cement content.
Sa
mp
le
Minimum Concrete Cover
to Vertical Reinforcement
(mm)
Minimum Concrete Cover
to Horizontal Reinforcement
(mm)
Minimum Concrete
Cover (mm)
Cement Content
by Weight of Sample
(%)
Depth of Carbonation
(mm)
Chloride Content
By Weight of Sample
(%)
7
25
38
Reinforcement Details
Chloride Content
By Weight of Cement
(%)
Corrosion Risk Level
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BIRMINGHAM CITY LABORATORIES REPORT REFERENCE: 12B/1394
APPENDIX 23
EXPOSED REINFORCEMENT BAR DIRECTION & CONDITION
4 Front 1st Column Vertical plain round bar 16mm dia, approximately 2mm section loss
8 Front Roof Beam Horizontal plain round bar 16mm dia, surface corrosion
8 Front Roof Beam Vertical square 20mm bar, surface corrosion
9 Front Roof Beam Vertical plain round bar 8mm dia, surface corrosion
14 Front 1st Column Vertical plain round bar 16mm dia & horizontal plain round bar 8mm dia, surface corrosion
16 Front Roof Beam Horizontal plain round bar 20mm dia, approximately 2mm section loss
19 Front Roof Beam Horizontal plain round bar 20mm dia, approximately 2mm section loss
20 Front 1st Column Vertical plain round bar 10mm dia & horizontal plain round bar 6mm dia, surface corrosion
23 Front Roof Beam Vertical square bar 20mm & horizontal plain round bar 16mm dia, surface corrosion
39 Front Ground Column Vertical plain round bar 20mm dia, approximately 2mm section loss
59 Front 1st Beam Vertical square bars 25, scaling & 2mm section loss
63 Rear 1st Beam Horizontal plain round bar 12mm dia, approximately 2mm section loss
67 Rear 1st Beam Horizontal plain round bar 16mm dia, approximately 2mm section loss
74 Rear 1st Beam Horizontal plain round bar 16mm dia, approximately 2mm section loss
77 Rear 1st Beam Horizontal plain round bar 16mm dia, approximately 2mm section loss
Defect Ref.
Elevation FloorItem
AffectedDefect Details
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE: 12B/1394
APPENDIX 24
EXPOSED REINFORCEMENT BAR DIRECTION & CONDITION
78 Rear Ground Column Horizontal plain round bar 16mm dia, approximately 2mm section loss
88 Rear 1st Beam Horizontal plain round bar 16mm dia, approximately 1mm section loss
90 Rear Ground Column Horizontal plain round bar 16mm dia, approximately 2mm section loss
94 Rear 1st Column Vertical plain round bar 16mm dia, approximately 2mm section loss
101 Rear Roof Beam Horizontal plain round bar 16mm dia, approximately 2mm section loss
105 Right Roof Beam Vertical square bars 30mm, scaling & 1mm section loss
106 Right 1st Beam Vertical square bars 30mm, surface corrosion
Defect DetailsDefect
Ref.Elevation Floor
Item Affected
TIC INTERNATIONAL LTD ISLAMIC RELIEF CENTRE
BIRMINGHAM CITY LABORATORIES REPORT REFERENCE: 12B/1394
APPENDIX 25
CARBONATION DEPTHS
Max Mean
4 Beam Front Elevation
5 Column Front Elevation
6 Beam Rear Elevation
7 Column Rear Elevation
8 Column Rear Elevation
9 BeamRight (East) Gable
Elevation
Bold red type indicates reinforcement located within carbonated concrete
>50
7
12
25
>50
38
ElementSample Location
Depth of Carbonation (mm)
PETROGRAPHICREPORT
DEGRADEDCONCRETETHEISLAMICRELIEFCENTRE49LANDORSTREETBIRMINGHAMB81AG
REPORTNUMBER:12B‐1394
Dr Alan Bromley
Aston Services
Report for Birmingham City Laboratories
Ref: BCL/PR/020113
2 January 2013
PETROGRAPHICREPORT
DEGRADEDCONCRETETHEISLAMICRELIEFCENTRE49LANDORSTREETBIRMINGHAMB81AG
REPORTNUMBER:12B‐1394
CONTENTS
1 Samples........................................................................................................................................1
2 Methods of Investigation.............................................................................................................3
3 Petrography..................................................................................................................................4
3.1 Composition of the Concrete.............................................................................................43.2 Aggregates..........................................................................................................................53.3 Binder.................................................................................................................................63.4 Voids...................................................................................................................................73.5 Fractures.............................................................................................................................8
4 Summary and Conclusions...........................................................................................................9
Appendix 1..............................................................................................................................................10
Plates 1 ‐ 3........................................................................................................................................12 ‐ 14
PETROGRAPHICREPORT
DEGRADEDCONCRETETHEISLAMICRELIEFCENTRE49LANDORSTREETBIRMINGHAMB81AG
REPORTNUMBER:12B‐1394
1 SAMPLES
Two samples of concrete, from a beam and column, were provided for petrographic investigation and analysis. Brief sample details are presented in table 1.
