International Journal of Research and Innovation (IJRI)
International Journal of Research and Innovation (IJRI) 1401-1402
ASSESSMENT OF SELF COMPACTING CONCRETE IMMERSED IN ACIDIC SOLUTIONS WITH PARTIAL REPLACEMENT OF CEMENT WITH MINERAL ADMIXTURE
K. Santosh Gautham1, S.Uttamraj 2, 1 Research Scholar, Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Hyderabad, India. 2 Assistant professor , Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Hyderabad, India.
Abstract The present investigations are proposed to study the acid resistance behavior of M40 grade SCC with partial replacement of cement with mineral admixture Fly Ash at 10, 20, and 30%. Rational method of mix design was adopted for mix design of M40 grade SCC for the trial mixes in the absence of BIS code for SCC mix design. Experimental investigations were carried out to study the acid resistance of SCC from hydrochloric acid (HCl) and sulphuric acid (H2So4) which are effective acids expected to cause damage for strength and durability of structures, by observing the effect for 14, 28 and 60days strengths and performance at different percentages of mix with flyash. Based on these studies, inference was drawn for durability of structures exposed to such aggressive environment. *Corresponding Author:
BACKGROUNDSELF-COMPACTING CONCRETE (SCC)
K. Santosh Gautham, Research Scholar, Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Hyderabad, India.
Self-Compacting Concrete
Published: August 03, 2015 Review Type: peer reviewed Volume: II, Issue : III
Citation: K. Santosh Gautham, Research Scholar (2015) "AS-
SESSMENT OF SELF COMPACTING CONCRETE IMMERSED IN ACIDIC SOLUTIONS WITH PARTIAL REPLACEMENT OF CEMENT WITH MINERAL ADMIXTURE"
INTRODUCTION GENERAL Concrete is the most widely used material and it is likely to gain much more importance in the coming future because of recent developments and inventions. Concrete has undergone several changes in its composition, manufacture and handling with the development of admixtures that can modify the behavior significantly earlier the performance parameter of concrete such as workability, tensile strength and durability were assumed to be related to its compressive strength the greater the compressive strength the better the performance. Now the performance criteria is specified besides the compressive strength, all the predefined properties can be adopted but suitable composition of mix and admixture Even though the concrete has achieved significant progress in material science and construction technology, still it is having its own limitations, viz concrete cannot flow through past obstructions and in to nook and corners though compaction is essential for achieving strength and durability of concrete., since concrete is not produced under ideal conditions at site, we do often end up with poor results, leading to rock pockets sand streaks and honey combing structures with poor workmanship problems. The best remedy for all above problems is utilization of self-compacting concrete.
Self-consolidating concrete is a highly flowable concrete that spreads into the form without the need of mechanical vibration. Self-compacting concrete is a non-segregating concrete that is placed by means of its own weight. The importance of self-compacting concrete is that is maintains all concrete’s durability and characteristics, meeting expected performance requirements. In certain instances the addition of super plasticizers and viscosity modifier are added to the mix, reducing bleeding and segregation. Concrete that segregates loses strength and results in honeycombed areas next to the formwork. A well designed SCC mix does not segregate, has high deformability and excellent stability characteristics. Self-Compacting Concrete Properties Self-compacting concrete produces resistance to segregation by using mineral fillers or fines, and using special admixtures. Self-consolidating concrete is required to flow and fill special forms under its own weight, it shall be flowable enough to pass through highly reinforced areas, and must be able to avoid aggregate segregation. This type of concrete must meet special project requirements in terms of placement and flow. Self-compacting concrete with a similar water content or cement binder ratio will usually have a slightly higher strength compared with traditional vibrated concrete, due to the lack of vibration giving an improved interface between the aggregate and hardened paste. The concrete mix of SCC must be placed at a relatively higher velocity than that of regular concrete. Self-compacting concrete has been placed from heights taller than 5 meters without aggregate segregation. It can also be used in areas with normal and congested reinforcement, with aggregates as large as 2 inches.
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International Journal of Research and Innovation (IJRI)
Self-Compacting Concrete Uses
Cement
Self-compacting concrete has been used in bridges and even on pre-cast sections. One of the most remarkable projects built using self-compacting concrete is the Akashi-Kaikyo Suspension Bridge. In this project the SCC was mixed on-site and pumped through a piping system to the specified point, located 200 meters away. On this particular project the construction time was reduced from 2.5 years to 2 years.
Cement is a hydraulic binder, i.e. a finely ground inorganic material which, when mixed with water, forms a paste which sets and hardens by means of hydration reactions and processes and which, after hardening, retains its strength and stability even under water. Cement constituent is only 10% of the mix, it is the active portion of the binding medium and the only scientifically controlled ingredient of the concrete.
