海工高性能混凝土及其使用壽命預(yù)測研究
2005-07-25 00:00
[摘要]近年來，我國在海工高性能混凝土及海工混凝土使用壽命預(yù)測的理論研究取得了一定進(jìn)展,但是在這方面的工程應(yīng)用技術(shù)研究成果尚未出現(xiàn)。本文從工程應(yīng)用的角度，在對杭州灣地區(qū)既有海工混凝土工程作實地調(diào)研的基礎(chǔ)上，研究分析杭州灣地區(qū)既有海工混凝土結(jié)構(gòu)的腐蝕特點和破壞原因；以海工高性能混凝土為研究對象，著重研究復(fù)合膠凝材料體系對混凝土性能的影響，并應(yīng)用激光粒度儀、EMPA等分析手段，就復(fù)合膠凝材料的作用機(jī)理進(jìn)行初步探討；試驗研究混凝土暴露時間、膠凝材料對氯離子的吸附、環(huán)境溫度、應(yīng)力和裂縫狀態(tài)等因素對混凝土中氯離子遷移運動的影響，并結(jié)合國內(nèi)外相關(guān)研究報導(dǎo)，探討這些因素在混凝土使用壽命預(yù)測模型中的表征；在上述研究基礎(chǔ)上，提出以氯離子侵蝕為基礎(chǔ)的海工混凝土使用壽命預(yù)測的工程應(yīng)用模型。
本文創(chuàng)新性研究工作及主要研究結(jié)論有：
1．研究分析了杭州灣地區(qū)既有海工混凝土結(jié)構(gòu)的腐蝕特點和破壞原因，認(rèn)為，海洋環(huán)境下，氯離子侵蝕是引起混凝土結(jié)構(gòu)破壞，決定混凝土結(jié)構(gòu)使用壽命的最主要的也是至關(guān)重要的原因。而混凝土保護(hù)層厚度和氯離子表觀擴(kuò)散系數(shù)的波動也在很大程度上決定著混凝土結(jié)構(gòu)的使用壽命。
2．研究了復(fù)合膠凝材料體系對混凝土性能的影響。結(jié)果表明，礦物摻合料的摻入可以極大地改善混凝土的性能，特別是抗氯離子侵蝕性能，從而提高混凝土結(jié)構(gòu)的使用壽命。應(yīng)用激光粒度儀、EMPA等分析手段，就復(fù)合膠凝材料的作用機(jī)理進(jìn)行初步探討，發(fā)現(xiàn)不同礦物摻合料的復(fù)合可以發(fā)揮其各自特長。由于其交互疊加效應(yīng)的作用，復(fù)合摻合料對混凝土性能的改善，特別是對抗氯離子侵蝕性能的改善比單一摻合料更為優(yōu)越。
3．試驗研究了混凝土中氯離子遷移的多種影響因素。研究表明，暴露時間、膠凝材料對氯離子的吸附作用、混凝土保護(hù)層應(yīng)力和裂縫狀態(tài)、環(huán)境溫度等對混凝土中氯離子的遷移均有較大的影響，這些影響因素可以通過對氯離子表觀擴(kuò)散系數(shù)的修正來表征，將其引入使用壽命預(yù)測模型。
4．在海工混凝土使用壽命模型的研究中，以Fick第二定律為基礎(chǔ)建立了基本數(shù)學(xué)模型，引入混凝土氯離子擴(kuò)散系數(shù)的時間修正因素、溫度修正因素、應(yīng)力和裂縫狀態(tài)等修正因素，并結(jié)合可靠度理論，從而建立了海工混凝土壽命預(yù)測模型及其計算軟件SLPMC。
現(xiàn)場調(diào)查研究杭州灣地區(qū)既有海工工程的使用狀態(tài)，獲得必要的現(xiàn)場檢測數(shù)據(jù)，為高性能混凝土在海工工程中的應(yīng)用提供了科學(xué)依據(jù)。
研究復(fù)合膠凝材料在海工高性能混凝土中的應(yīng)用，探討復(fù)合膠凝材料的作用機(jī)理，對于促進(jìn)礦物摻合料的高效利用、海工高性能混凝土應(yīng)用技術(shù)水平的深化、加速混凝土摻合料技術(shù)發(fā)展有一定的經(jīng)濟(jì)、技術(shù)和社會意義。
研究分析各種因素對混凝土中氯離子遷移的影響，并在前人研究成果的基礎(chǔ)上，建立以氯離子侵蝕為基礎(chǔ)的海工混凝土使用壽命預(yù)測的工程應(yīng)用模型及其計算軟件，可以用于海洋環(huán)境下的混凝土結(jié)構(gòu)或構(gòu)件的使用壽命預(yù)測，為擬建海工建筑物的耐久性設(shè)計提供指導(dǎo)性意見，對建設(shè)中的海工工程質(zhì)量控制體系的建立提供必要的依據(jù)，就現(xiàn)存海工工程的使用壽命進(jìn)行預(yù)測，并制定相應(yīng)的維護(hù)措施和修補方案，因而具有一定的實用價值。
ABSTRACT
In the past few years, much progress has been made in the theory study of HPC used in Marine and the prediction of its service life, but few has been achieved in engineering application technique of these theories. From the angle of engineering application, this article analysed the corrosion characteristics and damage causes of the current structural used concrete in the region of Hangzhou gulf， on the basis of on-site survey of all the Marine concrete projects in that area. Taking HPC used in Marine as research objective, this article put great emphasis on the influence of the composition cementing material system to concrete performance, and make a preliminary probe into the action mechanism of the composite effects of various mineral materials in improving the performance of concrete by laser measuring size machine and EMPA. Through experiments, the article discussed how chloride ingression in concrete will be effected by such factors as exposure time, chloride binding, environment temperature, stress and cracks conditions; and also analysed the symptoms of these factors in the model of concrete service life prediction by conference to all related research reports both home and aboard. On the foundation of abovementioned research, this paper brought up an engineering model of service life prediction of marine concrete, which is based on chloride-induced corrosion.
The innovative research work and main conclusion are as follows:
