Major Project: High Strength Concrete in Construction - Report

This report provides a comprehensive overview of high strength concrete (HSC) in construction, focusing on its application in high-rise buildings. It explores the definition of HSC, its constituents, and its advantages, such as reduced column sizes and enhanced stiffness, alongside its disadvantages. The report delves into the use of HSC in various structural elements like columns, walls, and flexural members. It also highlights the impact of HSC on building design, construction costs, and user comfort. The report includes an analysis of the factors affecting high-rise concrete construction and compares HSC with structural steel. The document is a literature review and includes an executive summary, introduction, and conclusion, along with references. The report serves as a valuable resource for civil engineering students seeking to understand the benefits and drawbacks of high strength concrete in construction projects, particularly in high-rise applications.

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Executive Summary
High strength concrete is usable in minimization of the column sizes in high-rise buildings
mostly in the lower level floors. High strength concrete comes with extra advantage of higher
elastic of modulus which may lower the deflection. It as well has lower specific creep which
renders it possible to use higher stresses linked with high strength concrete. It has been
demonstrated through research that using high strength concrete is able to lower the construction
cost with the current prices of steel and concrete.

Contents
Executive Summary.....................................................................................................................................2
Introduction.................................................................................................................................................4
High strength concrete................................................................................................................................4
Application of High strength concrete.....................................................................................................6
Constituents of High strength Concrete..................................................................................................8
High strength concrete in High rise Buildings............................................................................................13
High strength concrete for flexural members........................................................................................14
High strength concrete for walls............................................................................................................15
High strength concrete for columns......................................................................................................15
Advantages and Disadvantages of High Strength Concrete.......................................................................16
Advantages............................................................................................................................................16
Disadvantages........................................................................................................................................17
High-rise buildings of high strength concrete............................................................................................18
Impacts of High strength concrete on comfort of user..............................................................................23
Conclusion.................................................................................................................................................25
References.................................................................................................................................................27

Introduction
Concrete which is a composite made up of aggregates contained in a matrix of cement paste
inclusive of possible pozzolana is made up of two main components: cement paste alongside
aggregates. The strength of concrete is a factor of the strength of such components, the properties
of their deformation as well as the adhesion between the surface of the aggregate and paste.
Concrete can be made to the tune of 120 MPa compressive strength with the presence of natural
aggregates through enhancing the strength of cement paste that is controllable through the choice
of the water content ratio as well as the type alongside dosage of admixtures (Ahmmad et al.,
2016). Nevertheless, with the current development in concrete technology as well as the
availability of different kinds of chemical admixtures as well as minerals and special plasticizes,
concrete possessing a compressive strength to the tune of 100 MPa may not be commercially
produced using acceptable levels of variability with the aid of ordinary aggregate. Such
developments have resulted in enhanced applications of high strength concrete all over the
world.
High strength concrete
The bottom range of strength of high strength concrete is a factor of the time as well as
geographical location which is mainly dependent on the availability of raw materials as well as
technical-know how alongside the demand from the industry. Concrete that were treated to be
high strength half a decade ago are now treated as low strength. For example concrete
manufactured with compressive strength of about 30 MPa was treated to be of high strength in
the 1950s which was later taken over by compressive strength of 40 MPa to 50 MPa in the

1960s, 1970s had 60 MPa while 100 MPa was developed in the 1980s and beyond (Al-zharani,
Demirboga and Khushafati, 2016).
These changes over time in what is regarded as high compressive strength concrete makes it’s a
nightmare to define the term high strength concrete using a single unique number or even
generate a limit between the conventional normal strength concrete as well as high strength
concrete. Provided the attained concrete or target strength is almost the same quality as the local
materials, age, curing conditions as well size of the testing specimens, it makes clear the notion
that neither unique nor unified definition of high strength concrete can be attained leave alone
being necessary (Aslani et al., 2015). Another factor in the definition of the ranging lines of high
strength concrete is as well as demand for certain strengths or concrete performances. In the
categorical case of the USA alongside some other factors growing Asian economies, a
compressive strength of 95 MPa is high strength concrete which is found in most of the concrete
plants and established to be economical efficient besides being cost effective.
Gaining control on the column sizes in high-rise buildings is of utmost importance, Suppose
normal concrete has been adopted, the sizes of the column are likely to be large and thus to a
great extent limit the flexibility of the layout of the floors besides consuming a significant
amount of rentable space. Hence, the most important application of high strength concrete
revolves around minimization of the column sizes more specifically in the lower storeys of high
rise buildings. The greatest strength of concrete that has been used in real life is 135 N/mm2 that
was used for Seattle’s Union Square building. Besides, the modulus of elasticity of 49 kN/mm2
attained with 135 N/mm2 is almost double as high for ordinary strength concrete (Choe et al.,
2015). The high concrete stiffness may be used in regulating the lateral defection thus the

