Abstract
When exposed to sulfuric acid environments, the service life of concrete structures would be reduced due to the high alkalinity of concrete. The influence of three factors including water/cement ratio, the pH value of the solution, and the chemical composition of the aggregate on the resistance of concrete subjected to sulfuric acid has been widely investigated by previous researchers. This paper aims to investigate the influence of these three factors on the durability evaluation indicators including mass loss and surface fractal dimension through orthogonal experiments, which has been reported rarely in previous research. Four combinations of coarse and fine aggregate including gravel and river sand, gravel and crushed marble sand, crushed marble stone and river sand, and crushed marble stone and marble sand were adopted, and three water/cement ratios including 0.35, 0.45, and 0.55 were selected, and the sulfuric acid solution pH values 0.95, 2, and 4 were chosen in this paper. The results showed that the larger the water/cement ratio, the smaller the mass loss and the surface fractal dimension of the specimens, and with the decrease of the pH value of the sulfuric acid solution, the mass loss and the surface fractal dimension of the specimens would be increased. The concrete specimen containing gravel and river sand had the greatest surface fractal dimension and greatest mass loss, while the concrete specimen containing crushed marble sand had a smaller surface fractal dimension and a smaller mass loss. The dominant and secondary order of three factors on mass loss and surface fractal dimension of concrete subjected to sulfuric acid was the pH value of the solution > the chemical composition of the aggregate > the water/cement ratio.
Highlights
Concrete has become the most widely used material in the world due to the wide availability of resources of concrete components, the low cost for construction, the convenience for molding, and if properly used, concrete structures are usually designed and built for a minimum period of 50 years [1,2,3,4,5,6,7,8]
The results showed that the loss in weight for cubes made from concrete with high water/cement ratios was lower than that for cubes made with lower water/cement ratios
The mass loss ω for specimens could be expressed as follows: It can be seen in Figure 8 that the surface of the uncorroded specimens was flat and smooth, and the color of the surface ω of
Summary
Concrete has become the most widely used material in the world due to the wide availability of resources of concrete components, the low cost for construction, the convenience for molding, and if properly used, concrete structures are usually designed and built for a minimum period of 50 years [1,2,3,4,5,6,7,8]. The concrete structures were damaged only in a few years due to acid attacks. (2) In concrete sewer pipes, sulfur-containing compounds could be decomposed under the action of bacterial activity. 2021, 5, 146 that eventually produces sulfuric acid [10,12]. (3) Sulfuric acid, which could be formed by the oxidation of sulfur oxides produced by automobiles and industrial production activities, was a major component of acid rain in most parts of the world [12]. The deterioration of concrete subjected to sulfuric acid resulted in significant environmental problems and economic losses of billions of dollars annually. The cost of replacing and repairing corroded concrete sewer pipes each year in the UK and Germany was USD 130 million and USD
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