entroy and shaclock mix design for hsc

8/20/2019 Entroy and Shaclock Mix Design for HSC

1/9

MIX DESIGN OF HIGH STRENGTH CONCRETE

The properties of a high-strength concrete-mix with a compressive strength of more than 40 MPa is greatly influenced by

the properties of aggregates in addition to that of the water-cement ratio. To achieve high strength, it is necessary to use

lowest possible water-cement ratio, which invariably affects the worability of the mix and necessitates the use of special

vibration techni!ues for proper compaction. "n the present state of art, a concrete with a desired #$ day compressive

strength of upto %0 MPa can be made with suitably proportioning the ingredients using normal vibration techni!ues for

compacting the concrete mix.

Erntroy and Shacklock’s Empirical Graphs: &rntroy and 'hacloc have suggested empirical graphs relating the

compressive strength to an arbitrary (reference number) for concrete made with crushed granite, coarse aggregates and

irregular gravel. These graphs are shown in figure * and # for mixes with ordinary Portland cement and in figure + and 4

for mixes with rapid hardening Portland cement. The relation between water cement ratio and the reference number for

#0mm and *0mm maximum sie aggregates is shown in figure , in which four different degrees of worability are

considered. The range of the degrees of worability varying from extremely low to high corresponds to the compacting

factor values of 0. and 0./ respectively

The relation between the aggregate-cement and water-cement ratios, to achieve the desired degree of worability with agiven type and maximum sie of aggregate are compiled in table-* and # for two different types of cements. The

limitations of these design tables being that they were obtained with aggregates containing +0 percent of the material

passing the 4.% mm "' sieve. Thus, if other ingredients are used suitable adustments have to be made. 1ggregates

available at site may be suitably combined by the graphical method to satisfy the above re!uirement. "n view of the

considerable variations in the properties of aggregates, it is generally recommended that trial mixes must first be made

and suitable adustments in grading and mix proportions effected to achieve the desired results.

Table 2 *3 1ggregate cement ratio by weight5 re!uired to give four degrees of worability with different water 2cement

ratios using ordinary Portland cement

Table 2 #3 1ggregate cement ratio by weight5 re!uired to give four degrees of worability with different water 2cement

ratios using rapid hardening cement


2/9

MIX DESIGN PROCEDURE:

*. The mean design strength is obtained by applying suitable control factors to the specified minimum strength.

#. 6or a given type of cement and aggregates used, the reference number corresponding to the design strength

at a particular age is interpolated from figure * to 4.

+. The water-cement ratio to achieve the re!uired worability and corresponding to the reference number is

obtained from figure for aggregates with maximum sies of #0mm and *0mm.

4. The aggregate-cement ratio to give the desired worability with the nown water cement is obtained by

absolute volume method.

. 7atch !uantities are wored out after adustments for moisture content in the aggregates.


3/9

6ig.*3 8elation between compressive strength and reference number &rntroy and 'hacloc5


4/9

6ig-#3 between compressive strength and reference number &rntroy and 'hacloc5


5/9

6ig-+3 8elation between compressive strength and reference number &rntroy and 'hacloc5


6/9

6ig-43 8elation between compressive strength and reference number &rntroy and 'hacloc5


7/9

6ig-3 8elation between water-cement ratio and 8eference 9umber

6ig-3 :ombining of 6ine aggregates and :oarse aggregates

Table 2 +3 7atch ;uantities per cubic metre of concrete


8/9

MIX DESIGN EXMP!E


9/9

*.*$mm 2

00 micron 2 0

+00 micron *0

*0 micron 2 0

DESIGN O& MIX

Mean strength = 0 @ 0.$05 = + MPa

8eference number fig.*5= #

Aater cement ratio fig 5 = 0.+

6or a *0mm maximum sie aggregate and very low worability, the aggregate-cement ratio for the desired worability

table-*5 =+.#

The aggregates are combined by the graphical method as shown in figure , so that +0 percent of the material passes

through the 4.% mm "' sieve.

8atio of fine to total aggregate = #B

8e!uired proportions by weight of dry materials3

:ement 2 *

6ine aggregates 2 C#@*005x+.#D = 0.$

:oarse aggregates 2 C%@*005x+.#5D = #.4

Aater = 0.+

"f : = weight of cement re!uired per cubic meter of concrete, then

entroy and shaclock mix design for hsc

Documents