The Application Of Damage Theory On Research On The Mechanical Properties Of Corroded Concrete

The corrosion of concrete in the sewage delivery and processing system is a new subject. Current research on the corrosion of concrete mainly concentrates on corrosion substance and mechanism, while deep study on the evolvement rules of physics mechanics properties and constitutive relationship of corroded concrete has not been dealt with yet. It is great significant to further study on this subject to improve environment protection and energy saving.In this thesis, it is discussed on the concrete corrosion due to living waste water, then established the evolvement equation of strength damage of corroded concrete based on damage mechanics theory, and the constitutive relationship of corroded concrete under uniaxial compression . The main research works in this thesis are as follows: summary of the corrosion mechanism of concrete under the variety of corrosion factors;discussion on the causation and process of concrete corrosion due to living waste water;confection over twenty groups of testing liquid, containing matter of mineral, organic matter and microbe respectively as a result of sampling and analyzing of living waster water. conducting soaking experiment with cube and prism concrete specimens.establishment of the evolvement equation of strength damage of corroded concrete;establishment of the uniaxial press stress-strain model of corroded concrete The conclusions are as follows:The developing process of the concrete strength under the corrosion is a complex. On the one hand, the concrete post increasing strength continues for several years, which appears great difference in term of difference materials and environments. On the other hand, the concrete is destroyed gradually and corrosion substance and external environment (such as the temperature) have great influence on concrete corrosion. Thus under these two actions, concrete strength appears to be random variation. The strength damage variable of corrosion concrete is less sensitivity to the density varieties. The strength damage has indifferent change at a certain scope of intensity during the same time. With the time increasing, it increases gradually and tends to 1 and the concrete is destroyed totally.The corroded concrete has almost same damaged process as the un-corrosion concrete. But it has some special features: the concrete corroded heavily has severe crack in compressing process, and the main fissure develops rapidly and observably while other fissures develop indistinctively.Compared to the un-corrosion concrete, the initial elastic modulus and peak stress of corroded concrete descend, and the former has much decrease than the latter. With the deep corrosion, the initial elastic modulus is much close to the secant modulus at the peak stress, and meanwhile the stress-strain curve tends to a tip shape. But corroded concrete and normal concrete have the similar shape general stress-strain curve under uniaxial compression. Beginning with the damage theory of micro-statistics, the constitutive model of corroded concrete under uniaxial compression is established which is proved by the experimental outcomes. The uniaxial press stress-strain curve could be founded if only the initial elastic modulus, peak stress and its secant modulus are determined.