Navegando por Assunto "Aditivos"

Agora exibindo 1 - 11 de 11

Acesso aberto (Open Access)
Análise das causas de aditivos de custo e de prazo em obras públicas de instituições federais de ensino
(Universidade Federal do Pará, 2019-03-19) ALVARENGA, Felipe Campos; MAUÉS, Luiz Maurício Furtado; http://lattes.cnpq.br/7497951647889934
Completing works within the cost and schedule stipulated in the planning phase is a major problem faced by managers in the construction industry. With this, several studies have been carried out around the world to identify the main reasons that lead to noncompliance with the works at the time and cost initially established. The present study aims to analyze the contractual additions made in public works of the Federal Institutions of Education (IFEs) and the main reasons that led to their conclusion. To achieve this goal, statistical tools were used to compare the cost and time changes between the country regions. The data of this work includes public construction projects divided in all the 5 regions of the Country, filtered from the database of the Ministry of Education. A diagnosis was made showing the percentage of additives among the regions and the main justifications of the same ones indicated in a sampling in this database. Statistical techniques such as the Kruskall-Wallis Analysis of Variance and the Mann-Whitney U-Test were used for data analysis and inference. As results, the differences in the distribution of time and cost additives were statistically significant among the regions, with the South and Central-West regions presenting the greatest differences and the North, Northeast and Southeast regions with a statistically similar behavior among them. Of the 2178 projects collected, 69.05% had additives of term and 61.89% of cost. The main factors that affect time and cost of the projects were the inclusions and / or modifications of design and the additions of services. The ways to reduce the incidence of overruns point to the use of Building Information Modeling (BIM) technology, lean construction and greater experience in the management of works.
Acesso aberto (Open Access)
Argamassa autonivelante para contrapiso: efeito do tipo de cimento no comportamento físico-mecânico
(Universidade Federal do Pará, 2020-04-24) ALVES, Brenda Maiara Oliveira; CORDEIRO, Luciana de Nazaré Pinheiro; http://lattes.cnpq.br/9126233381230999; https://orcid.org/0000-0001-7931-4042
Self-leveling mortar (SLM) is inserted in the construction market as an innovative product due to its special properties when compared to conventional mortars due to the filling of empty spaces and self-compacting only under the effect of gravity, the ability to flow and level without the occurrence of segregation. The use of CP V – ARI cement is common for its production, since its high fineness favors the fluidity of the material and for providing fast hardening, fundamental characteristics that must be considered in self-leveling mortars (SLM’s). However, the rare availability of this type of cement becomes a limiting factor for its applicability in the region. Therefore, the objective of this research is to develop the study of SLM dosage for screed, adapting it to local materials that favor its design and evaluating its influence on rheological and mechanical characteristics. For the production of these mortars, we used the adaptation by Lopes et al. (2018) of Tutikian's methodology (2004) for self-compacting concrete (CAA), using fines in partial replacement of cement, adopting as controllable factors the type of cement (CP I, CP II-E, CP IV and CP V-ARI) and the type of mineral addition (silica fume and metakaolin). For the characterization of SLM in the fresh state, the mini slump, mini V-funnel, flow retention, mass density and incorporated air content, determination of exudation and healing time tests were performed. In the hardened state, the mechanical resistance to compression and traction in flexion and the retraction of these materials were verified, since it is one of the main pathologies of SLM. Analyzing the results obtained, it was observed that the surface area of the tested cements was the factor that most influenced the performance of the produced mortars, where cements with larger surface areas needed more additive to achieve fresh properties and had the highest rates of retraction. Mineral additions contributed to the cohesion of mortars and reduced shrinkage in mixtures with contents of up to 25% metakaolin and 15% silica fume.
Acesso aberto (Open Access)
Efeitos da utilização de inoculantes microbianos em silagem de capim elefante com ou sem o uso de melaço
(Universidade Federal do Pará, 2012-02-06) SILVA, Jefferson Salvador Lima Padilha da; SILVA, Almir Vieira; http://lattes.cnpq.br/9485881672181545; BERNARDES, Thiago Fernandes; http://lattes.cnpq.br/9614321233731548
Acesso aberto (Open Access)
Elephant grass silage with the addition of crambe bran conjugated to different specific mass
(Universidade Federal do Pará, 2016-12) CARDOSO, Arilson Moraes; ARAÚJO, Saulo Alberto do Carmo; ROCHA, Norberto Silva; DOMINGUES, Felipe Nogueira; AZEVEDO, Jorge Cardoso de; PANTOJA, Lilian de Araujo
This study aimed to evaluate the effects of inclusion of crambe bran concentrations (Crambe abyssinica Hochst.) with different specific masses in elephant grass silage (Penninsetum purpureum Schum.). For that, the bromatological and microbiological compositions of the experimental silages were determined. We used 48 mini silos distributed in a completely randomized design, arranged in a factorial 4 × 3, four levels of inclusion of crambe bran (0; 10; 20 and 30%) and three specific masses (400; 500 and 600 kg MN m-3), with four replications. After 240 days of fermentation the silos were opened. It was observed linear effect on DM, CP, NDFap, ADFap, HEM, LIG, NFC, TC and population of bacteria that produce lactic acid with the addition of crambe meal. There was interaction between the crambe bran factors and specific masses on the values of pH and N-NH3. For MM variables and yeast count there was a negative linear effect due to the evaluated specific mass. The inclusion of crambe bran helps to increase the fermentative profile and the bromatological composition of elephant grass silages studied, and the best results were obtained with the addition of 30% of this coproduct, based on the natural matter.
