The development of Portland cement and concrete in the 19 th and 20 th centuries revolutionised the construction industry, and provided a means of achieving architectural and structural feats that were previously impossible. While reinforced concrete bridges provided a means of simultaneously spanning vast distances and carrying significant loads, the material was little understood and designs reflected this. As a result, many early reinforced concrete structures suffer from significant durability issues and there is a growing requirement for their maintenance and repair, but the extent of the issue is unclear. As such, this review of historic test data intends to provide insight into previous reinforced concrete bridge design in Scotland, compare their design to current engineering codes, and discuss the implications for maintaining and preserving these unique examples of architectural heritage.
Microbially induced concrete corrosion
is a major deterioration
process in sewers, causing a huge economic burden, and improved mitigating
technologies are required. This study reports a novel and promising
effective solution to attenuate the corrosion in sewers using calcium
nitrite-admixed concrete. This strategy aims to suppress the development
and activity of corrosion-inducing microorganisms with the antimicrobial
free nitrous acid, which is generated in situ from calcium nitrite
that is added to the concrete. Concrete coupons with calcium nitrite
as an admixture were exposed in a sewer manhole, together with control
coupons that had no nitrite admixture, for 18 months. The corrosion
process was monitored by measuring the surface pH, corrosion product
composition, concrete corrosion loss, and the microbial community
on the corrosion layer. During the exposure, the corrosion loss of
the admixed concrete coupons was 30% lower than that of the control
coupons. The sulfide uptake rate of the admixed concrete was also
30% lower, leading to a higher surface pH (0.5–0.6 unit), in
comparison to that of the control coupons. A negative correlation
between the calcium nitrite admixture in concrete and the abundance
of sulfide-oxidizing microorganisms was determined by DNA sequencing.
The results obtained in this field study demonstrated that this novel
use of calcium nitrite as an admixture in concrete is a promising
strategy to mitigate the microbially induced corrosion in sewers.
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