Our ref: LO1094.008/E/PW Asset Management Team Brighton ... Engineers Report... · Chloride Ion Content Chloride attack on reinforcement is aggressive and can occur despite the alkalinity

Our ref: LO1094.008/E/PW 15 March 2012 Asset Management Team Brighton & Hove City Council Housing Centre Unit 1, Fairway Trading Estate Eastergate Road Brighton East Sussex BN2 4QL For the attention of Mr John Currell Dear Sirs Re: Structural Appraisal of No-Fines High Rise Blocks, Bristol Estate, Brighton With reference to the above, we write regarding the exploratory investigations prescribed in our correspondence of 12 and 17 January 2012. Having since concluded our studies, we hereby advise our findings as follows. For the sake of good order, we have presented our commentary in the form of a short advisory report making reference where necessary to the appendices listed below.

• Appendix A: Property Type Description (2006 Report Extract)

• Appendix B: Concrete Cover and Carbonation Results

• Appendix C: Laboratory Analysis Results and Certificates

• Appendix D: Insitu Pull-Out Test Results

• Appendix E: Construction Details (DRG № LO1094-001 & LO1094-002)

• Appendix F: Photographic Record 1. Introduction In November 2011, Curtins Consulting were invited to submit proposals in connection with undertaking an appraisal of five Wimpey No-Fines high rise blocks that were originally investigated by ourselves as part of a much wider stock condition survey for Brighton & Hove City Council in 2006. Our appointment was subsequently confirmed by Mr Allen Shaw of Mears Projects on 5 December 2011.

2. Requirements of the Brief The purpose of this study is to verify the durability of the concrete, specifically that pertaining to the reinforced elements of the structure, with a view to determining whether the properties are sufficiently robust to be over-clad with an external wall insulation system. In keeping with the methodology adopted for the 2006 stock condition survey, the investigations will again comprise visual and intrusive exercises, the latter of which will primarily entail obtaining concrete samples for laboratory analysis. Upon completion of the above, it was agreed that Curtins would assimilate their findings and present details pertaining to their observations, recommendations and conclusions in the form of a short advisory report. 3. Property Location Chadbourne Close and Donald Hall Road, Brighton, East Sussex The investigation was confined to five seven-storey blocks of flats which collectively form part of the Bristol Estate, namely:

• Allamanda (146-192 Donald Hall Road)

• Hazel (1-24 Chadbourne Close)

• Jasmine (2-48 Donald Hall Road)

• Meadowsweet (74-120 Donald Hall Road)

• Sorrel (1-47 Chadbourne Close) The properties are orientated to face due south occupying a relatively exposed hilltop position located approximately 500m from the sea front.

4. Property Type Description No-Fines dwellings were built by several companies, the most well known being George Wimpey & Co who is understood to have been responsible for building somewhere in the region of 300,000 houses alone between the 1940s and 1970s. The system of construction, which is more particularly described within Appendix A, entailed casting the entire outer structure in a single operation using reusable formwork. Numerous types of Wimpey No-Fines bungalows, houses and low rise blocks of flats were produced, generally ranging in height from one to five storeys. The designs incorporate flat, hipped and gable roofs, porches and in some cases bay windows. The basic structure is composed to provide for a high degree of natural robustness, its overall stability being achieved through the internal masonry partition walls working in combination with the diaphragm action afforded by the floors. The five blocks encountered in this instance, which are understood to have been built circa 1957, each accommodate 24 self-contained flats arranged over six floors. The dwellings, 18 of which benefit from a private balcony, are accessed via a central staircase/lift core that leads from the lobby rising through to the plant room at roof level. In addition to the main entrance areas, the ground floor has been configured to provide for a communal bin storage facility as well as individual lock-ups/sheds. Being as no significant material or structural alternations appear to have been made, it accordingly thought the properties are largely present in their original form.

5. Scope of the Investigations The extent of the investigation has been largely influenced by Curtins’ impressionistic survey together with our knowledge and experience of the potential defects that can occur in buildings of this type. The work may be categorized as follows:

• Visual inspections.

• Intrusive (exploratory) investigations.

