Banca de DEFESA: AMANDA REGINA DE SOUZA MACEDO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : AMANDA REGINA DE SOUZA MACEDO
DATE: 20/01/2022
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), compressive strength.

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

ABSTRACT:

Concrete is a composite, being considered the most 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 hydration and which are mainly 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 minimize environmental impacts. This is possible through the use of
supplementary cementitious materials (SCM), which can be used as clinker substitutes
or as addition or replacement in the production of concretes. Diatomite is 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% by volume, in the production
of conventional concretes with fck estimated at 30Mpa. Initially the starting materials
were characterized as to their physical, chemical, mechanical, structural and
microstructural properties). Then, concretes were produced with a mass ratio of 1:
1.33:2.33 and a/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 (X-ray diffraction) and
TGA (thermogravimetry) techniques at 7, 28 and 91 days. The results showed that the
incorporation of diatomite caused a small reduction in the compressive strength of the
concretes. Despite this, the concretes produced with 15%v. and 20%v. of diatomite
presented a greater evolution in the values of compressive strength (20.07% and
16.16%, respectively) from 28 to 91 days, as a consequence of the pozzolanic reaction.
While the 0%v. and 10%v. concretes presented an evolution of 4.33% and 5.20%,
respectively. This observation was confirmed in the results of XRD and TGA, where it
was observed that there is a greater consumption of portlandite and a greater amount of
combined water in these mixtures. The total porosity, water absorption and capillary
absorption decreased in the concrete with 10%v. of 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.

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