Joke Monteny

CHEMICAL, MICROBIOLOGICAL AND IN SITU TEST METHODS FOR BIOGENIC SULFURIC ACID CORROSION OF CONCRETE

Abstract Biogenic sulfuric acid corrosion is often a problem in sewer environment: it can lead to a fast degradation of the concrete structures. Since the involvement of bacteria in the corrosion process was discovered, considerable microbiological research has been devoted to the understanding of the corrosive process. Mechanical engineers have focused on experiments comparing the resistance of several concrete mixes against biogenic sulfuric acid corrosion. Because of a lack of standardised methods, different test methods have been used, and various parameters have been modified to evaluate the resistance of the materials. The research done on sulfuric acid corrosion of concrete can roughly be divided in three groups: chemical tests, microbial simulation tests, and exposure tests in situ. In this article, an overview of the recent developments in the test methods for biogenic sulfuric acid corrosion and the obtained results are presented. Possible differences between biogenic sulfuric acid corrosion and chemical sulfuric acid corrosion are delineated.

Chemical and microbiological tests to simulate sulfuric acid corrosion of polymer-modified concrete

Abstract In certain industrial activities sulfuric acid is used during the production process, which may cause degradation of concrete structures. Another important phenomenon where sulfuric acid is responsible for concrete corrosion is biogenic sulfuric acid corrosion, which occurs often in sewer systems. Because previous investigations have already pointed out the difference between purely chemical sulfuric acid corrosion and biogenic sulfuric acid corrosion two different tests were performed: a chemical test and a microbiological test. Five different concrete compositions were used in the tests, including a reference mixture with high sulfate resistant portland cement and four different polymer cement concrete with a styrene–acrylic ester polymer, an acrylic polymer, a styrene butadiene polymer and a vinylcopolymer, respectively. The concrete composition with the styrene–acrylic ester polymer showed in both tests a higher resistance than the reference mixture while the compositions with the acrylic polymer and the styrene butadiene polymer had a lower resistance than the reference mixture. The concrete composition with the vinylcopolymer did not induce the same results in both tests. The results of the chemical test indicated a slight increase in resistance compared with the reference mixture while the opposite was noticed for the microbiological test.

INFLUENCE OF POLYMER ADDITION ON BIOGENIC SULFURIC ACID ATTACK OF CONCRETE

A simple and reproducible microbiological simulation procedure in combination with a chemical procedure was used to test concrete for its potential resistance towards biogenic sulfuric acid. Concerning fundamental aspects of the corrosion reaction, it was shown that particularly the penetration of H2S inside the concrete crevices accelerated the corrosion process. The influence of different polymer types and silica fume additions on the resistance of the concrete samples was determined. The addition of the styrene acrylic ester polymer resulted in an increased resistance while the addition of the acrylic polymer or silica fume caused less resistant concrete. For the vinylcopolymer and the styrene butadiene polymer, no significant effect was observed on the resistance of the concrete samples. The results of the two different test methods confirmed the difference between corrosion due to purely chemical sulfuric acid and corrosion due to microbiologically produced sulfuric acid.

A new test procedure for biogenic sulfuric acid corrosion of concrete

A new test method is described for biogenic sulfuric acid corrosion of concrete, more specifically in sewer con-ditions.The aim of the new test method is the development of an accelerated and reproducible procedure formonitoring the resistance of different types of concrete with regard to biogenic sulfuric acid corrosion. This exper-imentalprocedure reflects worst case conditions by providing besides H2S, also an enrichment of thiobacilli andbiologically produced sulfur. By simulating the cyclic processes occurring in sewer pipes, significant differencesbetween concrete mixtures could be detected after 51 days. Concrete modified by a styrene-acrylic ester polymerdemonstrated a higher resistance against biogenic sulfuric acid attack.