Table 1. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Sample details.
Sample number Dimensions (mm) Mass (g) Surface Reinforcement Depth to reinforcement
12B‐1394 02 core: 75 (diam) x 90 762 plain finish 5 mm wire 45 mm
12B‐1392 03 chisel: 160 x 80 x 45 693 plain finish not identified 40 mm
Both samples are from the same type of concrete. It is made with crushed epidosite coarse aggregate, quartz sand and Portland Cement. The binder is uniform pale red in colour (Munsell Colour Index = 10YR 7/3). There is no segregation of the major components. There is no laitance. There are occasional clusters of large complex voids near the surface of the concrete in sample 12B‐1394 02 but there are no zones of honeycombing.
Surface‐related carbonation extends to a depth of at least 35 mm in sample 12B‐1394 02. The carbonation front is irregular and there are apparently isolated patches of carbonated binder at deeper levels in the core. The binder in sample 12B‐1394 04 is completely carbonated.
There are no fractures in sample 12B‐1394 02 and the wire at 45 mm is only superficially corroded. Discontinuous open fissures at the margins of coarse aggregate fragments are common and easily visible in hand specimen. Two faces of chisel sample 12B‐1394 03 are bounded by open fractures that originate from corroded reinforcement at a depth of 40 mm. The concrete adjacent to the corroded metal is iron oxide‐impregnated for a distance of 1 mm – 2 mm.
Photographs of the structure, provided by Mr John Walsh, City of Birmingham Laboratories, show the concrete is severely degraded (figures 1 – 4). Beams and columns show severe cracking, spalling and pop‐outs that often expose strongly corroded reinforcement. Paint on the concrete is cracked and badly flaked. There have been previous attempts at local repair (figures 1C and 1D). The repair mortar is locally cracked parallel with earlier failures, suggesting continued corrosion and expansion of the underlying reinforcement.
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Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
Figure 1. Concrete degradation. The Islamic Relief Centre, 49 Landor Street, Birmingham.
A Predominantly longitudinal fractures on surface of column, typical of expansion associated with corrosion of reinforcing bars.
B Severe spalling and cracking in beam above window opening.
C Repair mortar covering junction between column and beam. Cracking has continued after application of new mortar.
D Severe cracking and fall‐out of concrete at edge of column adjacent to a window opening. Repair mortar, applied between the column and the brick panel, has also cracked. Paintwork is in very poor condition.
Page 2
A B
C D
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
2 METHODSOFINVESTIGATION
Preliminaryinvestigation
Both samples were examined as received, and after removal of loose debris, using a Nikon SMZ‐U stereomicroscope. The microscope has a continuous zoom range of 7.5x to 75x and it is equipped with a 150W continuous ring, fibre optic illuminator. It is useful for the preliminary examination of samples and it is possible to discriminate and sometimes identify features as small as 100 µm in size. The microscope has a trinocular head and can be used for low power photomicrography.
Samplepreparation
Core sample 12B‐1394 02 was sawn in half parallel with its axis. Chisel sample 12B‐1394 03 was sawn normal to the surface of the concrete and arranged to include iron oxide‐impregnated binder adjacent to the corroded reinforcement. The cut face of one part of each sample was carefully ground, finishing with #900 grit carborundum powder. Digital images of ground surfaces were prepared using a flat bed scanner operating at a scan resolution of 1200 dpi. These images are useful for illustrating the general structure of the concrete and the position of any major fractures.
A single 75 mm x 50 mm thin section was prepared from the remaining part of each sample. Section 12B‐1394 02 was oriented parallel with the core axes and section 12B‐1394 03 was positioned normal to the surface of the concrete.
