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Mass Concrete
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concrete brings with it many challenges, among them the generation
of high heat and problems that can stem from it. While creating
these projects can be difficult, careful design of mass concrete
can minimize or eliminate issues, and new research points to approaches
that will allow us to create bigger projects than ever before.
Defining Mass Concrete
ACI Committee 116 defines mass concrete as “any large volume
of cast-in-place concrete with dimensions large enough to require
that measures be taken to cope with the generation of heat and attendant
volume change to minimize cracking.” This categorization can
include structural components with moderate- to high-cement-content
concrete, massive structural elements of mat foundations, and to
dams and other large structures that use concrete with a low cement
content.
In any mass concrete application, temperatures rise through heat
of hydration. As the interior concrete rises in temperature, the
outer concrete may be cooling and contracting; if the temperature
varies too much within the structure, the material can crack. A
variety of factors influence temperature changes, including the
size of the component, the amount of reinforcement, the ambient
temperature, the initial temperature of the concrete at time of
placement and curing program.
Design Options
Engineers use a variety of approaches to tackle the potential for
thermal cracking and successfully create mass concrete. These methods
include: refining concrete mix proportions, protecting exposed surfaces
and formwork from environmental extremes, using aggregate with desirable
thermal properties, pre-cooling the concrete constituent materials,
using internal pipes to cool the concrete itself, and placing the
concrete in several lifts or pours. More.
Some designs include supplementary cementitious materials in the
mix, including slag cement or fly ash. The Slag
Cement Association offers some guidance on specifying slag cement
for mass concrete here.
The American Coal Ash Association
offers information here
on the benefits and specification of fly ash.
Industry Resources
CTLGroup offers
a collection of articles on mass concrete here.
ACI publication 207.1R-96:
Mass Concrete examines mass concrete in detail.
| Publications |
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Specifications
for Structural Concrete for Buildings (ACI 301-05)
(LT188)
This is the most widely used structural concrete reference specification
for buildings, covering materials and proportioning of concrete;
reinforcing and prestressing steels; production, placing, finishing,
and curing of concrete; and formwork design and construction.
Methods of treatment of joints and embedded items, repair of
surface defects, and finishing of formed and unformed surfaces
are specified. Separate sections are devoted to architectural
concrete, lightweight concrete, mass concrete, prestressed concrete,
and shrinkage-compensating concrete. Provisions governing testing,
evaluation, and acceptance of concrete as well as acceptance
of the structure are included. Published by the American Concrete
Institute. |
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Design
and Control of Concrete Mixtures, 14th Edition (EB001)
This definitive reference on concrete technology covers fundamentals
and detailed information on freshly mixed and hardened concrete.
Extensively updated and expanded, this new edition discusses
materials for concrete, such as portland cements, supplementary
cementing materials, aggregates, admixtures and fibers; air
entrainment; procedures for mix proportioning, batching, mixing,
transporting, handling, placing, consolidating, finishing, and
curing concrete; precautions necessary during hot- and cold-weather
concreting; causes and methods of controlling volume changes;
commonly used control tests for quality concrete; special types
of concrete, such as high-performance, lightweight, heavyweight,
no-slump, roller-compacted, shotcrete, mass concrete and many
more. Applicable ASTM, AASHTO, and ACI standards are referred
to extensively. |
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High-Strength
Concrete in Massive Foundation Elements (RD117)
Evaluates high-strength concrete in drilled shafts (caissons)
for temperature rise, strength, stiffness, cracking and other
characteristics.
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Engineering Mass Concrete
Structures (RP437)
Upon reading this reprinted article and completing the quiz
to earn CEU credits, the reader will learn how to minimize
the likelihood of cracking and improve the durability of mass
concrete by optimizing the mix design, as well as predicting,
monitoring, and controlling concrete temperatures.
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More information is also available online from CTLGroup:
Mass
Concrete Consulting Overview
Save
Time and Money on Mass Concrete Construction
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Design Resources:
Codes and Standards
Concrete Tanks
Design for Security
Detailing
Emerging Trends
ICF Buildings
Masonry Buildings
Mass Concrete
Novice Engineers Series
Post-Tensioned Concrete
Precast/Prestressed Concrete
Reinforced Concrete
Shotcrete
Sustainable Design
Tilt-Up Concrete
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