Made available in DSpace on 2014-07-29T15:18:25Z (GMT). No. of bitstreams: 1 dissertacao marcus vinicius mendes.pdf: 2369089 bytes, checksum: 841841ae88caf7c6c9adb67b65e533c5 (MD5) Previous issue date: 2009-10-06 / The durability of reinforced concrete structures is damaged by the degrading action of the penetration of substances in the form of gases, vapors and liquids through the pores and cracks. It is known that water both in its pure form or containing dissolved ions such as chloride, sulphate, carbon dioxide or oxygen ions, can compromise the durability of concrete structures. In reinforced concrete structures at the marine environment, for example, the towers of wind power plants, this degradation can be more intense and accelerated. Thus, in the present study were analyzed concretes with different mineral additions (silica fume, blast furnace slag) and water / binder ratios (0.35, 0.45 and 0.55), with the objective to verify if the inside and cover thickness of concrete have some effect on the mechanisms of transport and also the effect of carbonation (only for concrete with w/b equal to 0.55) in the surface layer of concrete is important enough to make dificult the entry of aggressive agents in concrete. For this, the following tests to evaluate the mass transport in concrete were performed: capillary water absorption (NBR 9779:1995), water penetration under pressure (NBR 10787:1994), air permeability (method Figg), penetrability of chloride ion (ASTM C 1202: 2009), non-steadystate migration test (NT BUILD 492:1999). As a result, it was found that the mineral addition used generally provided an improvement in front of the concrete mechanisms of mass transport. In one of the properties, namely the diffusion coefficient (non-steady-state migration) of concrete with the use of silica fume and blast furnace slag, this has been reduced dramatically, around 11 times for the concrete with w/b equal to 0.55, when it is compared with concrete without mineral addition. It was observed that the inner region of concrete behaved better, in an unexpected way, than concrete cover region for some properties (capillary absorption, water penetration under pressure, penetration of chloride ions). From this conclusion, it can be said that the inner part of concrete is composed of transition zones (aggregated interface / mortar) exposed to facilitate the entry of fluids, gases and ions. About the effect of carbonation, this affected the capillary absorption and air permeability. The results led to explain that the clogging of the pores resulting from the product of carbonation (CaCO3), promoted the refinement of the pores, thus increasing capillary force and, consequently, increasing the capillary absorption. However, for air permeability this effect has damaged the passage of air through the surface layer. Finally, it is important noting that significant correlations were found among tests that evaluated the mechanisms of mass transport, namely, penetration of chloride ions and capillary absorption, diffusion coefficient (non-steady-state migration) and capillary absorption, permeability air and water penetration under pressure, penetration of chloride ions and the diffusion coefficient. / A durabilidade das estruturas de concreto armado é prejudicada pela ação deteriorante da penetração de substâncias na forma de gases, vapores e líquidos através de poros e fissuras. Sabe-se que a água, tanto no seu estado puro ou com íons dissolvidos, como os cloretos, sulfato, dióxido de carbono ou oxigênio, pode comprometer a durabilidade das estruturas de concreto. Em estruturas de concreto armado localizadas em ambiente marítimo como, por exemplo, as torres de energia eólica, essa deterioração pode ser mais intensa e acelerada. Diante disso, no presente trabalho foram analisados concretos com diferentes adições minerais (sílica ativa e escória de alto-forno) e relações água/aglomerante (0,35; 0,45 e 0,55), tendo como objetivo principal verificar se a parte interna e o cobrimento do concreto exercem algum efeito nos mecanismos de transporte e, se o efeito da carbonatação (somente para concretos de relação a/g igual a 0,55) na camada superficial do concreto é relevante a ponto de dificultar a entrada de agentes agressivos no concreto. Para isso, foram realizados os seguintes ensaios para avaliar o transporte de massa no concreto: absorção de água por capilaridade (NBR 9779:1995), penetração de água sob pressão (NBR 10787:1994), permeabilidade ao ar (método de Figg), penetrabilidade de cloretos (ASTM C 1202: 2009), ensaio de migração em regime não estacionário (NT BUILD 492:1999). Como resultado constatou-se que as adições minerais empregadas propiciaram de maneira geral uma melhoria dos concretos frente aos mecanismos de transporte de massa. Em uma das propriedades avaliadas, a saber, o coeficiente de difusão (migração regime não estacionário) dos concretos com o emprego de sílica ativa e escória de alto-forno, esse foi reduzido drasticamente, em torno de 11 vezes para os concretos com relação a/ag igual a 0,55, quando comparado com os concretos sem adição mineral. Quanto à região do concreto, notou-se para algumas propriedades (absorção capilar, penetração de água sob pressão, penetrabilidade de cloretos) que a região interna comportou-se melhor, de maneira inesperada, que a região do cobrimento. Diante dessa conclusão, criou-se uma hipótese para tal comportamento que consistiu em afirmar que a parte interna é composta por zonas de transição (interface agregado/pasta) expostas que facilitam a entrada de fluidos, gases e íons. Já com relação ao efeito da carbonatação, esta afetou a absorção capilar e a permeabilidade ao ar. Os resultados levaram a explicar que a colmatação dos poros, advindos do produto (CaCO3) da carbonatação promoveu o refinamento dos poros, aumentando, assim, a força capilar e, conseqüentemente, o aumento da absorção capilar. No entanto, para permeabilidade ao ar esse efeito dificultou a passagem de ar através da camada superficial. Por último, cabe destacar, que correlações importantes foram obtidas entre os ensaios que avaliaram os mecanismos de transporte de massa, a saber, penetrabilidade de cloretos e absorção capilar, coeficiente de difusão (migração regime não estacionário) e absorção capilar, permeabilidade ao ar e penetração de água sob pressão, penetrabilidade de cloreto e coeficiente de difusão.