Sub‐samples, used for thin section preparation, were impregnated with epoxy resin containing yellow dye. This facilitates the identification of small voids, fractures and regions of porous binder. A high resolution, low magnification digital image of each section was prepared using a Nikon 9000 Superscan film scanner operating at a scan resolution of 4,000 dpi (plate 1). These images are useful for identifying and illustrating the lithologies of the aggregate and sand and assessing the general structure of the concrete.
Thinsectionexamination
Both sections were examined by conventional transmitted light microscopy and by reflected light fluorescent microscopy using a Nikon E600 Eclipse research polarising microscope. It is fitted with six strain free objectives having primary magnifications of 2.5, 5, 10, 20, 40 and 60. Digital photomicrographs were taken using a Nikon DS‐U1 five megapixel camera fitted to the trinocular head of the microscope. Image enhancement and processing were carried out using Adobe Photoshop CS6 Extended and Fovea Pro 4.0 image processing and analysis software.
Quantitativeinvestigations
Modal analyses were performed using a Conwy Valley Systems automatic stepping stage with Petrog® control software. The stage is capable of traversing the full area of the 75 mm x 50 mm thin sections at stepping and traverse intervals determined by the total count. One thousand points were counted from each thin section. Water:cement ratio was estimated by comparing the fluorescent intensity of the least altered uncarbonated paste in sample 12B1394 02 with that of standard mortars when viewed under high intensity reflected ultraviolet illumination.
Page 3
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
3 PETROGRAPHY
Both samples are from the same type of concrete. It is made with crushed epidosite (coarse aggregate), quartz‐dominated sand and Portland Cement, probably OPC. There is no evidence for the presence of cement replacements or admixtures though it should be noted that the latter are very difficult to identify by petrographic methods.
3.1 COMPOSITIONOFTHECONCRETE
The volumetric composition of the concrete was determined by modal analysis (point counting). One thousand points were counted from each thin section. Data are presented in table 2.
Table 2. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Modal analyses.
Sample number Coarse aggregate Sand Binder Voids
12B‐1394 02 41.3 19.6 37.5 1.6
12B‐1394 03 40.7 19.2 37.5 2.6
Mean composition 41.0 19.4 37.5 2.1
Water:cement ratio was estimated by comparing the fluorescent intensity of the dye‐impregnated uncarbonated paste with that in thin sections of standard mortars when viewed under reflected high intensity ultraviolet illumination. Only a small area of thin section 12B‐1394 02 was suitable for the determination so results should be treated with caution. A range of values between approximately 0.6 and 0.8 were obtained. Water:cement ratio = 0.70 was used for the mix design estimation (table 3).
Table 3. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Estimated mix design.
Component Volume percent
Density (kgm3)
Estimated mix design
Coarse aggregate 41.0 2670 Coarse aggregate 1095 kgm3
Fine aggregate 19.4 2620 Fine aggregate 508 kgm3
Binder 37.5 3140 Cement 368 kgm3
Voids 2.1 Water 258 kgm3
Total 100.0 Density 2229 kgm3
Cement content 16.5 %
Fluorescent intensity equivalent 0.6 – 0.8 Slump 60 ‐ 180 mm
Water:cement ratio 0.70 28‐day strength 31 N/mm2
Maximum aggregate size (mm) 12 crushed
No petrographic evidence for presence of plasticiser
Cement content of two samples were chemically determined by City of Birmingham Laboratories (Mr John Walsh – personal communication).
12B‐1394 04 (beam) 7.9%12B‐1394 07 (column) 10.8%
Page 4
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
The discrepancy between petrographically‐estimated and chemically‐determined cement content cannot be explained. The aggregate and sand are chemically stable and unlikely to interfere with the chemical analyses. Modal analyses of the two samples are very similar. The estimated volumetric composition is not influenced, for example, by local segregation of a major component. This aspect of the study requires further investigation.
3.2 AGGREGATES
The main features of the coarse aggregate and sand are summarised in table 4 and illustrated by plate 1.
Table 4. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Aggregates.