• Laboratory testing. Information obtained during the impressionistic survey that was undertaken on 11 January 2012 has been used to determine the scope of the investigation work, namely:

• Extent and location of inspections.

• Number and type of site tests.

• Number and type of samples for laboratory analysis, where required. The regime adopted is such that where components are accessible, a representative sample of those either noticeably suffering from or most likely to suffer from degradation are tested. Where the components are not visible, testing has been undertaken in areas considered to be most vulnerable to degradation. The results obtained are used as the basis of the recommendations and are given as being representative of the stock as a whole. However, as the entire structural fabric of every building cannot be inspected, there is no guarantee that the worst or most aggressive areas of degradation have been identified. This appraisal is largely confined to an assessment of the external walls and more particularly the reinforced concrete elements of the structure. The condition of the masonry, roof coverings and windows, together with any other materials and/or components which comprise the building envelope, are all excluded from consideration. 6. Assessment of Potential Defects Deterioration of the reinforced concrete elements is instigated by corrosion of the steel reinforcement which subsequently expands causing the exposed surface to crack and eventually spall. Concrete is inherently alkaline and it is this alkalinity which protects the encased steel from decay. However, the protection can be reduced by the action of acidic gases present in the air (such as carbon dioxide and sulphur dioxide). This process is called carbonation. If the carbonation depth coincides with or exceeds the depth of the reinforcement, the risk of corrosion increases, reducing the integrity of the concrete thereby leading to a reduction in its structural capacity. Corrosion can increase or be more severe in the presence of high levels of chloride ion within the concrete; common if chloride based admixtures were used during the construction process (normal practice up to the late 1960’s). In order to properly determine the condition and future durability of the concrete, the following characteristics will therefore need to be assessed:

• Chloride ion content.

• Cement content.

• Carbonation depth.

• Cover to reinforcement.

Chloride Ion Content Chloride attack on reinforcement is aggressive and can occur despite the alkalinity of the surrounding concrete. It sets up an electrolytic cell, which encourages the migration of chloride ions from surrounding areas to the site of the attack. This results in localised deep pits in the reinforcement, which decreases its cross sectional area significantly before sufficient rust has formed to crack the concrete to the surface. As this form of reinforcement attack is hidden from view, it is potentially a serious cause of weakness to reinforced concrete and it can progress undetected. Consequently, it is important that the level of chloride in the concrete is established. Concrete samples are taken, either by drilling holes and collecting the debris or by chipping pieces from the corners of components. Cement Content Cement content is determined under laboratory conditions in accordance with methods set out in BS 1881: Part 124: 1988. Its analysis is required in order to properly assess the concrete’s composition with respect to chloride ion content as well as confirm its strength. Carbonation Depth There are four basic factors that contribute towards the resistance of concrete to carbonation. These are as follows:

• The type and proportions of the materials used in the concrete mix.

• The compaction achieved during casting.

• The curing regime to which the concrete has been subjected.

• The environment in which the concrete is located. The depth of carbonation is a good indicator of the quality of the concrete; the degree to which the concrete has suffered from weathering and the approximate time scale before the reinforcement is affected by the environment. The depth of carbonation in concrete is determined by spraying the surface of the drilled hole with liquid Phenolphthalein indicator. This clear liquid turns un-carbonated concrete purple. The colourless zone can be measured as the carbonation depth. Cover to Reinforcement Measuring the depth of cover is necessary to establish the potential vulnerability of corrosion occurring in the reinforcement. It is of importance that reinforcement is afforded adequate protection from the carbonation process in order for it to remain effective within the concrete section; too little cover can lead to premature corrosion resulting in cracking and spalling of the concrete face and ultimately, failure of the component.

7. Details of the Investigations External Visual Inspections Visual inspections were undertaken primarily to assess the condition of the external walls (rendered finishes), for signs of cracking and/or de-bonding. Intrusive (Exploratory) Investigations Intrusive investigations entailed obtaining concrete samples for chloride ion analysis and where appropriate cement content determination. The works also comprised locally opening up the structure in order to confirm: a) The exact composition of the external walls, including the type and thickness of

internal/external finishes. b) The construction details in relation to the concrete window surrounds. In addition, a number of pull-out tests were undertaken in order to determine the most appropriate type of fixing for the proposed EWI system as well as establish whether the no-fines substrate can safely accommodate the anticipated loading conditions. Concrete Testing Programme Using a 20mm diameter drill, concrete dust samples were extracted from each of the five blocks listed under Section 3.

