Banca de QUALIFICAÇÃO: AMANDA REGINA DE SOUZA MACEDO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : AMANDA REGINA DE SOUZA MACEDO
DATE: 24/12/2021
TIME: 13:00
LOCAL: Sala Virtual
TITLE:

EFFECTS OF DIATOMITE AS PARTIAL REPLACEMENT FOR PORTLAND CEMENT IN THE PROPERTIES OF CONVENTIONAL CONCRETES

KEY WORDS:

Keywords: conventional concrete, diatomaceous earth, supplementary cementitious material (SCM)

PAGES: 115
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

ABSTRACT

Concrete is a composite and is considered the most widely used construction material in the world. Its main component is Portland cement, responsible for the formation of calcium silicate hydrates (C-S-H) formed during its hydration and are primarily responsible for the compressive strength of concrete. However, currently the search for alternative, more sustainable materials has increased, aiming to reduce CO2 emissions and consequently minimizing environmental impacts.  This is possible through the use of supplementary cementitious materials (SCMs), which can be used as clinker substitutes or as addition or replacement in the production of concretes. Diatomite, considered a natural SCM, with high SiO2 concentration is able to react with calcium hydroxide (CH) released during cement hydration to produce additional calcium silicate hydrate (C-S-H). Thus, the present work aims to study the effects of replacing Portland cement by diatomite in the proportions of 0%, 10%, 15% and 20% in the production of conventional concretes with fck estimated at 30Mpa. For this, initially the materials were characterized as to their physical, chemical, mechanical and microstructural properties). Then, they were produced with concretes with a mass ratio of 1: 1.33:2.33 and w/c ratio = 0.44.  The concretes were evaluated for their properties in the fresh state (slump test) and in the hardened state (compressive strength, porosity, water absorption, capillary water absorption and chloride ion diffusion). Cement pastes with the same proportions of the concretes were analyzed by XRD and TGA techniques at 7, 28 and 91 days. The results showed that the incorporation of diatomite caused a slight reduction in the compressive strength of the concretes. Despite this, the concretes produced with 15% and 20% diatomite presented a greater evolution in compressive strength from 28 to 91 days, as a result of the pozzolanic reaction. This observation was confirmed in the results of XRD and TGA of the pastes, where it was observed that there is a greater consumption of portlandite and a greater amount of combined water in these mixtures. Total porosity, water absorption and capillary absorption decreased in the concrete with 10% diatomite, due to the filler effect. The incorporation of diatomite reduced the chloride ion diffusion coefficient of the concretes due to the refinement of the pore structures.

Keywords: conventional concrete, diatomaceous earth, supplementary cementitious material (SCM).

BANKING MEMBERS:
Interno - 1300987 - CARLOS ALBERTO PASKOCIMAS
Interno - 345842 - UILAME UMBELINO GOMES
Externa ao Programa - 1330408 - DIANA CARLA SECUNDO DA LUZ
Externa à Instituição - ARIADNE DE SOUZA SILVA - IFRN