Essay: Cement and concrete

INTRODUCTION
1.1 General:
Now a days the use of concrete in infra- structural activity is on the rise and with cement being the most important but costly component of concrete, effort to reduce the cost by partial replacement of cement with supplementary cementitious materials has gained momentum and is even made as a government regulation. However, the production of concrete is not environmentally friendly.
In this scenario, the use of conventional waste materials, such fly ash, Rice husk ash, Ground granulated blast furnace slag, silica fume, sugar cane bagasse etc. as a replacement for Portland cement in concrete presents one viable solution with multiple benefits for the sustainable development of the concrete industry. Currently, industrial waste such as Fly Ash (FA) and Rice Husk Ash (RHA) are being used as supplementary cement replacement materials. Therefore, a great potential exists to reduce the concrete industry`s contributions to greenhouse gases through reduction in cement consumption.
1.2 Concrete:
An artificially built up stone resulting from hardening of a mixture of a cement, aggregates, and water with or without a suitable admixture is generally known as concrete. When the materials are mixed together so has to form a workable concrete, it can be moulded into beams, and slabs etc. a few hours after mixing the material undergo a chemical combination and has a consequence the mixture solidifies and hardens attaining greater strength with age. Concrete posses a high compressive strength and has a poor tensile strength. It also develops shrinkage stresses.
A freshly mixed concrete must possess the under mentioned properties like,
1. Good Workability
2. No Segregation
3. No Bleeding
1.2.1. Workability:
It is defined as the property of freshly mixed concrete or mortar which determines the ease and homogeneity with which it can be mixed, placed, consolidated and finished.
The factors effecting concrete to have more lubricating effect to reduce internal friction for helping easy compaction are,
a. Higher the water content per cubic meter of concrete, higher will be fluidity of concrete which leads in increase of workability
b. Higher the aggregate-cement, the linear is concrete that is less quantity of paste is available for providing lubrication, per unit surface area of aggregate and by this workability decreases.
c. Workability of concrete increases by the increase of the size of aggregate.
d. Based on the type of surface texture and on surface area workability changes, it is more for rough than smooth texture.
e. A well graded aggregate is the one which has least amount of voids or less excess paste is available to give better lubricating effect.
f. The use of plasticizers and super plasticizers greatly improve workability.
1.2.2. Segregation:
A good concrete is one in which all the ingredients such as cement, aggregates and water are properly distributed to make a homogeneous mixture. Segregation can be defined as ‘the separation of constituent materials of concrete’.
Segregation can be of three types, one is coarse aggregate out or settling down from the rest, secondly the paste of matrix separating away from coarse aggregate and finally water separating out from rest of the material being the material of lowest specific gravity.
Vibration of concrete is one of the important methods of compaction. It should be remembered that only comparatively dry mix should be vibrated, if the mix is too wet and excessively vibrated is likely that the concrete gets segregated.
Segregation can be avoided by proper mix proportions, using air entraining agents and also by proper handling, transporting, placing, compacting, finishing.
1.2.3. Bleeding:
Bleeding is a form of segregation, where water comes out on the surface of concrete as it has lowest specific gravity among all ingredients of concrete mix. In the field, bleeding can be identified easily by the appearance of thin layer of water on the top of the surface of fresh concrete.
Bleeding occurs due to lack of fines and too much of water content in the design mix. It results in poor bond between layers and also reduces pump ability. Concrete bleeding can be avoided or partially reduced using finely ground cement, adjusting grades, entrained air, reducing water content and also by using fly ash and other pozzolans.
Effect of Temperature on Concrete:
Due to the elevated temperatures, the effects in concrete are
a. Spalling of concrete
b. Loss of compressive strength
c. Loss of weight/mass
d. Change in colour
The main ingredients used in concrete mix are,
‘ Cement
‘ Coarse aggregate
‘ Fine aggregate
‘ Mineral / Chemical admixtures (if any)
‘ Water
1.3 Cement:
Cement is the most important material used in constructions. It has adhesive and cohesive properties so as to render it to form a good bond with other materials. As it is a binder material in concrete, when it is mixed with aggregates and water it turns the particles into a whole compound and solidifies. Cement is the most important and costliest ingredient of concrete, and it is obtained by burning a mixture of the siliceous, argillaceous and calcareous material in a definite proportions.
It can be manufacture in two processes i.e., wet process and dry process. In modern plants the wet process is replaced by dry process. Dry process consumes less fuel and therefore reduces the requirement of coal. The main constituents in cement that give cementitious properties are di-calcium silicate(C2S), tri calcium silicate(C3S), tri calcium aluminate(C3A) and tetra calcium alumina ferrite(C4AF).
1.3.1 Types of Cement:
By altering the proportions of the ingredients of cement, by adding other ingredients or by changing the intensity of grinding, different types of cement useful for particular situations can be manufactured.
IS 456-2000 has recognized the following types of cements for construction purpose.
1. Ordinary Port Land Cement
i. 33 Grade (IS 269)
ii. 43 Grade (IS 8112)
iii. 53 Grade (IS 12269)
2. Rapid Hardening Cement(IS 8041)
3. Portland Slag Cement(IS 455)
4. Hydrophobic Cement(IS 8043)
5. Portland Pozzolona Cement(IS 1489)
6. Low Heat Portland Cement(IS 8042)
7. Sulphate Resisting Portland Cement(IS 1233)
8. White Portland Cement(IS 8042)
9. High Alumina Cement(IS 6452)
In this thesis work the Ordinary Portland Cement of 53 (OPC 53) grade cement and Ordinary Portland Special cement OPC 53 S cements are used. The typical chemical compositions of cement is given in table-1
Table I: Oxide and Compound Compositions of a Typical Portland cement
Typical Oxide Composition percent
CaO 63
SiO2 20
Al2O3 06
Fe2O3 03
MgO 10.5
S03 02
K2O / Na2O 01
Calculated Compound Composition percent
C3A 10.80
C3S 54.10
C2S 16.60
C4AF 9.10
Heat of Hydration of Cement:
The reaction of cement with water is exothermic reaction which liberates a considerable quantity of heat. This liberation of heat is called as heat of hydration. On mixing cement with water a rapid heat evolution, lasting a few minutes is occurred.
This evolution is probably due to the reaction of solutions of aluminates and sulphates; actually early heat of hydration is mainly contributed form the hydration of C3S. This is the product of reaction of cement with water. In the presence of water, the silicates and aluminates of Portland cement form products of hydrates, which in time produce a firm and hardened cement paste. As stated earlier, the low calcium silicates (C3S and C2S) are the main cementations compounds in cement, the former hydrating much more rapidly than the latter. In commercial cements, the calcium silicates contain small impurities from some of the oxides present in the clinker. These impurities have a strong effect on the properties of the hydrated silicates.
1.4 Special Cements (OPC S):
The Special Cements are a special type of cements which are used for the specified requirements. Among its OPC 53 S is the special type of cements which are used for construction of sleepers. OPC represents Ordinary Portland Cement, 53 represent the compressive strength of cement after 28 days curing, and S represents the special cements. The main differences between Ordinary Portland Cement and Ordinary Portland Special cements is the
‘ Minimum Fineness ‘ 225 m2/kg for OPC53 & 370 m2/kg for OPC 53 S as per IS4031 (part2)
‘ Maximum Tricalcium aluminate content, is10.0 % by mass
‘ Maximum Tricalcium silicate, 45.0 % by mass
It is a specialty cement manufactured as per specifications originally formulated by the Indian Railways vide their specification No.IRS T-40 for manufacturing concrete sleepers. However, there was an amendment (No.6) to IS 12269, IRS T-40 cement and then, this was brought under the ambit of BIS. It is now designated as 53-S Ordinary Portland cements and conforms to BIS specification IS: 12269-1987. 53-S OPC’s negligible chloride content protects it against corrosion. High fineness enhances workability and high early strength enables improved mass production cycle of Railway Sleepers. Apart from its main usage in the manufacture of concrete sleepers, it can also be put to use in pretest concrete elements or high rise buildings where early strength is required.
1.5 Aggregate:
The aggregates have a definite influence on the strength of hardened concrete. Hence, the aggregate used for concrete should be durable, strong, chemically inert and well graded. The aggregate occupy about 75% of the volume of concrete and they greatly influence the properties of concrete. These gives body to the concrete and reduce the shrinkages effect of cement and make the concrete durable.