Acesso aberto (Open Access)
Farelo de dendê como aditivo sequestrante de umidade na silagem de capim-elefante
(Universidade Federal do Pará, 2013-08-12) SANTOS, Ivan Alberto Palheta; RÊGO, Aníbal Coutinho do; http://lattes.cnpq.br/4330113577933018; DOMINGUES, Felipe Nogueira; http://lattes.cnpq.br/1461187309835749
The objective of this work to review existing literature on the use of additives sequestering moisture, as well as the use of palm kernel meal as a additive for elephant-grass silage, after that, there was a scientific experiment in which we evaluated the effect of adding bran oil palm as an wet kidnapper additive in elephantgrass silage. The chemical qualitative and fermentation were analyzed in a completely randomized design with six treatments and six replications, where the averages of the results of days of closing and opening were analyzed by regression analysis. In the aerobic stability analysis was employed subdivided plots, so that the treatments were randomized in plots and the evaluation times in the subplots. Samples were collected at the time of ensiling and after 190 days of storage for evaluation of dry matter, crude protein, carbohydrates (total, non-fibrous, watersoluble, cellulose and hemicellulose), mineral material, lignin and lipids. In the days aerobic samples were collected for pH, nitrogen for ammonia, fungi and yeasts. The elephant grass this experiment showed values of 13.9% DM and 8.25% CP while the FD has 77.2% DM and 16.9% CP. The inclusion of FD had a direct influence on the populations of fungi and yeasts during the aerobic stability, the higher the dose, the less proliferation as a result, the values of pH and NH3-N also showed similar behavior. The inclusion of bran Palm at doses in the range of 10% to 15% can be used in silage of elephant, inhibiting undesired fermentation and making them more stable, doses above this value may affect the nutritive value of silage by high lignin content of the additive.
Acesso aberto (Open Access)
Influência da granulometria e de aditivos no comportamento reológico do rejeito de lavagem da bauxita
(Universidade Federal do Pará, 2014-03-13) GONÇALVES, Silvane Gonçalves e; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; FELIPE, Augusta Maria Paulain Ferreira; http://lattes.cnpq.br/8871741271063047
In the bauxite mining in Parogominas-PA city, tailings are discarded in the processing with 33,5% of solids content and small granulometry with D50 below 5 μm. These factors contribute to this suspension basically formed by sílico aluminates, with high concentrations of kaolinite clay, have high viscosity and high initial tension flow. It was performed granulometric analysis and determined the chemical and mineralogical composition of the material. The granulometric analysis was made by wet sieving and the small particles were determined by laser diffraction. The determination of the chemical composition was made by Fluorescence Spectrometry X-ray, identifying considerable amounts of alumina available, 21,28%. The mineralogical composition was determined by X-ray diffraction (XRD), obtaining gibbsite, hematite, quartz and kaolinite. It was performed the determination of the friction factors pulp, using equation to fluids that have Herschel-Bulkley behavior and using the Dodge and Metzner correlations. It was used VT550 viscosimeter, with coaxial cylinder sensorSV1, to make defloculation and flocculation test using different rheological additives. The additives used were: sodium hexametaphosphate, hydroxamate, aluminum sulphate, sodium polyacrylate and 25% anionic polyacrylamide. The trials were realized in shear rate of 100 s-1, time 20s and temperature of 32ºC.It was performed also, analysis of viscosity of pulps with different pH and in samples less 38μm (400# Tyler), with the objective of evaluate how the particle size and pH influenced in the behavior of additives. The study showed that particle size and pH influence on the behavior of additives, because if the particle size is very small better is the behavior of the additive. The behaviors of the additives as flocculation or defloculation depend of the pH.
