Evaluation of the matrix of plaster with incorporation of rubber of tires for use in construction

[EN] The use of gypsum in the Brazilian construction industry has been growing steadily in recent years, when the drywall system started to be used in the internal seals of all types of buildings. The new use this should be added the traditional use of gypsum as coating material applied directly on walls and ceilings and as casting material. Given the above, this paper studies some physical characteristics of gypsum composites produced with the addition of tire rubber residues. The experimental program included the completion of the following tests: mass density in plastic and hardened state, tensile strength in bending, compressive strength, tensile strength in bending, ultrasound and scanning electron microscopy (SEM). The incorporation of crumb rubber content was 5% and 10% relative to the mass of gypsum. Two different tire rubber particle sizes were used: a thin called (#0.075 mm) and thick (# 2.38 mm). The results provide a reduction in the bulk density value. It was found that the adhesion of the rubber particles in the gypsum matrix does not present satisfactory results in coarse. This adhesion deficiency, found in SEM testing, was responsible for the lower flexural strength, tensile strength in bending and compression in plaster composites with coarse when compared to the results of composites with fine grain. With respect to ultrasound testing, it was found that the rubber delays sound propagation time. Lastly, the technical feasibility of the study was tested by means of test specimens, which proved to be efficient.[PT] O uso do gesso na construção civil brasileira vem crescendo continuamente nos últimos anos, quando o sistema drywall passou a ser utilizado nas vedações internas de todos os tipos de edificações. A essa utilização nova somam-se os usos tradicionais do gesso como material de revestimento e como material de fundição. Diante do exposto, este trabalho estuda algumas características físicas de compósitos de gesso produzidos com a incorporação de resíduos de borracha de pneus. No programa experimental foram realizados os seguintes ensaios: densidade de massa no estado plástico e endurecido, resistência à ruptura na flexão, resistência à compressão, resistência à tração na flexão, ultrassom e microscopia eletrônica de varredura (MEV). O teor de incorporação da borracha de pneus foi de 5% e 10% em relação à massa de gesso. Duas diferentes granulometrias de borracha foram utilizadas: a denominada fina (#0,075 mm) e a grossa (#2,38 mm). Os resultados proporcionaram uma redução no valor da densidade de massa. Identificou-se que a aderência das partículas de borracha na matriz de gesso não apresenta resultados satisfatórios na granulometria grossa. Esta deficiência de aderência, constatada na MEV, foi responsável pela menor resistência à flexão, à tração na flexão e à compressão nos compósitos com a granulometria grossa, quando comparados aos resultados dos compósitos com a granulometria fina. Com relação aos ensaios de ultrassom, constatou-se que a borracha retarda o tempo de propagação do som. Por fim, a viabilidade técnica do estudo foi testada por meio de corpos de prova, onde se mostrou ser eficiente.À agência de fomento FAPESP – Fundação de Amparo à Pesquisa do Estado de São Paulo, pelo auxílio financeiro.Pinto, N.; Fioriti, C.; Paya Bernabeu, JJ.; Akasaki, JL. (2016). Avaliação de matriz de gesso com incorporação de borracha de pneus para utilização na construção civil. Revista Tecnológica. 25(1):103-117. https://doi.org/10.4025/revtecnol.v25i1.29894S10311725

About the study of compounds incorporating rubber tires

In this paper we have studied some physical characteristics of gypsum composites incorporated with two different tire rubber granulometry. The experimental program was formed by the following tests: consistency (mini-slump), compressive strength and scanning electron microscopy (SEM). The rubber used in the composites came from the retreading of tires with 5 and 10% incorporation in relation to the plaster mass and the two different granulometry used were denominated thicknesses (# 0.6 mm) and thick (# 1.19 mm ). The results were compared with the control paste, in which there was no incorporation of rubber. The rubbers of different granulometry stood out in different points. The thin rubber presented a compressive strength close to the value observed in the control, with an addition of 5% by mass, which may be due to its adherence to gypsum paste, which occurred in a less porous manner and with a closer interface between the rubber particles and pulp, observed through the SEM. The thick rubber presented the best results in consistency, contributing to the workability of the pulp, which was also observed in SEM, where the thick rubber presents less adherence to the gypsum plaster, compared to the composite with incorporation of fine rubber. It was possible to affirm, then, that rubber as residual material presented interesting characteristics in applications in plaster composites

Safety of hospital discharge before return of bowel function after elective colorectal surgery

Background: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien\u2013Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9\ub72 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4\u20137) and 7 (6\u20138) days respectively (P < 0\ub7001). There were no significant differences in rates of readmission between these groups (6\ub76 versus 8\ub70 per cent; P = 0\ub7499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0\ub790, 95 per cent c.i. 0\ub755 to 1\ub746; P = 0\ub7659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34\ub77 versus 39\ub75 per cent; major 3\ub73 versus 3\ub74 per cent; P = 0\ub7110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients