International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.2 (2015) pp. 1919-1924 © Research India Publications; http://www.ripublication.com/ijaer.htm
Strength And Durability Studies On High Performance Concrete With Manufactured Sand As Fine Aggregate T.Shanmugapriya
Dr.R.N.Uma
Assistant Professor, Department of Civil Engineering, Sri Ramakrishna Institute of Technology,Perur, Coimbatore, Tamil Nadu -641010, India. Ph. No.: +91 98421 17484 , E Mail ID:
[email protected]
Professor & HOD, Department of Civil Engineering, Sri Ramakrishna Institute of Technology, Department of Civil Engineering, Sri Ramakrishna Institute of Technology,Perur, Coimbatore, Tamil Nadu -641010, India. Ph. No.: +91 9894475863, E Mail ID:
[email protected]
Abstract: Concrete is the second largest consumed product than water all over the world due to rapid industrialization across the major cities. InIndia, conventional concrete is produced by using natural sand across the river beds as fine aggregates. It poses a serious environmental issue is dwindling the sand resourcesand hence government restrictions on sand quarrying resulted in scarcity and significant increase in its cost. This paper presents comparative study based upon experimental work on important properties of concrete i.e. strength& durability of high performance concrete by usinglocally available material with manufactured sand as fine aggregatewith 7.5% replacement of cement by silica fume. The tests results indicate that the concrete exhibits excellent strength and durable with 60% replacement of natural sand with manufactured sand, so it can be used in concrete as viable alternative to natural sand. The promotional use of manufactured sand will conserve the natural resources for the sustainable development of the concrete in construction industry.
cement produced, a major contributor for green house effect and global warming[3,4]. In order to compensate the lack of natural resources and to find alternative solution for conserving the environment, and to make the construction industry sustainable, the natural sand was replaced by Manufactured Sand (M-Sand) and silica fume as replacement of cement for making concrete. High Performance Concrete in general contains high powder content and mineral admixtures like GGBFS, fly ash, Metakaolin, Silica fume etc. The strength and durability properties of HPC is mainly affected by the use of these mineral admixtures mainly due to their filler effect and Pozzolonic reaction[5,6]. Silica fume is a by product resulting from the manufacture of silicon and ferrosilicon alloys. Compared with other supplementary cementitious materials the peculiar characteristics that make silica fume a very reactive pozzolona are its high SiO2 content, its amorphous state and its extreme fineness improves strength and durability properties[7, 8]. The replacement of cement by silica fumein the range of 5-10% with a smaller dosage of super plasticizer improve the workability and strength of concrete [9-11]. Researchers found that at 5-10% replacement of cement by silica fume with a smaller dosage of super plasticizer improve the workability and strength of concrete[12-14]. In contrast, strength increases with silica fume addition but optimum replacement level was not constant and depends on water cementitious ratio of the mix [15]. The addition of silica fume reduces the permeability of both cement paste and concretes, reduces the size of pores and porosities, resistance to aggressive environments. Common river sand (RS), which is most commonly used fine aggregate in the production of concrete, is expensive due to excessive cost of transportation from natural sources. Also large-scale depletion of these sources creates environmental problems. Economy and sustainability objectives are better served if locally-available, durable aggregates can be used – even if some of the individual aggregate sizes do not meet grading or other physical properties normally specified.M-Sand is a crushed aggregate produced from hard granite stonewhich is rough, flaky shaped with sharp edges, washed and graded with
Keywords: High Performance Concrete, Manufactured Sand, Natural Sand, Silica fume
INTRODUCTION Globally many countries are witnessing a rapid growth in the construction industry which involves the use of natural resources for the development of the infrastructure. Ultimately the infrastructural development leads to lack of natural resources that are available. In general, the demand of natural sand is quite high in developing countries to satisfy the infrastructural growth, in these situation developing countries like India is facing shortage in good quality natural sand [1, 2]. Increasing extraction of natural sand from river beds causing many problems, like loosing water retaining sand strata, river bank slides, lowering the underground water table etc. On the otherhand the cement plays a vital role in the construction industry, worldwide the production of cement is increasing at a faster rate, nearly 3,300 million tones of cement has been produced during last year. The amount of CO2 emitted by a cement industry is nearly 900 kg of CO2 for every 1000 kg of
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.2 (2015) © Research India Publications; http://www.ripublication.com/ijaer.htm consistency to be used as a substitute of river sand.The mechanical and durability properties of concrete incorporating M-sand are enhanced due to its filler content and interlocking effect between the particles. [16-18]. On the contrary,the angular shape of the M-Sand particles tends to reduce the workability which can be improved by the use of water reducers and mineral admixtures.[19, 20] In this research both the materials silica fume and M – Sand are combined replacement for cement and natural sand. Taking into consideration of the above mentioned points, this research work poses to use the manufactured sand as a replacement of natural sand in varying percentages (0%, 20%, 40%, 60%, 80% and 100%) which would be efficient in conserving the natural resources if adopted in the construction sector throughout the country and world. The cement was replaced by 7.5% of silica fume with the addition of superplasticizer equal to 1.5% by weight of binder(cement & silica fume).Further, the study helps to identify an alternate material for natural sand and to minimize the usage of cement content to some proportion in the High Performance Concrete.