Aggregates gap‐graded
Coarse aggregate epidotised quartz – feldspar porphyry (epidosite) Abundance 41.0%
Major components quartz, epidote, chlorite, plagioclase feldspar
Minor components magnetite, leucoxene
Size range 2.5 mm to 12 mm Average 7.5 mm
Grading good Rounding angular
Shape equant – oblate Sphericity low
Fine aggregate quartz‐dominated sand Abundance 19.4%
Major components quartz from acid igneous rocks, sandstone, quartzite and veins
Minor components chert (1% ‐ visual estimate), stable silicates (tourmaline, muscovite, K‐feldspar, glauconite), iron oxide
Size range 100 µm to 400 mm Average 300 µm
Grading good Rounding sub‐angular ‐ spherical
sub‐spherical morphologies predominate
Shape mainly equant Sphericity moderate – high
Percentage passing 600 µm > 90% (Visual estimate)
The coarse aggregate is a quarried product of unusual composition. Its provenance is not known. It contains no minerals that are normally considered reactive when used as concrete aggregate and there is no evidence of in situ instability or reaction with pore fluids in the concrete.
The sand contains about 1% chert. This is considered potentially reactive in terms of alkali – silica reaction (ASR). There is no petrographic evidence of in situ instability of chert or any other components of the sand in this concrete.
Page 5
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
3.3 BINDER
The binder is made with Portland Cement, probably OPC. In sample 12B‐1394 02 maximum surface‐related carbonation penetration is about 35 mm. The carbonation front is irregular and there are some apparently isolated patches of carbonated paste at deeper levels in the concrete. The binder in sample 12B‐1394 03 is completely carbonated. Mineralogical and textural features of the uncarbonated binder suggest the concrete is between about 40 and 60 years old. Its main properties are summarised in table 5 and illustrated by plate 2.
Table 5. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Uncarbonated paste.
Binder
Cement type Portland Cement (probably OPC)
Replacement none found
Optical properties of least altered paste Munsell Colour Index
Colour (thin section) medium brown (often opaque) Isotropy weakly anisotropic
Texture mottled Disseminated calcite replaced portlandite locally
Dye absorption variable, generally strong Fluorescence variable, generally strong
Portlandite
In paste present Distribution irregular
Maximum size (µm) 75 Shape mainly tabular
Replacement calcite
At aggregate margins common Distribution irregular
Maximum size (µm) 50 Shape outgrowths
Replacement dissolution, calcite
Cement clinker grains alite ~ belite
Alite common Maximum size (µm) 50
Max. birefringence not determined Colour colourless
Hydration completely hydrated Reaction rims broad brown rims (common)
Alite (clusters) present Maximum size (µm) 300
Matrix dark brown ferrite‐rich glassy phase, granular iron oxide
Hydration variable, weak – strong Reaction rims broad brown – opaque rims (common)
Belite common Maximum size (µm) 50
Max. birefringence not determined Colour dull brown
Hydration moderately hydrated Reaction rims narrow opaque rims
Belite (clusters) common Maximum size (µm) 250
Matrix sparse brown glassy phase
Hydration weak – strong Reaction rims narrow opaque rims
Ferrite/ferrite‐rich glass present Maximum size (µm) 30
Alteration strongly oxidised Colour dark brown ‐ opaque
Other minerals unidentified blue‐green crystalline phase in some alite clusters
Page 6
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
The main properties of the carbonated paste in both samples are summarised in table 6.
Table 6. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Carbonated binder.
Carbonated Binder
Transition zones complex, irregular (sample 12B‐1394 02)
Carbonation fronts diffuse
Width of transition zones 250 µm – 1 mm (weak anisotropy of uncarbonated paste suggests widespread incipient carbonation)
Mineralogy and texture
Colour pale yellowish brown – medium brown Texture furfuraceous
Calcite size range 1 µm to 10 µm Porosity variable, locally very high
Relict clinker grains common (replaced by CSH, calcite and opaque iron oxides)
Residual gel irregular patches up to 100 µm maximum size
Granular iron oxide abundant (flakes and irregular grains up to 50 µm maximum size)
Microporosity variable, generally high – very high Pore size range 5 µm to 200 µm
Secondary minerals microcrystalline calcite
Dye absorption strong Fluorescent intensity high
Mineralogical and textural features of the uncarbonated paste (12B‐1394 02) suggest the concrete is between about 40 and 60 years old. These include presence of coarse cement clinker grain clusters and high belite content (plate 2A and B). Fineness and alite:belite ratio have increased progressively over several decades. The fluorescent intensity of the paste is variable but generally high, indicating high water:cement ratio. Portlandite is only moderately abundant and its crystal size is smaller than that usually found in old concrete made at high water:cement ration (plate 2C). This may be partly explained by leaching. Both uncarbonated and carbonated binders have high secondary microporosity and peripheral fissures are common locally round coarse aggregate fragments. The latter are almost certainly a result of dissolution of portlandite.
