Mechanical Properties of Binary Blended Concrete

M. Vijaya Sekhar Reddy¹*, Dr. I.V. Ramana Reddy², K. Madan Mohan Reddy¹, N. Krishna Murthy³, T. Venumadhav⁴

¹Department of Civil Engineering , Srikalahasteeswara Institute of Technology, Srikalahasti, AP, India,

²Department of Civil Engineering, Sri Venkateswara University College of Engineering, Tirupati, AP, India,

³Engineering Department, Yogi Vemana University, Kadapa, AP

⁴Department of Civil Engineering, Audi Sankara College of Engineering, Gudur, AP, India.

ABSTRACT:

This paper presents the evaluation of mechanical properties of binary blended concrete. Binary blended concrete have been developed by the individual replacement of Supplementary Cementing Materials (SCM’s) like Fly-ash, Silica fume and Metakaoline. The results of binary blended concrete are compared with those of control concrete. The main purpose of this investigation is to develop confidence among user agencies in India to use mineral and chemical admixtures in a desirable proportion in most of the construction works. The paper presents experimental studies conducted on M₃₀grade of concrete using SCMs and chemical admixtures in various proportions. The cubes and cylindrical specimens after de-moulding were stored in curing tanks and on removal of cubes and cylinders from water the compressive strength and split tensile strength were conducted at 7days, 28days, 90 days and 180 days. The test results were compared with individual percentage replacements of SCMs for M₃₀ grade concrete with and without chemical admixture.

KEY WORDS: Supplementary Cementing Materials (SCMs), Binary Blended Concrete, Compressive Strength, Split Tensile Strength, Flyash (FA), Silica Fume (SF), Metakaoline.

INTRODUCTION:

When Ordinary Portland cement is mixed with any one of the above supplementary cementitious materials, it is called binary blended cement. The development of binary blended concrete was considered by adding SCMs as the mineral admixture. The partial replacement of cement by SCM’s at the rate of 20% of FA, SF and Metakaoline by 10%, by weight was considered to predict the optimum replacement level in the binary blended system. The optimum replacement level of mineral admixtures in the binary system was determined based on the compressive strength of the concrete cube specimens and split tensile strengths of the cylindrical specimens, while other parameters like total cementitious material content, water binder ratio, fine and coarse aggregate content were maintained as constant.

The addition of pozzolanic materials with OPC, a century old practice, is an alternative practice in the construction industry to improve the durability performance of concrete

Industrial by-product based SCMs like FA, SF, etc., is worldwide accepted pozzolanic materials and employed for making blended cement concrete. Now-a-days the use of blended cement concrete is growing rapidly mainly due to the considerations of cost and energy saving, environmental protection and conservation of resources. It is generally recognized that the addition of pozzolanic material reduces the calcium hydroxide content in cement concrete and improves the impermeability of concrete. This helps to increase the strength properties and durability properties of concrete. The investigation results from various parts of the world indicate that the replacement of cement by FA reduces the initial strength development rate and increases the setting time of concrete due to the slower pozzolanic reactions where as the strength and durability during the later age improved by reducing the pore size of the concrete. Efforts have been made to promote the initial strength development rate and reduce the setting time of concrete.

Cement manufacture causes environmental impacts at all stages of the process. These include emissions of airborne pollution in the form of dust, gases, noise and vibration when operating machinery and during blasting in quarries. The amount of CO₂ emitted by the cement industry is nearly 900kg of CO₂ for every 1000kg of cement produce the cement industry produces about 5% of global man-made CO₂emissions.

[1] An investigation on the use of metakaoline and silica fume as supplementary cementing materials in enhancing the near surface properties of concrete. Metakaoline and silica fume mixtures, each with 10% replacement, were prepared and tested for initial surface absorption, water absorption and sorptivity. Metakaoline and silica fume were found to enhance the overall near surface characteristics of the concrete. The inclusion of metakaoline and silica fume greatly reduced the initial surface absorption, water absorption and sorptivity of concrete in varying magnitudes. Generally, the curing method adopted had significant effects on the near surface properties of concrete incorporating metakaoline or silica fume. From their studies, the following conclusions were made.