Fine aggregates Locally available river sand having bulk density 1726 kg/m3 was used and the specific gravity is 2.65. The Fineness modulus of river sand is 2.69. Manufactured sand M- Sand was used as partial replacement of fine aggregate. It was collected from TECHNOMAX Building Solutions India Pvt.Ltd. Coimbatore, India. The bulk density of manufactured sand was 1822 kg/m3, specific gravity and fineness modulus was found to be 2.71 and 2.20 respectively.The percentage of particles passing through various sieve were compared with natural sand and it was found to be similar. The results are presented in Table.2. Table 2. Details of sieve analysis for natural sand and M-sand Sieve Size
4.75mm 2.36mm 1.18mm 600µm 300 µm 150 µm
MATERIALS AND METHODS Materials Cement: Ordinary Portland cement of 53 Grade was used and the specific gravity of cement was found to be 3.15. The physical and chemical properties of cement are presented in Table 1. Silica fume: Silica fume was collected from ELKEN South Asia Pvt.Ltd. Mumbai, was named Elkem – Micro silica 920 D conforming to ASTM C1240(1998)[21]. It is available in dry densified form. The physical and chemical properties of cement and silica fume are also presented in Table 1. Cement Physical Properties Specific gravity 3.15 Surface area, m2/kg 320 Size, micron Bulk density, kg/m Initial setting Time (min) 45 Final setting Time(min) 375 Chemical Properties, Percentage
Silica fume 2.2 20,000 0.1 576 -
SiO2
90-96
20-25
Al2O3
0.5-0.8
4-8
MgO
0.5-1.5
0.1-3
Fe2O3
0.2-0.8
0.5-0.6
CaO
0.1-0.5
60-65
Na2O
0.2-0.7
0.1-0.5
K2O
0.4-1
0.4-1.3
0.7-2.5
0.1-7.5
Loss of Ignition
M-Sand % Passing
IS Grading limits for Zone II
IS Grading limits for Zone III
99.8 87.4 75 66.4 38 10 Conforming to grading Zone III of IS 383
90-100 75-100 55-90 35-59 8-30 0-10 -
90-100 85-100 75-100 60-79 12-30 0-10 -
Coarse Aggregate Locally available crushed coarse aggregate having maximum size 12.5 mm was used. It was confirming as per Indian standard (IS- 383-1970)[22] and satisfied its requirement. Coarse aggregate passing through 12.5 mm sieve was 90–100%. Passing through 10 mm sieve was 40–80% and passing through 4.75 mm sieve was 0–10%. The specific gravity of coarse aggregate is 2.71. Superplasticizer In order to improve the workability of high-performance concrete, super plasticizer in the form of poly-carboxylic ether based superplasticizer (Glenium B233) was used as chemical admixture. The product has specific gravity of 1.09 and solid contents not less than 30% by weight. Water Fresh portable water, which is free from acid and organic substance, was used for mixing the concrete. Mix Proportions Concrete mix design in this investigation was designed as per the guidelines specified in ACI 211.4R-08 - “Guide for selecting proportions for high strength concrete with portland cement and other cementations materials”. Among the six concrete mixes, one for control mix without silica fume and MSand, and in other five mixesthe different proportions of natural sand was replaced with manufactured sand (ie 20%, 40%, 60%,
Table 1. Physical and Chemical Properties of Cement & Silica fume Properties
River sand % Passing 97 92.2 77 52.2 10.6 2 Conforming to grading Zone II of IS 383
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International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.2 (2015) © Research India Publications; http://www.ripublication.com/ijaer.htm 80% and 100%) with 7.5% of cement replaced with silica fume. The details of mix proportions are presented in Table 3. Table 3. Mix proportion for High Performance Concrete Cement
Ce me nt (%)
Silic a Fum e (%)
Fine Aggregate M Natur Sa al nd Sand ( (%) % )
Conventional Concrete
92. 5
7.5
80
20
60
40
40
60
20
80
0
10 0
Cement
Cem ent (kg/ m3) 551. 87
492. 66
Fine Aggregate
Silic a Fum e (kg/ m3)
Nat ural San d (kg/ m3)
MSan d (kg/ m3)
-
672
-
537. 6 403. 2 268. 8 134. 4
134. 4 268. 8 403. 2 537. 6
-
672
41.3 9
Coars e aggre gate (kg/m 3 )
W /B rat io Fig.1.Test on Compressive strength
1149. 8
0. 32
Casting and curing of Test specimens: The preparation of specimens used for various types of strength and durability tests is done by following procedure. The quantities of cement, fine aggregate, coarse aggregate, silica fume, M-Sand for each proportion is measured and homogeneous mixing of the above is achieved by means of pan mixer. The water to binder ratio was kept as 0.32 and the dosage of super plasticizer was kept constant at 2% by weight of binder(Cement + Silica fume) to get the workability of concrete.The concrete was thoroughly mixed until it achieved homogeneous and uniform consistency. The fresh concrete was casted and it was compacted by table vibrator. All freshly cast specimens were left in the moulds for 24 hours before being de moulded. The de moulded specimens were cured in water for7& 28 days as required.
