“EXTERNAL SELF CURING OF CONCRETE”

BY,

SAGAR.S.R

HEMANTH KUMAR.E.K

MITHUN.H.V

PRASHANTH JADHAV.R.UNDER THE GUIDENCE OF

HEMANTH M.C B.E

LECTURER DEPT OF CIVIL ENGG

Introduction Construction industry is growing like day by day even in remote

Areas and desert regions

Even India and other countries are facing lot of problems in supplying drinking water to their citizens.

Hence construction industries are under pressure in finding out alternative curing methods of curing concrete.

Self curing concrete is the one which can meet the present and future requirements of curing concrete.

As a result of successful and recent tests and research , have recently put external self curing in the forefront of breakthroughs of ideas of how to make better concrete

What is Self curing concrete ?S.C.C is the one which can cure itself by

retaining its moisture content. A concrete can be made to self cure either by

adding curing admixtures or by the application of curing compounds.

S.C.C by adding admixtures

Various admixtures used are concure WB, conplast NC, conplast C N and conplast S D 110 etc... Rheocure is the curing admixture used in U K for plane concreting. The admixtures used for curing concrete certain chloride which will lead to corrosion of reinforcement. Hence its use is restricted only within plain concrete.

S.C.C by adding curing compounds Curing compounds available are wax based and resin

based. The curing compound applied on concrete acts as a protective layer and seals the moisture content within the concrete. The curing compounds available are CONCURE WB, CONCURE LP 90 etc…

Methods of self curing concreteExternal self curing of concrete Internal self curing of concrete

What is external self curing of concrete ? External self curing concrete is the one which can

cure itself by retaining its moisture content

within the concrete by the application of curing

compounds on the surface of the concrete.

Applications of external self curing concreteAs a spray applied membrane to retain moisture in

concrete for effective curing.

Suitable for all general concreting applications and of

particular benefit for large area concrete surfaces,

such as airport runways, roads and bridgeworks.

It is also suitable for piece works. Where, it is difficult

to curing.

It is also suitable for tunnel lining work.

ESC compound is used in piece work

ESC compound is used in piece work

Advantages of external self curing concreteImproved curing of concrete enhances cement

hydration and provides a more durable concrete.Lower maintenance. Control of moisture loss improves surface quality.Reducing permeability.Producing a hard wearing and dust free Surface.Minimizing potential for surface cracking and

shrinkage.Fugitive colour provides visual guide during

application. Water based, therefore, non-flammable.Increases early age strength.Spray application reduces labour costs and eliminates

the need for alternative curing systems.

Curing compound usedThe curing compound used is “CONCURE WB” which is a

product of Fosroc chemicals.Specifications of CONCURE WB Base –waxShelf life – 12 months Coverage – 3.5 to 5 m2/litre Cost - Rs.90/litre Features single application no other curing necessaryeasy and safe spray applicationendures hard wearing surface

CONCURE WB

Application procedure

The curing compound is applied by brush or by

spraying while the concrete is wet. In case of

columns and beams the application is done after

the removal of formwork. On the horizontal

surface, the curing compound is applied upon the

complete disappearance of all bleeding water.

Mode of application

Materials used and their properties:

It is well known that strength of the concrete is dependent on the properties of its ingredients. The materials used in the present investigations are as follows. 

53 grade O.P.C.River sand as fine aggregate.Quarried and crushed stone as coarse aggregate.Potable water.

TEST ON INGREDIENT MATERIALS

Introduction:

The present investigation is carried out to study the behavior of normal and self cured concrete and ingredient material by using O.P.C. 53 grade cement. The tests were carried out at the Concrete Laboratory of Civil Engineering Department, AIT, Chikamaglur.

Test on cement: 53 grade O.P.C. cement was used throughout the

investigations. The cement was tested according to B.I.S. specifications to determine its various properties.

The overall quantity of cement required for the investigation was procured in a single lot and stored in the appropriate manner.

The specific gravity, normal consistency, initial setting time, final setting time and compressive strength of cement were found as per B.I.S specifications. The results are tabulated in tables

.