There is no obvious petrographic evidence of abnormal set. There is no post‐hardening degradation other than that related to deeply‐penetrating carbonation and corrosion of reinforcement.
3.4 VOIDS
The main properties of the air void system are summarised in table 7.
Table 7. Concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham. Voids.
Void system
Mean modal volume 2.1% Shape spherical ‐ sub‐spherical
spherical voids predominate
Size range 100 µm to 2.5 mm Average size 500 µm
Distribution regular (visual assessment)
Interconnectivity generally isolated
Secondary void filling minerals in uncarbonated paste
Minerals calcite Abundance trace
Secondary void filling minerals in carbonated paste
Minerals calcite Abundance present
Page 7
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
There is no excessive voidage or zones of honeycombing. There are no secondary minerals in voids that might indicate aggregate – cement reaction or degradation resulting from ingress of reactive fluids (soluble sulphate or chloride).
3.5 FRACTURES
There are no fractures in core sample 12B‐1394 02.
Two faces of sample 12B‐1394 03 are bounded by open fractures that originate from corroded reinforcement and extend to the surface of the concrete.
Fracture aperture cannot be assessed. They follow the margins of coarse aggregate fragments rather than cutting through them. Their walls are coated with 50 µm – 100 µm thick layers of brown iron oxide for a distance of 1 mm – 2 mm from their point of origin at the edge of the corroded reinforcement (plate 3A). Carbonated paste adjacent to the walls is impregnated with iron oxide. Binder at the edge of the sample, presumably adjacent to the reinforcement is similarly impregnated with iron oxide.
A few subsidiary fractures branch and reunite with the major open fractures. They have apertures between a few micrometres and about 500 µm (plate 3B). Some cut impartially through aggregate fragments and the binder (plate 3C). Most of the subsidiary fractures are open but a few are partially‐filled with secondary calcite (plate 3D).
Page 8
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
4 SUMMARYANDCONCLUSIONS
1. Two samples of concrete from the Islamic Relief Centre, 49 Landor Street, Birmingham were submitted for petrographic examination and analysis.
2. The samples are from a reinforced beam and column respectively.
3. Photographs of the structure (Mr John Walsh, City of Birmingham Laboratories – personal communication) show severe cracking and spalling of the concrete that appears to be associated with corrosion of reinforcement and concomitant expansion.
4. Both samples are from the same type of concrete.
5. The concrete is made with crushed epidosite (coarse aggregate), quartz‐dominated sand and Portland Cement, probably OPC.
6. There is no petrographic evidence of in situ aggregate instability or of abnormal set.
7. There is no excessive voidage.
8. The mix design is within normal limits though the water:cement ratio, and hence the capillary porosity of the paste, is high for concrete with ferrous reinforcement.
9. Reinforcement is placed at a depth of circa 40 mm.
10. Because of the high capillary porosity carbonation penetration commonly exceeds the depth of placement of ferrous reinforcement.
11. In concrete with uncarbonated paste ferrous reinforcement is rendered passive and protected from corrosion by the high pH of pore fluids.
12. When the binder is carbonated the pH of pore fluids falls from > 12 to about 8.5. The reinforcement is no longer protected and, in the presence of atmospheric oxygen and moisture, it begins to corrode with concomitant expansion and cracking of the enclosing concrete.
13. Cracking facilitates ingress of air and moisture so if no remedial action is taken the rate of deterioration may accelerate.
14. Degradation may be exacerbated in severe winter conditions by freeze – thaw action of water trapped in the fractures.
15. This concrete is in poor condition for the following reasons.
● The paste has high capillary porosity and this has permitted deep carbonation.
● Ferrous reinforcement is placed too close to the surface of the concrete (approx. 40 mm).
● Photographs of the structure suggest it has not always been well‐maintained.
