3. Globalización y territorio
3.6 Claves para el estudio de la relación entre
101 For selection of structural concrete materials, DNV-OS-C502 Sec.4, “Structural Concrete and Materials”
shall apply.
102 The present subsection, B, provides a short summary of DNV-OS-C502 Sec.4, focusing on issues which
typically pertain to offshore concrete structures, but not necessarily to standard concrete design. For all design purposes, the user should always refer to the complete description in DNV-OS-C502 and the text in Subsection B shall be considered application text for the text of DNV-OS-C502 with respect to offshore wind turbine concrete structures.
B 200 Material requirements
201 The materials selected for the load-bearing structures shall be suitable for the purpose. The material
properties and verification that these materials fulfil the requirements shall be documented.
202 The materials, all structural components and the structure itself shall be ensured to maintain the specified
quality during all stages of construction and for the intended structural life.
203 Constituent materials for structural concrete are cement, aggregates and water. Structural concrete may
also include admixtures and additions.
204 Constituent materials shall be sound, durable, free from defects and suitable for making concrete that will
attain and retain the required properties. Constituent materials shall not contain harmful ingredients in quantities that can be detrimental to the durability of the concrete or cause corrosion of the reinforcement and shall be suitable for the intended use.
205 The following types of Portland cement are, in general, assumed to be suitable for use in structural
concrete and/or grout in a marine environment if unmixed with other cements: — Portland cements
— Portland composite cements
— Blastfurnace cements, with high clinker content.
Provided suitability is demonstrated also the following types of cement may be considered: — Blastfurnace cements
— Pozzolanic cements — Composite cements.
The above types of cement have characteristics specified in international and national standards. They can be specified in grades based on the 28-day strength in mortar. Cements shall normally be classified as normal hardening, rapid hardening or slowly hardening cements.
Guidance note:
Low heat cement may be used where heat of hydration may have an adverse effect on the concrete during curing. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---
206 The required water content is to be determined by considering the strength and durability of hardened
concrete and the workability of fresh concrete. The water-to-cement ratio by weight may be used as a measure. For requirements to the water-to-cement ratio, see B305.
207 Salt water, such as raw seawater, shall not be used as mixing or curing water for structural concrete. 208 Normal weight aggregates shall, in general, be of natural mineral substances. They shall be either
crushed or uncrushed with particle sizes, grading and shapes such that they are suitable for the production of concrete. Relevant properties of aggregate shall be defined, e.g. type of material, shape, surface texture, physical properties and chemical properties.
Aggregates shall be free from harmful substances in quantities that can affect the properties and the durability of the concrete adversely. Examples of harmful substances are claylike and silty particles, organic materials and sulphates and other salts.
209 Aggregates shall be evaluated for risk of Alkali Silica Reaction (ASR) in concrete according to
internationally recognised test methods. Suspect aggregates shall not be used unless specifically tested and approved. The approval of aggregates that might combine with the hydration products of the cement to cause ASR shall state which cement the approval applies to. The aggregate for structural concrete shall have sufficient strength and durability.
210 An appropriate grading of the fine and coarse aggregates for use in concrete shall be established. The
grading and shape characteristics of the aggregates shall be consistent throughout the concrete production.
211 Maximum aggregate size is to be specified based on considerations concerning concrete properties,
spacing of reinforcement and cover to the reinforcement.
212 Latent hydraulic or pozzolanic supplementary materials such as silica fume, pulverized fly ash and
granulated blast furnace slag may be used as additions. The amount is dependent on requirements to workability of fresh concrete and required properties of the hardened concrete. The content of silica fume used as additions should normally not exceed 10% of the weight of Portland cement clinker. When fly ash, slag or other pozzolana is used as additions, their content should normally not exceed 35% of the total weight of cement and additions. When Portland cement is used in combination with only ground granulated blast furnace slag, the slag content may be increased. The clinker content shall, however, not be less than 30% of the total weight of cement and slag.
213 The composition and properties of repair materials shall be such that the material fulfils its intended use.
Only materials with established suitability shall be used. Emphasis shall be given to ensure that such materials are compatible with the adjacent material, particularly with regard to the elasticity and temperature dependent properties.
B 300 Concrete
301 Normal Strength Concrete is a concrete of grade C30 to C65. 302 High Strength Concrete is a concrete of grade in excess of C65.
303 The concrete composition and the constituent materials shall be selected to satisfy the requirements of
DNV-OS-C502 and the project specifications for fresh and hardened concrete such as consistency, density, strength, durability and protection of embedded steel against corrosion. Due account shall be taken of the methods of execution to be applied. The requirements of the fresh concrete shall ensure that the material is fully workable in all stages of its manufacture, transport, placing and compaction.
304 The required properties of fresh and hardened concrete shall be specified. These required properties shall
be verified by the use of recognised testing methods, international standards or recognised national standards. Recognised standard is relevant ASTM, ACI and EN standard.
305 Compressive strength shall always be specified. In addition, tensile strength, modulus of elasticity (E-
modulus) and fracture energy may be specified. Properties which can cause cracking of structural concrete shall be accounted for, i.e. creep, shrinkage, heat of hydration, thermal expansion and similar effects. The durability of structural concrete is related to permeability, absorption, diffusion and resistance to physical and chemical attacks in the given environment, a low water/cement-binder ratio is generally required in order to obtain adequate durability. The concrete shall normally have a water/cement-binder ratio not greater than 0.45. In the splash zone, this ratio shall not be higher than 0.40.
306 The demands given for cement content in DNV-OS-C502 Sec.4 C209 shall be considered as demands
for cement/filler content calculated according to a recognised standard. The demands may be waived based on conditions such as less strict national requirements or track records for good performance and durability in marine environments for similar structures.
307 The concrete grades are defined as specified in DNV-OS-C502 Sec.6.
The properties of hardened concrete are generally related to the concrete grade. For concrete exposed to seawater the minimum grade is C40. For concrete which is not directly exposed to the marine environment, the grade shall not be less than C30.
308 The concrete grades are defined in DNV-OS-C502 Sec.4 Table C1 as a function of the Characteristic
Compressive Cylinder strength of the concrete, fcck. However, the grade numbers are related to the Characteristic Compressive Cube strength of the concrete, fck (100 mm cube).
B 400 Grout and mortar
401 The mix design of grout and mortar shall be specified for its designated purpose.
402 The constituents of grout and mortar shall meet the same type of requirements for their properties as
those given for the constituents of concrete.
B 500 Reinforcement steel
501 Reinforcements shall be suitable for their intended service conditions and are to have adequate properties
with respect to strength, ductility, toughness, weldability, bond properties (ribbed), corrosion resistance and chemical composition. These properties shall be specified by the supplier or determined by a recognised test method.
502 Reinforcement steel shall comply with ISO 6935, Parts 2 and 3 or relevant national or international
standards for reinforcement steel.
the standard used. In general, hot-rolled, ribbed bars of weldable quality and with high ductility shall be used. Where the use of seismic detailing is required, the reinforcement provided shall meet the ductility requirements of the reference standard used in the design.
504 Fatigue properties and S-N curves shall be consistent with the assumptions of design. B 600 Prestressing steel
601 Prestressing steel shall comply with ISO 6934 and/or relevant national or international standards for
prestressing steel.