Acesso aberto (Open Access)
Influência de aditivo polimérico no comportamento mecânico e reológico das argamassas produzidas com rejeitos industriais
(Universidade Federal do Pará, 2015-05-12) SILVA, André Luis Mileo Ferraioli; FELIPE, Augusta Maria Paulain Ferreira; http://lattes.cnpq.br/8871741271063047; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
Mortars are considered to be particulate systems in suspension with fine aggregate, binder, water and organic polymeric additive. Factors such as granulometry, cement, ash and additive contents in their composition influence mortar properties in both the fresh and hardened states. A rheological study and mechanical test were performed on mortar prepared for floors and coatings through incorporating civil construction wastes (RCC) such as fine aggregate and fly ash, a mineral waste derived from combustion in boilers at the HYDRO ALUNORTECompany. This study seeks to develop a polymeric mortar that uses CPII E-32RS Portland cement andflyashas binders and fine sand and RCC with polyvinyl acetate (PVA) as aggregates. A study was performed on the influence of cement, ash, granulometry of aggregates and use of PVA based-polymeric additives on mortar properties.The materials were submitted to physical and chemical characterization using granulometric analysis, X-ray fluorescence and FTIR. In preparing the specimens, 6 formulas with 5% cement and 3 formulas with 10% cement were used, both with different levels of ash, sand and RCC andmaintaining a constant level of Portland cement content. A comparison of the mechanical and rheological properties of formulas with and without PVA was also made.Formulas in a fresh state were submitted to rheological tests. After 28 days of curing specimens of these formulas, by then in a hardened state, were submitted to tests for mechanical resistance to compression, specific mass, apparent absorption and apparent porosity. The research demonstrated that employing a PVA-based polymeric additive improved the mechanical properties of the mortar prepared with industrial wastes, as well as guaranteeing satisfactory rheological behavior for possible applications of such mortars in civil construction.
Acesso aberto (Open Access)
Óxido de cálcio e Lactobacillus buchneri NCIMB 40788 na ensilagem de cana-de-açúcar in natura ou queimada
(Universidade Federal do Pará, 2011-11) SIQUEIRA, Gustavo Rezende; SCHOCKEN-ITURRINO, Ruben Pablo; ROTH, Anna Paula de Toledo Piza; DOMINGUES, Felipe Nogueira; FERRAUDO, Antonio Sergio; REIS, Ricardo Andrade
The objective of this trial was to evaluate the effects of the inclusion of calcium oxide (CaO) and/or L. buchneri (LB) on the losses and chemical composition changes of in natura and burned sugar cane silages. Silage treatments were: in natura sugar cane without additive (IS), with Lactobacillus buchneri (ISLB), with calcium oxide (ISCaO) equivalent to 1% of natural matter, and the combination of LB and CaO (ISLBCaO). Experimental design was completely randomized in a factorial scheme (2 × 4) considering status (burned or not) and additives (LB, CaO and LB+CaO) with three replications per treatment. Dry matter variation was lower for in natura and burned silages treated with CaO; regardless of the LB presence, the mean difference was 5.85 percentage units. In sugar cane silages without additives, higher dry matter recoveries were observed when the plant was ensiled with in natura silage (63.5%) compared with burned silage (46.8%). However, when additives (CaO and LB) were used, no significant differences occurred between the in natura and burned silage treatments. The presence of calcium oxide was the factor that provided the greatest discrimination among the data. Calcium oxide is effective in reducing losses and chemical changes on the in natura and burned silages. The L. buchneri acts effectively on burned sugar cane silages, and the latter are more susceptible to losses than those of in natura sugar cane.
