Building Materials, Third Edition

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——˜Light weight cellular element can be easily sawn, drilled or nailed which makes
for easy construction and repairs.

i™ Due to light weight and high strength to mass ratio, the cellular products are quite
economical.

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The basic economy of LWC can be demonstrated by the savings achieved in associated
reinforcement requirment. LWC has superior resistance of shear elements to earthquake loading
since seismic forces are largely a direct function of deal weight of a structure, is also one among
the other advantages of LWC. Due to lower handling transportation, the construction cost, the
light weight concrete is ideally suited for the production of precast concrete elements and
prefabricated elements.

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1. Low density cellular concrete is used for precast floor and roofing units.


2. As lood bearing walls using cellular concrete blocks.


3. As insulation cladding to exterior walls of structures.

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For mix made with normal weight aggregates, high strength concrete (HSC) is considered to be
the one having a compressive strength in excess of 40 MPa. To produce concrete above this
strength more stringent quality control and more care in selection and proportioning of materials
are needed. The tentative classification of HSC is as given in Table 20.5. The tricalcium aluminate
component is kept as low as possible (<8%). Most cements used to produce HSC have fineness
in the range of 300–400 m^2 /kg with an exception of high early strength cement for which
fineness should be at least 450 m^2 /kg. For HSC a smaller maximum size of coarse aggregate
leads to higher strength. Fine aggregate should have a F.M >3.
Experimental studies also show that in many respects the microstructure and properties of
HSC are considerably different from those of conventional or normal concretes.

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The porosity of the three phases of concrete (i.e., aggregate, the hardened cement paste and
the aggregate-cement bond) is the most important strength determining factor in HSC.
Determination of porosity of the individual micro-structural phases of concrete i.e., the matrix
and the transition zone is impractical, therefore, precise models of predicting strength cannot
be developed. However, over a period of time many useful empirical relations have been
propounded which for practical purposes account for the influence of numerous factors including
porosity of individual micro-structural phases on compressive strength. One such relation is
Abram’s water/cement ratio rule.