Durability Assessment And Life Analysis For Reinforced Concrete Of The Existing Gravity Piers Wharf

The world economy has indicated that the21st century is an ocean century, thevigorous development of offshore engineering and constructions have undergone aprosperous period. However, as is known to all, there is a atrocious corrosivity in themarine environment. The deterioration and too early failure of reinforced concretestructure on active duty under the harsh marine corrosion have been an increasinglyuniversal phenomena and a sever hidden danger which need to be solved urgently.Moreover, the corrosion damage of seaport wharf bears the brunt hereinto. Thereinforced concrete structure, which has experienced a long term effect of the waveimpact and immersion, sunlight insolation, dry-wet alternation, coastal salty air, andmarine organism, could evolve the pre-aging degradation in the early stage such as themicro-cracks, surface concrete looseness and mild denudation. Whatever, if thecorrosion detections and reparations is not timely prompt, there could be triggering thesplitting spalling, vertical spalling and even the serious safety accident such as thestructure cracking and collapse. Therefore, the concrete structure should be repaired toenhance the corrosion protection and service life before damage happens.First of all, the development of durability detection and evaluation as well as theservice life analysis of reinforced concrete structure in sea port wharf could providereasonable reparation methods and feasible maintenance projects for the multiplecorrosion causes in various construction parts with different function. On the otherhand, the corrosion environment and degradation development analysis for the underconstruction reinforced concrete structure would propose a rational and originalreference standard for protection solution and service life design. Moreover, it couldevaluate the benefit period of durability maintenance and reasonable method of safetydetection for new completion sea port wharf. It would form an effective instruction andpractical guarantee for the service life extension of marine infrastructure.The type of reinforced concrete structure of gravity piers is the main harbor wharffacilities, because of the particularity of its environment, the most serious corrosion.Based on the practical project of a coal terminal, it has targeted for durability test, evaluation dock and life analysis. The major is as follow:(1) According to the corrosion of gravity-type wharf, the carbonation depth,strength, chlorine corrosion depth and steel corrosion on the test.The chlorine content of concrete is up to0.15%at steel surface, it has more thanrequirement limits. T beam and box girder are detected for corrosion potential byhalf-cell potential, found that corrosive probability with twenty-five percent.(2) Some bars ( 22) were taken from structure where it is no impact on thestructural mechanical properties for mechanical test. Steel has mainly both corrosivesides, a drum cross section and rust pit, and weightlessness rate is about30%. But inthe mechanical properties of tensile test results has the obvious four stages. Theaverage value for yield strength of corrosive steel is0.4, and nominal ultimate strengthis0.42.(3) Based on the analytic hierarchy process (AHP), it adopts the Λ-typesubordinate function to set up the durability index assessment model of the existingreinforced concrete on the basis of fuzzy comprehensive assessment. Last, according tothe most subjection criterion the grade of durability of concrete construe is got. Andcombined with engineering example, choosing the testing data evaluate the durabilityof the wharf. Evaluation result was coincident with the reality, and show that themethod is generally feasible.(4) Service life prediction based on cracking of concrete cover induced bycorrosion. Choosing reasonable theoretical models and making use of experiment data,the durability remaining life was predicted. The factors were analyzed which influencethe structural service life including concrete cover, bar diameter, corrosive currentdensity and the concrete strength. The analysis results show that: rebar corrosioncurrent, the thickness of concrete cover and reinforced diameter on significantinfluence on concrete cracking, and improving the concrete tensile strength to delayconcrete cracking is not obvious.