Abstract
To understand the effect and mechanism of urban heat island (UHI) and the acid corrosion of concrete on the strength of concrete in superficial soil layers from Nanjing area, both laboratory and field tests of accelerated corrosion of concrete were carried out and analyzed. The laboratory test results indicate that the concrete corrosion depends on acid concentration, tested time, and also on the temperature. The maximum corrosion coefficient (K-value) of 45.86%, as observed at 10% of acid concentration, 40°C of tested temperature, and 90 days of tested time, was about 2 times that of specimens with 10% of acid concentration, 5°C tested temperature, and tested after 90 days. The field test showed that the compressive strength of specimens in urban station was lower than that of specimens in rural station. The K-value of specimens with same acid concentration observed at urban area was higher than that of specimens at rural area. Both the laboratory and field tests showed that the temperature has an increasingly powerful influence on the concrete corrosion under acid environment. Therefore, the UHI effect will accelerate the acid corrosion in concrete construction and may affect the stability and durability of buildings in urban areas. The safety and life assessment of concrete buildings therefore require great attention.
Highlights
Urban heat island (UHI) means that the temperature in urban areas is considerably higher than that in surrounding rural areas
unconfined compressive strength (UCS) of specimens with different acid corrosion medium concentration, ambient temperature, and tested time are presented in Table 3. e variation of compressive strength of concrete specimens with temperature and acid concentration is shown in Figures 3 and 4
The maximum monthly urban heat island intensity (UHII) is observed in November as 3.67°C, and the minimum monthly UHII is observed in July as 0.49°C; the 3-monthly UHII in the tested time is 1.25°C, 1.91°C, 3.61°C, and 3.26°C, respectively; and the yearly UHII is 2.51°C
Summary
Urban heat island (UHI) means that the temperature in urban areas is considerably higher than that in surrounding rural areas. It is becoming more and more significant in many major cities [1,2,3]. E urban heat island intensity (UHII), which is the temperature difference between the urban area and the surrounding rural areas, was used to quantitatively describe the UHI effect [6]. Variation in temperature affects the engineering properties of soil in urban area, and the strength and stability of various engineered structures differ [14]. Many previous studies have shown that the increasing superficial soil temperature influenced the soil permeability, suction of unsaturated soils, and shear strength of soil [15,16,17]
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