16. This petrographic investigation suggests concrete from beams and columns at the Islamic Relief Centre, 49 Landor Street, Birmingham needs immediate remedial treatment and local replacement.
17. In terms of the scheme of concrete classification provided by Eden (2010) this concrete is assigned to grades 5 – 8 (Appendix 1. Table 8). In the classification system used by this laboratory it is placed in Class B2/C (Appendix 1. Table 9).
Page 9
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
Appendix 1 – Classification of Concrete
A classification scheme for concrete degradation by petrographic investigation and analysis is outlined in A Code of Practice for the Petrographic Examination of Concrete (Eden, M.A., SR2, Geological Society of London, 2010). Details are presented in table 8.
Table 8. Grades of concrete degradation.
Coherent concrete with no macroscopic evidence of deterioration
1Normal homogeneous concrete with few microcracks. Void content in keeping with the amount of paste. Paste structure in keeping with water:cement ratio. Paste abundance in keeping with water:cement ratio.
2Slight deterioration, possibly through slight excess voidage, excess microcracking, uneven paste composition, low levels of alkali – aggregate reaction, drying shrinkage, low temperature curing, possibly slightly lean mixture.
3Moderately low deterioration, possibly with enhanced voidage, microcracking frequency fairly high, excessive paste porosity, evidence of leaching or other forms of secondary alteration, possible lean mixture.
Coherent concrete with macroscopic evidence of degradation
4Moderate deterioration, possibly with evident macrocracking or fine cracking, enhanced voidage, high frequencies of microcracking or fine cracks, evidence of significant leaching or other forms of secondary alteration, evidence of ettringite in cracks and voids, evidence of significant alkali – aggregate reaction with gel in cracks.
5Moderate deterioration, possibly with much fine cracking and some macrocracking, very high excess voidage, evidence of paste recrystallisation, excessive porosity, carbonation highly penetrative, evidence of significant alkali – aggregate reaction in some abundance.
6 As for 5, but with enhanced level of deterioration but with concrete remaining intact.
Concrete lacks coherence and is friable or readily decomposed
7 Concrete shows deterioration and may be partly decomposed or friable.
8 As 7, but enhanced friability and tending to break into fragments. Loose aggregate particles, honeycombed.
9 As 8, but enhanced deterioration. Much cracking and fragmentation.
10 All cementitious value, coherence and strength lost.
The system is complicated and often difficult to apply, especially if only one thin section is available per sample. For this reason a simplified three‐fold classification is offered here (Table 9). Each class of concrete corresponds approximately with the major divisions presented in the code of practice.
It must be remembered that petrographic classification of concrete is often based on intensive investigation of a thin section measuring only about 65 mm x 40 mm and more general study of a single core or other sample with a mass of about one kilogramme. Even good quality concrete has some short‐range inhomogeneity. Severely degraded material may grade into apparently sound concrete over distances of a few tens of millimetres.
Page 10
Petrographic Report Degradation of Concrete 49 Landor Street, BirminghamReport Number: 12B‐1394
Successful application of petrographic classification is heavily dependent on the quality of fieldwork and careful selection of an adequate number of sample positions.
Table 9. A simplified scheme for the petrographic classification of hardened concrete.
Class A concrete. The concrete is petrographically sound. (All of the following conditions are satisfied.)
The petrographically estimated mix design is within acceptable limits.
There is no evidence of in situ aggregate instability.
There is no excessive segregation of the major components of the concrete.
There is no excess voidage or zones of honeycombing.
Carbonation penetration is not excessive and must be less than the depth of placement of any reinforcement.
There is no significant corrosion of ferrous reinforcement.
There is no macro‐ or microcracking other than low density shrinkage microcracking.
There is no replacement of the binder by secondary minerals or gel.
There is no extensive growth of secondary minerals or gel in voids.
Class B1 concrete. The concrete shows petrographic evidence of unsoundness but appears serviceable.
(One or more of the following conditions is satisfied.)
Petrographically estimated mix design and/or derived parameters are outside acceptable limits.
The concrete contains unstable aggregate lithologies that show evidence of in situ reaction.
The concrete shows serious segregation of one or more major components.
The concrete has excess voidage, large voids below reinforcement or zones of honeycombing.
Class B2 concrete. The concrete shows petrographic evidence of post‐hardening degradation.
(One or more of the following conditions is satisfied.)