This work is devoted to study the influence of the composition on mechanical properties of high performance concret based on portland cement. 29 samples of high performance concrete (HPC) warying in composition were prepared. The constituents used for HPC preparation were: cement Aalborg White, silica fume, finelly ground blast furnace slag, finelly ground silica, calcinated bauxite and polycarboxylate based superplasticizer. The mechanical parameters (flexural and compressive strength) of the samples were observed after 7 and 28 days of moist curing. Compressive strength values after 28 days were in the range of 92 to 194 MPa and the flexural strength values were in the range of 7 to 23 MPa (without using of fiber reinforcement). The graphs showing mechanical parameters depending on the mixture composition were constructed and consequently evaluated.

The modern, contemporarily used cement composite types make use of various additives. This diploma thesis is focused on designs of mortars that have been enriched with micro and nano additives, which lead to higher mechanical strength through optimized grading of mortar mixes. This thesis also evaluates the influence of material properties on resulting properties of mortars in fresh and hardened state.

Civil engineering development is connected with the application of new construction methods and the development of new building materials. Concrete, as one of the basic building materials, is part of this development. A major turning point in the development of concrete and its properties occurred with the use of new, more efficient plasticizing additives. This allowed to produce concrete with lower water cement ratio, while increasing the strength of concrete. Gradually, the compressive strength of concrete boundary has moved by several levels, when there are currently commonly used concrete with strength of about 100 N/mm2 and with the special methods of concrete production strength range from 250 to 300 N/mm2. A negative aspect of the development of (ultra) high-strength concrete is their energy and economic demands. A characteristic feature of high-strength concrete is a high content of cement and very fine admixtures, especially silica fume. One way to improve the economics of these types of concrete is the application of cheaper admixture based on industrial waste. The content of this work is the observation and description of the properties of high-strength concrete and reactive powder concrete, in which the admixtures were based on industrial waste were applied. Part of this work is the comparison of economic parameters for individual types of concrete.

Autoclaved aerated concrete is long-time ecological building material with usefull properties. There needs to be done research of its mineralogical compound for reengineering the production. The main mineral compound of AAC is tobermorite, it increases its mechanical properties. In the presence study, we examine the usage of nature and artificial silicious materials. Also, we investigate the influence of sulfate and alumina admixtures, as well as fluidized bed combustion ash, which can be used as the lime and gypsum replacement. Closure of the study is design of the optimal raw material composition, also hydrothermal treatment of autoclaved aerated concrete. In relation to its mechanical properties, mineralogical composition and cost.

Fire resistance is becoming increasingly important along with the development of new concrete types with high strength and dense structure with reduced porosity. Such concrete types are susceptible to fire spalling and extensive crack formation. At the moment, there are a limited number of methods for enhancement of fire resistance of existing structures, which could be applied in underground structures with restricted space and limited air exchange, such as tunnels, underground garages or nuclear powerplants. This work is focused on the development of two methods, and both are dealing with porous structure modification. The first method is intentional heat treatment (IHT) method, suitable for the enhancement of fire resistance of existing structures. The second method emphasized the design of air-entrained concrete (AeA-FiResCrete) with the use of “new generation” air-entraining agents suitable for enhancement of fire resistance of newly designed concrete. Testing of compressive strength, porous structure modification was completed by the analysis of “moisture clog,” which contributes to explosive spalling and extensive cracking. The efficiency of developing methods was verified during large-scale testing according to modified ISO834 (m-ISO) curve. No extensive crack formation or explosive spalling was observed during the exposure period during the large-scale testing of slabs with the applied IHT method. The total thickness of the IHT method with configuration IHT200/2, composed of IHT zone and IHT transition zone, penetrated to the depth of 25,5 to 43,0 mm depending upon various concrete types. Moisture clog in AeA-FiResCrete was more significant than in the case of slabs with applied IHT method, and it could be concluded that the IHT method enhances fire resistance of concrete exposed to elevated temperatures without influencing its compressive strength and durability. Results from AeA-FiResCrete testing showed only a slight improvement of its fire resistance.

