1. Technical requirementsTechnical requirements –Resistance to corrosion –Frost-resistance –Thickness protective layer of marine reinforced concrete –The maximum permitted crack Raw materials choiceRaw materials choice 4.7.6 Seawater-resistant concrete

2. Resistance to corrosion It is ensured mainly by raw materials which are used to produced concrete (such as cement and aggregate). Resistance to chlorine ionic corrosion –Its index is ensured mainly by measuring the coefficient of diffusion of chlorine ion in concrete.

3. Frost-resistance Average monthly temperature in the coldest month/ ℃ ≥0 ℃ 0～4℃0～4℃0～4℃0～4℃ -4 ～ -8 ℃ ≤-8 ℃ Required antifreeze of concrete no requirement ≥F250≥F300≥F350 Tab.4.7.8 Frost-resistance Frost-resistance of Seawater-resistant concrete is shown in Tab.4.7.8

4. Thickness protective layer area part the air- touched the wave- touched water level under water the north 50505030 the south 50655030 Tab.4.7.9 The minimum thickness of protective layer of marine reinforced concrete/mm

5. Tab.4.7.10 The minimum thickness of protective layer of deformed bar in sea circumstance/mm thickness of component part the air- touched the wave- touched water level under water ≥0.5m75907575 <0.5m Select the Max.;(a)2.5×prestressed reinforced concrete diameter (mm) ； (b)50 Thickness protective layer

6. The maximum permitted crack parts of structure conditions sea water fresh water above the water 0.130.20 water surface 0.200.25 under the water 0.300.35 Tab.4.7.11 The maximum permitted width of cracks in reinforced concrete components (JTJ268-96)/mm

7. Raw materials choice Cement: The cements whose hydrate contains little Ca(OH) 2 and hydrated aluminate should been chosen according to sea corrosion of concrete. If it is applied on the water surface, freeze-resistance, abrasive resistance, shrinkage should be taken into consideration. The strength grades should not be lower than 32.5MPa.

8. Raw materials choice Aggregate: Aggregate should shows strong fabric, clearness and good gradation To be specially noticed, the coarse aggregate ， which is used to produce seawater-resistant concrete ， should not contain active SiO 2, to prevent the reaction between alkali and aggregate. According to JTJ, if sea sand chosen as fine aggregate, it should be flowed by cleat water until the content of NaCl reaches below 0.1%. Admixture: such as water reducing, accelerator and anti-freezing mixture ， can be chosen according to the requirements of engineering.