Aggregates are classified as coarse aggregates and fine aggregates:
Coarse Aggregate:
Coarse aggregates are used for making concrete. The coarse aggregate are those most of which will retain on 4.75 mm IS sieve contain coarse material permitted for various types described in IS 383-1970. The aggregate fractions from 80mm to 4.75mm are termed as coarse aggregate. Machine crushed angular granite metal of 20mm passed and 10mm retained has been used. It is free from impurities such as dust, clay particles and organic matter. The coarse aggregate is tested for various properties according to IS 2386-1963
Fine Aggregate:
As per IS 383- 1970, fine aggregate are defined as the aggregate most of which passes 4.75 mm IS sieve and contains only so much fine material as it is permitted for various grading zones. The sand is free from clay, silt and organic impurities. The sand is tested for various properties according to IS 2386-1963.
1.6 Admixtures:
Chemical admixtures – Chemicals added to concrete to modify some of its mix properties is called as an admixture. It is surly a difficult task to predict the effect of result enchantment in presence of admixture. Few admixtures affect more than one concrete property and sometimes we need to go for more than one admixture for obtaining the desired properties in a single mix. If such case of more than one admixture arises then the task of predicting the properties become too difficult. This strength phenomena draws our at most attention in the selection of prefect admixtures in a concrete mix. As per the report of ACI committee 212, admixtures have been classified into groups based on type of constituent material.
Types of Chemical Admixtures:
1. Plasticizers
2. Super plasticizers
3. Retarders and retaining plasticizers
4. Accelerators and accelerating plasticizers
5. Air – entraining admixtures
6. Pozzolona or mineral admixtures
7. Damp- proofing and water proofing admixtures
8. Gas forming admixtures
9. Air – detraining admixtures
10. Alkali aggregate expansions inhibiting admixtures
11. Working admixtures
12. Grouting admixtures
13. Corrosion inhiting admixtures
14. Fungicidal, germicidal, insecticidal admixtures
15. Bounding admixtures
16. Coloring admixtures
Mineral admixtures – In this advanced world of technology there is a terrible need for development of high strength and high performance concrete. Admixtures possessing pozzolona nature containing cementatious in nature other than Portland cement are used more commonly. According to a survey of Portland Cement Association published in 2000, around 60% of binding material in ready mix concrete contains other cementatious materials called mineral admixtures also known as ‘Supplementary Cementing Material’. These Mineral admixtures can come to use in addition to the normal OPC amount or as a substitute depending on the desired properties of concrete. Generally used when special performance is needed in construction. By adding mineral admixtures strength is increased, water demand, impermeability is reduced, low heat of hydration, higher age strength ie, durability, control of alkali-aggregate reactivity, retarding setting time and reduces cost.
Replacement of cement by these mineral admixtures leads to cost saving and it is energy required process. Environmental damage and pollution is minimized by usage of these byproducts. Mineral admixtures used as cement replacement are
i. Rice Husk Ash (RHA)
ii. Ground Granulated Blast furnace Slag (GGBS)
iii. Fly-Ash
iv. Silica Fume
v. Metakaoline
1.7 Water:
Water should be considered as an important material for construction, where it is mainly used with cement for making mortar, concrete, etc. and also for curing of cement works. The suitability of the available water for the construction can be obtained from the data specified in IS 456 Clause 5.4.3. The pH value should not be less than 6.
1.8 Rice Husk Ash
India has a large agribusiness sector which has achieved remarkable successes over decades. Rice paddy is the primary source of food for billions of people. The paddy grain when generated to milling about 80% of weight is converted into rice and the remaining 20% weight of paddy is turned into husk. In the majority of rice producing countries much of the husk produced from the processing of rice is burnt or dumped as waste. This can mostly be avoided by using the produced husk as fuel in the boilers for paddy processing, which shows that husk acts as ideal fuel for electricity generation. The concept of generating energy from Rice husk has great potential, particularly in those countries that are primarily dependant on imported oil for their energy needs.
Fig.1: Showing Rice husk Ash from paddy grain to grinded ash form
The rice husk is unusually high in ash compared to other biomass fuels. During the firing process of rice husk about 25% is converted into Rice husk ash and remaining is turned into organic volatile matter. The obtained rice husk ash is an agro-waste material which is high in ash containing 92 to 95% silica. It is highly porous and lightweight material with high external surface area.
Rice husk ash has recently been recognized as pozzolona. A pozzolona is a siliceous/ aluminous material which increases its strength and impermeability. Addition of rice husk ash to Portland cement forms a calcium silicate hydrate (CSH) gel around the cement particles which is highly dense and less porous, and may increase the strength of concrete against cracking.
The particle size of the cement is about 45 microns. There may be formation of void in the concrete mixes, if curing is not done properly. This reduces the strength and quality of the concrete. RHA is finer than cement having very small particle size of 25 microns, so that it fills the interstices in between the cement. This reduces the quantity of cement.
1.8.1 Properties of RHA:
Rice Husk Ash is a Pozzolanic material. It has different physical & chemical properties. The product Rice Husk Ash is identified by trade name Silpoz which is much finer than that of cement.
Chemical Properties –
Table2: Chemical Composition of RHA
Particulars Proportion, %
Silica – SiO2 90.63
Al2O3 1.78
Fe2O3 0.79
Carbon 0.70
CaO 0.13
MgO 0.87
K2O 2.45
Others 2.65
Moisture 0.63
Physical Properties ‘
Table3: Physical Properties of RHA
Particulars Properties
Colour Gray
Shape Texture Irregular
Mineralogy Non Crystalline
Particle Size < 45 micron
Odour Odourless
Appearance Very fine
Specific gravity 2.3
1.8.2 Advantages: Rice husk ash (RHA) can be used as high reactive pozzolanic material to increase the microstructure of the interfacial transition zone (ITZ) between the cement paste and the aggregate in high-performance concrete. The utilization of rice husk ash as a pozzolanic material in cement and concrete provides several advantages, such as
‘ Increases compressive strength
‘ Enhances concrete durability properties
‘ Reduce materials cost due to the cement saving
‘ Environmental benefits related to the disposal of waste materials
‘ Reduce carbon dioxide emission
LITERATURE REVIEW
Ramezanianpour A et al (2012) In this paper, in order to supply typical RHA, a special furnace was designed and constructed in Amirkabir University of Technology. XRD and XRF techniques were used to determine the amorphous silica content of the burnt rice husk. Consequently, temperature of 650 degrees centigrade and 60 minutes burning time was found to be the best combination. Then, various experiments were carried out to determine properties of concretes incorporating optimum RHA.
Kartini K et al (2011) has done intensive study on Rice Husk Ash to determine its suitability. Experimental work was conducted on various grades of concrete such as 30, 40 and 50 grades which shows 30% replacement of OPC by RHA. By referring his complete study it shows that RHA has potential to use as partial replacement of cement with high compressive strength and durability. Increase in RHA % reduces the workability of concrete, which can be overcome by adding super plasticizers. He also concluded that presence of RHA in high grade concrete reduces coefficient of permeability which in turn increase durability of concrete structure. Optimum dosage of RHA as replacement of cement at 28-days strength for grade30, 40 is 30% and that of grade 50 is 20%. Finally shows that RHA contribute to sustainability of construction material.
Makarand Kulkarni et al (2014) evaluated physical and chemical properties of concrete by adding RHA in different contents. Sample Cubes were tested with different percentage of RHA, replacing in mass the cement. Properties like Compressive strength, flexural strength, Water absorption and Slump retention were evaluated. By replacing RHA, increase in compressive strength is observed up to 20% replacement which is the optimum dosage of RHA for M30 grade. RHA as an alternative for cement reduces corrosion and thereby increases durability of concrete. As RHA is an agro-waste material, when it is used as partial replacement of cement, the cost of construction is reduced and also environmental, disposal of waste material is reduced. Utilization of RHA has promising prospects as it softens the impact on environment. RHA is used in manufacturing of load bearing blocks, brick tiles in a low cost.
Dao Van Dong et al (2008) presented several key properties of high strength concrete using rice husk ashes (RHAs). RHAs obtained from two sources: India and Vietnam were used with various contents to partially replace for cement binder in high strength concrete. Key properties of concrete, including: slump, density, compressive strength, water and chloride permeability resistances, were investigated in comparison between samples without using RHA and samples using two types of RHAs. Experimental results showed reasonable improvements in compressive strength, water and chloride permeability resistances of concrete using the RHAs. The results also presented that the improvements of samples composed the India RHA was much better than that of the Vietnam RHA. The utilisation of RHA in concrete can obtain several benefits. On the one hand, it contributes to reduce of agricultural waste that is the main cause of environmental problems in agricultural countries. On the other hand, it is an approach to improve the quality of concrete without using costly additives such as silica fume.
