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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Therefore, good compaction is most important. The action of magnesium ions in concrete is complex, but a key mechanism is the replacement of calcium in calcium silicate cohcrete that form much of the cement paste. Model procedures for the management of land concretf. A note of any visible seepage and the directions from which it comes will help in a groundwater mobility assessment.
This may be detrimental to concrete over a period of time. British Standard BS and several recent reports from CIRIA and the Environment Agency[5—10] are recommended for guidance on the additional requirements required for planning, executing and interpreting site investigations, for identifying any other hazards, and for the management of the risks involved in developing contaminated land.
Since the concrete quality takes account of a possible external source of carbonate, it also inherently caters for an internal source from carbonate in aggregates and consequently aggregate carbonate range is redundant. UK gdound is not available on the concentration of ammonium ions that can be tolerated by different types of concrete. Other aims and changes are discussed later. Figure C3 Coal mining areas of Great Britain where sulfate bearing, coal mining wastes and metal processing slags are most likely to be encountered There also may be unusual sulfates, such as ammonium sulfate, conccrete soil and groundwater as a result conncrete past industrial use and agriculture.
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This is greater than the hydraulic gradient of 5 that generally calls for increased provision against chemical attack on concrete. However, subsequent backfilling with the clay appeared to have led to an increase in the sulfate content to levels for which the choice of Portland cement would have been inappropriate. Acidic iin from the oxidation of pyrite aggresdive reported in fills derived from Carboniferous mudstone and Oxford Clay.
Aggressive carbon dioxide Carbon dioxide CO2 dissolved in water essentially comprises three fractions: Calculate SO4 equivalent of Cl Cl x 1. The principal reaction is with the calcium hydroxide Ca OH 2 in the matrix of concrete, the end products being calcite CaCO3 and water: Where the history of a site is not known, it should be abgressive as a brownfield site until there is evidence to classify it as natural. Part D  Price W F.
Sources of information for site investigations in Britain. In winter and spring, when water tables are generally at their highest, the presence of static groundwater conditions can be established on a proposed construction site by either digging a trial pit or drilling a borehole to the intended full depth of concrete.
The concept of aggregate carbonate range is therefore no longer included, since the revised concrete specification simultaneously caters for an internal source from carbonate in aggregates.
For pipeline systems, box culverts and segmental linings, the exposure conditions include the internal flow of aggressive water or effluent when the products are used in water and sewer services. Drains should be inspected and maintained to avoid leakage close to buried concrete. Concrete in Aggressive Ground: It is dependent on the presence or absence of substances including magnesium ions, pyrite, and, for pH less than 5.
These can be allowed for by adjusting the determined soluble sulfate content. The necessary enhancement may be determined from Table D2 on page As in the laboratory, it is likely that the extent of TSA will be increased at the cooler temperatures if the chemical conditions are satisfied. Guidance in BRE Digests has necessarily evolved to cater for successive adverse field findings; to take advantage of the emergence of new concrete constituents and construction methods; and to maintain harmony with newly published standards, latterly European ones.
Concrete in Aggressive Ground:3rd edition
B2 Principal types of chemical attack on concrete B2. The most widely recognised damage of bacterial origin is the deterioration of concrete in sewers or sewage treatment works caused by bacteria that feed on sulfate in effluent, ultimately producing corrosive sulfuric acid. The list of recommended test methods in Box C10 on page 35 is based on recent BRE experience and the outcome of a review of test procedures for determining sulfur species reported in TRL Report .
The procedures given for the ground assessment and concrete specification cover the fairly common occurrences of sulfates, sulfides and acids, and the more rarely occurring aggressive carbon dioxide found in some ground and surface waters, which affects concrete foundations and sub-structures. Concrete surfaces that are carbonated are less prone to this form of attack.
During the reaction, ammonia is liberated and escapes as a gas. Caution should be exercised in using this APM if attack could affect the structural integrity; for example, by introducing gagressive forces or by reducing frictional forces.
Since such carbonation provides a degree of resistance to sulfate attack, the recommendations for the derivation of DC Class in respect of sulfates is relaxed by one level.
SD 1 Concrete in aggressive ground. 3rd edition, BRE – Publication Index | NBS
Detrimental mechanisms include the reaction of calcium and magnesium chlorides with calcium aluminate hydrates to form chloroaluminates which may result in low-to-medium expansion of concrete. Examples based on Table D1 are: These minerals do not usually present a hazard to concrete.
Representative samples should be taken for sulfate classification from key depths in the ground in each test pit or borehole, bearing in mind the preliminary structural design concept aggressige the likely distribution of sulfides as indicated in Section Griund.
Rainwater is therefore the common source. Precautions should be taken to protect site workers and site neighbours if the desk study indicates the presence of substances harmful to health. In this case the recommended APM may often be achieved by redesigning the construction so that the concrete remains surrounded by impermeable ground that forms a barrier to movement of aggressive groundwater; for example, using a piled foundation or trenchfill foundation for a structure rather than a spread footing constructed in an open excavation.
Specification, performance, production and conformity BS EN University of Nottingham, April If breaching the naturally impermeable ground around concrete is unavoidable, the APM can often be achieved by resealing the possible routes eg by trenches for service pipes by which groundwater can reach the concrete.
Note that new limiting values are introduced in SD1: More rarely, sulfate may also be present in relatively insoluble forms, as in the mineral barite barium sulfate. In respect of environmental conditions, bacterial action has been widely reported as aiding the oxidation, particularly so when conditions are acidic. Sulfate Class This is a five-level classification of sulfate concentration that is applied to individual series of tests on soil or groundwater.
Assessing the aggressive chemical environment Box C10 Recommended source documents and test methods Chemical Symbol Recommended Soil determinations unit pH in 2. Sometimes, however, these recommended modifications were overlooked or incorrectly applied by designers and specifiers.
In contrast to this unwanted consequence that can arise from deep penetration of a carbonation front, carbonation of the surface of concrete is beneficial in respect of sulfate attack.