Fig.2.Test on Split Tensile strength
Durability Related Tests: The durability related tests such as Saturated Water Absorption (SWA) test, Acid resistance test and Sea water resistance test were carried out on hardened concrete specimens at the age of 28 days of curing. Test for Saturated Water Absorption: The water absorption was determined on 100mm cubes as per ASTM C-1585[23] by drying the specimens in an oven at a temperature of 105° C to constant mass and then immersing in water after cooling to room temperature. The specimens were taken out of water at regular intervals of time and weighed. The process was continued till the weights became constant (fully saturated). The difference between the water saturated mass and oven dry mass expressed as a percentage of oven dry mass gives the SWA. The SWA of concrete is a measure of the pore volume or porosity in hardened concrete, which is occupied by water in saturated condition. It denotes the quantity of water, which can be removed on drying a saturated specimen. Acid Resistance Test and Sea Water Attack Test: The acid resistance tests and Sea Water resistance tests were carried out on 100 mm size cube specimens at the age of 28 days curing. The cube specimens were weighed and immersed in water diluted with one percent by weight of sulphuric acid and 3% by weight of sodium chloride for acid resistance tests and Sea Water resistance tests respectively for 28 and 56 days continuously and then the cubes were taken out and weighed. The percentage loss in weight was calculated. The cubes are immersed in acid solution are shown in Fig.3
EXPERIMENTAL INVESTIGATIONS Strength Related Tests: The compressive strength of HPC with silica fume and MSand were studied on 150mm size cubes at 7 days and 28 days of curing. The strengths were compared with conventional concrete and the optimum replacement level of M-Sand and silica fume was arrived. The split tensile strength and flexural strength of HPC were obtained on 150mm x 300mm cylinders and 100mm x 100mm x 500mm beams at 28 days of curing. Fig 1&2 shows the testing on compressive strength and Split Tensile Strength of cube and Cylinder specimens.
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Split tensile strength in N/mm2
International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.2 (2015) © Research India Publications; http://www.ripublication.com/ijaer.htm
6 5 4 3 2 1 0
7 days 28 days
CC
10
20
30
40
50
Percentage replacement of natural sand by M-sand with 7.5% of Silica Fume Fig.6. Split Tensile Strength of High Performance Concrete
RESULTS AND DISCUSSION The results of strength and durability tests have demonstrated the superior strength and durability characteristics of the concrete mixes containing Silica Fume and M-Sand. Strength Related Properties The results of compressive strength of concrete at the age of 7 days,14 days and 28 days are shown in the Fig.4. The variations of split tensile strength and flexural strength at the age of 7 and 28 days are shown in the Fig.5&6.
Fig. 4 shows the variation of compressive strength with 7.5 % replacement of cement by silica fume and various percentage of natural sand by M-Sand. There is a significant improvement in the compressive strength of concrete because of the high pozzolanic nature of the silica fume. Due to void filling ability and also the sharp edges of the particles in manufactured sand provide better bond with cement than the rounded particles of natural sand resulting in higher strength. The compressive strength with replacement of natural sand by M-Sand was increased gradually up to an optimum replacement level of 60% and then decreased. The compressive strength with 60% replacement of M-Sand shows 17 % greater than conventional concrete. The above observations are supported by the work of other researchers who studied the influence of manufactured sand as fine aggregate on the strength of high-performance concrete[24- 26].The same pattern was also observed for split tensile and flexural strength tests. Tests for Saturated Water Absorption: The results of the saturated water absorption (SWA) tests of various concrete mixes are given in Fig.7.
