Banca de DEFESA: ITALO BATISTA DA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ITALO BATISTA DA SILVA
DATA : 27/07/2018
HORA: 09:30
LOCAL: Laboratório de Cimentos da UFRN
TÍTULO:

EFFECT OF THE ADDITION OF POLYURETHANE (PU) IN THE THERMOMECHANICAL PROPERTIES OF PORTLAND CEMENT PASTES SUBJECT TO HIGH TEMPERATURES

PALAVRAS-CHAVES:

 Cementation; Flexible cement pastes; Thermomechanical properties; Thermal expansion; Polyurethane (PU).

PÁGINAS: 100
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

In order to adapt Portland cement to well at high temperature conditions and thermal gradients, the application of additives of polymeric nature can be a way to improve their thermomechanical behavior. The objective of this work is to evaluate the effect of the addition of different concentrations of polyurethane (PU) on the thermo-mechanical properties of cement pastes submitted to temperatures of up to 300 ° C and 3 kpsi pressure. Formulations added were prepared with 1, 2 and 3 gpc of polyurethane, respectively named PU1, PU2 and PU3. A standard paste (without PU) was also prepared. The slides were cured for 14 days (38 ° C thermal bath for 11 days plus 3 days in the curing chamber at 300 ° C), 28 days (38 ° C thermal bath for 11 days plus 3 days in the 300 °C) and 90 days (38 °C thermal bath for 11 days plus 3 days in the curing chamber at 300 °C). These conditions are characteristic of pastes subjected to high temperatures in steam injection operations. The mechanical properties of the cured pastes were analyzed by compressive strength using strain gauges, diametrical compression tensile strength, resonance frequency for the calculation of the Poisson's coefficient and ultrasonic test for the calculation of the modulus of elasticity. The thermal properties were investigated by the study of the behavior of the coefficient of linear thermal expansion (CTE) in argon atmosphere and also by the thermogravimetric (TG) analysis to monitor the mass variation under the same conditions temperature and heating rate of the dilatometry. The samples were also characterized by X - ray diffraction (XRD) and field emission scanning electron microscopy (SEM - FEG). The results of compressive strength showed a slight reduction of values with addition of polyurethane. After 14 days of curing, the compressive strength was 24.7 MPa, 22.3 MPa and 20.0 MPa, for the formulations PU1, PU2 and PU3 respectively. The tensile strength was 4.5 MPa, 4.0 MPa and 2.8 MPa, respectively. The standard slurry, without PU, had compressive strength of 28.4 MPa and tensile strength of 4.8 MPa. After 28 days, PU2 obtained higher compressive strength of 27.8 MPa and tensile strength of 4.82 MPa, while the standard sample had 29.88 MPa and 5.03 MPa. At 90 days of cure, the behavior pattern of the compositions was similar to those at 14 and 28 days. The PU2 sample also showed good elastic behavior after 28 days of curing, evidenced by the modulus of elasticity and the Poisson's coefficient, 16.5 GPa and 0.22 (reference paste obtained 17.6 GPa of elastic modulus and Poisson ratio of 0.20). After 28 and 90 days, the samples had high peaks of xonotlite, which gives higher stability to the cement according to literature data. The presence of polyurethane also affected the coefficient of thermal expansion of the materials in the dilatometry test, since its presence decreases the hydration kinetics of the samples. As the concentration of polyurethane in the sample increased (sample PU1 to PU3), the expansion behavior characteristic of the polymer required longer cure times to become apparent. Thus, the results show that the thermomechanical properties of PU formulations were satisfactory compared to the standard paste, mainly with 28 and 90 days of curing, presenting better stability in the crystallographic and morphological characterization, in the study of the compressive and tensile strength , in the plastic (elastic) and dilatometric behavior, as they diminished the thermal incompatibility between the cement sheath and the steel sheath. In addition, it reduces the brittle behavior of the cement, contributing in general to the thermomechanical behavior of the sheath material subjected to high temperatures and gradients

MEMBROS DA BANCA:
Presidente - 1298936 - ANTONIO EDUARDO MARTINELLI
Externo à Instituição - ANTONIO FARIAS LEAL - UFPB
Interno - 1804366 - JÚLIO CÉZAR DE OLIVEIRA FREITAS
Externo ao Programa - 1754344 - MARCOS ALLYSON FELIPE RODRIGUES
Externo à Instituição - WENDELL ROSSINE MEDEIROS DE SOUZA - UFERSA