maximum acceleration as result of the wind loads. There is need to regulate the maximum
acceleration as a result of the wind to attain the comfort needs of the occupants of the structure.
One fundamental property which has enabled the sue of high strength concrete in columns of
high-rise buildings is regarding the low specific creep, the creep strain as a result of units stress.
There is a decrease in the specific creep with an increase in the strength of concrete. High
strength concert do not any more suffer total shortening in comparison with the normal strength
concrete columns with reduced levels of stress owing to the lower specific creep (Choi et al.,
2016).
Using high strength concrete comes along with numerous benefits including high strength or
units cost, high stiffness or unit weight as well as high strength or unit weight. It is of importance
to note that when there is an increase in the strength of concrete, the price per unit tends to
increase. Since the higher strength is attained through regulating, the water cement ratio as well
as the use of a few additives includes fly ash, silica fume, admixtures including super plasticizers
with the main constituent materials remaining almost the same. Hence, there is just a marginal
increase in the cost of high strength concrete and hence at significantly lesser rte. The adoption
of high strength concrete may as well allow the elimination of false work and shuttering early
thus permitting an increase in the rate of construction. As a result of the smaller sizes of the used
members, the foundation loads will as well be reduced. All such benefits alongside the
availability of good quality aggregates encompass the major encouraging factors for wider
adoption of high strength concrete especially in high-rise buildings among nations around the
world (Eid et al., 2018).

Application of High strength concrete
High strength concrete is needed in numerous engineering projects which have components of
concrete that have to be resistive of high compressive loads. High strength concrete is basically
used in the construction of high rise structures. It has been applied in components including
columns in most cases on lower floors in which the loads are determined to be greatest, shear
walls as well as foundations. High strength concrete is as well at times used in the bridge
applications.
In high-rise structures, high strength concrete has established successful application in numerous
cities of the USA. A high rise structure adequate for high strength concrete use is taken as
structure that is to be more than 30 storeys. Special concrete has been used in such projects not
just as a result of the load capacity but as well enabled the lowering of the dimensions of beams
and columns. Lower dead loads are attained lowering the loads linked with the design of the
foundation. Still, the owners of the structures enjoy the economic benefits as the amount of
rentable space mainly on the lower floors in increases since the space consumed by the columns
is reduced (El-Dieb, 2016).
It is approximated that a storey structure that is 50 floors high and a column diameter of 4 foot
using 4000 psi concrete is able to lower the diameters of the column by about 33% through the
use of 8000 psi concrete. High strength concrete is at times used in the construction of highway
bridges. High strength concrete allows prestressed or reinforced concrete girders to effectively
span more lengths as compared with the normal concrete girders. Still the greater capacities of
the individual girders may allow a decrease in the number of girders needed hence presenting an
economical advantages for the producers of concrete for concrete would be promoted for

application in specific bridge project rather than steel. The high strength mixes of high strength
concrete are as shown in the table below
Table 1: Proportions of commercially available high strength concrete mixtures
Constituents of High strength Concrete
 High strength concrete is made up of constituents otherwise known as raw materials just
as is the case with the traditional normal strength concrete (Gan et al., 2017). Materials
that take part in high strength concrete proportioning included:
 Fly ash
 Supplementary cementitious materials
 Silica fume alongside some other mineral admixtures
 Aggregates of proven high quality as well as high compressive strengths including
dolomites, quartz and granite
 Super plasticizers

It is of importance that high strength concrete bear raw materials of the highest quality that are
free from any compromise for lower or even marginal qualities. Suppose the raw materials are
properly portioned and mixed, high strength concrete can be generated with lasting compressive
strength alongside other mechanical features. All Portland cement types generally have proved to
be adequate in the production of concrete having a compressive strength of to the tune of 60 MPa
at the age of 28 days (Gan et al., 2017). Nevertheless, there is need to design as well as evaluated
the reactions that occur between mineral admixtures and extra chemical admixtures in order to
attain higher strength and accompanied increase in the workability as well as performance.
The use of Blended hydraulic cement in the production of high strength concrete tends to be
common alongside Portland cement. Blended hydraulic cement defines a mixture of Portland
cement alongside other supplementary cementitious substances also called mineral admixtures.
The advantages of blended hydraulic cements revolve round lower heat development rate, higher
strength, enhanced durability, lower permeability as well as an increase in the general
performances.
Mineral admixtures have been identified as the greatest contributors for acceleration of the
development of high strength concrete technology and are often denoted as supplementary
cementitious materials. Such are the materials that developed as well as enhanced the
performance alongside strength of concrete of fresh and hardened concrete. Mineral admixtures
are generally alumina siliceous and siliceous materials that upon the addition of water undergo a
chemical reaction with calcium hydroxide to carry out the cementitious features (Gharehbaghi
and Chenery, 2017). The most commonly used types of supplementary cementitious materials in
the preparation of high strength concrete include silica fume, fly ash as well as cement slag.
Volcanic ashes, ultra fly ash, meta-kaolin, diatomaceous earths as well as calcined natural