Compressive strength in N/mm2
Fig.3 Cubes are immersed in Acid solution
80 70 60 50 40 30 20 10 0
7 Days 14 Days 28 Days
CC
20
40
60
80
100
percentage replacement of natural sand by M-sand with 7.5 % silica fume Saturated Water Absorption in %
2.5
Flexural strength in N/mm2
Fig.4. Compressive Strength of High Performance Concrete
12
2
1 0.5
CC
8 4
1.5
0
10 6
2
7 days
20
40
60
80
100
Percentage replacement of natural sand by M-sand with 7.5% of Silica Fume
28 days
0
Fig.7. Saturated Water Absorption of concrete at the age of 45 Days
CC 20 40 60 80 100 percentage replacement of natural sand by M-sand with 7.5% silica fume
From the results, it was inferred that the percentage of water absorption goes on decreasing and reached the minimum of 1.35% for partial replacement of 60% natural sand by M-Sand with 7.5% of silica fume. It is also to be noted that the SWA of HPC mixes containing SF and M- Sand are lower compared to
Fig.5. Flexural Strength of High Performance Concrete
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International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.2 (2015) © Research India Publications; http://www.ripublication.com/ijaer.htm
Weight loss in %
that of conventional cement concrete. This is due to the improvement in microstructure due to pozzolanic reaction and micro filler effects of SF, resulting in fine and discontinuous pore structure and proper gradation of fines by M-Sand. 4.3 Acid Resistance Test and Sea Water Attack Test: The results of the acid tests of various mixes after soaking the cubes in acid for45 days are given in Fig.8&9 4 3.5 3 2.5 2 1.5 1 0.5 0
The High Performance Concrete with M-sand can be used as an alternative material to natural sand in the presence of silica fume. The Compressive strength of concrete showed gradual increase as the percentage of M-Sand is increased upto 60% after which decreases the strength for further replacement level. The same pattern was also observed for split tensile and flexural strength tests. The optimum percentage of natural sand replacement by M-Sand is 60% in presence of replacement of cement by 7.5% of silica fume for achieving maximum compressive, split tensile and flexural strength. The saturated water absorption and of HPC mixes containing silica fume, and M-Sand were lower when compared with conventional cement concrete. The High Performance Concrete with replacement of cement by 7.5% silica fume and natural sand by 60% MSand is showed higher values of acid resistance and sea water resistance. The results of the strength and durability related tests have demonstrated superior strengthand durability characteristics of HPC mixes containing silica fume and M-Sand. This is due to the pozzolanic action and filler effects of silica fume, and the sharp edges of particles in M-Sand provide better bond with cement than rounded particles of natural sand. The dwindling sources of natural sand, and its high cost could encourage the adoption of M-sand. It is recommended that 60 % of M-Sand as replacement of natural sand can be suitably used in making High Performance concrete Hence, the environmental friendly High Performance Concrete with M-sand and silica fume can be effectively used in the construction industry to minimize the environmental pollution.
28 days 56 days CC
20
40
60
80
100
Percentage replacement of natural sand by M-sand with 7.5% of Silica Fume
Weight loss in %
Fig.8. Acid Resistance of concrete at the age of 45 Days
3 2 1
28 days
0 CC
20
40
60
80
100
56 days
Percentage replacement of natural sand by M-sand with 7.5% of Silica Fume
Fig.9. Sea Water Resistance of concrete at the age of 45 Days
REFERENCE
From the results,it was inferred that the percentage of weight loss starts decreasing upto 60% replacement of M-Sand and starts increasing further replacements. Hence, HPC mixes containing SF are more durable against acid and sea water attack.Also Manufactured sand addition seems to affect in a positive way in durability of concrete. Similar results were reported by researchers that in presence of silica fume and Manufactured sand resistance to acid and sea water[27- 29]. From above results it was concluded that inclusion of M – Sand up to 60% in presence of 7.5 % of silica fume decreased the percentage of weight loss in high performance concrete, which indicates that concrete, has become denser and impermeable.
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CONCLUSIONS
[5]
Based on the investigations carried out on HPC mixes the following conclusions are drawn.
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