1. The corrosion characteristics and damage reason of the current structural used concrete in region of Hangzhou gulf have been studied and analysed. It is suggested that, under marine environment, chloride ingression is a main cause to the concrete construction breakage and therefore mostly determined the service life of concrete construction. The service life of the concrete construction is also in a large extent decided by the flunctuation of the thickness of concrete cover and the apparent diffusion coefficient Da of chloride.
2. The influence of the composition cementing material system to concrete performance has been studied. The research results indicated that the performance of concrete, particularly the performance of resistance to chloride ingression, has been greatly improved by adding various reactive mineral materials, such as ground granulated blast furnace slag, fly ash and silica fume. As a result, the service life of the concrete construction will also be lengthened. The action mechanism of the composite effects of various mineral materials in improving the performance of concrete has been researched by the application of laser measuring size machine and EMPA. It is found out that those mineral materials composite could bring mutual advantages into action. With composition of those mineral materials, the concrete performance, particularly the performance of resistance to chloride ingression, has been improved more than any one of them alone.
3. Experiments show that chloride ingression in concrete is influenced by many factors. The research indicated that chloride ingression is largely determined by exposure time, chloride binding, environment temperature, stress and cracks conditions, the symptoms of which could be found with the modifier of the apparent diffusion coefficient Da of chloride, in the model of concrete service life prediction.
4. In the research of the model of the service life prediction of marine concrete, the Fick’s II laws is taken as the basic mathematics model, considering the effect elements, such as exposure time, chloride binding, environment temperature, stress and cracks conditions, and united reliability analysis method, which established the model of the service life prediction of marine concrete and its calculation software SLPMC.
It provided scientific evidence for HPC applied in marine concrete by acquiring the necessity experiment data by the spot investigation to study the usage appearance of the current structural used concrete in region of Hangzhou gulf.
It has a certain economical, technical and social meaning to promote an efficient use of mineral admixture so as to deepen the technique level of HPC applied in marine concrete, and accelerate the development of concrete admixture technique through the study of the composition cementing material system applied to HPC in marine and the discussion of the action mechanism of the composite effects of various mineral materials in improving the performance of concrete.
The engineering application model of the service life prediction of marine concrete based on chloride-induced corrosion and its calculation software is established in this article by analysing all factors influencing chloride ingression and referring to some other researchers conclusions. All of those conclusions can be used to predict the service life of concrete in marine environment, provide a guiding idea for the endurance design of marine project intending to build, offer necessity basis for establishing of quantity control system of marine project in building, and predict the current structural used concrete in marine so as to establish relevant maintenance and repair scheme. In this way, it is also expected to have a certain practical meaning.
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