• 2 № from balcony slabs at 1st floor level

• 2 № from balcony slabs at 2nd

floor level

• 2 № from columns at ground floor level

• 2 № from downstand floor beams at 1st floor level

• 6 № from window lintels at ground/1st floor level

Depth of cover was accurately measured using an electronic cover-meter at each of the 14 locations where samples were systematically extracted. The depth of carbonation was established using Phenolphthalein solution, in accordance with the recognised procedure. The samples obtained for laboratory analysis were subsequently dispatched to CMT (Testing) Ltd who are a UKAS accredited specialist. All were duly tested for chloride content. In addition, one random sample from each block was analysed for cement content.

8. Findings and Discussions Concrete Testing Programme Being as these properties are largely built of un-reinforced concrete, corrosion is not generally considered to be an issue that might serve to compromise structural integrity. However, reinforcement is present within the lintels, balcony slabs and associated floor beams which, if subject to water penetration or interstitial condensation, are liable to deteriorate. Curtins’ investigations therefore sought to target an examination of these more vulnerable reinforced components. Concrete samples were extracted for laboratory analysis and at each location measurements taken to establish the depth of carbonation in relation to reinforcement cover. An examination of the lintels was achieved by carefully hacking off a small area of external wall render in order to expose the component local to its bearing position. (Refer to Photo № 1, Appendix F). A close visual inspection was subsequently undertaken in order to check for any signs of the reinforcement having corroded. Those assessed were found to be in good order with no cracking or spalling evident. The concrete was considered to be quite dense and upon locating the reinforcement only nominal surface corrosion was noted. Results pertaining to the concrete cover/carbonation tests and associated laboratory analysis are incorporated for reference within Appendices B and C. Taking each of the blocks in turn, we would summarise our findings as follows: Allamanda (146-192 Donald Hall Road):

• The depth of cover, as measured to the face of the concrete, averaged 43.4mm, whilst the mean depth of carbonation measured 2.6mm.

• The chloride ion content, quantified as a percentage of the cement content, averaged 0.11%.

Hazel (1-24 Chadbourne Close):



Jasmine (2-48 Donald Hall Road):



Meadowsweet (74-120 Donald Hall Road):



Sorrel (1-47 Chadbourne Close):



The average values for chloride ion content (quantified by mass of cement) range from 0.11% to 0.46%. With the exception of Jasmine, these figures are considered to be low and are particularly comforting in view of current Building Research Establishment (BRE) guidelines which recommend a limit of 0.4%. Being as the carbonation depth did not generally coincide with or exceed the depth of cover, these results can be taken to represent a low risk of corrosion. The results obtained with respect to cement content determination, derived values ranging between 14.05% and 19.44%. The average figure of 15.81% is more than sufficient given that 14% is widely regarded as being acceptable on the basis this quantum equates to a concrete strength of approximately 20N/mm². It is important to remember that cement content is one of the factors which directly contribute towards concrete durability, specifically its resistance to carbonation. A mix exhibiting a high as opposed to low cement content will be comparatively dense and impermeable. These properties will, in turn, help guard against the carbonation process. The external finishes (sand/cement and spar dash render) appear to be in reasonable condition although it is clear from the buildings rather ‘tired’ appearance that the coastal weather conditions are taking their toll. Not surprisingly, some isolated areas of de-bonded render were noted. (Refer to Photo № 2, Appendix F). Furthermore, there was also evidence pertaining to a number of past repairs, almost all of them at high level. (Refer to Photo № 3, Appendix F). Of course it is fully anticipated that the render will become increasingly weathered with time. Consequently, in the event the properties are not over-clad, its continued deterioration could result in water penetrating the permeable no-fines concrete and thereafter promote damp conditions internally.