Nagrale S D et al (2012) evaluated how different contents of Rice Husk Ash added to concrete may influence its physical and mechanical properties. Sample Cubes were tested with different percentage of RHA and different w/c ratio, replacing in mass the cement. Properties like Compressive strength, Water absorption and Slump retention were evaluated. With the addition of RHA weight density of concrete reduces by 72-75%.Thus, RHA concrete can be effectively used as light weight concrete for the construction of structures where the weight of structure is of supreme importance. Thus, the use of RHA in concrete leads to around 8-12% saving in material cost. So, the addition of RHA in concrete helps in making an economical concrete. The Compressive Strength will increase with the addition of RHA. The use of RHA considerably reduces the water absorption of concrete. Thus, concrete containing RHA can be effectively used in places where the concrete can come in contact with water or moisture. RHA has the potential to act as an admixture, which increases the strength, workability & pozzolanic properties of concrete.
Mauro M Tashima et al. (1985) studied how different grades of RHA concrete can influence its physico-mechanical properties was studied. Concrete specimens were moulded with 5% and 10% of ash replacing with cement, and measured its compressive strength and water absorption that, by adding RHA a decrease in water absorption was noted and compressive strength was decreased with increase in RHA levels when compared to control sample.
Alireza Naji Givi et al. (2010) studied the use of RHA as partial replacement of cement in mortar and concrete. Reported properties in this study are the mechanical, durability and fresh properties of mortar/concrete and concluded that incorporation of RHA as a partial cement replacement in between 12% to 15% may be sufficient to control deleterious expansion due to alkali-silica reaction in concrete and also concluded that use of RHA leads to enhanced resistance to segregation of fresh concrete compared to normal concrete.
Subash C et al. (2010) studied briefly on the effect of strength properties on concrete when cement is replaced by RHA. Tests conducted on replacement of cement with 10%, 20% and 30% of RHA and test results were compared that of normal concrete with no percentage of RHA. Increase of 18% of compressive strength is observed with 20% replacement of RHA than that of normal concrete. There is reduction in workability of fresh concrete with the increment of RHA. Performance of concrete varies with the change of particle size of RHA. Strength of concrete also depends on fineness of RHA. Therefore, concluded that with increase in fineness of RHA compressive-strength can be increased. It is observed that there is 11% reduction in surface water absorption with 20% replacement of RHA controlled to normal control concrete.
From the above studies it can be concluded that the cement is partially replaced by many materials such as Fly ash, Rice husk ash, GGBS, Metakoline, Silica fume, SDA at different percentages. The super plasticizer dosage and water cement ratio has also varied in some papers. The strengths are also compared.
Both OPC 53 and Special cement OPC 53 S is used as partial replacement by rice husk ash. Our main study related to partial replacement of cement by Rice Husk Ash at four different percentages. To maintain the slump as 100mm for normal M40 grade concrete with water cement ratio of 0.45. The tests are conducted for compressive, flexure and split tensile strengths. Comparison of OPC 53 and OPC 53S cement and optimum dosage of RHA is studied in this present experimental study.
Aim and Scope of Project:
The primary aim of experimental work is to study the properties of Rice Husk Ash and OPC 53 and OPC 53 S cements, preparation of desired mix design and replacement of cement with RHA at different increasing proportions.
The main objective of this thesis is to study the suitability of the RHA as a pozzolanic material for cement replacement in concrete. However it is expected that the use of RHA in concrete improve the strength properties of concrete. Also it is an attempt made to develop the concrete using rice husk ash as a source material for partial replacement of cement, which satisfies the various structural properties of concrete like compressive strength and Flexural strength and split tensile strength. It is also expected that the final outcome of the thesis work done will have an overall beneficial effect on the use of rice husk ash as cement replacement in concrete in the field of civil engineering construction.
Literature review presented previously has given good outcome for the concrete with the mineral admixture rice husk ash. Following parameters influences mostly the behavior of the rice husk ash concrete, so these parameters are kept constant for the thesis work.
‘ Increase of percentage replacement of cement by RHA
‘ Rice husk ash particle size ie Fineness
‘ Chemical composition of RHA
‘ Water to cement material ratio (w/c ratio)
‘ Curing type
Also from the literature survey, percentage partial replacement of cement by rice husk ash and method of mix design is fixed as constant after primary investigation.
Objective:
‘ To study the effect of Rice Husk Ash on the workability of concrete.
‘ The effect on Compressive strength of concrete with OPC 53 and OPC 53 S
‘ The effect on flexural strength of concrete with OPC 53 and OPC 53 S
‘ The effect on split tensile strength of concrete with OPC 53 and OPC 53 S
‘ Comparison of result of different tests with varying proportion of RHA.
‘ Comparison of test results of different Mechanical Properties of concrete using OPC 53 and OPC 53 S with partial replacement of RHA.
WORKING METHODOLOGY
Work Methodology:
The work methodology of the present thesis work contains collection of raw materials, determining the physical properties of the collected materials and confirming the test results to the standard values. Further, determining the proper mix design by using obtained physical properties. With different trial mix designs desired mix proportion is determined and further work was continued using those proportions by increasing the percentage of Rice Husk Ash used as a partial replacement of cement. Hardened concrete tests like were conducted and results were determined.
Few initial tests have been conducted on raw materials of concrete like fineness test, water absorption, fineness modulus, % passing, specific gravity, normal consistency, initial and final setting time e.t.c. depending on the results derived from these tests the mix design have been performed. As the mix was a trial mix we are supposed to cast few samples testing the target strength, once it has been clarified that the tests where giving good results Mix variations like alteration of binding material ratio can be selected.
Each variation will be labled after a mix designation and the samples will be casted for determining tests like Compressive Strength, Flexural Strength and Split tensile strength with standard specimen sizes and later on comparison between the results with increase in percentage of partial replacement of Rice Husk Ash.
Cubes are casted of 100 x 100 x 100mm dimension to find compressive strength, 150 x 300mm dimension cylinder to find split tensile strength, 100 x 100 x 500mm prism to find flexural strength. All together 10 mix designations have been formed and each mix comprises of 15 cubes to be tested for 3, 7, 14, 28 and 56days of curing duration similarly 3 cylinders and 3 prisms are casted to test for 28 days of curing duration.
3.1 Collection of Materials:
Cement: The cement, used for this present thesis study is JPJ (OPC 53) grade cement confirming all conditions of IS 8112-1989.
Special Cement: OPC 53-S is a special type of cement is also used in this study. It is an example for Portland pozzolona cement. It is generally used in construction of railway sleeper and marine structures.
Rice Husk Ash: Preliminary studies where done for selection of perfect mineral admixtures that is available to conduct research. As a part of this job Rice Husk Ash has been selected, as it is available and easily purchased from market nearby. Although the Rice Husk Ash product selected was imported from a rice mill near Rajahmundry and further grinding of RHA into fine powder was done in a rice mill nearby Visakhapatnam. This selected RHA mineral admixture is more adaptive in nature and a perfect available choice as a mineral admixture in replacement of binding material.
Fine aggregate: The sand used for our investigation is collected form Godavari river sand which is conforming to Zone III as per Indian Specification 383-1970 codal provisions.
Coarse aggregate: The coarse aggregate of 20mm and 10mm size with an angular shape which is well graded are collected and used for the experimental work
3.2 Physical Properties of Materials:
The materials used in the experimental work are namely OPC 53 cement, OPC 53 S cement, Rice Husk Ash, fine aggregate and coarse aggregate (20mm, 10mm). These materials have been tested in a Climate Controlled Laboratory as per standard procedures mentioned in related code provisions of the materials for the use in mix designs. The details are presented below,
3.2.1 Cement:
The cement, used for this present thesis work is JPJ (OPC 53) grade cement conforming all conditions of IS 8112-1989 code. It is most recently manufactured while confirming all the conditions such as uniform color, smooth texture, free from lumps. The physical properties of the cement are determined considering different codal provisions as specified. Tests like Fineness of cement, normal consistency, specific gravity, initial and final setting time, soundness test, and compressive strength of cement were determined.
Special Cement, used for this present thesis work is Nagarjuna Cement (OPC 53 S) conforming all specifications originally formulated by the Indian Railways vide their specification No.IRS T-40 for manufacturing concrete sleepers and also IS 12269.