[2] Experimental studies on the rheological properties of cementitious materials containing fine particles, such as mineral admixtures (MA), using a Rotovisco RT 20 rheometer (Haake) with a cylindrical spindle. The mineral admixtures were finely ground blast furnace slag, fly ash and silica fume. The cementitious materials were designed as one, two and three components systems by replacement of ordinary portland cement (OPC) with these mineral admixtures. The rheological properties of one-component system (OPC) were improved with increasing the dosage of PNS-based superplasticizer. For two-component systems, yield stress and plastic viscosity decreased with replacing OPC with blast furnace slag (BFS) and fly ash (FA). In the case of OPC-silica fume (SF) system, yield stress and plastic viscosity steeply increased with increasing SF. For three components systems, both OPC-BFS-SF and OPC-FA-SF systems, the rheological properties improved, compared with the sample with SF.

The utilization of pozzolan was become establish especially in achieving a high strength and high performance of concrete. For the time being the pozzolans only used in binary blended system and the optimum replacement of the pozzolan to OPC was reported to be not more than 20%. This study focus on utilization of waste pozzolans products such as fly ash (FA) and rice husk ash (RHA) added together with OPC to produced ternary blended cement with an objective to increase up the optimum percentage replacement of pozzolan to OPC without effecting the concrete properties. Beside that, the utilization of pozzolanic materials used tends to put a commercial value to the waste product such as FA and RHA [3].

This paper evaluates the different proportions of cement with and without replacements of SCM’s on the mechanical properties (compressive strength, split tensile strength) of those different mixes.

Materials used in the present study:

Cement:

Ordinary Portland cement Zuari-53 grade conforming to IS: 12269-1987 [4] were used in concrete. The physical properties of the cement are listed in Table 1.

Aggregates:

A crushed granite rock with a maximum size of 20mm and 12mm with specific gravity of 2.60 was used as a coarse aggregate. Natural sand from Swarnamukhi River in Srikalahasthi with specific gravity of 2.60 was used as fine aggregate conforming to zone- II of IS 383-1970 [5]. The individual aggregates were blended to get the desired combined grading.

Water:

Potable water was used for mixing and curing of concrete cubes.

Supplementary Cementing Materials:

Flyash:

Fly ash was obtained directly from the M/s Ennore Thermal Power Station, Tamilnadu, India. The physicochemical analysis of sample was presented in Table 2.

Silica Fume:

The silica fume used in the experimentation was obtained from Elkem Laboratory, Navi Mumbai. The chemical composition of Silica Fume is shown in Table 3.

Metakaoline:

The Metakaoline was obtained from M/s. 20 Microns Limited, Baroda, India. The chemical composition of Metakaoline is shown in Table 4.

Super Plasticizer:

VARAPLAST SP123 is a chloride free, Superplasticising admixture based on selected synthetic polymers. It is supplied as a brown solution which is instantly dispersible in water and also it can provide very high level of water reduction and hence major increase in strength can be obtained coupled with good retention of workability to aid placement.

RESULTS AND DISCUSSIONS:

In the present work, proportions for high strength concrete mix design of M₃₀was carried out according to IS:10262-2009 [6] recommendations. The mix proportions are presented in Table 5.

The tests were carried out as per IS: 516-1959 [7] and IS: 5816-1999 [8]. The 150mm cubes and cylindrical specimens (15mm dia and 300mm height) of various concrete mixtures were cast to test compressive strength and split tensile strength. The cubes and cylindrical specimens after de-moulding were stored in curing tanks and on removal of cubes and cylinders from water the compressive strength and split tensile strength were conducted at 7days, 28days, 90 days and 180 days. The test results were compared with individual percentage replacements for M₃₀ grade concrete with and without chemical admixture. Results of compressive strength of M₃₀ with and without chemical admixture were shown in Figure 1 and Figure 2 respectively. Results of split tensile strength for M₃₀ with and without chemical admixture were shown in Figure 3 and Figure 4 respectively.

Table 2. Physicochemical properties of Flyash sample.

Sample	Specific Gravity	Specific Surface Area (m²/g)	Moisture Content (%)		Wet density (gram/cc)		Turbidity (NTU)	pH
Flyash	2.20	1.24	0.20		1.75		459	7.3
	Chemical Composition, Elements (weight %)
	SiO₂	Al₂O₃	Fe₂O₃	CaO	K₂O	TiO₂	Na₂O₃	MgO
	56.77	31.83	2.82	0.78	1.96	2.77	0.68	2.39

Table 3. Chemical composition of Silica Fume (SF).

