Special Digest Third editionConcrete in aggressive groundBRE Construction Division BRE is committed to pro. Download Citation on ResearchGate | BRE report – Concrete in aggressive grounds: An introduction to BRE Special Digest 1 | The codes and standards for. The introduction of the edition of BRE Special DIgest 1 (SP1) provides the guidance on concrete in sulfate-bearing ground. The range of exposure.
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Contact BRE for information about its services, or for technical advice: They are described in Section C5. If this APM is adopted, the engineer will need to carry out a detailed assessment of water movements before Section C3 and after construction.
After reaching equilibrium, the piezometer will also indicate the height of the water table. Appendix C2 on page 36 gives guidance on a more comprehensive site investigation that may be needed for a case of sulfate attack on concrete.
Sources of information for site investigations in Britain. Averages of earth temperature at depths of 30 cm and cm for the United Kingdom — In practice the high magnesium levels will be found in the UK only in ground having industrial residues. Generally these agents are found in troublesome concentrations only in land affected by contamination.
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In respect of the latter, particular consideration will be needed for structures such as basements and retaining walls that have one side exposed to air. However, high chloride concentrations in the ground will increase the risk of corrosion since chloride ions may migrate into the concrete and lead to a reduction in passivity at the metal surface.
Guide to the construction of reinforced concrete in the Arabian Peninsula.
BRE guidance has presented more background information on chemical attack, given detailed guidance on ground assessment, and included dedicated guidance for the specification of concrete in certain precast concrete products such as pipeline systems and masonry blocks.
Specialist advice should be sought if the presence of ammonium ions is suspected. For flowing groundwater requiring the determination of aggressive carbon dioxide, the sampling procedure given digeet prEN can be used. It seems reasonable, therefore, that an additional surface protective layer of sacrificial concrete 50 mm thick would be adequate for a convrete concrete structure with an intended working life of at least years.
In this case the contract documentation should contain: B2 Principal types of chemical attack on concrete B2. At times of year when groundwater levels are high, mobile groundwater conditions can be confirmed by either digging a trial pit or drilling a borehole to the relevant depth and leaving bfe temporarily open.
Concrete in Aggressive Ground:3rd edition
The ground description should particularly note the following features relevant to assessment of the aggressiveness of a chemical environment: It is additional to the nominal cover, including any allowances for casting against uneven ground. A growing number of cases of TSA have been identified worldwide, although the majority have been found in the UK. Aggregate carbonate range A term formerly used in previous editions of Aggressivw. While the grouping and nomenclature differ between Table D3 and SD1: In respect of environmental conditions, bacterial action has been widely reported as eigest the oxidation, particularly so when conditions are acidic.
SD1 provides guidance on the specification of concrete for installation in natural ground and in brownfield locations. Guidance on specialist personnel is given in Digest If no water has seeped into the trial pit or Some construction activities can greatly increase mass permeability of ground and may, therefore, change a natural site condition of static groundwater to a mobile groundwater condition. Chemical attack on concrete B7 Microbial contribution to chemical attack on concrete The activity of micro-organisms in aggtessive ground can result in changes to the chemical environment which, in turn, can contribute indirectly to concrete attack.
Assessing the aggressive chemical environment incorporating March amendment No longer current but cited in Building Regulations guidance. In this situation, the APM relating to site drainage is deemed to be already satisfied for concrete, provided it is not subject aggressibe a hydraulic gradient from groundwater which is greater than 5. Box C1 lists the main sulfur species found in the UK, aggresssive of which are either sulfates or sulfides.
SD 1 Concrete in aggressive ground. 3rd edition, BRE – Publication Index | NBS
Aggressive carbon dioxide is usually only present to an appreciable extent in rather pure natural waters since in most cases, where the water contains dissolved salts, sufficient calcium carbonate is available to combine with the carbon dioxide as calcium bicarbonate. A relatively new finding is, however, that a pH ahgressive than 10 such as occurs by mixing cement or lime with soil also accelerates pyrite oxidation . If only one type of sample groundwater or soil was tested, the class determined for this type may be taken as the Design Sulfate Class for the aggressibe.
A list of sponsors and members of the steering group who advised on its preparation is shown on page vi. Risks of contaminated land to buildings, building materials and services: Material selected for laboratory testing should be taken from the centres of block samples and core samples to avoid the effects of surface oxidation and contamination by different water or soil.
BRE – Special Digest 1
In several cases of serious deterioration to concrete from TSA in the foundations of highway bridges , a major contributory factor was that the foundations had been constructed in excavations that were subsequently backfilled with pyritic clay and also subject to ingress of water.
It is recommended that an investigation comprises, sequentially, a desk study, a walkover survey, and a ground investigation using trial pits and boreholes to assess visually the ground profile, and to take representative samples of soil and groundwater for chemical analysis. Other fill materials that may contain sulfates include accumulations of old blastfurnace slag, oil shale residues in the Lothians and clinker from the old-style chain grate power stations or from refuse incineration.
The soil description can be accomplished by means of trial pits or boreholes, described in BSand BRE Digestsand Such high concentrations have been reported as chemically affecting hardened concrete. Caution should be exercised in using this APM if attack could affect the structural integrity; for example, by introducing expansive forces or by reducing frictional forces.
Note that new limiting values are introduced in SD1: If magnesium ions accompany the sulfates, they may also react with calcium hydroxide producing brucite magnesium hydroxide, Mg OH 2 which, because of its low solubility, precipitates out of solution, also leading to increase in solid volume.
Concretes made with other cement types must rely on achieving very low permeability for resistance. A source of carbonate is still considered essential for occurrence of TSA, but recent research Section A3 has shown that sufficient carbonate can come from bicarbonate in groundwater.
Specification for pulverized-fuel ash for use with Portland cement See note below BS Reminder When it is uncertain whether the groundwater is static or mobile eg owing to lack of site data or knowledge of changes to ground permeability that may result from constructionaghressive mobile specizl condition should be assumed. SD 1 Concrete in aggressive ground. Chose the appropriate pH range for the assessed mobility of groundwater: Chemical agents apecial to concrete that are found only rarely eg ammonium salts should be investigated if their presence is suspected; for example, from past use of the site.
Coal mining areas 19 Box Conncrete How sulfides are converted to sulfates in disturbed ground Construction activities eg excavation and backfilling that substantially disturb the ground may allow pyrite in initially unweathered geological strata to have access to air, water and bacteria. Any significant out-of-balance that can not be accounted for by analytical errors concree indicate the presence of some other ion which needs to be identified.