Self-Compacting Concrete Benefits
Water
Using self-compacting concrete produce several benefits and advantages over regular concrete. Some of those benefits are: • Improved constructability. • Labor reduction. • Bond to reinforcing steel. • Improved structural Integrity. • Accelerates project schedules. • Reduces skilled labor. • Flows into complex forms. • Reduced equipment wear. • Minimizes voids on highly reinforced areas. • Produces superior surface finishes. • Superior strength and durability. • Allows for easier pumping procedure. • Fast placement without vibration or mechanical consolidation. • Lower noise level produced by mechanical vibrators. • Produces a uniform surface. • Allows for innovative architectural features. • It is recommended for deep sections or long-span applications. • Produces a wider variety of placement techniques.
Generally cement requires about 3/10 of its weight of water for hydration. Hence minimum water content is 0.35. Water is an important ingredient of concrete as it actively participates in chemical reaction with cement. Since it helps to form strength giving cement gel, the quantity and quality of water is required to look carefully. This addition of water must be kept to be the minimum, adding too much water reduce the strength of concrete.
EXPERMENTAL PROGRAM GENERAL The aim of experimental program is to compare the selfcompacting concrete made with and without fly ash at 10,20 and 30% as a replacement to cement and checking out the compressive strength variations for each cube after curing with normal water and acid up to 14,28 and 60 days respectively. The basic test carried out on concrete samples are discussed in this chapter, followed by brief description about mix design and curing procedure adopted. At the end, the various test conducted on the specimen are discussed. MATERIALS USED The ingredients of concrete can be classified in to two groups namely active and in active group, the active group consists of cement and water, where as in active comprises of fine and coarse aggregate
Aggregate Aggregate are important constituents in concrete. They are body to the concrete, reduce shrinkage and effect economy. Aggregates were considered as chemically inert material. The mere fact that the aggregates occupy 70 to 80 percentage of volume of concrete. Water and aggregates are natural materials and can vary to many extent in many of their properties. Aggregates can be classified on the basis of the size of aggregate as coarse and fine aggregate. Coarse Aggregate: The size of aggregate more than 4.75 mm is considered as coarse aggregate. For heavily reinforced concrete member the nominal maximum size of aggregate should usually be restricted to 5mm less than the minimum, clear distance between the main bars or 5 mm less than the minimum cover to the reinforcement, whichever is smaller. Fine Aggregate: Aggregate of size less than 4.75mm is considered as fine aggregate. The fine aggregate should be hard, clean and free from adherent coating and organic matter and shall not contain appreciable amount of clay. The fine aggregate shall be of quartz, light grey and shall be free from silt.it shall be angular shape of grains approximately to spherical form and shall be well graded. Admixtures A material other than water, aggregate or cement that is used as an ingredient of concrete or mortar to control setting and early hardening, workability or to provide additional cementing properties. These may be mineral or chemical type. Mineral Admixtures: SCC invariably incorporates mineral admixtures like Fly As, GGBS, Silica Fume, and Rice Husk etc...The mineral admixture we used is Fly Ash.
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International Journal of Research and Innovation (IJRI)
Fly Ash Fly ash is obtained by electrostatic or mechanical precipitation of dust-like particles from the flue gases from furnaces fired with pulverized coal. Ash obtained by other methods shall not be used in cement.. Fly ash can be used as pozzolona or cementing material in concrete. Fly ash may be siliceous or calcareous in nature. The former has Pozzolanic properties; the latter may have, in addition, hydraulic properties with the growing threat to ecology and environment due to increased production of fly ash. Extensive researches going on for the probable utilization of fly ash. Now it has become a widely used material both in producing pozzolona cement and also for making various type of concrete. In SCC fly ash increase the workability and at the same time is economical. Chemical Admixtures: SCC invariably incorporates chemical admixtures, in particular a HRWRA and sometimes VMA.HRWRA helps in achieving excellent flow at low water content and VMA reduces bleeding and improves the stability of the concrete mixture. An effective VMA can also bring down the powder requirement and still give the required stability.