Surface‐related carbonation penetration is close to or deeper than the level of placement of ferrous reinforcement.
Reinforcement shows evidence of corrosion and associated expansive microcracking.
The concrete has pervasive, high density microcracking associated with severe aggregate shrinkage.
The concrete has pervasive, high density microcracking resulting from growth of secondary minerals and/or gel with concomitant expansion.
The concrete shows spalling and/or high density microcracking resulting from other causes (salt crystallisation, fire or frost damage).
The binder has zones of high secondary porosity.
There is extensive growth of secondary minerals and/or gels in voids.
Class C. The concrete is deemed unsound. (One or more of the following conditions is satisfied.)
Serious corrosion of reinforcement with associated spalling of concrete and growth of long‐range open fractures.
Extensive dissolution of unstable aggregate lithologies with widespread expansion cracking, growth of secondary minerals and/or gel in voids and fractures, and gel‐impregnation of the cement paste. The concrete is locally or generally incoherent.
Frequent long range open or partially open fractures extend from the surface to depths beyond the level of placement of reinforcement.
Serious surface‐parallel spalling that may lead to detachment of flakes or slabs of concrete.
The binder is replaced by soft secondary minerals or gel in large domains that are at least locally interconnected, leading to loss of coherence and compressive strength.
Page 11
Page 12
Plate 1. Sample number 12B-1394 03.
High resolution low magnification digital image of part of the thin section. The image shows the general
structure of the concrete and the lithology of the coarse aggregate (epidosite: epidotised quartz -
feldspar porphyry). The sand is mainly quartz (white). It is very fine-grained. The binder appears medium
brown. Voids are filled with epoxy resin containing yellow dye.
Most edges of the section lie outside the scanned area though the inclined upper right margin is defined
by the wall of a fracture that originates from a corroded rebar.
Petrographic Report Degradation of Concrete 49 Landor Street, Birmingham
Report Number: 12B-1394
25 millimetres
epidosite
epidosite
fracturesurface
Page 13
Plate 2. Mineralogy and texture of the binder.
A, B Sample 12B-1394 02. Uncarbonated paste at a depth of about 55 mm below the surface of the
concrete. Coarse partly hydrated alite and belite clusters in strongly mottled paste are visible in
plane polarised light (A). Sparse tabular portlandite crystals may be seen between crossed
polars (B). Pale yellow domains (especially adjacent to some quartz particles) are secondary
micropores, probably formed by partial dissolution of portlandite.
C Same field of view as above seen under reflected high intensity ultraviolet illumination. The
fluorescent intensity of the paste is variable over short distances but generally corresponds to
that of standard mortars having water:cement ratio between 0.6 and 0.8.
D Sample 12B-1394 03. Carbonated paste with coarse furfuraceous (bran-like) texture and high
secondary porosity. The texture is typical of atmospheric carbonation of Portland Cement
concrete made at high water:cement ratio. High secondary porosity facilitates penetration of air
and moisture into the concrete.
A - plane polarised light. B, D - crossed polars. C - reflected high intensity ultraviolet illumination.
A B
C D
Petrographic Report Degradation of Concrete 49 Landor Street, Birmingham
Report Number: 12B-1394
100 µm
100 µm100 µm
100 µm
alitecluster
alitecluster
belitecluster
quartz
quartz
micropore
void
portlandite
Page 14
Plate 3. Fractures associated with corrosion of reinforcement.
A Sample 12B-1394 03. Coating of brown iron oxide and oxide-impregnated binder at the
wall of an expansion-induced fracture about 2 mm from the edge of a corroded rebar.
B Sample 12B-1394 03. Subsidiary open fracture cutting binder about 5 mm from the
edge of a corroded rebar.
C Sample 12B-1394 03. Network of open microfractures cutting impartially through
epidosite aggregate fragment and binder about 5 mm from the edge of corroded
reinforcement.
D Sample 12B-1394 03. Subsidiary fracture partly filled with secondary calcite, about
10 mm from the edge of the reinforcement.
Thin sections photographed in plane polarised light.
A B
C D
Petrographic Report Degradation of Concrete 49 Landor Street, Birmingham
Report Number: 12B-1394
100 µm
quartz
oxide-impregnatedbinder
iron oxidecoating
250 µm
250 µm 250 µm
openfracture
openfracture
epidosite(aggregate)
binder
openfractures calcite