Influence of Calcined Diatoms on the Properties of Conventional Concrete

Abstract

Today, the construction industry has expressed its preference for the use of sustainable materials due to
the significant impact they have on the environment. Although concrete is widely used in construction due to its
diverse properties, one of its main components, known as clinker, is a major contributor to CO2 pollution. Therefore,
the feasibility of partially replacing this material with alternatives is being investigated. Among them, calcined
diatoms are presented as a promising option. These are an extremely fine and highly porous material, composed
mainly of silica, which has a large specific surface area. The abundant presence of active silica improves the
properties of concrete, such as its strength, while the ultrafine particles of diatoms densify the concrete structure,
thus achieving a concrete with greater durability. The objective of this study was to evaluate the properties of
conventional concrete, both fresh and hardened, by adding calcined diatomite in proportions of 5%, 10% and 15%,
with the purpose of determining the optimum percentage of calcined diatomite to achieve adequate concrete
development. Test specimens were elaborated without the addition of calcined diatoms and with the addition of
calcined diatoms, then immersed in water for 7d, 14d and 28d. Tests were carried out in the fresh state to obtain
workability, bleeding, setting time, air content, temperature, and unit weight. In the hardened state, tests were carried
out to obtain compressive strength, static modulus of elasticity and permeability. It was found that with a lower
addition of calcined diatomaceous earth, the concrete can develop as a normal concrete, and improvements in
compression were obtained, increasing with respect to the control concrete. However, by increasing the percentage
of calcined diatomite, the workability is reduced and in general, the properties do not show an improvement. Concrete
with the addition of calcined diatomite can be used as a thermal insulator, since it presents very fine particles that
perform a filling effect, densifying the concrete matrix, and it can also be used for lightweight concrete since it
reduces 17kg/m3. On the other hand, the compressive strength with 5% calcined diatomite increased by 9% with
respect to the standard, due to its high pozzolanic activity. In addition, a lower permeability was found with the
addition of 5% calcined diatomite. In general, calcined diatomite in lower proportions can generate resistant and
durable concrete.