Masonry External Walls These properties differ from the archetypal Wimpey No-Fines form of construction in as much as they feature one of the more commonly encountered variations whereby one or more of the external walls is built of masonry. This being the case, we took the liberty of broadening our intrusive investigations to include a cursory inspection of the cavities with a view to us obtaining a feel for the presence, adequacy and condition of the wall ties. In order to facilitate an inspection of the wall ties, a number of openings were formed within the face brickwork at ground floor level. (Refer to Photo № 4, Appendix F). Measuring approximately 450mm x 225mm, these were sized so as to permit an unencumbered view of the cavities. Whilst a conventional endoscopic examination would have entailed less disruption, this more intrusive method was favoured on the basis the cavities could have been obstructed by debris (mortar) which may have impeded the exercise. Upon opening up the structure the walls were found to be composed of two leaves of brickwork separated by a clear cavity. (Refer to drawing № LO1094-002, Appendix E). Where inspected, our examination of the cavity widths suggests these are broadly consistent throughout with measurements averaging 75mm. Our observations determined that the steel vertical twist ties used have sustained largely nominal surface corrosion. (Refer to Photo № 5, Appendix F). Certainly there was no visible evidence of any suffering from loss of section. What is more, they appear to be present in sufficient number, i.e. spaced no more than 450mm centres vertically and 900mm horizontally, thus alleviating some concern for the integrity of the inner and outer leaves. Insitu Pull-Out Tests In order to determine whether the no-fines substrate offers sufficient anchorage for the proposed EWI system, Structherm engaged the services of EJOT Ltd to undertake a number of insitu pull-out tests. A total of 16 tests were conducted across the five blocks in accordance with the requirements prescribed under BS 5080-1:1993 ‘Structural fixings in concrete and masonry. Method of test for tensile loading’. An analysis of the results incorporated within Appendix D indicates pull-out values ranging between 1.2kN and 3.0kN. The average figure of 1.92kN is considered to be quite sufficient provided no less than five of the specified fixings (EJOT ejotherm STR-U) are used to secure each 1200mm x 600mm insulation board. In this instance, the same STR-U fixings are also considered the most appropriate for use with brickwork should the proposed over-cladding scheme look to encompass the masonry elements of the structure.

Concrete Window Surrounds Having followed the same regime of intrusive investigations adopted for the three storey blocks we note that the concrete window surrounds, which similarly feature throughout the high rise properties, are detailed no differently. The composition of the external walls, where these are of no-fines construction, was also found to be consistent with that encountered previously. (Refer to drawing № LO1094-001, Appendix E). Our report of 26 August 2011 (Ref: 70964.015/PW) tabled two options for installing the proposed EWI system so as to eliminate cold bridging around the window openings. Again, these may be summarised as follows: a) Leave the surround in place with a view to carrying the insulation over its face,

notching out the back of the board as may be necessary to accommodate the change in levels. In order to encapsulate the surround completely, a thinner strip of insulation (20-25mm) should be used to return the system against the window frame.

b) Break out the surround using appropriate hand tools. Owing to its overall

thickness, not to mention the relatively shallow step between this and the adjoining rendered finishes, we do not envisage there being any scope to cut the surround back mechanically. Upon seeing to its removal, dub out the exposed no-fines concrete to achieve the desired line and level characteristics in readiness to receive the insulation board as above.

We understand ‘Option A’ reflects Structherm’s preferred detail, which they have accordingly prescribed in their associated scheme drawings. In the event the Contractor wishes to adopt ‘Option B’, special care will need to be taken when breaking out the surrounds so as to avoid damaging the adjoining no-fines concrete. Owing to the time implications associated with each, we would recommend the Contractor reviews both on site before deciding on which one to adopt. Other Noteworthy Observations Whilst undertaking our impressionistic survey, we encountered a limited number of what may be classed as ‘superficial’ defects. Although of little consequence where this report is concerned, we would nevertheless advise the Client makes provision for some appropriate remedial measures; irrespective of whether the blocks are over-clad or not. These may be summarised as follows. All of the exposed reinforced elements, primarily the balconies, have been treated with what is believed to be masonry paint. Over the years, sustained weathering has continued to erode this finish and in places it has begun to blister and de-bond. (Refer to Photo № 6, Appendix F). It is accordingly recommended all of the exposed concrete surfaces are mechanically cleaned, i.e. grit blasted, and thereafter treated with an anti-carbonation paint system that will help guard against further deterioration. Whilst on focussing on the balconies, we note that the some of the wall panels have begun to spall; specifically where the balustrade rail fixings have corroded. (Refer to Photo № 7, Appendix F). In addition to effecting some localised concrete repairs, it may be prudent to consider replacing the railings should their widespread condition prohibit them from being refurbished.

