Concrete, a ubiquitous material in our modern world, is a composite of cement, water, and aggregate (inert filler material like sand, gravel, or crushed stone). This versatile material has revolutionized construction, enabling the creation of durable, resilient, and affordable structures that have shaped our cities and landscapes.
From humble beginnings in ancient civilizations, concrete
has evolved into a sophisticated and adaptable material, catering to a diverse
range of construction needs. Its key attributes, namely strength, durability,
and workability, have made it indispensable for a wide spectrum of
applications.
Strength
and Durability:
Concrete's ability to withstand compressive forces makes it an ideal material
for load-bearing structures like buildings, bridges, and dams. Its resistance
to weathering and environmental factors ensures the longevity of these
structures, reducing maintenance costs and extending their lifespan.
Workability
and Adaptability:
Concrete's fluidity and moldability allow it to be shaped into various forms,
catering to diverse architectural and structural designs. This versatility has
enabled the construction of iconic structures like the Sydney Opera House and
the Petronas Twin Towers, showcasing the creative potential of concrete.
Environmental
Impact: While
concrete production generates emissions, advancements in technology and the use
of supplementary cementitious materials (SCMs) have reduced its environmental
footprint. Additionally, concrete's durability and longevity minimize the need
for frequent replacements, reducing overall resource consumption.
Normal-weight concrete
Concrete containing only coarse and fine aggregates that
conform to ASTM C33 and having a density greater than 2160 kg/m3. Concrete that
is normal weight, normally has a density of 2160 to 2560 kg/m3 and is commonly interpreted
to be 2320–2400 kg/m3.
Lightweight concrete
Concrete that contains lightweight aggregate and having a
determined equilibrium density between 1440 and 2160 kg/m3 according to ASTM
C567.
Sand-lightweight concrete
Lightweight concrete consisting only of normal weight,
conforming fine aggregate in accordance with ASTM C33 and lightweight coarse
aggregate complies with ASTM C330.
In sand Lightweight concrete
all fine aggregate replaced by sand. This statement might not agree with
material providers where the majority—but not all—of the light-weight particles
are substituted by sand. For the appropriate use of the code requirements, the
replacement limits shall be mentioned, with interpolation, if only a portion of
the sand is replaced.
Values of λ for lightweight concrete
λ shall be determined based on the equilibrium density of the concrete mixture utilized in the design, or the assumed composition of the aggregate in the concrete mixture as applicable. It shall be permitted to take λ as 0.75 for lightweight concrete. The value of λ shall be taken as 1.0 for normal weight concrete.
Values of λ based on equilibrium density [ACI 318-19, Table 19.2.4.1(a)]
|
wc, kg/m3 |
λ |
|
≤ 1600 |
0.75 |
|
1600 < wc
≤ 2160 |
0.0075wc ≤
1.0 |
|
> 2160 |
1.0 |
Values of λ based on composition of aggregates [ACI 318-19,
Table 19.2.4.1(b)]
|
Concrete |
Composition of aggregates |
λ |
|
All-lightweight |
Fine: ASTM C330M |
0.75 |
|
Lightweight, fine |
Fine: Combination of ASTM C330M and C33M |
0.75 to 0.85[1] |
|
Sand-lightweight |
Fine: ASTM C33M |
0.85 |
|
Sand-lightweight, |
Fine: ASTM C33M |
0.85 to 1[2] |
|
[1] Linear interpolation from 0.75 to 0.85 is permitted
based on the absolute volume of normal weight fine aggregate as a fraction of
the total absolute volume of fine aggregate.
|
Great Post... So many information in one place. Carry on.
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