pozzolans are on the other hand rarely used. The advantages of blended hydraulic cement
inducing higher strength, lower hydration heat as well as lower permeability are as well the
benefits of supplementary cementitious materials.
Figure 1: Common Mineral Admixtures
The most commonly used type of supplementary cementitious materials is fly ash and a by-
product of pulverized coal combustion which is spherical in shape and yields a glassy residue.
Fly ash is often added to all concretes to enhance the performance. Combining fly ash and slag
cement alongside Portland cement generate concrete that have compressive strengths of about 70
MPa (Golov et al., 2018). Silica fume also known as micro silica is a by-product of metals of
silicon and ferrosilicon alloys produced during the reduction of quartz in production of alloys of
ferrosilicon and silicon metals. The ultra-fine crystalline by-product allowed widespread high
strength concrete as well as the ability to generate ultra-high sound strength concrete.
Silica is often described as grey to black dust and the fumes of silica are often present in the form
of raw powder or water based slurry that are densified or even palletized. The most common
practice is silica fume that are in the form of densified powder for direct addition into concrete

mix (Kong, 2017). The grains of silica fume re about 100 times smaller in size in comparison
with the grains of Portland cement have sizes in the range of between 0.1μm and 0.3μm. In as
much as silica fume or micro silica comes along with a lot of benefits, the fineness may need
greater percentage of water that may result in a decrease in the workability as well as other good
features in case high range water reduction admixtures are not incorporated.
The principle of micro-filling using silica fume brought benefits of strengthening of the bond that
exists between the coarse aggregate as well as concrete paste with the possibility of attaining
compressive strength of more than 105 MPa (Kurad et al., 2017). Silica fume as well tends to be
effective in the reduction of the demand of other cementitious substances for example 1 kg of
silica fume may substitute between 2 kg and 5 kg of cement even as the remaining content is
water.
The production of high strength concrete would not be a possibility in the absence of super
plasticizers including high range water reducers as well as retarders among others. As
supplementary cementitious materials or mineral admixtures, the chemical admixtures enhance
fresh and hardened concrete. In the absence of chemical admixtures, the ability of transporting,
placing as well as curing the traditional ordinary strength concrete remains in question and thus
lack of chemical admixture in high strength concrete would result in an impossibility of making
high strength concrete.
High range water admixtures just as the most common super plasticizers lowered the water
cement ration even though it is of importance to establish the appropriate dose as well as type of
admixture hence high range water admixtures enhanced the strength with a decrease in the water
cement ratio even as it maintains the slump alongside increasing the slump while keeping the
water cement ratio constant.

In comparison with the conventional ordinary strength concrete, the water cement ratio in high
strength ratios tend to be lowering changing from 0.22 to 0.40. It is of importance nevertheless to
conduct an analysis if some decrease in the water cement ratio is need and if it results in the
requested increase in the strength of concrete as well as its performance (Li et al., 2017).
The volume of the aggregate takes the greatest percentage of the volume of concrete hence the
importance of choosing on the appropriate aggregate as high strength concrete needs the best
quality as well as strongest aggregate. The quality of the aggregates is affected by the density,
composition of the grain size, shape as well as texture of the surfaces of the aggregate. The
mechanical cement paste aggregate bond is increased in high strength concrete with the use of
rough textured as well as angular aggregates and hence such aggregates are likely to be more
workable for the case of high strength concrete. Among the aggregate that are ideal for high
strength concrete include granite, dolomite, trap rock, quartzite among other mineralogy kinds of
aggregates.
In as much as high strength concrete is associated with lower resistance to fire in comparison
with the ordinary strength concrete, it still possesses relatively higher fire resistances in
comparison with any other type of structural materials and tends to be economically efficient
solution that can enhances the fire resistance.
As per the common standards of the time, high strength concrete as well as ultra-high strength
concrete are among the top concretes having compressive strengths more than 50 MPa and 150
MPa in that order. Most of the countries are to some extent limited to the maximum concrete
strengths to about 60 MPa as a result of lack of demand for higher strength as well as higher
performance concretes or due to the lower development rate. Nevertheless, regions under quick
as well as constant development and construction especially in the vertical direction often