development of mathematical model to predict early age …€¦ · · 2001-01-02development of...

Development of Mathematical Model to Predict Early Age Strength for Blended Cement through

Accelerated Curing

Poorav Shah#1, Smt.BhavnaShah#2 #1 PG student, Department of Structural Engg., B.V.M. Engg. College, V.V. Nagar, Gujarat

[email protected]

#2 Associate Professor, Department of Structural Engg. B.V.M. Engg. College, V.V.Nagar, Gujarat

[email protected]

Abstract - Traditionally, strength of concrete in construction work is evaluated in terms of its 28 days compressive strength of cubes/ cylinders. This procedure requires 28 days of moist curing before testing as per IS: 516 – 1959 [9]. This time duration may be considered as a long period. Hence, needs for an accelerated curing technique has arisen, where 28 days strength of concrete can be easily predicted. The main objective of this paper is to develop mathematical model, which gives relation between accelerated curing strength and normal curing strength for 28 and 56 days compressive strength.

Warm water curing at 80˚ 3˚ C is applied to accelerate the strength gain of concrete for the early prediction of 28 days and 56 days compressive strength. Various concrete mixes in terms of cement (OPC), cement replacing materials likes activated fly ash, Metakaolin and iron oxide were considered to prepared cubes.

Keywords – Concrete compressive strength, accelerated curing, Activated fly Ash, Metakaolin, Iron Oxide

I. INTRODUCTIONRecent trend in engineering technology is to develop economic concrete and complete the project within time limit. To develop the economic concrete, mix design is to be developed and to complete project within time limit, the compressive strength of concrete cubes for selected mix design should be determined earlier in the laboratory.The compressive strength of hardened concrete is most common property required for the structural use. The prediction of 28 days strength at early age is needed for different purpose such as,

The fast trend of construction progress and its economic benefits attained from accelerating construction schedule.

Testing for quality control purposes To check the suitability of concrete mixes much earlier

than 28 days test

The rate of strength gain mainly depends upon the rate of hydration and the rate of hydration depends on the surrounding temperature. The strength gain could be accelerated at early age and related to 28 days and 56 days compressive strength

through calibration curves. Various techniques of accelerated curing of concrete are classified as heat water techniques, oven curing techniques, maturity methods, pressure and elevated temperature technique and expanded polystyrene molds technique [1]. The ACI 214.1 R [2] suggests two procedures, which can be used to provide an indication of 28 days strength of concrete only after 24 hours.

Warm water method : 23 to 24 hours at 35˚ 3˚C

Boiling Water method : 23 hours at 21˚C and 3.5 hours at 100˚C

The ASTM C 684 [3] recommends three different accelerated curing techniques.

Warm water method : 24 hours at 35˚ 3˚C

Boiling Water method : 23 hours at 21˚C and 3.5 hours at 100˚C

Autogenous Curing method: 5 hours at 150˚C with external pressure

The British standards, BS 1881, Part 112 [5] provide three curing temperature 35˚, 55˚ and 85˚ 2˚C for accelerating the rate of gain of strength.The IS: 9013-1978[13] recommends two methods of accelerated curing

Warm-water method

Boiling-water methodThe aim of this research work is to study the relation between accelerated curing strength at 3 days (1 days normal curing + 24 hour accelerated curing at 80˚ 3˚C) with normal curing for 28 days and 56 days concrete made of blended cement.

II. MATERIAL A.Cement

Ordinary Portland Cement (53 grade) confirming to IS: 12269-1987 [10]. was used for the experimental investigation.The cement was tested as per IS: 4031-1988 [11]. The results given in Table -1.

National Conference on Recent Trends in Engineering & Technology

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

B.Flyash: Fly Ash comprise of the non- combustible mineral portion of coal. Fly ash particles are glassy spherical shaped, ball bearings, finer than cement particles, which helps to reduce amount of water and improve workability. It also reduces heat of hydration and improves durability; the chemical compositions of fly ash are given in Table 1. And physical properties are given in Table 2.

C.Metakaolin

It is highly pozzolanic material. It is obtained by calcinations of Algerian kaolin at 700˚ C for 7 hours. The silica and alumina contained in the metakeolin are active and react with free lime to form C-S-H and alumina-silicates which greatly improve the strength. The chemical compositions ofMetakeolin are given in Table 1.

TABLE I

COMPOSITION OF CEMENT,FLYASH & METAKAOLIN

%age by massChemical

Composition Cement Flyash Metakaolin

SiO2 20.1 48.53 51.6

Al2O3 4.51 24.61 41.3

Fe2O3 2.5 7.59 0.64

CaO 61.3 9.48 0.52

MgO 1 2.28 0.16

Loss on

Ignition

2.41 0.93 0.72

TABLE II

PHYSICAL PROPERTY OF FLYASH

Property Experimental

Value

1 Fineness (passing 45μ IS: sieve) 78.9%

2 Specific Surface 4620 cm2/g

3 Unit weight 950 kg/m3

4 Specific gravity 2.13

D .Iron Oxide During the processing of steel in steel mills, iron oxide will be formed on the surface of metal. This oxide is known as mill scale, occurs during continuous casting, reheating and rolling operation. This is used as replacement for the fine aggregate.