Aim: To find out the soundness of cement. Apparatus: Le-Chatelier Apparatus, Cement, Water, Glass plate. Procedure: i) The cement is gauged with 0.78 times the water required for standard consistency (0.78P) in a standard manner and filled in to the Le-Chatelier mould kept on the glass plate. ii) The mould is covered on the top with another glass plate. iii) The whole assembly is immersed in water at temperature of 27oC to 32oC and kept there for 24 hrs. iv) Measure the distance between the indicator points. v) Submerge the mould again in water, heat the water up to boiling point in 30 minutes and keep it boiling for 3 hrs. vi) Remove the mould from hot water and allow it to cool and measure the distance between the indicator points. vii) The distance between these two measurements gives the expansion of cement. viii) This must not exceed 10mm for OPC, RHC, LHC, etc. ix) If the expansion is more than 10mm, the cement is unsound. Result: The soundness of cement= 8mm
Super plasticizing admixtures: The use of super plasticizers (high range water reducer) has become a quite common practice. This class of water reducers were originally developed in Japan and Germany in the early 1960s; they were introduced in the United States in the mid-1970s. Viscosity modifying admixture: Admixture that modify the cohesion of the SCC without significantly altering its fluidity are called viscosity modifying admixture (VMA). Viscosity Modifying Admixtures make the concrete more tolerant to variations in the water content of the mix so that plastic viscosity is maintained and segregation prevented. The concrete has become more robust to small, but normal changes in the moisture of the aggregate. However, they should not be regarded as a way of avoiding the need for a good mix design and careful selection of other SCC constituents.
Le-Chatelier Apparatus
Normal Consistency of Fineness of Cement Aim: To determine the percentage of water required for preparing cement paste of standard consistency, used for other tests. Apparatus: Vicat apparatus with plunger, I.S. Sieve No. 9, measuring jar, weighing balance
TEST METHODS ON CEMENT AND AGGREGATE Soundness of Cement: Unsoundness of cement means, that the cement having excess lime, magnesium sulphates, etc. due to excess of these items there will be volume changes and large expansions, there by reduces the durability of the structures.
Procedure: The vicat apparatus consists of a D- frame with movable rod. An indicator is attached to the movable rod, which gives the penetration on a vertical scale. A plunger of 10 mm diameter, 50 mm long is attached to the movable rod to find out normal consistency of cement. Take 300 gm of cement sieved through I.S. Sieve No. 9 and add 30% by weight (90 ml) water to it. Mix water and cement on a non-porous surface thoroughly with in 3 to 4 minutes. The cement paste is filled in the vicat mould and top surface is leveled with a trowel. The filled up mould shall be placed along with its bottom non-porous plate on the base plate of the vicat apparatus centrally below the movable rod. The plunger is quickly released into the paste. The settlement of plunger is noted. If the penetration is between 33 mm to 35 mm from top (or) 5 mm to 7 mm from the bottom, the water added is correct. If the penetration is less than required, the process is repeated with different percentages of water till the desired penetration is obtained.
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Result: The normal consistency of cement =5mm
TEST METHODS ON FRESH SELF COMPACTING CONCRETE
Mix design for SCC by Rational Method:
SCC differ from conventional concrete in that its fresh properties are vital in determining whether or not it can be placed satisfactorily. The various aspects of workability which control its filling ability, its passing ability and its segregation resistance all need to be carefully control to ensure that its ability to be placed remains acceptable. (efnarc 2002)
Input data Grade of concrete: M40 Bulk density of course aggregate: 1338 kg/m3 Bulk density of fine aggregate: 1463 kg/m3 Calculation of coarse and fine aggregate: Packing Factor (y)= 1.175 – 0.0008 x Grade of concrete(x) = 1.175 – 0.0008 x 40 = 1.143 Content of course aggregate: Wg = PF x WgL (1-(S/a)) Wg = 1.143 x 1338 (1-0.542) = 700.434kg Content of fine aggregate:
A concrete mix can only be classified as self-compacting concrete if the requirements for all three characteristics are fulfilled. • Filling ability: Ability to fill a formwork completely under its own weight. • Passing ability: Ability to overcome obstacles under it own weight without hindrance. Obstacles are e.g. reinforcement and small openings etc. • Segregation resistance: Homogeneous composition of concrete during and after the process of transport and placing. Slump Flow Test method
Ws = PF x WsL (S/a) Ws = 1.143 x 1463(0.542) = 906.337kg Calculation of cement content: Cement content(y) = 10.238 + 9.535 x grade of concrete(x) = 10.238 + 9.535 x 40 = 391.638kg
The slump flow is used to assess the horizontal free flow of SCC in the absence of obstructions. It was first developed in Japan for use in assessment of underwater concrete. The test method is based on the test method for determining the slump. The diameter of the concrete circle is a measure for the filling ability of the concrete.