Acesso aberto (Open Access)
Propriedades termodinâmicas: querosene, bioquerosene, aditivos e mecanismos de detecção de explosivos
(Universidade Federal do Pará, 2018-11-23) MORAES, Edimilson dos Santos; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699
In this work we perform the characterization of thermodynamic potentials, obtaining predictions based on Density Functional Theory and statistical thermodynamics, through the canonical ensemble model. The study compared two theoretical methods, B3lyp/6-311 ++ g(d, p) and the semi-empirical method PM3, with the experimental values of the thermodynamic property of CP with the objective of validating the method with better precission. All simulations were performed conformation of the global minimums and optimizations of the molecules in thermal equilibrium and for a temperature range of 0.5 - 1500 K. We will analyze the thermal properties, such as energy, enthalpy, Gibbs free energy, entropy, heat capacity at constant pressure with respect to temperature. In the combustion enthalpy the following methods were used: B3lyp/6-311 ++ g(d, p), B3lyp/6- 31+g(d), CBS-QB3, G3, G4 and the G3 / G4 mean, obtaining results that show a good agreement with the experimental values, and verifying which of the methods best predicts the thermodynamic properties for reactions of combustion of the kerosene and bioquerosene. Also, a theoretical analysis was performed in DFT to calculate the thermodynamic properties of three molecules of additives. We simulated a composition of JP-8 with mixtures of the three additives together and separated in order to observe its efficiency over other existing methods. Then, the thermodynamic properties of the gasoline with additives were predicted under the same conditions already described. These calculated amounts included standard gasoline mixed with the following oxygenated additives: methyl tert-butyl ether, ethyl tert-butyl ether, diisopropyl ether, ethanol and methanol. It is possible to estimate some relevant fuel properties in the injection and combustion stage, showing substantial agreement with the experimental data, presenting relative errors of less than 2%, thus establishing an excellent method to calculate and predict the thermodynamic properties of the combustion reactions for with additives. In the last stage of this work, we present a theory of a simulated sensor device to identify explosive molecules that is of extreme interest for the area of public security in the fight against terrorism. For this, an armchair-type carbon nanotube (CNT) was modeled under the action of an external, longitudinal and uniform electric field, causing the molecules of the explosives: 2,4,6 trinitrotoluenes, triacetin triperoxide, hexogen, hexamethylene triperoxide diamine, octogen and pentaerythritol tetranitrate. Turn around the CNT, behaving as a sensor depending on the temperature and the radius of rotation of the molecules. In this way, we study the physico-chemical properties of the interactions of the molecules with the CNT.
Acesso aberto (Open Access)
Resíduos da agroindústria de frutas como aditivos para ensilagem de capim elefante
(Universidade Federal do Pará, 2015-03-27) AZEVEDO, Jorge Cardoso de; ROCHA, Norberto Silva; http://lattes.cnpq.br/7845601346733559; DOMINGUES, Felipe Nogueira; http://lattes.cnpq.br/1461187309835749
The mean purpose of that research was to measure the potential of agribusiness fruit production waste use (banana, mango, passion), such as absorbing additives oh humidity at ensilage of elephant grass (Pennisetum purpureum) cultivate Napier, through different specific masses, defining its effect on fermentation quality, microbiological characteristics, and chemical composition. Treatments were distributed in a completely randomized design with four replicates, in factorial 4 x 3, being composed of witness, banana waste (BW), mango waste (MW), passion waste (PW) and three specific masses (400, 500 and 600 kg MV/m3). After 240 days of fermentation on experimental silos samples were opened and excluded to determine the content of dry matter (DM), crude protein (CP), ether extract (EE), neutral detergent fiber corrected to ash and protein (NDFap), acid detergent fiber corrected to ash and protein (ADFap), hemicellulose (HCEL), lignin (Lig), total carbohydrates (TC), nonfiber carbohydrates (NFC), neutral detergent insoluble nitrogen (NDIN), acidic detergent insoluble nitrogen (ADIN, % total N), potential of hydrogen (pH), ammonium nitrogen (N-NH3), lactic acidic bacteria (LAB), filamentous fungi (FUN), and yeast. The software R was used to analyze the treatments, considering the significance of 5% probability (P<0.05). To compare the average of each treatment, when it influenced the variable response, the Tukey test of 5% of significance was used. The effect of specific mass on silo is more effective in exclusive silage of elephant grass, the compaction of 600 kg MV/m3 contribute for improvements on the fermentative and microbiological process. The specific mass does not influence a lot on the chemical composition. The addition of banana waste on elephant grass ensilage contribute improvements only on the chemical composition, rising the values of DM, PB, NFC and reduction of fibrous components (NDFcp and ADFcp), but it does not improve the fermentative and microbiological process. The addition of passion and mango by-products foment the improvement of DM and promote the fermentative, microbiological, and chemical process of silage, no matter the specific mass.
Acesso aberto (Open Access)
Vacas terminadas em campo nativo suplementadas com farelo de trigo ou farelo de arroz integral contendo ou não monensina sódica
(2008-12) OSMARI, Milene Puntel; ARBOITTE, Miguelangelo Ziegler; BRONDANI, Ivan Luiz; KUSS, Fernando; ALVES FILHO, Dari Celstino; RESTLE, João
The performance, physical composition, income of commercial cuts the quality of the meat of twenty eight cows Charolais, Nellore and its cross, were evaluated with initial average live weight of 409kg, finished in native grass with high participation of Eragrostis plana Nees., supplemented per 99 days with wheat bran or rice bran 0.5% of the alive weight in the DM with or without the inclusion of sódica monensina. The use of wheat bran provided a better conformation of the carcass (P<0.05), classifying it as "regulate +" (9.90 points). The others characteristic studied was not influenced (P>0.05) by the type of supplement. The inclusion of sodic monensin did not provide significant differences (P>0.05) in the variable studied.