E. Fine AggregateNatural river sand confirming to zone II as per IS: 383-1987 [12] was used. Fine aggregate of size 1.18 mm down were used. Physical properties of fine aggregate are presented in Table- III.

F. Coarse aggregate

Crushed coarse aggregate confirming to IS: 383-1987[12] was used. Coarse aggregate of size 20 mm down were considered.Physical properties of coarse aggregate are presented in Table III.

TABLE III

PHYSICAL PROPERTIES OF FINE & COARSE AGGREGATE.

Aggregate Fineness

Modulus

Density

(kg/m3)

Specific

Gravity

Fine Agg. 3.64 1696 2.58

Coarse Agg. 7.07 1770 2.87

III. APPARATUS

A. Cube MouldAs per IS: 10086 – 1982, 150 x 150 x 150 mm size mould have been used.

B. Curing TankCuring tank shall be constructed from any material of suitable strength that will resist the effect of corrosion. Internal dimension should be adequate to accommodate the required number and size of test specimen. The tank shall contain sufficient water and be controlled so that temperature of water around the specimen immersed in the tank is maintained at the desired level.

Fig :1 Accelerated curing Tank



IV. EXPERIMENTAL PROGRAMMETo get the early age strength through accelerated curing, warm water method was adopted. In this method, after the casting of cubes, specimen was cured at normal temperature for 24 hours and then put in accelerated tank on second day with temperature 80˚ 3˚ C for 5 hours and then 80˚c to falling temperature up to next day. After this period of curing, concrete cube specimen was tested for compressive strength and results are co-related with 28 and 56 days compressive strength of standard water curing. This co relation of accelerated strength and normal curing strength is achieved for all types of cement. To find the confident level of these relation seven different types of cement were used. The composition of different types of cement is given in table IV. For each type of cement, four different w/c were used. Mix design was prepared by ACI method.Different water cement ratios and constituent materials proportions of the various concrete mixes are given in Table V.

Table IV

Composition of Different Types of Cement

TypeComposition

A OPC

B 88% OPC + 10% Metakaolin + 2% Iron Oxide

C 78% OPC + 10% Metakaolin + 2% Iron Oxide + 10% Fly Ash

D 68% OPC + 10% Metakaolin + 2% Iron Oxide + 20% Fly Ash

E 58% OPC + 10% Metakaolin + 2% Iron Oxide +

30% Fly Ash

F48% OPC + 10% Metakaolin + 2% Iron Oxide +

40% Fly Ash

G38% OPC + 10% Metakaolin + 2% Iron Oxide +

50% Fly Ash

Table V

Different Water Cement Ratio and Constituent Materials Proportions of the Various Concrete Mixes

Mix Proportions (kg)

W/C ratio Proportion

Cement Sand C.A. Water

0.4 1:1.72:2.28 450 774.0 1026.60 180

0.45 1:2.03:2.56 400 812.0 1026.60 180

0.5 1:2.35:2.85 360 846.0 1026.60 180

0.55 1:2.67:3.13 327.17 873.55 1026.60 180

As per above table, it is seen that amount of water is constant and amount of cement is decreased according to w/c ratio. Total 216 cubes of size (15x15x15) cm were casted.

V. RESULTS AND DISCUSSIONS

Table VI represents the results of the 28 and 56 days Normal curing compressive strengths and also accelerated strengths.

Table VI:Results of the 28 &56 days normal curing compressive strength and

accelerated curing strength



AM1-AM4 refer to type A cement, BM1-BM4 refer to type B cement

CM1-CM4 refer to type C cement, DM1-DM4 refer to type D cement, EM1-EM4 refer to type E cement,FM1-FM4 refer to type F cement

GM1-GM4 refer to type G cement.

The arthematic equation developed for accelerated curing strength and 28 days normal curing strength for all types of cement are given in Table:VII

Table VIIRelation between accelerated strength and normal curing strength at 28 days

Types of cement

Relation between accelerated strength and normal curing strength at 28 days

A F28 = 1.195 Facc + 2.679

B F28 = 1.223 Facc + 1.85

C F28 = 1.169 Facc – 2.698

D F28 = 0.766 Facc + 13.02

E F28 = 1.162 Facc + 1.209

F F28

= 1.765Facc

– 13.68

G F28

= 0.809Facc

+ 5.481

The arthematic equation developed for accelerated curing strength and 56days normal curing strength for all types of cement are given in Table:VIII

Table VIII


Types of cement


A F56

= 0.931 Facc

+ 21.41

B F56

= 0.827 Facc

+ 15.67

C F56

= 1.427 Facc

– 3.999

D F56

= 1.060 Facc

+ 10.47

E F56

= 1.677 Facc

– 7.967

F F56

= 1.031 Facc

+ 3.401

G F56

= 0.721 Facc

+ 8.752

The Mathematical model developed to show the relation between accelerated curing compressive strength and 28 days normal curing compressive strength for only OPC is derived from following graph.