Calculation of water cement ratio: Grade of concrete (y) = 22.456 x (w/c)-1.17 40 = 22.456 x (w/c)-1.17 W/c = 0.6105 Calculation of fly ash: % fly ash in total powder (y) = 68.43 – 0.535 x grade of concrete (x) = 68.43 – 0.535 x 40 = 47.03 % Calculation of super plasticizer: The dosage of SP used was ranging from 1.5 to 1.8% by weight of cement. 1.5% of cement content = 1.5% x 391.638 = 5.875kg Calculation of viscosity modifying agent: The dosage of VMA used was ranging from 0.1 to 1.5% by weight of cement. 0.5% of cement content = 0.5% x 391.638 = 1.958kg ESTIMATED QUANTITIES RATIOS SCC (M40) mix design ratios Cement
CA
FA
Fly ash
Water
SP
VMA
391.638
700.434
906.337
184.187
239.094
5.875
1.958
1
1.7885
2.3142
0.4703
0.6105
0.015
0.0049
Assessment of test This is a simple, rapid test procedure, though two people are needed if the T50 time is to be measured. It can be used on site, though the size of the base plate is somewhat unwieldy and level ground is essential. It is the most commonly used test, and gives a good assessment of filling ability. It gives no indication of the ability of the concrete to pass between reinforcement without blocking, but may give some indication of resistance to segregation. It can be argued that the completely free flow, unrestrained by any boundaries, is not representative of what happens in practice in concrete construction, but the test can be profitably be used to assess the consistency of supply of ready-mixed concrete to a site from load to load. Equipment The apparatus is shown in figure. • Mould in the shape of a truncated cone with the internal dimensions 200 mm diameter at the base, 100 mm diameter at the top and a height of 300 mm, conforming to EN 12350-2 • Base plate of a stiff non absorbing material, at least 700mm square, marked with a circle marking the central location for the slump cone, and a further concentric circle of 500mm diameter • Trowel 196
International Journal of Research and Innovation (IJRI)
• Scoop • Ruler • Stopwatch (optional) Procedure 1. About 6 litre of concrete is needed to perform the test, sampled normally. 2. Moisten the base plate and inside of slump cone, place base plate on level stable ground and the slump cone centrally on the base plate and hold down firmly. 3. Fill the cone with the scoop. Do not tamp, simply strike off the concrete level with the top of the cone with the trowel. 4. Remove any surplus concrete from around the base of the cone. 5. Raise the cone vertically and allow the concrete to flow out freely. 6. Simultaneously, start the stopwatch and record the time taken for the concrete to reach the 500mm spread circle. (This is the T50 time). 7. Measure the final diameter of the concrete in two perpendicular directions. 8. Calculate the average of the two measured diameters. (This is the slump flow in mm). 9. Note any border of mortar or cement paste without coarse aggregate at the edge of the pool of concrete.
The following results are the compressive strengths of self-compacting concrete of M40 grade with different percentages of fly ash mix after curing the cubes in normal water at 14, 28, 60 days. Showing Strengths of cubes immersed in normal water Mix type
Strength in Mpa
(M40)
14 days
28 days
60 days
SCC Normal
38.53
57.17
63.02
FA 10%
36.43
55.57
62.85
FA 20%
33.21
51.63
59.34
FA 30%
32.68
47.53
55.89
Interpretation of result The higher the slump flow (SF) value, the greater its ability to fill formwork under its own weight. A value of atleast650mm is required for SCC. There is no generally accepted advice on what are reasonable tolerances about a specified value, though ± 50mm, as with the related flow table test, might be appropriate. RESULTS AND DISCUSSIONS TEST RESULTS The following tables gives the test results of compressive strength of self-compacting concrete with the addition of fly ash admixture at different percentages after the effect of normal(water) and acid curing (HCL & H2SO4).
SCC cube on effect of sulphuric acid curing.
The following results are compressive strengths of selfcompacting concrete of M40 grade with different percentages of fly ash mix after curing the cubes with 5% concentration of sulphuric acids at 14, 28, 60 days. Strength of cubes immersed in sulphuric acid of 5 % concentration Mix type (M40)
Strength in Mpa 14 days
28 days
60 days
SCC Normal
35.21
54.34
59.37
FA 10%
34.23
51.03
59.63
FA 20%
32.53
49.52
57.26
FA 30%
30.95
44.93
52.68
Compressive strength test of cube
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International Journal of Research and Innovation (IJRI)
SCC Cube WithThe Effect On Hydrochloric Acid Curing
The following results are compressive strengths of selfcompacting concrete of M40 grade with different percentages of fly ash mix after curing the cubes with 5% concentration of hydrochloric acids at 14, 28, 60 days. Strength of cubes immersed in hydrochloric acid of 5 % concentration Mix type (M40)
Strength in Mpa 14 days
28 days
60 days
SCC Normal
36.23
55.93
63.53
FA 10%
36.07
53.85
62.09
FA 20%
33.62
50.83
59.34
FA 30%
30.43
45.34
54.32
SCOPE FOR FURTHER STUDY ON SCC The following experimental studies can be conducted in future with respect to self-compacting concrete • The addition of more percentage of fly ash i.e. more than 30% , shows the effect on resistance to acid on self-compacting concrete. • Different strengths such as flexural strength, tensile strength etc. can be known with the effect of acid on SCC. • The effect on strength, creep and shrinkage of self-compacting concrete due to different mix proportion with replacement of mineral admixture at different proportions can be calculated. • Different mineral admixture such as GGBS, Rice Husk etc. can be used for the experiment with higher grade and can be tested different strengths. CONCLUSION
Compressive Strength Test Machine under Process
GRAPHS The following graphs shows the strength variations with respective to time with normal and acid curing.