In 2017, the Swedish Parliament stated a new climate law with the goal that Sweden should be climate neutral by 2045. The concrete industry has developed a roadmap on how the goal for 2045 can be achieved, where one way to reduce the carbon emissions from concrete is by replacing a part of the cement clinker with alternative binders in the concrete mix. Ground granulated blast furnace slag (GGBS), fly ash, silica fume and trass are alternative binders that are possible to use in concrete mixes to reduce the amount of ordinary Portland cement (OPC). GGBS, fly ash and silica fume are by-products from other industries, while trass is volcanic ash that can be extracted. Besides the positive environmental impact that comes from using alternative binders and reducing the amount of cement clinker, the alternative binders have other properties, both positive and negative, that affect the concrete. The aim of this thesis was to investigate whether concrete with alternative binders does fulfill the regulations set by Swedish standards and how concrete with alternative binders does affect the material parameters. The concrete mixes were divided into three different types of concrete: concrete for bridges (w/c ratio 0.4), hydropower structures (w/c ratio 0.45) and wind powerplant foundations (w/c ratio 0.55). A total of seven concrete mixes were cast in a laboratory and the concrete mixes were investigated in the three hardening stages of concrete: fresh, young and hardened. The analyzed material parameters were compressive strength, shrinkage, frost resistance, workability, air voids and temperature development. Beyond the experimental testing, a global warming potential (GWP) comparison was made to compare the reduction of GWP for each concrete mix compared to a reference concrete for each usage area. The mix containing a CEM II/A-V fly ash cement and 15% GGBS showed great potential regarding the different material parameters. This mix, however, is according to Swedish standards not possible to certify for structures in exposure class XF4, such as bridges, but is possible to certify for structures in exposure class XF3, such as wind powerplant foundations. The mix containing 30% GGBS and 5% silica fume also showed beneficiary properties, but superplasticizers are required in this mix to ensure good workability. For hydropower structures, the mix containing 35% GGBS showed a great compressive strength but a high temperature development and low workability. The mix containing trass had a notably low temperature development, but with an increase in shrinkage and low workability. Moreover, all concrete mixes showed a frost resistance which, according to standard, is classified as “Very Good”. / Sveriges regering antog 2017 ett nytt klimatpolitiskt ramverk med målet att Sverige ska ha noll nettoutsläpp av växthusgaser år 2045. Betongindustrin har tagit fram en färdplan för hur betong kan bli klimatneutralt, där ett sätt att reducera klimatpåverkan från betong är att byta ut en del av cementklinkern mot alternativa bindemedel. Mald granulerad masugnsslagg (GGBS), flygaska, silikastoft och trass är alternativa bindemedel som är möjliga att använda i betongblandningar för att reducera mängden Portlandcement. GGBS, flygaska och silikastoft är restprodukter från andra industrier medan trass är en vulkanisk aska som kan utvinnas. Utöver den positiva miljöeffekten som erhålls när alternativa bindemedel ersätter cementklinker, så har de alternativa bindemedlen andra egenskaper, både positiva och negativa, som påverkar betongen. Målet med denna studie var att undersöka och jämföra om betongblandningar där en del av cementklinkern har ersatts med alternativa bindemedel når upp till de krav som ställs i nuvarande regelverk. Utöver det så undersöktes även hur betongblandningarnas materialparametrar påverkades av alternativa bindemedel. Betongblandningarna delades in i tre olika typer av betong: betong för broar (vct 0.4), vattenbyggnader (vct 0.45) och vindkraftverksfundament (vct 0.55), där totalt sju betongblandningar tillverkades i ett laboratorium. Betongblandningarna undersöktes i de tre olika faserna för hårdnande av betong, vilka är färsk, ung och hårdnad betong. De materialparametrar som analyserades var tryckhållfasthet, krympning, frostresistens, arbetbarhet, luftporhalt och temperaturutveckling. Förutom de experimentella testerna gjordes en jämförelse kring hur mycket koldioxid som kan reduceras för varje betongblandning, jämfört med en referensbetong för varje användningsområde. Betongblandningen med ett CEM II/A-V flygaska-cement och 15% GGBS visade stor potential med avseende på de olika materialparametrarna. Denna blandning är dock enligt svensk standard inte möjlig att certifiera för betongbyggnad i exponeringsklass XF4, exempelvis broar, men kan certifieras för betongbyggnad i exponeringsklass XF3, exempelvis fundament för vindkraftverk. Blandningen med 30% GGBS och 5% silikastoft visade även positiva egenskaper, men flyttillsatsmedel måste användas i denna blandning för att erhålla en god arbetbarhet. För vattenbyggnadsbetong så visade blandningen med 35% GGBS en hög tryckhållfasthet, men samtidigt en hög temperaturutveckling och en låg arbetbarhet. Blandningen med trass hade en noterbart låg temperaturutveckling, men med ökad krympning samt låg arbetbarhet. Avslutningsvis så uppvisade alla blandningar en frostresistens som enligt standard klassificeras som ”Mycket bra”.