Resistance to biogenic sulphuric acid corrosion of polymer-modified mortars

Abstract The use of polymer-modified mortar and concrete (PMM and PMC) is investigated to improve the durability of concrete sewer pipes. The aim of the research is to ameliorate the resistance of concrete to biogenic sulphuric acid attack through polymer modification. Prior to the durability tests, experimental research is carried out to reveal the influence of polymer modification on the physical and mechanical properties of mortar and concrete. The results of this research are presented in this paper. Due to the interaction of the cement hydrates and the polymer particles or film, an interpenetrating network originates in which the aggregates are embedded. The density, porosity and location of the polymer film depend on the type of polymer emulsion and on its minimum film-forming temperature (MFT). If air entrainment is restricted, an increased flexural strength is measured. Scanning electron microscope (SEM) analyses reveal the presence of polymer film and cement hydrates in the mortar. The polymer film causes a retardation of the cement hydration as well as a restriction of crystal growth.

Resistance of different types of concrete mixtures to sulfuric acid

The resistance of seven different concrete mixtures against a 0.5% sulfuric acid solution was examined. The difference between high sulfate resistant Portland cement and blast furnace cement, as well as the influence of polymer modifications of the concrete and the addition of silica fume were issues of the investigation. All concrete mixtures were submitted to an alternating immersion and drying during 18 weeks in a 0.5% sulfuric acid solution using a testing apparatus for accelerated degradation tests. The corrosion of the concrete was quantified by measuring the change in dimensions of the test specimens with laser sensors. The mixture with addition of silica fume was most vulnerable to corrosion. Depending on the polymer type used, polymer modification of the concrete resulted in an increase and a decrease in the resistance of the concrete respectively. The concrete made with blast furnace cement had the highest resistance of all tested concrete types.RésuméLa résistance de sept bétons différents à l’action corrosive d’une solution contenant 0,5% d’acide sulfurique a constitué le sujet de cette recherche. La différence entre un ciment Portland à haute résistance aux sulfates et un ciment de haut fourneau, ainsi que l’influence de la modification de polymères et de l’ajovt de fumée de silice ont été examinées. Tous les bétons ont été soumis, en alternance pendant 18 semaines, à une immersion dans la solution sulfurique et à un séchage, au moyen de l’appareil d’essais de corrosion accélérée. L’action de la corrosion a été mesurée avec des lasers mettant en évidence les changements de dimension des éprouvettes. Le béton contenant de la fumée de silice a présenté la moins bonne résistance par rapport aux autres bétons. La résistance du béton augmente ou diminue suivant le type de polymère utilisé. Parmi tous les bétons, c’est le béton fait de ciment de haut fourneau qui a offert la meilleure résistance.

Resistance of concrete containing styrol acrylic acid ester latex to acids occurring on floors for livestock housing

Abstract Lactic and acetic acid cause a quick degradation of concrete floors in pig houses in the vicinity of the feeders. A testing apparatus for accelerated degradation tests was developed to simulate in a standardized and automatized way chemical attack by aggressive liquids and abrasion caused by animals and cleaning. Polymer cement concrete, containing different amounts of styrol acrylic acid ester, was subjected to an accelerated deterioration test in a liquid containing both feed acids. The average attacked depth and the Ra-value, which is a measure of surface roughness, were measured with laser sensors, connected to a computer. It appeared that increasing the concentration of polymer by weight of cement from 0% to 2.5%, 5%, and 7.5% each time caused an additional significant decrease in average attacked depth. No significant improvement was observed by increasing the polymer content from 7.5% to 10% or 15%; therefore, a polymer concentration of 7.5% would provide an economic optimum. No significant difference could be found between two concrete types with 10% polymer addition, cured during 1 or 3 days at 90–95% relative humidity.

Behaviour problems: a brief guide

Behavioural problems may be a reason for presentation by the owner or may be noted during a consultation for another reason. In either event it is important to investigate them. As well as affecting the dog itself, behavioural problems can threaten the human-animal bond, and society itself: a behaviour problem in an otherwise healthy animal may result in rehoming or euthanasia of the dog, social stress for owners, and even injury to third parties. This chapter looks at canine body language, puppy development and behaviour, a clinical approach to behaviour problems and clinical approach to some common presentations.