Results of test on cement

SL No. Particulars References

Type of cement 53 grade

O.P.C.

-------------

1 Normal Consistency 34.00 % IS:269-1958

2 Specific Gravity 2.85 IS:269-1976

3 Setting time (in min)

(a) Initial setting time

(b) Final setting time

80 min.

460 min.

IS: 269-1976

Should more

Than 30 min.

Should not be

More than 600min.

Sl.No. Particulars Compressive strength in N/mm2

Type of cement 3 days 7 days 28 days

1 53 grade O.P.C 30.20 45.70 59.80

Compressive Strength of Cement

53 grade O.P.C.

In this type of cement, the 28 days cement strength is expected to have a minimum value of 53 Mpa.

Size of the specimen=70.6mm X 70.6mm X 70.6mm

`

Sl

No.

Particulars Fine

Aggregate

Coarse

Aggregate

Reference

1 Specific gravity 2.50 2.60 IS:2386(partIII)-1963

2 Fineness modulus 2.85 7.13 Is:2836(partIII)-1963

IS:383-1970

IS:460-1962

3 Grading zone Zone II 20 mm and

Downsize

IS 383-1963

Test on fine and coarse aggregates

Properties of the aggregate used

The specific gravity and fineness modulus of fine aggregate and coarse aggregate was found according to the norms of the Indian Standards.

Cement used Ordinary Portland cement

Grade of cement 53 grade

Specific gravity of cement 2.85

Specific gravity of fine aggregate 2.50

Specific gravity of coarse aggregate 2.60

Slump value 90 to 100mm

Maximum size of aggregate 20mm

Fine aggregate falls into Zone-II

Design stipulations:

Characteristic compressive strength required in the field at 28 days: 25N/mm2

Degree of quality control : GoodType of exposure : Mild

Test data for materials

W/C ratio Water

In litre

Cement

In Kg

Fine

aggregate

In Kg

Coarse

aggregate in

Kg

0.55 197 358.18 660.08 1073.72

1 1.84 3.00

Mix proportion for 1 m3 concrete

TESTS ON FRESH CONCRETE

Slump test

Slump test gives an idea about consistency of concrete mix and indirectly measures workability of the concrete.Depending on the slump values of concrete can be classified into different categories as per IS:1199-1959

Slump test values of concrete mixes

Sl.No. Grade of

concrete

w/c ratio Slump (mm)

1 M25 O.P.C. 0.55 90

TESTS ON HARDENED CONCRETE

Details of the standard specimens

Type of test Type of specimen Dimensions (mm)

Compression test Cubes 150 x 150 x 150

Split tension test Cylinder 100 ᴓ x 200 depth

Test for compressive strengthAverage compressive strength of conventionally cured concrete.

Average compressive strength of external self cured concrete.

Comparison between average compressive strength of external self cured concrete

and conventionally cured concrete

It is observed that the increase in compressive strength of external self cured concrete is about 22.10% at the age of 3

days, 5.24% at the age of 7 days and 3.32% at the age of 28 days as compare to conventional cured concrete.

Test for split tensile strength

Average split strength of external self cured concrete.

Average split strength of conventional cured concrete.

Comparison between average split tensile strength of external self cured concrete and conventionally cured concrete

It is observed that the increase in split tensile strength of external self cured concrete is about 4.95% at the age of 3 days, 11.11% at the age of 7 days and 20.94% at the age of 28 days as compare to conventional cured concrete.

CONCLUSION

The following conclusions are drawn based on the present investigations.  The variation between concrete cured conventionally and with self curing compound is about 3.32% for compression strength and 20.94% for split tensile strength.Hence self curing technique may be economically and efficiently adapted in remote as well as in water scarcity areas.  The surface of the self cured cement paste is less permeable to water vapour than that of normal cured cement paste. Curing compound increases early strength of concrete than normal cured concrete. Concrete with curing compound gives smooth and fine finished surface than concrete without curing compound. About 100% of results have been attained in compressive strength with small amount of water this method can be implemented in construction field.

THANK YOU