Table-3.1 Physical Properties of OPC-53 and OPC-53-S grade cements
Properties OPC 53 OPC 53-S
Fineness of cement 8% 1%
Standard consistency 32% 35%
Initial setting time 40 minutes 22 minutes
Final setting time 330 minutes 150 minutes
Specific gravity 3.15 3.15
soundness 2mm 1mm
Table-3.2 Compressive-Strength of OPC 53 and OPC 53-S grade Cement
S.No
Compressive-Strength of OPC 53, N/mm2
Compressive-Strength of OPC 53 S, N/mm2
3-days 7-days 28-days 3-days 28-days
1 29.5 38.8 54.2 42 58
2 28.5 37.2 53.8 38 56
3 29 37.5 53 41 54
Average 29 37.83 53.667 40.33 56
3.2.2 Fine Aggregate:
The sand which is used is comes under Zone ‘III as per IS 383-1970. The physical properties like zoning of sand, bulk density, specific gravity are determined according to the codal provisions.
Table -3.3 Physical Properties of Fine Aggregate
Properties Test results
Specific gravity 2.52
Fineness modulus 2.2
Bulk density 1.69
‘ Sieve analysis of fine aggregate:
Table-3.4: Fine Aggregate Sieve Analysis
Size of sieve Retained Weight (g) Cumulative Retained Weight (g) Retained % Cumulative Weight % Passing through
4.75mm 0.013 0.013 1.3 98.7
2.36mm 0.019 0.032 3.2 96.8
1.18mm 0.046 0.078 7.8 92.2
600” 0.238 0.316 31.6 68.4
300” 0.518 0.834 83.4 16.6
150” 0.122 0.956 95.6 4.4
pan 0.044 1 100 0
Result:
Fineness modulus of fine aggregate = (‘cumulative % weight retained)/100 = 222.9/100 = 2.2
The given sand belongs to ZONE-III and Coarse Sand
‘ Specific gravity:
The specific gravity of fine aggregate is determined by using pycnometer
Specific gravity of fine aggregate of the given by empirical formula
(W2-W1)
Specific Gravity = —————————- = 2.52
(W4-W1)- (W3-W2)
‘ Bulk density:
The bulk density of the fine aggregate for the given sample is 1.690kgs/ Lit
3.2.3 Coarse Aggregate:
The coarse aggregate used is from well-established quarry, satisfying the code IS 383:1970. The mixture of coarse aggregates used is not more than 20 mm, the material is of uniform color and has good angular shape. The physical properties like fineness- modulus, specific-gravity bulk-density, water-absorption, and aggregate-impact value have been determined a standard specification.
Table -3.5 Physical Properties of Coarse Aggregate:
Properties Test values
Specific gravity 2.73
Fineness Modulus 6.6
Water absorption 0.5
Bulk density 1.67
Aggregate impact value 24%
3.3 Mix Design:
The grade of concrete depends up on the mix design of the concrete. The mixes up to M20 are nominal mix, i.e. M5, M10, M15, M20. Where as the mix above M20 is designed mix. The mix design is based in strength criteria and durability criteria used for moderate environment. The ratios by weight of cement, fine aggregate and coarse aggregate are obtained using the specifications given in IS: 10262-2009 are given below. These proportions are maintained strictly same throughout the casting process to obtain a uniform standard and workable concrete mix. Normally Cubes were tested for compressive strength after 7 and 28 days curing. In this thesis work the age of curing at 3, 7, 14, 28, 56days are conducted.
The process of considering required amount of ingredients of concrete and also calculating their relative amounts with the objective of producing a concrete of the required, strength, durability, and workability as economically as possible, is termed the concrete mix design. The proportioning of ingredients of concrete is governed by the required performance of concrete in two states, namely the plastic and the hardened states. If the plastic concrete is not workable, it cannot be properly placed and compacted. The property of workability, therefore, becomes of vital importance
The compressive strength of hardened concrete which is generally considered to be an index of its other properties, depending upon many factors, e.g. w/c ratio quality and quantity of cement, water, aggregate, exposure conditions, material properties, mixing, placing, compaction and soaked condition. In this project we consider the design specifications such as,
Grade of concrete = M 40
Exposure condition = severe
W/C = 0.45
Slump = 100mm
Required quantity of cement fine aggregate coarse aggregate is designed and final mix proportion is obtained. By considering the above design specifications and by considering the codal provisions in IS 10262-2009 the obtained mix design for M 40 is 1:1.3:2.7
The quantities of M40 [1:1.3:2.7] mix for 1 meter cube is given below,
Cement = 437 kg
Fine aggregate = 584 kg
Coarse aggregate = 1174 kg
Water = 197 lit, W/C = 0.45
3.4 Trial Mix:
By considering the deign mix per portions of M 40 [1:1.3:2.7]. Considering the economical point of view different trial mixes are conducted by reducing the cement content and keeping the fine aggregate, coarse aggregate, and water content as constant.
Trial -1:
In this trial the cement content is reduced to 400 kg/m3 for OPC 53 and OPC 53 S cements. And the reaming materials are kept constant.
Quantity’s for 1 meter cube is,
Cement = 400 kg
Fine aggregate = 584 kg
Coarse aggregate = 1174 kg
Water = 197 litre
By considering this trial -1 design mix values, the cubes of (150*150*150 mm) are casted and are tested for 7 days and 28 days the results are given in the below table.
Table 3.6 – Compressive Strength for Trial-1 Mix
Mix Designation Compressive-Strength N/mm2
7-days 28-days
M1 36 52
M1 36.2 53
M1 40 58
Average 37.4 57.33
For M40 mix the Compressive Strength for 7 days is 2/3rd of the strength of concrete.
As per codal provision the compressive strength of concrete for 7 days = 26.66 N/mm2
Obtained Strength value is more than required value, which is uneconomical. So another trial mix is considered.
Trial -2:
By considering the M40 design mix [1:1.3:2.7], the cement content reduced to 380 kg/m3 and the reaming are kept constant. The quantities for 1 meter cube is
Cement = 380 kg
Fine aggregate = 584kg
Coarse aggregate = 1174 kg
Water =197 litre
The cubes of 150* 150*150 mm is casted and tested for 7 and 28 days the result are given in the below table
Table 3.7 – Compressive Strength for Trial-2 Mix
Mix Designation Compressive-Strength, N/mm2
7-days 28-days
M2 28.4 35.11
M2 26.4 34.33
M2 20.4 33.11
Average 25.06 34.18
For M40 mix the compressive strength for 7 days is 2/3rd of the strength of concrete.
As per codal provision the compressive strength of concrete for 7 days = 26.66 N/mm2
The obtained strength value did not satisfied the required strength value, so another trial mix is considered.
Trail – 3:
By considering the M40 design mix [1:1.3:2.7], the cement content reduced to 400 kg/m3 and the reaming are kept constant. The quantities for 1 meter cube is
Cement = 400kg
Fine aggregate = 584kg
Coarse aggregate = 1174 kg
Water =197 liter
The cubes of 150* 150*150 mm is casted and tested for 7 and 28 days the result are given in the below
Table 3.8 – Compressive Strength for Trial – 3 Mix
Mix Designation Compressive-Strength, N/mm2
7-days 28-days
M3 30.88 45.0
M3 32.0 46.0
M3 32.20 44.0
Average 31.6 45
For M40 mix the compressive strength for 7 days is 2/3rd of the strength of concrete.
As per codal provision the compressive strength of concrete for 7 days = 26.66 N/mm2
3.5 Mix Proportion:
By considering the 7 days and 28 days Compressive Strength of three different trial mixes, design mix proportion is considered for further work of thesis keeping fine aggregate, coarse aggregate and water as constant. The Design Mix Proportion for 1m3 are given below,
Cement = 410 kg/m3
Fine aggregate = 584 kg/m3
Coarse aggregate = 1174 kg/m3
Water = 197 liter/m3
W/C ratio = 0.45
Table 3.9 ‘ Mix Proportions for 1 m3
Mix Designation Cement
kg/m3 RHA
kg/m3 FA
kg/m3 CA
kg/m3
W/C ratio
R0 410 0 584 1174 0.45
R10 369 41 584 1174 0.45
R20 328 82 584 1174 0.45
R30 287 123 584 1174 0.45
R40 246 164 584 1174 0.45
RS0 410 0 584 1174 0.45
RS10 369 41 584 1174 0.45
RS20 328 82 584 1174 0.45
RS30 287 123 584 1174 0.45
RS40 246 164 584 1174 0.45
TESTS ON CONCRETE
In this chapter the methods that are adopted and tests that are conducted are explained briefly. The method adopted to obtain the design mix for M40 grade concrete is done according to IS: 10262-2009. For fresh concrete the slump cone test has been conducted and for hardened concrete the tests like Compressive Strength for cubes of size 150mm x 150mm x 150mm, Flexural Strength for prisms of size 500m x 100mm x 100mm and Split Tensile Strength for cylinders of size 150mm diameter by 300mm height has been conducted.
