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Concrete and buried steels, can be "attacked" and weakened by acids within soils. This lead to problems such as "concrete cancer" and in general will shorten the life span of the concrete and structural steel elements being considered.
Aggressive ground is a term used in numerous technical writings with regard to unfavorable pH or resistivity within soils and rocks. The primary standard by which aggressivity is assessed is BRE SD1.
There are numerous geological units in the UK that are known to create the potential for aggressive ground. These are the:
Where you foundation are to be sited within these geological units it is important to consider that the choice of concrete, or grout will differ to sites where ground aggressivity is not as pronounced.
Acids from the ground acting on buried concrete can effect its strength in the medium to long terms. Water is required for the rection to take place. The reaction of these with water leads to setting and hardening of cement when it is gauged with water. The C~ (Tricalcium aluminate), C3S (Tri calcium silicate) and C,.AF (Tetra calcium alumina ferrite) phases react very rapidly.
Soil resistivity indicates the ability of a soil environment to carry corrosion currents. It is subsequently a function of the soil moisture content and the concentration of the current carrying soluble ions (Palmer, 1989). Soil resistivity is generally controlled by ‘spaces, fractures and the amount and composition of fluids that fill the pore spaces within a soil mass’ (Alhazzaa, 2007).
BRE Special Digest 1 provides guidance on the specification for concrete for installation in natural ground and in brownfield locations. 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. Gives procedures for specification of concrete and applies to both buildings and civil engineering construction.
The below section was written by a machine.
Aggressive ground conditions pose a significant threat to the long-term structural integrity of buried concrete, such as foundations and piles. Chemical attack, primarily from naturally occurring sulfates and acidic groundwater, can lead to the expansion and eventual disintegration of concrete elements if the design does not account for the specific subterranean environment.
To mitigate these risks, geotechnical assessments must be conducted in accordance with BRE Special Digest 1: Concrete in Aggressive Ground. This industry-standard guidance provides a methodology for classifying the ground and specifying the appropriate concrete mix.
Identifying aggressive ground early is a critical component of a robust Geotechnical Site Investigation. During the drilling phase, soil samples are recovered to perform laboratory testing for water-soluble sulfate (2:1 extract) and total potential sulfate. This data is often gathered alongside Building Regulation Part A investigations to provide a comprehensive foundation design recommendation.
Failure to correctly classify the ground can lead to premature structural failure or, conversely, excessive project costs due to over-specification. By linking these findings with a broader Geotechnical Engineering strategy, developers can ensure that the specified concrete mix—whether using sulfate-resisting cement or ground granulated blast-furnace slag (GGBS)—is both cost-effective and durable. SWEL provides the technical expertise required to interpret complex chemical data and satisfy building control requirements across the UK.
Our team has delivered technical support for over 900 projects, ensuring that structural designs are resilient to the diverse geological conditions found throughout England, Wales, and Scotland.