دانلود رایگان مقاله توسعه و اعتبار تجربی ملات پوشش با فعالیت بیوسیدال

abstract

Biodeterioration of concrete by microorganism colonisation may be a problem in several structures, especially in irrigation and hydroelectric canals. The main problem in such structures is the proliferation of algae and cyanobacteria that affect the performance of the structure, increase the maintenance costs and affects its durability. A research was conducted to develop a novel cement-based material with biocide activity that can be used as an overlay mortar in existing structures, such as canals and pipes. With this aim, ten commercial biocides were evaluated in a laboratory campaign to assess the effectiveness of the compounds against the microbial colonisation of concrete. Both mono- and multicomponent formulations were designed from the commercial products, to increase their antimicrobial effect obtaining a set of biocide formulations. The formulations were submitted to a flowchart process to determine their influence on the physical properties of the concrete, evaluate the release of the actives, and their antimicrobial efficiency both before and after accelerated aging processes. During the campaign, some formulations were observed to diminish the strength of the concrete. Such behaviour was normally due to the interaction of the active with the cement hydration process. Other formulations showed a high release of active from the concrete in water, compromising the durability of the treatment. In general, monocomponent formulations did not succeed to fulfill all the requirements, thus multicomponent formulations were analysed. One studied multicomponent formulation presented particularly good results in all properties analysed. This product did not significantly change the properties of concrete and the release of active in water from the concrete was low, while the antimicrobial effects were long lasting.

4. Conclusions

Fifteen biocide formulations were studied during this campaign to assess their biocide effects when incorporated into concrete. These formulations were elaborated from different commercially available antimicrobial products that were chosen for costeffectiveness, non-toxicity, and capacity as disinfectants in other applications, such as floor and wall coverings. The biocide formulations were composed of one (monocomponent) or more antimicrobial products (multicomponent) as well as incorporating different additives in some cases. A three-phase process was performed to evaluate the physical properties, release of active and antimicrobial properties of the concrete samples incorporating the different formulations. The study showed that monocomponent formulations were insufficient to inhibit biological growth in concrete without either significant detriment to the mechanical properties of the material or losing efficient biostatic activity after a short period. To obtain a longlasting effect against a wide spectrum of microorganisms, the use of multicomponent formulations was necessary. The use of existing commercial products such as Vanquish 100®, Densil P®, and BC 98-56 presented significant reductions in the mechanical resistances of concrete, typically with influences during the hardening process. The formulations BXT/AB and BXT/11, which incorporated IRGASAN DP 300®, also showed decreases in the strengths of the concrete. This active principle, in certain compositions, caused a decrease in density through air entrapment in the concrete mix. Some multicomponent formulations, such as BXT/ 12C, BXT/10P, and BXT/1, also presented poor performance regarding mechanical properties. The effect of the biostatic agents in the cement hydration process was the main reason for the mechanical degradation of the concrete, especially at low ages. Many of the formulations affected significantly the physical and mechanical properties of the concrete samples, thus presenting lower mechanical performances. Two different behaviour were observed. According to the results obtained, some formulations presented an interaction of the actives with the cement hydration process. The low mechanical performance of the samples at early ages may be related with the retardation of the hydration reactions. Furthermore, air-entrapping was also observed. The formulations Vanquish 100®, Densil P®, and BC 98-56, as well as BXT/AB and BXT/ 11, which incorporated IRGASAN DP 300®, were discarded from the evaluation process.