There are many tests available for testing the quality of concrete. The important test for quality check of concrete is that to detect the variation of concrete quality with given specification and mix design during the concrete mixing and placement. It will be ensured that right quality of concrete is placed at the site and with complete checks for concrete placement in place, the quality of the constructed concrete members will be as desired.
4.1 Preparation of test Specimen:
4.1.1. Mixing:
In the present work, machine mixing process is employed. The individual mix ingredients are weighed with their proportions exactly and then the materials are placed in machine. The materials are thoroughly mixed in their dry condition before water is added and then continuous revolution of 3-5minutes of machine is done after adding of water. The prepared mix was then immediately used for testing workability of fresh concrete mix. In case of replacement cement with Rice Husk Ash, the rice husk ash is thoroughly mixed with cement in dry state and then this was mixed with aggregate and later on water is added to the mix.
4.1.2. Casting of Specimens:
The cast iron moulds are cleaned of dust particles and applied with oil on all sides before concrete is poured in to the moulds. The moulds are placed on a level platform. The mixed concrete is placed in the oiled mold in 3 layers. After placing, each layer it is tampered 25 times using a slandered tampered rod. The strokes penetrated into the underlying layer and the bottom layer was ridded throughout its depth. And then filled concrete moulds are vibrated using machine vibrator. Excess concrete was removed with trowel and top surface is finished level and smooth as per IS 516-1959.
4.1.3. Compaction of Concrete:
Compaction of concrete is the process adopted for expelling the entrapped air from the concrete. In the process of placing and mixing of concrete, air is likely to get entrapped in the concrete. If air is not removed fully, the concrete loses strength considerably. In order to achieve full compaction and maximum density Table vibrator is used in this experiment.
4.1.4. Curing Of Test Specimen:
After casting, the moulded specimens are stored in laboratory in room temperature for 24 hours. After these periods the specimens were marked and removed from the moulds and immediately submerged in clean, fresh water curing tank for required period as per IS 516-1969. The specimens are cured for 3, 7, 14, 28 and 56days in present experimental work.
4.1.5. Tests conducted on Concrete:
Concrete tests are done on both fresh and hardened concretes. The test on fresh concrete gives the workability of the concrete mix and that of hardened concrete gives the strength parameters like Compressive Strength, Flexural Strength and Split Tensile Strength which have to be determined on increasing the age of concrete. And obtained results should fulfill the standard specifications of code provision.
4.2. Fresh Concrete:
4.2.1 Workability: Workability is the ability of a fresh concrete mix to fill the mould properly with the desired vibration and without reducing the concretes quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration) and can be modified by adding chemical admixtures, like super plasticizer. Raising the water content or adding chemical admixtures will increase concrete workability. More water content will lead to increase in bleeding and segregation of aggregates, with the results in concrete strength reduction. The use of an aggregate with an undesirable gradation can result in a very harsh mix design with a very low slump, which cannot be readily made more workable by addition of reasonable amounts of water. Workability of fresh concrete is determined by following methods,
‘ Slump Test
‘ Compacting Factor
‘ Vee- Bee Test
The slump test results in a slump of behaviour of the compacted inverted cone of concrete mix under action of gravity. It measures the consistency or the wetness of concrete mix.
In the present thesis work only Slump test is used to determine the workability of fresh concrete. The test is done as per IS: 1199 ‘ 1959.
Internal surface of mould is cleaned and then oil is applied thoroughly. Mould is placed on a surface and filled with concrete in four layers. Each layer is tamped for 25times by taming rod, tamping should be done uniformly all over the cross section. After tamping, top layer is leveled with trowel and mould is removed slowly from the concrete in vertical direction. Difference in height between level of mould and highest point of concrete is noted, which is the slump of the concrete mix.
There are three types of slump that may occur in a slumps test, namely, true slump, shear slump and collapse slump.
‘ True slump is a general drop of the concrete mass equally all around the concrete mix level without disintegration.
‘ Shear slump indicates that cohesion is less in concrete. This type of concrete mix may undergo segregation and bleeding and thus it is undesirable for the long life ie durability of concrete.
‘ Collapse slump clearly indicates that the concrete mix is too wet and it is regarded as harsh and lean.
Fig 4.1: Slump dimensions and its types
4.3. Hardened Concrete:
4.3.1. Compressive Strength:
After 28 days of curing the sample cubes are tested for compressive strength under compressive testing machine. The test samples are taken out from curing tank at least 4 to 5 hours of testing. For one trail at least three specimens are to be tested. Concrete specimen cubes are used to determine compressive strength of concrete and were tested as per IS 516-1959.
Description of Compression Testing Machine:
The compression testing machine used for testing the cube specimens is of standard make. The capacity of the testing machine is 2000KN. The machine has a facility to control the rate of loading with a control valve. The plates are cleaned and oil level is checked, and kept ready in all respects for testing.
After the required period of curing, the cube specimens are removed from the curing tank and cleaned to wipe off the surface water. It is placed on the machine such that the load is applied
Fig 4.2 Compression testing machine
centrally. The smooth surfaces of the specimen are placed on the bearing surfaces. The top plate is bought in contact with the specimen by rotating the handle. The oil pressure valve is closed and the machine is switched on. A uniform rate of loading 140kg/sq.cm/min is maintained. The compression testing machine is shown in fig 4.2
4.3.2. Flexural Strength Test:
Concrete specimen beams are used to determine flexural strength of concrete and were tested by applying two point loading as per IS 516-1959.
Description of Testing Machine for Flexural Strength:
The testing machine may be of any reliable type of sufficient capacity for the test. The bed of the testing machine shall be provided with two steel rollers, 38mm in diameter, on which the specimen is to be supported, and these rollers shall be so mounted that the distance from centre to centre 40cm for 10cm specimens. The load shall be applied through two similar rollers mounted at the third points of the supporting span i.e. spaced at 13.3cm centre to centre. The axis of the specimen shall be carefully aligned with the axis of the bearing surfaces of the specimen and the rollers. The load shall be applied without shock and increasing continuously at a rate such that the extreme fibre stress increases at approximately7kg/sqcm/min i.e., 180kg/min for the 10.0cm specimens. The arrangement for loading of flexural specimen is shown in fig 4.3 and universal testing specimen is shown in fig,
Fig 4.3 Arrangement for loading of flexural test specimen
Fig 4.4 Universal testing machine
4.3.3 Split Tensile Test:
The specimens are tested for tensile strength for 28 days on split tensile testing machine. Specimens, preferably from different batches, should be made for testing for each selected age. Specimens are removed from water before 4 to 5 hours of testing.
Fig 4.5: Split tensile strength Specimen
In the case of cylinders the specimen should be placed in the machine in such a manner that the load is applied on the surface of the cylinder, (i.e. along the length of the cylinder) continuously load is applied at the rate of approximately 140Kg/cm2/min. until the resistance of the specimen to the increasing load breaks down and no greater load can be sustained. The measured split tensile strength of the 29 specimen is calculated by dividing the two times of the load during the test by the surface area, calculated from the mean dimensions of the section. Average of the three values should be taken as the representative of the batch, provided the individual variation is not more than 15% of the average. Otherwise test should be repeated.
RESULTS AND DISCUSSION
Tests are conducted for concrete made of replacement of cement with Rice Husk Ash and the compressive strength and flexure strength are studied for different ages of curing. In this thesis work OPC 53 and OPC 53 S two different types of cements are used and comparison between the obtained strength values have observed. The results are tabulated and discussions have been made.
5.1 Compressive Strength Results:
Concrete cubes are casted for normal mix at 0%, 10%, 20%, 30% and 40% replacement of Rice Husk Ash. The compressive strength for M40 grade is tested for 3 to 56days age of curing for both OPC 53 and OPC 53 S cements and the obtained results are tabulated in the form of table and graph.
