GOST 7473
At his speech at the conference <<Days of Concrete in Moscow>> the author of the standard, Mark Izrailevich Brusser (NIIZhB), announced the release of a new version of GOST 7473 <<Concrete Mixes>>. technical conditions, which should be approved and put into effect in the summer of 2011.
The standard will take into account industry practice since its adoption (1994) and harmonized with EN 206-1 (European standard for concrete).
Warranties and liability for concrete
. The concept <<supplier>> is defined - this is a company that has an agreement with the consumer and is responsible for the quality and quantity of the mixture. The fact that the document on the quality of the concrete mixture is issued by the concrete manufacturer does not affect the situation. All claims are directed to the supplier.
. Before unloading and acceptance, the supplier is responsible for the concrete mixture, after acceptance during unloading, the buyer is responsible
. Supplier's guarantees: the quality of the mixture at the time of delivery to the consumer - meets all the specified (in the contract) characteristics, the quality of the mixture at the time of design age - the achievement of indicators, subject to the requirements of regulatory and technical documents for hardening.
Brands and classes
The brand of concrete in terms of strength is not mentioned anywhere else in the standards, only the class of concrete remains. Nevertheless, it is allowed to formulate not only the class of concrete, but also the minimum average strength of concrete (based on which grades were previously considered).
Tolerances
The available deviations of the properties of the concrete mixture are introduced, the non-exit of which is not
. Cone spread: 3 cm,
. Draft of the cone, at values up to 10 cm: 1 cm, more than 10 cm: 2 cm,
. Cruelty: at values more than 10 cm: 3 cm, less than 10 cm: 2 cm,
. Average density: 20 kg/m3,
. Temperature: 3 degrees
. Preservation: at values up to 1.5 hours: 10 minutes, at values from 1.5 to 3: 20 minutes, at values over 3 hours: 30 minutes.
Documentary support
. The concepts <<concrete mixture of a given quality>> and <<concrete mixture of a given composition>> are introduced. In the second case, the manufacturer is not responsible for the quality of the products received - but only for providing the specified composition or the required properties.
. When ensuring the specified quality of the concrete mixture, TH must be provided with each load (=machine), with each delivery batch - copies of passports for raw materials
. It is allowed to form a single quality document for each batch, and not for each load, if this is specified in the supply contract.
Other
. According to European experience, the concept of mixture spreadability has been added to the indicators of cruelty / mobility. You can set specific values for workability (for example, a draft of a cone of 18 cm), and not a sufficiently wide mobility index (P 4, where the draft of a cone can be either 16 or 20 cm). System comment <<M 350>>: it is clear that it is difficult to achieve the required value of the property - but you can either provide a value with a margin, or count on an acceptable deviation,
. Accordingly, the mark for spread and the mark for compaction differ,
. Recommended average values for compaction factors are no longer given,
. It is allowed to add mortar - plasticizing additives to the mixture at the facility. The procedure for adding additives is described. Adding additives in the direction of the mixer from the plant to the facility does not contradict the standard, until the moment of acceptance, the supplier can do anything with the mixture.
. Incoming control over the quality of materials must be documented, but, according to the author, there is no point in incoming control of cement from different suppliers (it makes sense only when gradually checking batches of one supplier). The consumer has the right to demand preliminary data on the mixture that is supposed to be supplied to him. Thus, if a plant has never produced a mixture of a given quality, then in order for its words about the possibility of producing it to be unfounded, it must take 3 months from receiving an order to confirming the result in all respects (strength, frost resistance, water resistance)!
. It is required to specify the shelf life of properties so that the maximum duration of transportation corresponds to this.
The interpretation of the standards is the prerogative of the authors.
Therefore, in case of a discrepancy in the interpretation, Mark Izrailevich asked to be shy and contact the NIIZhB, where an answer to the request would be prepared.