Made available in DSpace on 2016-12-08T17:19:23Z (GMT). No. of bitstreams: 1 Andrea Luciane M Soares.pdf: 1356785 bytes, checksum: 08654c7f08e5db11d8746af3551cd3ed (MD5) Previous issue date: 2014-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work investigates the effect by partial replacement of nanosilica (nS) of Portland cement on the mechanical, physical, chemical and microstructural Portland cement mortar properties. For better understanding of the effects and a more detailed analysis of the results, the 33-1 fractional factorial design to design of experiments was used with three factors, each at three levels: nS content cement replacement (1, 2 and 3wt. %), water/cement ratio (1.1, 1.4 and 1.7 weight) and the aggregate/cement ratio (7.04 factor, 8.53 and 10.05 weight). The processing of the nine mortar mixtures was performed according to standards of the manufacture of such construction materials (composition, mixing, molding, curing and specimen preparation). Mechanical properties were evaluated in the fresh state (flow table) and in the hardened state (compressive strength at 7, 28 and 90 days of curing). In order to correlate the compressive strength with the microstructural characteristics, physic, chemical and microstructural characterization was performed. X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and scanning electron microscopic with energy-dispersive X-ray spectrometry (SEM/EDS) analyses were used on selected samples. The use of fractional factorial design and the response surface methodology was found to be in the design the experimental and statistical analyses. The addition of nS affects the mechanical properties of mortars, both in the fresh, and in the hardened state. Materials with adequate workability for use in construction industry (consistency of 230 ± 10 mm) and high compressive strength after 7 (≥ 3 MPa) and 28 days of curing (≥ 6 MPa) were obtained with the following composition: 1.5 wt. % nS, 1.3 water/cement ratio and aggregate/cement ratio kept constant of 10.1. The physical-chemical and microstructural characterization showed that nS contributes to improve the packing of the amorphous calcium silicate hydrate (C-S-H) and crystalline phases matrix and aggregate. Moreover, nS participates in the hydration reactions of Portland cement due to its reaction with calcium hydroxide. Thus, a more cohesive matrix and less calcium hydroxide contributes to lower porosity, thus reducing permeability, which contributes for better durability of the mortars containing nS. / Este trabalho investiga o efeito da substituição parcial de cimento Portland por nanosílica (nS) nas propriedades mecânicas, físico-químicas e microestruturais de argamassas de cimento Portland. Para melhor compreensão dos efeitos e uma análise mais detalhada dos resultados, foi usado o planejamento fatorial fracionado 33-1 para projeto dos experimentos. No projeto foram utilizados três fatores, cada qual em três níveis: o teor de nS em substituição ao cimento (1%, 2% e 3% em massa), a proporção de água/cimento (1,1; 1,4 e 1,7 em massa) e o fator agregado/cimento (7,04; 8,53 e 10,05 em massa). O processamento das nove misturas de argamassas foi realizado de acordo com as normas de fabricação desses materiais de construção civil (pesagem, mistura, moldagem, cura e preparação de corpos de prova). Propriedades mecânicas foram avaliadas no estado fresco (índice de consistência) e no estado endurecido (resistência mecânica à compressão em 7, 28 e 90 dias de cura). Com o objetivo de correlacionar a resistência à compressão com as características microestruturais, foi realizada a caracterização físico-química e microestrutural, por meio de análises de raios X (DRX), espectroscopia de infravermelho por transformada de Fourier (FTIR), análises térmicas (TG) e análise térmica diferencial (ATD) e de microscopia eletrônica de varredura (MEV/EDS) em amostras selecionadas. O uso do projeto fatorial fracionado se mostrou eficiente para o planejamento experimental e análises estatísticas juntamente com o uso da metodologia de superfície de resposta. A adição de nS nas argamassas afeta as propriedades mecânicas das argamassas, tanto no estado fresco, como no endurecido. Materiais com trabalhabilidade adequada para uso na construção civil (índice de consistência de 230 ± 10 mm) e elevada resistência à compressão após 7 (≥ 3MPa) e 28 dias de cura (≥ 6 MPa) foram obtidas com as seguintes composições: 1,5% de nS, 1,3 água/cimento e 10,1 agregado/cimento. A caracterização físico-química e microestrutural mostrou que a nS contribui para melhorar o empacotamento da matriz formada pelo silicato de cálcio hidratado amorfo (C-S-H), fases cristalinas e os agregados. Além disso, a nS participa das reações de hidratação do cimento Portland, por meio do consumo de hidróxido de cálcio. Dessa forma, uma matriz mais coesa e menos hidróxido de cálcio contribui para uma menor porosidade, reduzindo a permeabilidade, que se traduz numa melhor durabilidade das argamassas contendo nS.

Petroleum powered vehicles emit volatile organic compounds (VOCs) through combustion that contributes to the pollution of the environment. A technique in the 1970s was developed to decrease these emissions, especially for nitrogen oxides (NOx) and sulphuric oxides (SOx) which is called exhaust gas recirculation (EGR). The technique works by recirculating a portion of the combusted gas back into the engine, this limits the NOx and SOx emissions because of lower temperatures and less available oxygen. The problems that follow these effects is the formation and condensation of acids that corrode the material of the EGR system, which are created by many different reactions. It is of importance to understand how the compounds in the EGR system behaves through analysis of authentic and simulated condensates, which is why a quantitative method for these compounds are of interest. The aim of the project was to develop a simple quantitative analysis method for formic acid, acetic acid, and lactic acid in aqueous solution, which was done at Gränges Sweden AB. The technique used for detection and quantification was gas chromatography (GC) coupled to a flame ionization detector (FID) and a water compatible polyethylene glycol (PEG) column. Fractional factorial design (FFD) was used for determination of adequate operating parameters of the GC method and the sample preparation. Sample preparation only required filtration and pH adjustment prior to direct aqueous injection (DAI) to the chromatographic instrument. Detection of the analytes was very difficult because of non-compatibility with the FID, and quantification of asymmetric peak shapes made this problem worse, omitting lactic acid from further analysis. Limit of detection (LOD) and limit of quantification (LOQ) was 490 and 1640 ppm for formic acid and 120 and 400 ppm for acetic acid, with an injection volume of 0.3 μL and split ratio 10:1. Limits were too high for every EGR sample leaving no peaks detected for the sample preparation used. Further development should be done with complementary techniques and sample reprocessing in order to quantify the compounds.