Table -5.1 Compressive-Strength of OPC 53 Cement for different days, N/mm2
Mix Designation Compressive-Strength, N/mm2
3-days 7-days 14-days 28-days 56-days
R0 27.66 34.16 40.50 41.00 43.00
R10 30.83 35.50 41.83 44.00 49.30
R20 28.50 36.00 45.16 50.50 57.60
R30 27.16 31.66 43.00 48.50 49.50
R40 23.83 29.16 36.00 44.00 45.00
Note:
R0, R10, R20, R30, R40 ‘ Concrete mix with 0%, 10%, 20%, 30%, 40% replacement of Rice
Husk Ash with OPC 53 Cement
Graph 1: Compressive Strength of Concrete with OPC 53 at 3, 7, 14, 28 and 56 days age of curing
Table -5.2 Compressive-Strength of OPC 53 S Cement for different days, N/mm2
Mix Designation Compressive-Strength, N/mm2
3-days 7-days 14-days 28-days 56-days
RS0 30.66 35.16 43.10 46.50 48.00
RS10 33.66 38.00 47.00 48.50 55.30
RS20 29.00 38.50 50.83 54.50 58.50
RS30 27.50 37.00 46.16 52.00 54.50
RS40 24.00 31.00 38.83 49.50 53.00
Note: RS0, RS10, RS20, RS30, RS40 ‘ Concrete mix with 0%, 10%, 20%, 30%, 40% replacement of Rice Husk Ash with OPC 53 S Cement
Graph 2: Compressive Strength of Concrete with OPC 53 S at 3, 7, 14, 28 and 56 days age of curing
The above graphs for OPC 53 and OPC 53 S clearly shows that by increasing the percentage of RHA, compressive strength of concrete increased up to 20% partial replacement of RHA when comparing that of normal concrete. Further increase of RHA has decreased the compressive strength of concrete.
Comparison Compressive-Strength of Concrete with OPC 53 Cement and OPC 53 S Cement at different Ages of Curing:
The Compressive-Strength of Concrete cubes casted with both OPC 53 and OPC 53 S Cements with partial replacement of Rice Husk Ash with 0% to 40% at 3, 7, 14, 28 and 56days are shown in the below table.
Table -5.3 Compressive-Strength of OPC 53 and OPC 53 S Cement for different days, N/mm2
Mix Designation Compressive-Strength, N/mm2
3-days 7-days 14-days 28-days 56-days
R0 27.66 34.16 40.50 41.00 43.00
R10 30.83 35.50 41.83 44.00 49.30
R20 28.50 36.00 45.16 50.50 57.60
R30 27.16 31.66 43.00 48.50 49.50
R40 23.83 29.16 36.00 44.00 45.00
RS0 30.66 35.16 43.10 46.50 48.00
RS10 33.66 38.00 47.00 48.50 55.30
RS20 29.00 38.50 50.83 54.50 58.50
RS30 27.50 37.00 46.16 52.00 54.50
RS40 24.00 31.00 38.83 49.50 53.00
By observing the values of compressive strength of OPC 53 and OPC 53 with partial replacement of RHA it is clear that test results obtained for OPC 53 S are more than OPC 53 The same is shown in the below graphs at different ages of curing
Note:
R0, R10, R20, R30, R40 ‘ Concrete mix with 0%, 10%, 20%, 30%, 40% replacement of Rice
Husk Ash with OPC 53 S Cement.
RS0, RS10, RS20, RS30, RS40 ‘ Concrete mix with 0%, 10%, 20%, 30%, 40% replacement of
Rice Husk Ash with OPC 53 S Cement.
‘ At 3-days age of curing:
Graph 3: Comparison of OPC 53 and OPC 53 S Cements at 3-days age of curing
‘ At 7-days age of Curing:
Graph 4: Comparison of OPC 53 and OPC 53 S Cements at 7-days age of curing
‘ At 14-days age of Curing:
Graph 5: Comparison of OPC 53 and OPC 53 S Cements at 14-days age of curing
‘ At 28-days age of Curing:
Graph 6: Comparison of OPC 53 and OPC 53 S Cements at 28-days age of curing
‘ At 56-days age of Curing:
Graph 7: Comparison of OPC 53 and OPC 53 S Cements at 56-days age of curing
Comparing results with the literature review of Suresh Kulakarni with Project results of OPC 53 Cement:
Table 5.4 Comparison of Compressive-Strength at 28-days Results
Literature Review Project Results
Mix Proportion Compressive-Strength N/mm2 Mix Proportion Compressive-Strength N/mm2
M0 37.0 R0 41.0
M10 42.8 R10 44.0
M20 39.8 R20 50.5
M30 37.0 R30 48.5
– – R40 44.0
Graph 8: Comparison of Compressive Strength of OPC 53 Cement with Literature Review results at 28-days age of curing
5.2 Flexural Strength:
Concrete cubes are casted for normal mix at 0%, 10%, 20%, 30% and 40% replacement of Rice Husk Ash. The Flexural Strength for M40 grade is tested for 28days age of curing for both OPC 53 and OPC 53 S cements and the obtained results are tabulated in the form of table and graph.
Table 5.5: Flexural Strength of OPC 53 Cement at 28 days age of curing
Mix Designation Flexural-Strength N/mm2
R0 5.6
R10 6.0
R20 7.0
R30 6.5
R40 6.25
Graph 9: Flexural Strength of OPC 53 Cement at 28days age of curing
Table 5.6: Flexural Strength of OPC 53 S Cement at 28 days age of curing
Mix Designation Flexural-Strength N/mm2
RS0 6.4
RS10 7.0
RS20 7.75
RS30 7.5
RS40 6.5
Graph 10: Flexural Strength of OPC 53 S Cement at 28days age of curing
The above graphs for OPC 53 and OPC 53 S clearly shows that by increasing the percentage of RHA, flexural strength of concrete increased up to 20% partial replacement of RHA when comparing that of normal concrete. Further increase of RHA has decreased the flexural strength of concrete.
Comparing Flexural-Strength of Concrete with OPC53 Cement and OPC53S Cement at 28days Age of Curing:
The Flexural-Strength of Concrete Prisms casted with both OPC 53 and OPC 53 S Cements with partial replacement of Rice Husk Ash with 0% to 40% at 28 days are shown in the below table.
Table 5.7: Flexural Strength of OPC 53 S Cement at 28 days age of curing
Mix Designation Flexural-Strength, N/mm2
R0 5.6
R10 6.0
R20 7.0
R30 6.5
R40 6.25
RS0 6.4
RS10 7.0
RS20 7.75
RS30 7.5
RS40 6.5
By observing the values of flexural strength of OPC 53 and OPC 53 with partial replacement of RHA it is clear that test results obtained for OPC 53 S are more than OPC 53 The same is shown in the below graphs at 28-days ages of curing.
Graph 11: Comparison of Flexural-Strength of OPC 53 and OPC 53 S Cements at 28-days age of curing
5.3 Split Tensile Strength:
Concrete cylinders are casted for normal mix at 0%, 10%, 20%, 30% and 40% replacement of Rice Husk Ash. The Split Tensile Strength for M40 grade is tested for 28days age of curing for both OPC 53 and OPC 53 S cements and the obtained results are tabulated in the form of table and graph.
Table 5.8: Split Tensile Strength of OPC 53 Cement at 28 days age of curing
Mix Designation Split Tensile-Strength N/mm2
R0 5.6
R10 6.0
R20 7.0
R30 6.5
R40 6.25
Graph 12: Split Tensile Strength of OPC 53 Cement at 28days age of curing
Table 5.9: Split Tensile Strength of OPC 53 S Cement at 28 days age of curing
Mix Designation Split Tensile Strength N/mm2
RS0 6.4
RS10 7.0
RS20 7.75
RS30 7.5
RS40 6.5
Graph13: Split Tensile Strength of OPC 53 S Cement at 28days age of curing
The above graphs for OPC 53 and OPC 53 S clearly shows that by increasing the percentage of RHA, split tensile strength of concrete increased up to 20% partial replacement of RHA when comparing that of normal concrete. Further increase of RHA has decreased the split tensile strength of concrete.
Comparing Split Tensile Strength of Concrete with OPC 53 Cement and OPC 53 S Cement at 28days Age of Curing:
The Split Tensile Strength of Concrete Prisms casted with both OPC 53 and OPC 53 S Cements with partial replacement of Rice Husk Ash with 0% to 40% at 28 days are shown in the below table and graph.