Chemical

Composition

Silica

(SiO₂)

Alumina

(Al₂O₃)

Iron Oxide

(Fe₂O₃)

Alkalies as

(Na₂O + K₂O)

Calcium Oxide

(CaO)

Magnesium

Oxide (MgO)

Percentage

89.00

0.50

2.50

1.20

0.50

0.60

Table 4. Chemical composition of Metakaoline

Chemical Composition	SiO₂	Al₂O₃	Fe₂O₃	TiO₂	CaO	MgO	SO₃	Na₂O	K₂O	LOI
Mass Percentage	52 to 54%	42 to 44%	< 1 to 1.4%	< 3.0%	0.1%	< 0.1%	< 0.1%	< 0.05%	< 0.4%	< 1.0%

Table 5. Mix Proportion for M₃₀ Concrete.

Cement

Fine Aggregate

Coarse Aggregate (20mm 20% & 12.5mm 80%)

water

Secondary Cementing

Materials

Super-

plasticizer

Composition in Kg/m³

298

706

1117

186

115

7.7

Ratio in %

2.369

3.748

0.624

0.385

0.0258

Fig 1. Shows the Compressive Strength results of M₄₀ mix (without Chemical Admixture).

Fig 2. Shows the Compressive Strength results of M₄₀ mix (with Chemical Admixture).

Fig 3. Shows the Split Tensile Strength results of M₃₀ mix (without Chemical Admixture).

Fig 4. Shows the Split Tensile Strength results of M₃₀ mix (with Chemical Admixture).

CONCLUSIONS;

1. In binary blended concrete mix design as water/cement ratio adopted is low, super plasticizers are necessary to maintain required workability.

2. Present study reveals that in case of individual percentage replacement of mineral admixtures the maximum compressive strength achieved in M₃₀ grade concrete (without chemical admixture) is 40.70 MPa with replacement of 10% Silica Fume.

3. Experimental study shows that in case of individual percentage replacement of mineral admixtures the maximum compressive strength achieved in M₃₀ grade concrete (with chemical admixture) is 44.40 MPa with replacement of 10% Metakaoline.

4. From the results it can be observed in case of individual percentage replacement of mineral admixtures the maximum Split Tensile strength achieved in M₃₀ grade concrete (without chemical admixture) is 4.22 MPa with replacement of 10% Metakaoline.

5. In case of individual percentage replacement of mineral admixtures the maximum Split Tensile strength achieved in M₃₀ grade concrete (with chemical admixture) is 4.62 MPa with replacement of 10% Metakaoline.

REFERENCES:

[1] Abdul Razak H., Chai, H K, Wong H S. Near surface characteristics of concrete containing supplementary cementing materials. Cement and Concrete Research. 26; 2004: 883-889.

[2] Park C K, Noh M H, Park TH. Rheological properties of cementitious materials containing mineral admixtures, Cement and Concrete Research. 35; 2005: 842-849

[3] Fadzil A M, Megat Azmi M J, Badrol Hisyam A B and Khairun Azizi M A. Engineering Properties of Ternary Blended Cement Containing Rice Husk Ash and Fly Ash asPartial Cement Replacement Materials, The International Conference on Construction and Building Technology(ICCBT); 2008 - A - (10): 125 – 133.

[4] IS: 12269-1987, Specification for 53 Grade Ordinary Portland Cement, Bureau of Indian Standards, New Delhi, India, 1989.

[5] IS: 383-1970: specifications for Coarse and Fine Aggregates for natural sources of concrete, Bureau of Indian standards, New Delhi.

[6] IS: 10262-2009: Concrete Mix Proportioning-guidelines, Bureau of Indian Standards, New Delhi.

[7] IS: 516-1959: Methods of tests for strength of concrete, Bureau of Indian standards, New Delhi.

[8] IS: 5816-1999: Methods of tests for Splitting tensile strength concrete, Bureau of Indian standards, New Delhi.

Received on 13.11.2012

Modified on 23.11.2012

Accepted on 10.12.2012

Research J. Science and Tech. 4(6): November –December, 2012: 290-294

Sl. No.	1	2	3	4	5
Properties	Specific gravity	Normal consistency	Initial setting time	Final setting time	Compressive strength (Mpa)
Values	3.15	32%	60 min	320 min	3 days	7 days	28days
					29.4	44.8	56.5