REACTION BETWEEN CEMENT AND WATER AND INTERFACIAL TRANSITION ZONE...

Reaction between cement and water and interfacial transition zone.

Reaction between cement and water is known as heat of hydration it is exothermic reaction .

cement contains four components known as Bouge components.

C2S- DI CALCIUM SILICATE

C3S- TRI CALCIUM SILICATE

C3A - TRI CALCIUM ALUMINATE

C4AF- TETRA CALCIUM ALUMINO FERRITE.

when water reacts with cement they formed calcium silicate hydrate,calcium hydroxide and calcium aluminte trisulphate hydrate( known as ettringite)or calcium aluminate monosulphate hydrate which is final product of cement and water reaction.

C- S-H is cementitious product useful for concrete but Calcium hydroxide and ettringite is harmful for concrete.

when C3S reacts with water is generate less C-S-H  and more calcium hydroxide or more quantity of heat in comparison of C2S.

C3S causing initial strength for concrete where as C2S is causing gaining strength gradually for long time.

INTERFACIAL TRANSITION ZONE:

CONCRETE CONSIST MAINLY TWO ZONES

: PASTE PHASE  ( LIQUID PHASE)

: SOLID PHASE

Third phase is known as Transition zone which is lies between above these phase.

when aggregate of concrete settle down water is trapped underneath of aggregate due to which water cement ratio of that perticular area increase this zone is known as transition zone which is weaker part of concrete  causing cracks when load is applied and crackson is propagate from this zone to another zone and causing break of cube.

To minimise this zone we use POZZALANIC materials in concrete they are:

FLYASH

MICROSILICA

ALCOFINE

GGBFS

COMPRESSIVE STRENGTH OF WHITE CEMENT...

               

   COMPRESSIVE   STRENGTH   OF   WHITE   CEMENT  

As per IS 8042 compressive strength of white cement not less than

90% of specified strength of OPC 33.

Specified strength of OPC 33 after 28 days: 33N/mm2

If we calculate it is come 29.7 N/ mm2 (90%  of 33N/mm2.)


so the strength of white cement not less than 29.7 N/mm2....

EFFECT OF SPECIFIC GRAVITY ON CONCRETE...

Effect of specific gravity on concrete is given below:

• If the specific gravity of aggregate which we use to produce concrete is less than aggregate which we use in trial before to produce concrete in this case water requirement for concrete is more than trial to meet slump criteria due to which water cement ratio high and result less strength.

• In the case of low specific gravity we require more quantity of cement in mix to meetc strength criteria explaination : Let we have two types of aggregate 1) Low specific gravity 2) High specific gravity.

    fill 1m3 box with these both aggregate,

    we see that for same mass number of 

   aggregate in the case of low specific          

   gravity    is more than high specific gravity aggregate .

Hence number of aggregate more surface area of aggregate more due to this cement paste require to cover the surface of aggregate is more and water requirement more.

• If specific gravity of aggregate less than aggregate use in trial than in this case volume of concrete more I. e yield of concrete more because in this case volume of water maximum.
• If specific gravity of aggregate less it require more space in stock yard in comparison of high specific gravity of aggregate. 
• If specific gravity less density of concrete also less and vise versa.  

    

     

COMBINED GRADING OF AGGREGATE...

GENERAL QUESTIONS RELATED FOR CONCRETE

General Question:

Pace rate of C TM  for 150 mm cube size      -                 140 kg/ cm 2 /minute  -  5.25 kn/s

Pace rate of CTM for  100 mm cube size       -                 140 kg/cm 2/ minute  -   2.33 kn/s

Pace of     CTM   for cement mortar cube       -                350 kg/cm 2/ minute  -    2.9 kn/s

Pace rate of CTM for crushing value of aggregate   -      40 ton /10 minute  -        0.67 kn/s


DIFFERENT INDIAN STANDARDS .

O P C 33  -    IS 269
O P C 43  -     IS 8112
O P C 53  -     IS 12269
P S C        -     IS 455
P P C        -     IS 1489 PART 1ST ( FLY ASH BASED)
               -     IS 1489 PART 2ND( CALCINED CLAY BASED)

MASS CONCRETE WORK - IS 457

FLY ASH - 3812 PART 1ST USED AS          POZZALANIC MATERIAL.