Table -5.10 Split Tensile Strength of OPC 53 and OPC 53 S Cement for different days, N/mm2
Mix Designation Split Tensile-Strength, N/mm2
R0 5.6
R10 6.0
R20 7.0
R30 6.5
R40 6.25
RS0 6.4
RS10 7.0
RS20 7.75
RS30 7.5
RS40 6.5
By observing the values of split tensile strength of OPC 53 and OPC 53 with partial replacement of RHA it is clear that test results obtained for OPC 53 S are more than OPC 53 The same is shown in the below graphs at 28-days ages of curing.
Graph 14: Comparing Split Tensile -Strength of OPC 53 and OPC 53 S Cements at 28-days age of curing
CONCLUSION AND FUTURE SCOPE
Summary:
The need to study the role of supplementary cementing materials like Rice Husk Ash in concrete has been justified.
Concrete cubes were cast, cured and tested for Compressive strength. Flexural strength and Split tensile strength with OPC 53 and OPC 53 S cement. The results have been presented in the form of tables and graphs in detail.
6.1 Conclusions:
1. Early strength is slightly less in RHA Blended Cement Concrete than the conventional concrete.
2. An increase of around 23.1 %, 33.9% compressive strength for RHA blended cement concrete when replaced with 20% of OPC 53 cement at 28 and 56 days age of normal curing.
3. An increase of around 17.2 %, 21.8% of compressive strength is observed for RHA blended cement concrete when replaced with 20% of OPC 53 S cements at the age of 28, 56 days normal curing.
4. The split tensile, flexure strength results of RHA blended cement concretes when replaced up to 20 % is more than the conventional aggregate concrete at age of 28 days of normal curing
5. An increase of about 25 %, 8.74% of Flexural and Split tensile strength for RHA blended cement concrete when replaced with 20% of OPC 53 cement at 28 days age of normal curing.
6. Comparative study on Rice Husk Ash concrete with various replacement percentages of RHA showed that, a replacement level of 20% RHA in concrete performs and shows better strength than other replacements.
7. For M40 grade of concrete 20% replacement showed better Compressive Strength than normal concrete and also showed better strength values in case of Flexural and Split Tensile Strengths.
8. Hence the optimum replacement level of RHA is found to be 20% for M40 grade of concrete.
9. As the cement replacement by RHA in concrete increases, the workability of concrete decreases.
10. As the Rice Husk Ash is waste material, it reduces the cost of construction and reduces pollution in environment.
6.2 Scope for Further Study:
Although several studies were conducted on behavior of normal concrete and by replacing cement with RHA concrete were studied earlier. Different physical and mechanical properties on RHA concrete were also studied to find the optimum dosage of RHA. On normal concrete several studies conducted with sulphate attack and alkaline attacks on RHA were studied later, the research pertaining to the effect of sea water on RHA concrete studies are less. Following few avenues may be studied further to understand the behavior and to deliver guidelines useful for design of concrete structures.
‘ Effect of different admixtures to improve the strength of RHA concretes further.
‘ The grade of cement (OPC) used in present study is 53. The study can be further investigated with 43 and 33 grades of OPC.
‘ Durability studies of RHA concrete exposed to elevated temperatures with different cooling conditions.
‘ Studies on RHA concretes exposed to acid, alkaline media.
‘ Studies on reinforced RHA concretes exposed to acid, alkaline and sea water media.
‘ Durability studies of RHA concrete replaced by OPC 53 S cement to elevated temperatures with different cooling conditions.
REFERENCES
‘ Reddy D V., and Alvarez B S M, ‘Marine Durability Characteristics of Rice Husk Ash-Modified Reinforced Concrete’, Fourth LACCEI International Latin American and Caribbean Conference for Engineering and Technology (LACCET), June 2006.
‘ Kartini K, ‘Rice Husk Ash ‘ Pozzolanic Material for Sustainability’ International Journal of Applied Science and Technology, International Journal of Applied Science and Technology
‘ Thiruchelvam S, ‘Efficiency of Rice Production and Issues relating to Cost of Production in the Districs of Anuradhapura and Polannaruwa’, Natn J, Sci.Foundation Sri Lanka 2005 33(4), October 2005, pp. 247-256
‘ Nair D G, Jagadish K S, Fraaij A (2006). ‘Reactive pozzolanas from rice husk ash: An alternative to cement for rural housing.’ Cement and Concrete Research, (36), 1062-1071
‘ Barbhuiya A S, Nimityongskul P and Chitasombuti; (2006), ‘Use of classified rice husk ash for high strength concrete’, The Indian concrete journal, May, 11-16.
‘ Giaccio G, Sensale G R, and Zerbino R (2007), ‘Failure mechanism of normal and high strength concrete with rice husk ash’, Cement and concrete composites, 29
‘ Uduweriya R B Y B, Subash C, Sulfy M M A and Sudhira De Silva (2010) ‘Investigation of Compressive Strength of concrete containing Rice Husk Ash’, International Conference on Sustainable Built Environment (ICSBE-2010) Kandy, 13-14 December 2010.
‘ Makarand Suresh Kulkarni, Paresh GovindMirgal, Prajyot Prakash Bodhale, Tande S N (2014) ‘Effect of Rice Husk Ash on Properties of Concrete’, Journal of Civil Engineering and Environmental Technology, Print ISSN: 2349-8404; Online ISSN: 2349-879X; Volume 1, Number 1; August, 2014 pp. 26-2.
‘ Deepa G Nair, K. Sivaraman, and Job Thomas(2013) ‘Mechanical Properties of Rice Husk Ash (RHA) ‘ High strength Concrete’, American Journal of Engineering Research (AJER) e-ISSN : 2320-0847 p-ISSN : 2320-093, Volume-3 pp-14-19.
‘ Padma Rao P, Pradhan Kumar A, Bhaskar Singh B (2014) ‘A Study on Use of Rice Husk Ash in Concrete’, IJEAR Vol. 4, Issue Spl-2, Jan – June 2014 ISSN: 2348-0033 (Online) ISSN: 2249-4944 (Print).
‘ Dabai M U, Muhammad C, Bagudo B U and Musa A (2009) ‘Studies on the Effect of Rice Husk Ash as Cement Admixture’, Nigerian Journal of Basic and Applied Science (2009), 17(2)252-256
‘ Godwin A Akeke, Maurice E Ephraim, Akobo, I Z S and Joseph O Ukpata (2013) ‘Structural Properties of Rice Husk Ash Concrete’, International Journal of Engineering and Applied Sciences, May 2013. Vol. 3, No. 3
‘ Sathish Kumar R (2012) ‘Experimental study on the properties of concrete made with alternate construction materials’, International Journal of Modern Engineering Research (IJMER) Vol. 2, Issue. 5, Sept.-Oct. 2012 pp-3006-3012.
‘ Gyanen Takhelmayum, Ravi Prasad, Savitha A L (2014) ‘Experimental Study on the Properties of cement concrete using Rice Husk Ash’, International Journal of Engineering Science and Innovative Technology (IJESIT) Volume 3, Issue 6, November 2014.
‘ Ramadhyansyah Putra Jaya (2011)’Strength and permeability properties of concrete containing rice husk ash with different grinding time’, Central European Journal of Engineering, March 2011, Volume 1, Issue 1, pp 103112.
‘ Ettu L O, Ajoku C A, Nwachukwu K.C (2013) ‘Strength variation of OPC-rice husk ash composites with percentage rice husk ash’, Int. Journal of Applied Sciences and Engineering Research, Vol. 2, Issue 4, 2013.
‘ IS 383-1970(Properties of fine and coarse aggregate)
‘ IS 456-2000(w/c & cement)
‘ IS 4031-1988(Methods of physical tests for hydraulic cement)
‘ IS 12269-1987( Specifications of OPC 53 cement)
‘ IS 10262-2009(Design mix)
‘ IS 1727-1967( Methods of test for pozzolanic materials )
‘ IS 516-1959(Methods of test for strength of concrete )
APPENDIX
Appendix I
Method of Concrete Mix Proportion:
IS 10262-2009 suggests concrete mix design processes for both air-entrained and non-air-entrained concrete. Both the methods are based on the following principles:
‘ The workability of the mix depends on the water content and the maximum size of aggregates.
‘ The water-cement ratio (w/c ratio) is solely dependent upon the design strength with a restriction from the durability point of view. The w/c ratio is inversely proportional to the design strength.