Notwithstanding the above, there appears to be just a small handful of isolated instances where cracking and/or spalling has occurred as a likely consequence of low cover. (Refer to Photo № 8, Appendix F). Ideally, structural defects, particularly those involving concrete repair, should be attended to as soon as is reasonably practicable, i.e. within the next five years. In reality, individual components will probably continue to deteriorate for several years beyond this milestone without themselves becoming a serious concern. However, the longer one waits the more extensive and indeed expensive the repairs are likely to become.

9. Conclusions and Recommendations In view of our findings we envisage no reason why the properties should not be over-clad as proposed; the results arising out of our intrusive investigations having served to alleviate any concerns regarding the durability of the concrete and consequent robustness of the structure. We believe the introduction of external wall insulation will offer the most effective solution for prolonging the life of these dwellings as it will ensure the relatively porous no-fines walls remain in a dry, stable environment from the outset. This approach should, in turn, negate the need for an ongoing high level of maintenance as well as certain future fabric repairs given the manner in which the cladding will safeguard the structure against further deterioration. What is more, it will also provide for a notable improvement in the properties thermal efficiency as well as greatly enhance their aesthetic appeal. Should the Client opt to pursue implementing a scheme, we would suggest the proposed design solution looks to encompass the masonry elements of the structure. Whilst conventional cavity wall construction does not habitually suffer from the problems more particularly associated with no-fines, i.e. water penetration and interstitial condensation, treating all of the elevations will ensure efforts to improve the blocks overall thermal performance is not compromised. We note the proposed EWI system (Structherm NSC2A) is to incorporate an enhanced expanded polystyrene or ‘EPS’ type insulant. Having ascertained the exact composition of the external walls, where these are of no-fines construction, it is understood that a 90mm board will need to be applied in order to achieve the target U-value of 0.30W/m2K. In the event the Client wishes to go beyond the minimum requirements currently set out under Part L1B of the Building Regulations, consideration could be given to the following insulation thicknesses.

• 90mm Enhanced EPS: 0.28W/m2K



This concludes our report. Should you have any queries please do not hesitate to contact the undersigned. Yours faithfully PETER WRIGHT

For and on behalf of

Curtins Consulting Ltd Encs c.c Mears Group PLC – Mr Allen Shaw

APPENDIX A

PROPERTY TYPE DESCRIPTION

(2006 REPORT EXTRACT)

8.0 Property Type Description 8.2.6 No-Fines Type Flats

No-Fines dwellings were built by several companies, the most well known being

George Wimpey & Co who is understood to have been responsible for building somewhere in the region of 300,000 houses alone between the 1940s and 1970s.

Published information describes the system as follows: No-Fines properties of this type are generally built off conventional strip foundations

and have 255-305mm thick external walls made of coarse aggregate and cement with no sand used in the mix. The external walls are finished with roughcast render and internally with plaster, although variants can include flank walls of brickwork. The party walls are constructed likewise and are finished both sides with plaster whilst internal partitions can be of masonry, clinker block or timber studwork.

The same form of construction was used to build bungalows, houses, medium rise

and high-rise flats, accepting that the latter incorporate dense in-situ concrete frames to support the greater loads involved.

The ground and upper floors within flats are typically of solid in-situ construction.

Within two storey houses these are more commonly built off suspended timber joists. Potentially there is a problem with these properties where water penetration and/or

interstitial condensation can promote corrosion of the reinforcement within the lintels. Curtins’ investigations concluded that the properties inspected were generally

consistent with the description given above.