The following conclusions are drawn from the test results and analysis presented in this paper: • Percentage decrease in weights of the specimens without and with immersion in HCL and H2So4 solutions of 5 % concentration at 28 days was found to be 5.834, 6.132 and 5.481 % & 4.247, 3.498, 4.984 % on average of each 10, 20, and 30 % of fly ash respectively. • From these results it has been identified that the intensity of attack by H2S04 is comparatively more than the attack of HCL on the specimens. • The percentage decrease in compressive strength of the specimens without and with immersion in HCL and H2S04 solution of 5 % concentration after 28 days was found to be 3.09, 1.54 and 4.60 % and 8.16, 4.08, 5.47% average of each 10, 20, and 30 % respectively.
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International Journal of Research and Innovation (IJRI)
• For 30% fly ash replacement the fresh properties observed were good as compared to 10%, 20% fly ash replacement. Hence if we increase the fly ash replacement we can have better workable concrete. • The acid resistance of SCC with fly ash was higher when compared with concrete mixes without fly ash at the age of 14, 28, 60 days. • Compressive strength loss decrease with the increase in fly ash in concrete. • The compressive strength of cubes are less in H2So4 curing when compared with HCL and normal curing. With the increase in flyash content the resistance to acid increases and, the strengths of cubes slowly increases with time, but final strength obtains are same as normal mix. • When the specimen is immersed in acid solutions for 14, 28, 60 days respectively the average reduction in weight increases, and the weight is decreased when fly ash content is increased in the concrete. Compressive strength loss decreases with the increase in fly ash in concrete.
6. EFNARC.2005. European guidelines for self-compacting concrete, specification, production and use. 7 M. Nehdi, M. pardhanb, and S. Koshowskic. “Durability of self-compacting concrete incorporating high volume replacement composite cement”, cement and concrete research, 34(2004), pp. 2103-2112. 8. Madhusudhana Reddy, H. Sudarsana Rao, M.P George .Effect of Hydrochloric Acid (HCl) on Blended Cement (Fly Ash based) and silica fume blended cement and their concretes, International Journal of Science and Technology Volume 1 No. 9, September, 2012 9. by P. Murthi and V. Siva Kumar. Study on the Acid Resistance of Ternary Blended Concrete, ASIAN Journal of Civil Engineering (Building and Housing) VOL. 9, NO. 5 (2008).
Author
REFERENCES 1. OuchiM, HibinoM, Ozawa K, and Okamura H. a rational mix design method for motor in self-compacting concrete. Proceeding of sixth South EastAsia pacific conference of structural engineering and construction. Taipei, Taiwan, 1998, pp.1307-1312. 2. G. Kaur, S.P. Singh and S. K. Kaushik. Reviewing some properties of concrete containing mineral admixtures. The Indian concrete journal July 2012.
K. Santosh Gautham, Research Scholar, Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Bandlaguda,Hyderabad, India.
3. H. Said, H.A. Mesbah, H. khelafi, S. Kamali Bernard and M. Mouli. Influence of natural pozzolan on the behaviour of self-compacting concrete under sulphuric acid and hydrochloric acid attacks, comparative study. 4. Mohammad Kamran, Mudit Mishra, behaviour of selfcompacting concrete using PPC and OPC with different proportion of fly ash. International journal of research in engineering and technology. P ISSN: 2321-7308 5. Dhiyaneshwaram. S, Ramanathan. P, Baskar. I and Venkatasubramani.R. Study on durability characteristic of self-compacting concrete with fly ash. Jordan journal of civil engineering, vol 7, no.3, 2013
S.Uttamraj, Assistant Professor, Department of Civil Engineering, Aurora's Scientific Technological and Research Academy, Bandlaguda,Hyderabad, India.
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