1 General provision
1.0.1 This code is formulated with a view to ensure durability of the concrete structure reach the specified design service life and ensure engineering life requirements for intelligent use.
1.0.2 This code is applicable to municipal infrastructure like building construction, city bridge and tunnel, and normal concrete structure as well as durability design of its members in general structures under common environmental action, but not applicable to lightweight aggregate concrete and other special concrete structure.
1.0.3 The specified durability design requirement of this code shall be that it shall reach the design service life for the structure and be provided with the minimum requirements for necessity factor of assurance. It may improve the design according to specific features, local environmental conditions, and practical experience, as well as specific execution conditions of engineering properly.
1.0.4 Durability design of concrete structure shall not only comply with requirement of this code, but also meet the requirement of national current relevant standards.
2 Terms and symbols
2.1 Terms
2.1.1 Environmental action
Action of temperature, humidity and their variation as well as environmental factors like carbon dioxide, oxygen, salt and acid for the structure
2.1.2 Degradation
Material property degrade with time gradually
2.1.3 Degradation model
Mathematical expression describes the degradation process of material property
2.1.4 Structure durability
Capacity for structural members to keep its applicability and security within design service life when it is under environmental action, maintenance and operating conditions determined by the design
2.1.5 Structure service life
Properties of structure can reach the age limit for operating requirement
2.1.6 Chloride diffusion coefficient of concrete
Parameters describing diffusion process of chloride flow from high concentration district to light concentration district in the concrete void water.
2.1.7 DF (durability factor)
After required times' fast freeze-thaw cycle test, the concrete is measured with dynamic modulus of elasticity to initial dynamic modulus of elasticity ratio through standard test method.
2.1.8 Air entrainment
When mixing the concrete, it shall take technology measures to form a uniform stable spherical microscopic bubble in the concrete with surface active agent.
2.1.9 Concrete air content
Air bubble volume to concrete total volume ratio in the concrete. For concrete adopting air entrainment technology, the air bubble volume includes air bubble volume and coagulation formed after mixing with air-entraining agent.
Air volume entrains in the soil mixing process.
2.1.10 Air bubble spacing
Average distance between adjacent air bubble edges in hardened concrete cement mortar.
2.1.11 Maintenance
Technologies and management activities adopted for maintaining the required properties of structures in service life.
2.1.12 Restore
Restore the damaged structure to activity made for meeting the regular service through repair, change or reinforcement.
2.1.13 Major repair
It requires stopping regular service of the structure within certain period, or displaces damaged concrete in the structure in large area, or change repair action of structure primary members.
2.1.14 Restorability
Damaged structure or member has the capacity for being restored economy and rationally.
2.1.15 Cementitious material or binder
It is a generic term of supplementary cementitious materials (such as Portland cement and pulverized fuel ash with cementation action, pulverized fuel ash, silicon ash and milled slag) and the blended stock in raw materials of the concrete.
2.1.16 Water to binder ratio
Water consumption to cementitious material gross weight ratio in the concrete mixture
2.1.17 Concrete with high volume of supplementary cementitious materials
Concrete with high proportion of supplementary cementitious materials (such as pulverized fuel ash, silicon ash and milled slag) and blended stock in the cementitious material, and requires adopting lower water to binder ratio and special construction measures.
2.1.18 Concrete cover to reinforcement
Minimum distance between external rim of the nominal diameters from the concrete to reinforcement (including longitudinal reinforcement, hooped reinforcement and distribution reinforcement); for the post-tensioned prestressing reinforcement, it is distance from external rim of bushing or pore canal to concrete surface.
2.1.19 Additional protective measures
On the basis of such routine means as ameliorating concrete compactness, increasing protective layer thickness and utilizing waterproof and drainage measures, the additional measures adopted to further improve the durability of concrete structure , which includes concrete surface coating, anticorrosive surface layer, epoxy coating reinforcement, reinforcement anti-rust agent and cathodic protection.
2.1.20 Multiple protective strategy
Multiple additional protective measures adopted to ensure service life for the concrete structure and members.
2.1.21 Concrete structure
Structure mainly made of concrete structure, including plain concrete structure, reinforced concrete structures and prestressed concrete structures; structures without reinforcement or not placed with reinforcing bar are plain concrete structure, and reinforced concrete and prestressed concrete structure are go by the general name of reinforced concrete structure in this code.
2.2 Symbols
c——Thickness of concrete cover to steel reinforcement
c1——Testing value for thickness of concrete cover to reinforcement;
Ca30——Air entrainment concrete with strength grade of c30;
DRCM——Chloride diffusion coefficient measured with standard test method by adding electric field to accelerate ion migration;
DF——Durability factor (DF);
E0——Initial dynamic modulus of elasticity before the concrete experiencing the freeze-thaw cycle;
E1——Dynamic modulus of elasticity after the concrete experiencing the freeze-thaw cycle;
W/B——Water to binder ratio of the concrete
αf——Pulverized fuel ash to the cementitious material gross weight ratio in the raw material of the concrete;
αs——Milled slag to the cementitious material gross weight ratio in the raw material of the concrete;
△——Absolute value for permissible negative deviation of concrete cover construction
3 General requirements
3.1 Principle of design
3.1.1 Durability of the concrete structure shall be designed according to structural design service life, its located environmental types and action grades.
For important concrete structure under chloride environment, it shall also adopt quantitative method to make the auxiliary verification in accordance with those specified in appendix A of this code.
3.1.2 Durability design of concrete structure shall include the following content:
1 Structural design service life, environmental type and its action grades;
2 Conduce to alleviating structural style, arrangement and structure under environmental action;
3 Durability quality requirements for the concrete structure material;
4 Thickness of concrete cover to reinforcement;
5 Control requirements for concrete fracture
6 Structure measures like waterproof and drainage;
7 Reasonably adopt additional protective measures or multiple protective strategies in severe environmental action
8 Construction curing schedule and construction quality Acceptance Requirements for protective layer thickness required for the durability
9 Maintenance, repair and testing requirement during the operational phase of the structure
GB/T 50476-2008 The following standards are cited：
