Banca de DEFESA: JESSICA CONCEICAO QUEIROZ
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : JESSICA CONCEICAO QUEIROZ
DATE: 10/08/2023
TIME: 14:00
LOCAL: Ambiente virtual
TITLE:
The effects of crystallizer and superhydrophobic diatomite on the physical and mechanical properties of gypsum pastes
KEY WORDS:
Gypsum plaster, crystallizer, super-hydrophobic diatomite, contact angle, mechanical properties
PAGES: 159
BIG AREA: Engenharias
AREA: Engenharia Civil
SUBÁREA: Construção Civil
SPECIALTY: Materiais e Componentes de Construção
SUMMARY:
Gypsum plaster is a recyclable binder with low energy consumption and low CO2 emissions, but after hardening, it has low water resistance, compromising its integrity and durability. Therefore, several studies have been conducted to solve this problem. The use of additions with the potential to promote water-repellent characteristics to gypsum appears as one of the alternatives to reduce the susceptibility of gypsum to the action of water. The present study proposes evaluating the effects of different crystallizers and diatomite treated (DT) with silane modifier (OTS) on gypsum pastes' mechanical properties, porosity, and contact angle. For this, different statistical mixing projects were elaborated in the Design-Expert® software. The formulations generated for the studies of additions of crystallizer and treated diatomite were molded using the NBR 12129:2019 procedure and evaluated for dynamic modulus of elasticity (MOE), hardness (H), flexural tensile strength (ST), compressive strength (Sc), porosity (P) and contact angle (qc). Some formulations with low water content were formed under pressure as an alternative to improve the miscibility between the superhydrophobic treated diatomite and the gypsum paste. The pressed specimens were evaluated to determine MOE, ST, Sc, and qc. The optimized formulations of the crystallizer and treated diatomite statistical designs were subjected to natural aging for durability evaluation. The results show that using hydrated lime as a source of calcium hydroxide to react with the crystallizer compounds promotes an increase in H and reduces the P of pastes containing crystallizer. There was a significant increase of qc with the increase of crystallizer. However, with the maximum used crystallizing content, the pastes are still classified as hydrophilic (qc < 90°). Applying crystallizer contents above the maximum used in the formulations of the statistical mixture project allowed for obtaining hydrophobic pastes (90° < qc < 150°). The treatment of diatomite with OTS conferred superhydrophobic properties to diatomite (qc > 150°) and modification in its morphology. The increase in the mass fraction of treated diatomite paste and ethanol promoted the reduction of MOE, ST, and SC while qc increased; however, the highest values obtained for qc still classify the pastes as hydrophilic. With the pressure-forming process, the results were more satisfactory for MOE, ST, SC, and qc. However, they showed a tendency towards a reduction in mechanical properties and an increase in qc. After the first natural aging cycle, the specimens optimized with crystallizer and treated diatomite paste showed a reduction in mechanical properties and qc. Furthermore, the hydro-repellent materials showed promise for increasing the contact angle and reducing the gypsum's susceptibility to the water.
COMMITTEE MEMBERS:
Presidente - 2137887 - CLEBER MARCOS RIBEIRO DIAS
Interno - 1522482 - FRANCISCO GABRIEL SANTOS SILVA
Externa à Instituição - GLADIS CAMARINI
Externa à Instituição - CÍNTIA MARIA ARIANI FONTES