Research On Durability Of Autoclaved Prestressed High Strength Concrete Pipe In Southern Coastal Areas

Autoclaved prestressed high strength concrete pipe (hereinafter referred to pile) as a goodbuilding pile foundation material, it has many advantages with industrial production, high pilecapacity, low cost, convenient construction and so on, it has been widely used in southerncoastal areas. Currently, the performance evaluation of pile is strength, while the durabilityevaluation and life assessment of pile is very limlited,as for higher concentration ofaggressive ion in coastal areasgroundwater, how to ensure the durability of the pile hasbecome a burning problem.Thus, as for the southern coastal areas environment characteristics,it has important practical significance to study the pile durability.First of all, this article researchesperformance of cracks through the pile of concretecracks under stress simulation, the results show that:under the cracks, air maintenance, poolmaintenance, concrete resistance,with the increase of the compressive stresslevel, the value ofelectricity has an increasing trend, So in order to avoid the possible durability issues whichleaded by cracks, it is recommended using different concrete anti chloride ion performanceindex before and after construction.Secondly, the paper studied three technical measures (mixed with mineral admixtures, rustinhibitor, cementitious capillary crystalline waterproofing material) on the pile concreteimpact of short-term performance and long-term performance impact.,while the paper studiesa long performance test with the steel (pile plate, prestressed reinforcement, spiralreinforcement) and static pressure pile to explore the different corrosive environments piledurability.The study results showed that:(1) The value of electricity of existing ground sand mixed concrete is on the small side,along with the growth of age, the value of electricity of concrete changed limited under themicro-corrosion, weak corrosion and middle corrosion environment, so the pile do not need tobe protective; but under the strong corrosive environment the value of electricity has anincrease trend, so the pile should be taken protective measures.(2) Single mix of fly ash or slag powders instead of fine sand are making piles ofconcrete value of electricity increased, and the long-term experiments show that: mix slag powder can’t effectively improve the performance of resistance to chloride ion of concrete,further more the cost of the Slag powder is higher than the fine sand. So the paperrecommends using the fine sand as the admixture on the pipes.(3) The organic inhibitor has an adverse effect for the strength of steam-cured concrete,but it does not affect autoclaved strength, while the organic inhibitor has little effect onperformance of chloride resistance.Compared with the blank sample, organic inhibitors candelay the occurrence of corrosion of reinforcement in concrete time and reduce corrosionspeed in strong corrosive environments.(4) Mixed and brushing cementitious capillary crystalline waterproofing materials can’timprove the performance of resistance to chloride ion of pile concrete, and in strong corrosiveenvironments, combined with the actual project construction cost, waterproof material is moreexpensive than inhibitor, it is recommended to use inhibitor, and it does not recommend theuse of cementitious capillary crystalline waterproofing materials.(5) For the pile joint anti-corrosion, the pile joints don’t need protection inmicro-corrosion,weak corrosive environments, it can have simple protective measure with brushing orwrapping hot asphalt hot asphalt impregnated glass fiber cloth in middle corrosiveenvironments; in strong corrosive environments, it should consider making use of weatheringsteel as pile plates or increase the corrosion allowance2mm or more,and also can use groutfor pile steel to meet the durable life assurance requirements.Finally, based on the European Duracrete durable life assessment methods, through theresearch on several key parameters of concrete durability life, assumed equal to the ambientchloride ion concentration of chloride ion concentration, chloride ion diffusion coefficient ofconcrete piles almost no attenuation preconditions, the paper finds out the pile durable lifeassessment model in chloride environments, the study results showed that:(1)The autoclaved concrete pipe can used in the micro-corrosion, weak corrosion andmiddle corrosion environment, shouldn’t be used in the strong corrosive environment. Underthe micro-corrosion, weak corrosion and middle corrosion water area, the pile do not need tobe protective; in the wet dry zone, the pipe should mix with corrosion inhibitor and it will be better to avoid using in the is kind of environment.(2) Before construction chloride resistance of concrete piles3d instar performance can bemeasured specimen, specimens were cut ahead of1d water; piles after constructionperformance chloride resistance of concrete core samples can be measured pumping trailercoupling, when measured chloride ion in the tube pile outside, where electricity consumptionvalues measured using the chloride ion diffusion coefficient determined using RCM, becausepower law is simple and fast, and the value of electricity and chloride ion diffusion coefficientgood linear relationship exists between the recommended values evaluated using electricity.(3)The large amount of the experiment in the paper show that under the micro-corrosion,weak corrosion and middle corrosion environment, the design life-span of the pipe is50year,70year,100year, the construction condition should be: before the construction the concreteelectricity value index should be less than800C,700C,500C, or the Chloride ion diffusioncoefficient should be less than2.510-12m~2/s、2.010-12m~2/s、1.210-12m~2/s; after theconstruction the concrete electricity value index should be less than1000C,800C,600C,orthe Chloride ion diffusion coefficient should be less than3.510-12m~2/s、2.510-12m~2/s、1.510-12m~2/s.