The Mathematical model developed to show the relation between accelerated curing compressive strength and 28 days

Type of

Cement

W/C

RatioCompressive Strength

(N/mm2 )

Accelerated

Strength(N/mm2)

28(days) 56(days)

AM1 0.40 55.78 43.37 62.678

AM2 0.45 46.22 37.49 59.274

AM3 0.50 41.92 33.33 46.768

AM4 0.55 29.16 21.63 43.365

BM1 0.40 40.55 40.89 43.550

BM2 0.45 47.70 37.78 45.550

BM3 0.50 41.71 33.48 45.410

BM4 0.55 32.3 24.44 35.260

CM1 0.40 40.43 36.30 47.297

CM2 0.45 33.35 31.26 41.910

CM3 0.50 26.14 26.82 32.770

CM4 0.55 29.00 25.08 33.177

DM1 0.40 38.20 27.92 41.66

DM2 0.45 29.70 25.97 39.368

DM3 0.50 28.93 23.78 30.82

DM4 0.55 29.16 18.80 32.323

EM1 0.40 34.23 40.62 27.40

EM2 0.45 27.58 35.23 27.11

EM3 0.50 23.05 24.75 20.89

EM4 0.55 20.11 26.22 18.88

FM1 0.40 25.75 26.14 21.57

FM2 0.45 18.49 23.776 19.526

FM3 0.50 16.45 17.577 16.488

FM4 0.55 12.576 20.192 14.92

GM1 0.40 27.62 28.38 28.81

GM2 0.45 23.51 25.55 18.335

GM3 0.50 19.286 20.564 17.66

GM4 0.55 12.53 14.93 10.62



normal curing compressive strength for blended cement is derived from following graph.

The Mathematical model developed to show the relation between accelerated curing compressive strength and 56 days normal curing compressive strength for only OPC is derived from following graph.

The Mathematical model developed to show the relation between accelerated curing compressive strength and 56 days normal curing compressive strength for blended cement is derived from following graph.

Mathematical model which show the relation between accelerated curing compressive strength and 28 days normal curing compressive strength for OPC and blended cement as under

For, OPC F28= 1.195Facc+2.679

For, Blended cement F28= 1.276Facc-2.864

Mathematical model which show the relation between accelerated curing compressive strength and 56 days normal curing compressive strength for OPC and blended cement as under

For, OPCF56= 0.931Facc+21.41

For, Blended cementF56= 1.219Facc+2.215

VI. CONCLUSION

Early prediction of 28 days and 56 days compressive strength results through simple prediction factor is not possible for concrete mix containing cement replacement materials due to their physical and chemical properties on the rate of strength gain.Mathematical model for early prediction of 28days and 56 days compressive strength of cubes are proposed for OPC cementand blended cement individully which gives confident level around 95%. Due to this relation, this method will also helpful for Precast Manufactures. It can also be concluded that increase in curing temperature has more favourable effect on the strength gain of concrete with cement and cement replacing material.



VII. REFERENCES

[1] A. A. Torkey, Accelerated Strength for Quality Control of Mortar and Concrete, M.Sc. thesis, Faculty of Engineering, Cairo University, 1980.

[2] ACI 214.1 R 1987, Use of Accelerated Strength Testing, ACI Manual of Concrete Practice, Part 5, Americal Concrete Institute.

[3] ASTM C 684-95, Standard Method of Making, Accelerated Curing and Testing of Concrete Compression Test Specimens.

[4] Brent Vollenweider, “Various Methods of Accelerated curing for Precast Concrete Applications, and Their Impact on Short and Long Term Compressive Strength”. In March 2004.

[5] British Standards, BS 1881: Part 112, 1983, Methods of Accelerated Curing of Test Cubes

[6] Denny Meyer, “A statistical Compression OF Accelerated Concrete Testing Methods”, Journal of Applied Mathematics & Decision Science, 1997

[7] Felix F. Udoeyo, Robert Brooks, Philip Udo-Inyang& Richard O. Nsan,” Early Prediction Of Laterized Concrete Strength by Accelerating Testing”, October 2010.

[8] Hossam E.H. Ahmed, “Early Prediction of Concrete Compressive Strength through Accelerated Curing Regime”, Eleventh International Colloquium on structural and Geotechnical Engineering. In May 2005, Cairo-Egypt.

[9] IS: 516-1959 procedure for curing of concrete cubes[10] IS: 12269-1987 classification for cement[11] IS: 4031-1988 testing for cement[12] IS: 383-1987 classification for aggregate

[13] IS:9013-1978 Method of Making ,curing and DeterminingCompressive strength of accelerated cured concrete test specimens[14] Nur yazdani, “ACCELERATED CURING OF SILICA FUME CONCRETE”, July 2005. [15] M.S Shetty, “concrete technology”, S. Chand, 2009.[16] W. Calvin McCall “Accelerated concrete curing: the basis” the Aberdeen group 1996



development of mathematical model to predict early age …€¦ · · 2001-01-02development of...

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