                 -3812 PART 2ND  USED AS MINERAL ADMIXTURE.
         
                 -3812 PART 3RD  USED AS FINER MATERIAL IN CONCRETE.

IS      -   456      ( FOR P C C AND R C C)
IS      -  4925     ( SPECIFICATION FOR BATCHING CONCRETE AND MIXING PLANT)
IS      -  4926     ( SPECIFICATION FOR READY MIX CONCRETE)
IS      -   10262  ( CONCRETE MIX DESIGN)
IS      -   9103    ( SPECIFICATION FOR ADMIXTURE)
IS      -    9013    ( FOR ACCELERATED CUBE/CONCRETE STRENGTH TEST )
IS      -    650     ( STANDARD SAND)
IS      -   1343    (SPECIFICATION FOR PRE STRESSED CONCRETE)
IS      -   1344    ( SPECIFICATION FOR CALCINED CLAY FOR MAKING PPC)
IS      -   4031    (PART IST ( FINESS OF CEMENT BY SEIVE)
IS      -   4031    (PART 2 ND (FINESS BY BLAIN AIR PERMEABILITY METHOD)
IS      -   4031     (PART 3RD    ( SOUNDNESS OF CEMENT)
IS      -   4031     (PART  4TH ( FOR CONSISTENCY OF CEMENT)
IS      -   4031     ( PART  5 TH ( FOR INITIAL AND FINAL TEST OF CEMENT)3
IS      -   4031    ( PART  6TH ( FOR CEMENT MOTAR CUBE TEST)


SURFACE AREA

O PC  - NOT LESS THAN 225 M 2/KG
P SC  - NOT LESS THAN   225 M 2/KG
P PC  - NOT LESS THAN   300 M 2/ KG

MICRO SILICA  -15000 -20000 M2/KG
AL CO FINE       -1200 M 2 /KG
G G B F S          -  NOT LESS THAN 275 M 2/KG

SPECIFIC GRAVITY

O PC                               :          3.10 - 3.15
P PC                                :          2.9  -3.0
G G B F S                       :          2.9
MICRO SILICA             :          2.2
WATER                           :         1.0
AGGREGATE  COARSE :       2.7 - 2.9
FINE AGGREGATE         :       2.6 -  2.7
AL CO FINE                   :         2.9

P S C                                :        2.9-3.0

ACCEPTANCE CRITERIA FOR STRENGTH OF CONCRETE

Acceptance criteria for strength of concrete.

1st) variation in percentage of stregth of single cube not more than and not less than  15% of average strength percentage of sample.

Let start  with one example:
For M 35 grade of concrete the following results are arrives of a sample which is given below:

weight           load           strength         
kg                  kn               N/mm 2                       

8.720  -     1020.1   -        45.33
8.700  -     980.4     -        43.57         
8.724  -     965.1     -        42.89

Average strength  of sample: 43.93 N/mm2


If we convert individual strength in to percentage than we
N/mm 2             PERCENTAGE
45.33     -             129.51%                                                       
43.57     -              124.48%                                   calculation for % (45.33/35)=129.51%                                     
42.89     -             122.54%

And for average strength it will be come - 43.93- 125.51%

If we calculate variation of single strength percentage of cube to average strength percentage of sample than it will be following:

129.51     -      125.51    =     4%
124.48     -      125.51    =   -1.03%
122.54     -      125.51    =   -2.97%

So it is satisfy first criteria.



2nd) Strength of four non overlapping consecutive test result not less than

fck+3 or f ck +0.825* Standard deviation
( which ever greater)
and for individual it is f ck -3.


where f ck - characteristic of compressive strength of concrete.

if the sampling of concrete is not done by IS 456

Than it is

                         f ck+4  or   f ck+ 0.825*standard deviation (which is more)
                   
                         and for individual it is   f ck-2


WHAT IS THE MEANING OF FOUR CONSECUTIVE NON OVERLAPPING TEST RESULT IS GIVEN BELOW:


LET START WITH  EXAMPLE .

