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TECHNICAL PAPER

CONCRETE AS AN ARTIFICIAL

ROCK: MINERALOGY OF SWATHY MANOHAR*

AGGREGATES REVISITED K. MOHAMMED HANEEFA
BAHURUDEEN A.
B. S. DHANYA
MANU SANTHANAM

[5]
Abstract only by 3-fold . Since 70 % of the mass of concrete is typically
constituted by aggregates, they play a vitally significant role
Concrete is a conglomerate of aggregates encapsulated in a in determining the properties of concrete as well as on the
continuous matrix of binder phase. Concrete is comprised of environmental impact. Most of the concrete research over the
aggregates more than 70 % by its volume and has a significant past many decades are focused on the binder phases (cement,
influence on the quality of concrete. Irrespective of the binder supplementary cementitious materials (SCMs) or any chemicals
used, aggregates impart volume stability, stiffness and inertness associated to alter their properties). Research on aggregates is
to concrete. These properties are governed by the geo- again focused on alternate aggregates, recycled aggregates,
chemistry of aggregates, which depends on the mineralogy. and other neo forms. However, a deeper understanding of
Currently, various sources of aggregates are used in the concrete the prevailing standard aggregates used in concrete, their
production. A combined study on aggregate mineralogy, mineralogy, and behavior, which can directly influence and be
its influence on aggregate properties and performance in used to control the performance of concrete is limited. The
concrete is imperative to enable proper selection and effective current paper presents a detailed study on the mineralogy of
utilization of available aggregate resources. This paper reviews the concrete aggregates, and their petrographic properties,
eventually develops it as a review paper, combining data from
the mineralogy of aggregates with respect to their geo- interdisciplinary views such as geology of stones, and civil
chemistry, and discusses the relevance pertaining to engineering engineering application of aggregates. This work shall be
properties, physical, chemical, and thermal constancies. useful in choosing or reconsidering many aggregates in specific
Moreover, the paper also provides a colour atlas of common concrete purposes knowing their intrinsic properties, limitations,
minerals in aggregates. and scope. Also, the review may be used as a tool in developing
test protocols to determine various aggregate properties such
Keywords: Aggregates; Concrete; Geo-chemistry; Mineralogy; as alkali silica reaction (ASR) tests and any other chemical attacks
Petrography.
in general.
1. INTRODUCTION
2. CONCRETE – AN ARTIFICIAL ROCK
Concrete is the most common construction material in the In the forwarding notes of ‘Concrete petrography- A hand book
world and the most consumed material next to water [1, 2] . Due to of investigating techniques’, Sydney Diamond writes, “Concrete
its low cost, significant strength, desired mouldability, and better is in essence a man-made rock, with special characteristics that
durability, the production of concrete is far outstripping that of stem from its hybrid character- that is, it is a conglomerate of
any other construction materials used across the world .
[2]
natural rock grains (sand and coarse aggregate) encapsulates in
[6]
The story of concrete starts as early as 12000 years ago, the a continuous matrix of hydrated Portland cement” . Figure 1
recorded earliest use of limestone in the temple of ‘Göbekli pictorially depicts the above statement. The petrographic
Tepe’ now located in Turkey . There are hypotheses that image (1a) is captured on a standard thin section of concrete
[3]
Romans, and Egyptians had used early forms of modern with granite and river sand-based aggregates in plane polarized
concretes . They used wide range of available binders with light. The dark and continuous phases indicate the binder
[4]
rocks or broken bricks for producing concrete. phases; whereas, the bright and discrete phases represent
coarse and fine aggregates. The aggregates occupy the major
The invention of modern clinkered cement elicited the growth volume of the concrete. However, their distributions are uneven.
of concrete technology as exponential. The growth is in such a Figure (1b) presents a typical example of similar mineral texture
way that; in the past seven decades, the consumption of cement of a geological conglomerate representing a limestone based
has hiked by 34 times; whereas, the world population increased marine rock captured in plane polarized mode.

THE INDIAN CONCRETE JOURNAL | AUGUST 2022 5
*Corresponding author : Swathy Manohar, Email: swathym@iitb.ac.in