Análise de Argamassas Com Substituição Parcial do Cimento Portland Por Cinza Residual de Lenha de Algaroba

With the increase in cement consumption, it has quickly become one of the inputs most consumed by mankind over the last century. This has caused an increase in CO2 emissions, as cement production releases large quantities of this gas into the atmosphere. Adding this fact to the growing consciousness of environmental preservation, it has led to a search for alternatives to cement to complement its derivatives, in the form of waste materials like the ashes. This research aimed to analyze the properties of mortars in fresh and hardened state with partial replacement of Portland cement by residual algaroba wood ash (CRLA) potteries produced by the state of Rio Grande do Norte. The CRLA was collected and sieved, where part of it was ground and characterized in comparison with that just sifted, being characterized according to its chemical composition, grain size, fineness, density, bulk density and index of pozzolanic activity. It was found that the wood ash does not act as pozzolan, and grinding it has not changed its characteristics compared to those just sifted, not justifying its use. Two traces were adopted for this research: 1:3 (cement: fine sand) and 1:2:8 (cement: hydrated lime: medium sand); both in volume, using as materials the CRLA just sifted, CP II F-32 Portland cement, CH-I hydrated lime, river sand and water from the local utility. For each trace were adopted six percentages of partial replacement of cement for wood ash: 0% (control) 5%, 7%, 10%, 12% and 15%. In the fresh state, the mortars were tested towards their consistency index and mass density. In the hardened state, they were tested towards their tensile strength in bending, compressive strength and tensile adhesion strength, and its mass density in the hardened state. The mortar was also analyzed by scanning electron microscopy and X-ray diffraction. Furthermore, it was classified according to NBR 13281 (2005). The results showed that up to a content of 5% substitution and for both traces, the residual algaroba wood ash can replace Portland cement without compromising the mortars microstructure and its fresh and hardened state

Variação de temperatura e umidade e suas influências nas características físicas e mecânicas dos fios de algodão

Cotton is a hydrofilic textile fiber and, for this reason, it changes its properties according to the environment changes. Moisture and Temperature are the two most important factors that lead a cotton Spinning sector and influence its quality. Those two properties can change the entire Spinning process. Understanding this, moisture and temperature must be kept under control when used during the Spinning process, once the environment is hot and dry, the cotton yarns absorb moisture and lose the minimal consistency. According to this information, this paper was developed testing four types of cotton yarns, one kind of cotton from Brazil and the others from Egypt. The yarns were exposed to different temperatures and moisture in five different tests and in each test, six samples that were examined through physical and mechanical tests: resistance, strength, tenacity, yarn´s hairness, yarn´s evenness and yarn´s twisting. All the analysis were accomplished at Laboratório de Mecânica dos Fluídos and at COATS Corrente S.A., where, it was possible to use the equipments whose were fundamental to develop this paper, such as the STATIMAT ME that measures strength, tenacity, Zweigler G566, that measure hairiness in the yarn, a skein machine and a twisting machine. The analysis revealed alterations in the yarn´s characteristics in a direct way, for example, as moisture and temperature were increased, the yarn´s strength, tenacity and hairness were increased as well. Having the results of all analysis, it is possible to say that a relatively low temperature and a high humidity, cotton yarns have the best performance

Avaliação das propriedades das fibras de algodões coloridos naturalmente e ecologicamente corretas cultivados nos assentamentos do município de Guamaré/RN

In this work evaluate the technical characteristics of the fibers grown in settlements Guamaré, colored cotton seeds were donated existing in the Germplasm Bank of Embrapa Cotton. We sought through the breeding program, raising the resistance, fineness, length and uniformity of cotton fibers, as well as stabilize the staining of fibers in the BRS Topaz, BRS Brown and BRS Green shades and raise their productivity in the field. First, the individual selections to test progeny seeds, and thereafter the hybridization method followed by family selection to obtain variations in the color tones were performed. The BRS Topaz, BRS Brown and BRS Green varieties were produced, analyzed and compared with existing cottons in the region which is the White cotton. The properties amount of impurities and neps, length, length uniformity, short fiber content, fineness and tensile strength of the fibers were sized in Classifiber, NATI, Pressley and Micronaire devices. 10 trials each with 10 tests for all four fiber types were carried out. The White and Topaz fibers showed greater length (32-34mm) and greater resistance (7.94 lb/mg and 7.97 lb/mg respectively) and showed finesse with lower micronaire index 3,71μg/inch and 3, 73μg/inch and a low rate of short fibers. The results were very promising for the use of genetically improved cotton in the manufacturing of fabric and yarn in the textile industry. The fibers were brown colored cotton used in the manufacture of a composite fiber with thermoplastic resin