Hongfa Yu

Reinforcement corrosion research based on the linear polarization resistance method for coral aggregate seawater concrete in a marine environment

Purpose This paper aims to reduce the cost, limit the time and increase raw material source availability, coral aggregate seawater concrete (CASC) composed of coral, coral sand, seawater and cement can be widely used for the construction of ports, levees, airports and roads to achieve practical engineering values. However, the naturally porous coral structure and abundant Cl− in the seawater and coral lead to extremely severe reinforcement corrosion for CASC. It is well known that Cl− is the main cause of reinforcement corrosion in the marine environment. Therefore, it is necessary to research the reinforcement corrosion of CASC in the marine environment. Design/methodology/approach In this study, linear polarization resistance was adopted to test the linear polarization curves of reinforcement in CASC with different exposure times. Ecorr, Rp, Icorr and Vcorr were calculated according to the weak electrochemical polarization theory and Stern–Geary formula. The effects of concrete cover thickness, exposure time, reinforcement types and inhibitor on reinforcement corrosion in CASC were analysed. The reinforcement corrosion degradation rule was determined, which provided theoretical support for the durability improvement, security assessment, service life prediction and service quality control of CASC structures in marine islands and reef engineering. Findings The corrosion resistance was enhanced with increased concrete cover thickness, and the concrete cover thickness for organic new coated steel should be at least 5.5 cm to reduce the reinforcement corrosion risks in CASC structures. The corrosion resistance of different types of reinforcements followed the rule: 2205 duplex stainless steel > 316 stainless steel > organic new coated steel > zinc-chromium coated steel > common steel. In the early exposure stage, the anti-corrosion effectiveness of the calcium nitrate inhibitor (CN) was superior to that for the amino alcohol inhibitor (AA). With the extension of exposure time, the decreasing rate of anticorrosion effectiveness of CN was higher than that of AA. Originality/value Reinforcement corrosion of CASC in a marine environment was studied. Concrete cover thickness, exposure time, reinforcement type and inhibitor influenced the reinforcement corrosion were investigated. New technique of reinforcement anti-corrosion in marine engineering was proposed. Possible applications of CASC in marine engineering structures were suggested.

Microstructural Evolution of Concrete under the Attack of Chemical, Salt Crystallization, and Bending Stress

AbstractThe present work investigates the microstructural evolution process of concrete under chemical attack by magnesium sulfate solution or a composite solution (sodium sulfate and magnesium chl...

Research on A3 steel corrosion behavior of basic magnesium sulfate cement

In this paper, Tafel polarization technique is used to study the corrosion behavior of A3 steel basic magnesium sulfate, and then analyzing the ratio of raw materials cement, nitrites rust inhibitor and wet-dry cycle of basic magnesium sulfate corrosion of reinforced influence, and the steel corrosion behavior of basic magnesium sulfate compared with magnesium oxychloride cement and Portland cement. The results show that: the higher MgO/MgSO4 mole ratio will reduce the corrosion rate of steel; Too high and too low H2O/MgSO4 mole ratio may speed up the reinforcement corrosion effect; Adding a small amount of nitrite rust and corrosion inhibitor, not only can obviously reduce the alkali type magnesium sulfate in the early hydration of cement steel bar corrosion rate, but also can significantly reduce dry-wet circulation under the action of alkali type magnesium sulfate cement corrosion of reinforcement effect. Basic magnesium sulfate cement has excellent ability to protect reinforced, its long-term corrosion of reinforcement effect and was equal to that of Portland cement. Basic magnesium sulfate corrosion of reinforced is far below the level in the MOC in the case.

Deterioration of High Performance Hybrid Fibers Reinforced Expansive Concrete Exposed to Magnesium Sulfate Solution

Deterioration of fly ash concrete, high performance concrete, and high performance hybrid fibers reinforced expansive concrete (HPHFREC) exposed to 5% magnesium sulfate solution is investigated. Two corrosion regimes were employed: natural immersion and dry-wet cycle. From the experimental results, it is found that erosion of concretes under combined action of magnesium sulfate and dry-wet cycles is more severe than that in single magnesium sulfate corrosion, and the dry-wet cycle accelerates the deterioration of concretes in magnesium sulfate environment. In early exposure period, concrete has a structure reinforced phase during which dynamic modulus of elasticity and mass of concretes increase steadily. Among the four types of concretes tested, HPHFREC gets the best corrosion resistance and surface peeling resistance in magnesium sulfate environment.