Here we describe it with M 35 grade of concrete strength, result of samples are given  below:

wt.           Load        strength        Average
Kg              KN          N/ mm2        N/mm2
8.510       980            43.55
8.512       921            40.93             41.81
8.628       922            40.97                         


8.610        898             39.11             
8.598        878             39.02           39.22                     
8.602        890             39.55

8.600       1010            44.88     
8.624         990            44.00           43.55           
8.630         940            41.77             


8.600       900.1           40.00             
8.498       878.4           39.04           39.38 
8.598       880.1           39.11


8.604       940.1            41.78         
8.502       840.4            37.35          39.34 
8.558       875.4            38.90


8.648      899.4             39.97
8.548     1000.1            44.44            42.21 
8.595     950.4              42.24

For calculaing non overlapping consecutive test result: we must calculate results of strength of  four consecutive samples which is non overlap i.e in above six samples results we add average strength  of 1 2 3 4 sample for non overlapping consecutive result but we can't add 1 2 3 5 because in this case overlapping occure and non consecutive result.

If we need four consecutive test result for non overlapping cube from the above given example it must be

41.81+39.22+43.55+39.38 (average result of samples) = 40.99 N/mm 2

40.99 N/mm 2 is greater than f ck +3 i.e (35+3= 38 N/mm 2 ) than it is satisfy the 2nd criteria.

And for individual result it is come :35 N/mm 2 - 3 N/ mm 2 =  32 N/ mm 2  which is more than above any single result of sample.


HERE GRADE OF CONCRETE M 35...

FLAKINESS AND ELONGATION INDEX

FLAKINESS AND ELONGATION  TEST OF AGGREGATE

FLAKINESS INDEX: Percentage of aggregate by weight whose least dimension is less than 3/5 times of mean seive size is known as flakiness index

ELONGATION INDEX:Percentage of aggregate by weight whose greater dimension is more than 9/5 times of mean seive size is known as elongation index.

THIS TESTS IS NOT APPLICABLE FOR AGGREGATE SIZE LESS THAN 6.3 mm.

According To IS 383 :2016 COMBINED FLAKINESS AND ELONGATION VALUE IS NOT MORE THAN 40%.

PROCEDURE OF TEST IS GIVEN IN IS 2386 PART 1ST.

Meaning of 3/5 of mean seive size is:
mean seive size = aggregate passing from seive + aggregate retained on sieve ÷2

Then: 3/5× (20+16/2)= 10.8 mm

Here 20 mm is seive size where aggregate pass and 16 mm is seive where aggregate retained.


So here, when you see Flakiness gauge the gap between these particular seive 20 mm and 16 mm is 10.8 mm.
And in Elongation it is : 9/5× (20+16/2)= 32.4 mm.

Example for flakiness and elongation is given below:

Let we take 200 pieces of 20 mm after sampling and weight it
let it come : 2000 gm

seive size              Retained wt.          Passing
                                                             on gauge
                                     gm                        gm
20-16                          220                         21
16-12.5                       822                         220
12.5-10                       792                         190
10-6.3                         120                         16
                          Total  1954 gm               447 gm

% of Flakiness = 447/1954= 22.87%

Here 46 gm passing from 6.3 mm seive and retained on pan so it is not counted.


sieve size           Retained wt              Retained
                                                             on gauge

20-16                      199                         08
16-12.5                   602                         120
12.5-10                   602                         104
10-6.3                     104                         07
             Total        1507                         239

% Of Elongation = 15.85%


so combined Flakiness and Elongation value  : 22.87+15.85 = 38.72%

PACE RATE OF COMPRESSIVE TESTING MACHINE

As per Indian standard 516 pace rate of C. T. M must be 140 kg/cm 2/minute.  so what is meaning of this given below:

surface area of cube 15 cm dimension= 225 cm 2

so in one minute load applied on cube :140*225=31500 kg/minute

Than in one second it is : 31500/60=525 kg/second

one kilogram = 9.81 N (10 Newton)

so                  = 525*10= 5250 N/second

one newton= 0.001 kn

                  =5250*0.001=5.25 kn/second

If we use 10 cm cube than in this case surface area change and we calculate it will be come 2.33 kn/second.