APPENDIX B

CONCRETE COVER AND CARBONATION RESULTS

Brighton & Hove City Council Structural Appraisal of No-Fines Type Properties (Bristol Estate) CONCRETE COVER AND CARBONATION TEST RESULTS

PROPERTY DESCRIPTION: No-Fines High Rise Block of Flats PROPERTY ADDRESS: Allamanda (Block 146-192, Donald Hall Road)

Sample

№

Element/Location

Depth of

Hole

(mm)

Depth of

Carbonation

(mm)

Depth of

Cover

(mm)

S1 Balcony Slab (1st Floor) 70 1 32


S3 Balcony Slab (2nd

Floor) 70 2 22


Floor) 70 3 34

S5 Column (Ground Floor) 70 5 31


S7 Downstand Floor Beam (1st Floor) 70 4 84


S9 Window Lintel (Ground/1st Floor) 70 2 45






SUMMARY OF RESULTS

S1-S14 Average depth of carbonation (mm) 2.6

S1-S14 Average depth of concrete cover to reinforcement (mm) 43.4


PROPERTY DESCRIPTION: No-Fines High Rise Block of Flats PROPERTY ADDRESS: Hazel (Block 1-24, Chadbourne Close)

Sample

№

Element/Location

Depth of

Hole

(mm)

Depth of

Carbonation

(mm)

Depth of

Cover

(mm)




Floor) 70 3 51


Floor) 70 2 56











SUMMARY OF RESULTS




PROPERTY DESCRIPTION: No-Fines High Rise Block of Flats PROPERTY ADDRESS: Jasmine (Block 2-48, Donald Hall Road)

Sample

№

Element/Location

Depth of

Hole

(mm)

Depth of

Carbonation

(mm)

Depth of

Cover

(mm)




Floor) 70 2 22


Floor) 70 3 58











SUMMARY OF RESULTS




PROPERTY DESCRIPTION: No-Fines High Rise Block of Flats PROPERTY ADDRESS: Meadowsweet (Block 74-120, Donald Hall Road)

Sample

№

Element/Location

Depth of

Hole

(mm)

Depth of

Carbonation

(mm)

Depth of

Cover

(mm)




Floor) 70 2 45


Floor) 70 3 20











SUMMARY OF RESULTS




PROPERTY DESCRIPTION: No-Fines High Rise Block of Flats PROPERTY ADDRESS: Sorrel (Block 1-47, Chadbourne Close)

Sample

№

Element/Location

Depth of

Hole

(mm)

Depth of

Carbonation

(mm)

Depth of

Cover

(mm)




Floor) 70 7 53


Floor) 70 2 49











SUMMARY OF RESULTS



APPENDIX C

LABORATORY ANALYSIS RESULTS AND CERTIFICATES

APPENDIX D

INSITU PULL-OUT TEST RESULTS

APPENDIX E

CONSTRUCTIONS DETAILS

(DRG № LO1094-001 & LO1094-002)

APPENDIX F

PHOTOGRAPHIC RECORD

An examination of the lintels was achieved by carefully hacking off a small area of external wall render in order to expose the component local to its bearing position.

CURTINS CONSULTING ENGINEERS

40 Compton Street, London EC1V 0AP

Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012

Ref: LO1094 Photo №: 1

In places the rendered finishes look to have deteriorated quite considerably.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


One of the many render repairs which have been undertaken in the past.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


Openings were formed to facilitate an inspection of the wall cavities at ground floor level.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


Observations suggest the wall ties have sustained largely nominal surface corrosion.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


In places, sustained weathering of the concrete coatings has caused them to blister and de-bond.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


Spalled concrete where the balcony balustrade rail fixings have begun to corrode.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


One of the few isolated instances where exposed reinforcement was encountered.



Telephone: (020) 7324 2240 Fax: (020) 7324 2241

Client:

Brighton & Hove C.C

Photographic Record

Taken by:

Gethyn Hughes

Date:

9 February 2012


Our ref: LO1094.008/E/PW Asset Management Team Brighton ... Engineers Report... · Chloride Ion Content Chloride attack on reinforcement is aggressive and can occur despite the alkalinity

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