‘ The bulk volume of coarse aggregate per unit volume of concrete depends on the maximum size of the coarse aggregate and the grading of the fine aggregate, expressed as the fineness modulus.
‘ The design starts with the selection of water content for a given maximum size of coarse aggregate and workability required for the type of work, with workability being expressed by slump.
‘ Cement content is then found out simply from this water content and the w/c ratio, determined earlier on the basis of the design strength.
‘ The volume of coarse aggregate is then determined and fine aggregate content is found out by subtracting the volume (or weight) of other ingredients from the total volume (or weight) of concrete.
‘ The weight basis is a trial and error approach while the volume basis is more direct and gives a more accurate result.
Design Procedure:
The IS 10262-2009 Recommended Practice for Selecting Proportions for Concrete. The procedure is as follows:
M40 Mix Design Procedure:
Design Stipulations
Grade of concrete: M40
Size of aggregate: 20 mm & 10mm
Degree of workability: 0.90
Degree of quality control: good
Type of exposure: severe
Grade of cement: 53 grade ordinary Portland cement
Test Data for Materials
Specific gravity of cement: 3.15
Specific gravity of fine aggregate: 2.52
Specific gravity of coarse aggregate: 2.73
Water absorption of fine aggregate: 1%
Water absorption of coarse aggregate: 0.5%
Aggregate Impact value: 24% (Exceptionally Strong)
Fineness modulus of fine aggregate: 2.2
Fineness modulus of coarse aggregate: 6.6
Fine aggregate: Sand zone III according to IS: 383 – 1970
Coarse aggregate: Confirming to IS: 383 -1970
Target Mean Strength:
Fck’ = Target Mean Strength
Fck = Specified Compressive Characteristic Strength = 40 N/mm2
S = Standard deviation = 5
Target Mean Strength, Fck’ = Fck+1.65*S = 40 + 1.65*5= 48.24 N/mm2
Step-1 Choice of slump
The value of slump height is taken from the code based on the type of work. Slump Height is considered as 100 mm.
Step-2 Choice of maximum size of aggregate
It based on the principle that the Maximum size of aggregate should be the largest available so long it is consistent with the dimensions of the structure. When high strength concrete is desired, best results may be obtained with reduced maximum sizes of aggregate as they produce higher strengths at a given w/c ratio. The maximum size of Coarse aggregate is considered as 20 mm
Step-3 Estimation of mixing water
From table – 2 of IS 10262-2009, maximum water content for 20mm aggregate = 186 liters (for 25 to 50 mm slump)
Estimated water content for 100 mm slump = 197 liters.
Step-4 Selection of water/cement ratio
Step-5 Calculation of cement content
Water/cement ratio = 0.45
Water content = 197 kg/m3
Specific gravity = 3.15
Cement content = 197 / 0.45 = 437.77 kg
Step-6 Estimation of coarse aggregate and fine aggregate content
Form table -3 of IS 10262-2009. Volume of fine aggregate by considering coarse aggregate size 20mm and water cement ratio
The volume of coarse aggregate = 0.64
Considering the corrections the volume of the coarse aggregate is = 0.65.
Volume of fine aggregate = 0.35.
Step-7 Volume based calculation
Volume of water = 197/1000 = 0.197 m3
Volume of Cement = 437.77 / (3.15 x 1000) = 0.138m3
Volume of concrete = 1m3
Volume of cement = 0.13m3
Volume of water = 0.197 m3
Volume of all in aggregate = 0.675 m3
Mass of coarse aggregate = 1174 kg.
Mass of fine aggregate = 584 kg
Mix proportions for 1 meter cube:
Cement = 437 kg/m3
Fine aggregate = 584 kg/m3
Coarse aggregate = 1174 kg/m3
Water = 197 litre/m3
Final Mix Proportions-
C : F.A : C.A
1 : 1.3 : 2.7
Appendix II
Slump test:
Slump test is used to determine the workability of fresh concrete. The slump test result is a measure of the behavior of a self ‘ compacted inverted cone of concrete under the action of gravity. It is a measure of the concretes workability or the dampness of concrete. Slump test as per IS 1199-1959 is followed. The apparatus used for doing slump test are slump cone and tamping rod.
Procedure to determine workability of fresh concrete by slump test:
1) The internal surface of the mould is thoroughly cleaned and applied with alight coat of oil.
2) The mould is placed on smooth, horizontal, rigid and a nonabsorbent surface.
3) The mould is then filled in four layers with freshly mixed concrete, each approximately to one ‘ fourth of the height of the mould.
4) Each layer is tampered 25 times by the rounded end of tamping rod ( strokes are distributed evenly over the cross section).
5) After the top layer is tampered, the concrete is struck off the level with a trowel.
6) The mould is removed from the concrete immediately by raising it slowly in the vertical direction.
7) The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured.
8) This difference in height in mm is the slump of the concrete.
Compressive Strength:
The cube specimens are tested for compressive strength for 28 days on compressive strength testing machine, at least three specimens. Preferably from different batches, should be made for each selected age. Specimens are removed from just before 4 to 5 hours of testing.
In the case of cubes the specimen should be placed in the machine in such a manner that the load is applied to the opposite sides of the cubes are casted, continuously load is applied at the rate of approximately 140kg/cm2/min. until the resistance of the specimen to the increasing load breaks down and no greater load can be sustained. The measured compressive strength of the specimen is calculated by dividing the maximum load applied to the specimen during the test by the cross sectional area. Average of 3 values should be taken as the representative of the batch, provided the individual variation is not more than 15% of the average .otherwise test should be repeated.
Spilt Tensile Strength:
The specimens are tested for tensile strength for 28 days on split tensile testing machine. Specimens, preferably from different batches, should be made for testing for each selected age. Specimens are removed from water before 4 to 5 hours of testing.
In the case of cylinder the specimen should be placed in the machine in such a manner that the load is applied on the surface of the cylinder, (i.e. along the length of the cylinder) continuously load is applied at the rate of approximately 140 kg/cm2 / min. until the resistances of the specimen to the increasing load breaks down and no greater load can be sustained. The measured spilt tensile strength of the specimen is calculated by dividing the two times of the load during the test by the surface area, calculated from the mean dimensions of the section. Average of the three values should be taken as the representative of the batch, provided the individual variation is not more than 15% of the average. Otherwise test should be repeated.
Flexural Strength:
The bearing surfaces of the supporting and loading rollers shall be wiped clean, and any loose sand or other materials are removed from the surfaces of the specimen where they are to make contact with rollers, the specimen shall than be placed in the machine in such a manner that the load shall be applied to the uppermost surface as cast in the mould, along two lines sapped 20.0 or 13.3 cm apart.
The axis of the specimen shall be carefully aligned with the axis of the loading devices. No packing shall be used between the bearing surfaces of the specimen and the rollers. The load shall be applied without shock and increasing continuously at a rate such that the extreme fiber stress increases at approximately 7 kg/cm2/min, that is, at a rate of loading of 400 kg/min for the 15 cm. Specimens and at rate of 180 kg/min for the 10.0 cm specimens. The load shall be increased until the specimen fails, and the maximum load applied to the specimen during the test shall be recorded. The appearance of the fractured faces of concrete and any unusual features in the type of failures shall be noted.
The flexural strength would be the same as the tensile strength if the material was homogenous. In fact, most materials have small or large defects in them which act to concentrate the stress locally, effectively causing localizes weakness. When a material is bent only the extreme fibers are at the largest stress so, if those fibers are free from defects, the flexural strength will be controlled by strength of those intact fibers. However , if the same material was subjected to only tensile forces then all the fibers in the materials are at the same stress and failure will initiate when the weakest fibers reaches its limiting tensile stress. Therefore it is common for flexural strengths to be higher than tensile strengths for the same materials. Conversely, a homogeneous materials with defects only on its surfaces (e.g. due to scratches) might have a higher tensile strength than flexure strength.
For a rectangular sample under a load in a three- point bending setup
” = 3FL/2bd2
F is the load at the fracture point
L is the length of the support span
B is width
D is thickness
For a rectangular sample under a load in a four- point bending setup where the loading Span is one-third of the support span.
”= FL/bd2
For the 4pt bend setup, if the loading span is 1/2 of the support span (i.e. L=1/2L)
” = 3FL/4bd2
If the loading span is either 1/3 or 1/2 the support spans for the 4 pt bend setup
Appendix III
Collection of Materials, Batching, and Weighing:
Mixing and Placing:
Curing:
Testing: