PERFORMANCE STUDY OF LOCALLY AVAILABLE COARSE AGGREGATES OF AZAD KASHMIR.
ABSTRACT: This paper presents results of an experimental study carried out to investigate the suitability of using locally available coarse aggregates in Azad Kashmir to make concrete. Aggregate samples were collected from three different quarries according to ASTM sampling procedure. The experiments were performed on collected samples of coarse aggregates to evaluate their physical and mechanical properties as per ASTM and BS standards. Concrete compositions made using the same aggregates were tested for mechanical properties (compressive strength and tensile strength). The results of this study showed that the concrete made using locally available aggregates in Azad Kashmir performed satisfactorily in terms of mechanical properties. Moreover, their performance was found to be quite similar to those aggregates commonly available and used in Pakistan such as Margallah and Sargodha aggregates.
Key words: Concrete; coarse aggregate; physical properties; mechanical properties; ASTM.
Approximately three quarters of the volume of concrete is occupied by the aggregates. The strength, durability and structural performance of concrete are greatly affected by the properties of fine and coarse aggregates (Ayub et al. 2012; Joseph et al. 2012). Aggregates are formed either by the natural process of weathering and abrasion or by artificially crushing parent rock. Thus many properties of the aggregate such as chemical and mineral composition, specific gravity, hardness, strength, physical and chemical stability and porosity depend on the properties of parent rocks (Tasong et al. 1998; Elsharief et al. 2003; Makani, 2011). In addition to above mentioned properties, some other properties which are not dependent on parent rocks such as particle size distribution, surface texture and absorption considerably influence the quality of concrete in fresh and hardened state (Neville, 2005; Akcaoglu et al. 2004; Basheer et al. 2005, Makani et al. 2010; Meddah et al. 2010).
The use of locally available construction materials in any area may reduce the cost of the project appreciably. There are many quarries of aggregates in Azad Kashmir and the aggregates obtained from these sources are being used by the local construction industries in rigid pavements and buildings. However, no detailed and scientific research study has yet been carried out to determine the suitability of locally available aggregates to make concrete of required strength and durability.
The present research study deals with determination of physical and mechanical properties of three different types of aggregates collected from Azad Kashmir. Moreover, mechanical properties of concrete made by using the same aggregates have also been studied. The mechanical properties of concrete which were studied include compressive strength, tensile strength, and modulus of rupture.
For this study, three quarries named as Hajira, Kamser and Arja in Azad Kashmir were explored. Hajira is a tehsil of district Poonch, 29 km from the south east of Rawalakot. Kamser is a place 10 km north of Muzaffarabad city and is situated near Nisar camp on Nelum valley road. Arja is located 16 km North West of district Bagh and 30 km from district Poonch.
MATERIALS AND METHODS
A comprehensive experimental program was designed and carried out to determine physical and mechanical properties of aggregates. In addition to that, tests on hardened concrete made using aggregates from Azad Kashmir and also commonly used aggregates in Pakistan (Sargodha and Marghallah crush) were also performed under the scope of this experimental study.
Physical Properties of Aggregates: Following physical properties of aggregates were studied:
* Specific gravity and water absorption
* Unit weight and voids
* Flakiness and elongation index
Specific gravity and water absorption: Specific gravity and water absorption of aggregates under investigation were determined using ASTM standard C-127. The values of specific gravity and water absorption of aggregates investigated in this experimental study have been graphically presented in Fig.1 and Fig.2,respectively. It is obvious from these above figures that the specific gravity and water absorption of aggregates obtained from Azad Kashmir are similar to that of Marghalla and Sargodha aggregates.
Unit Weight: Unit weight of aggregates under investigation was determined following ASTM C-29 procedure. During this test, the volume of bucket is calibrated using water and then the calibrated bucket is used to determine the unit weight of coarse aggregate. The values of unit weight of different aggregates investigated under the scope of this study have been graphically presented in Fig.3 along with upper and lower limits as specified by ASTM. The results clearly indicate that unit weight of aggregate obtained from Kashmir is Pakistan and also satisfies the ASTM Limits.
Flakiness and Elongation Index: Flakiness and Elongation Index values of aggregates studied were determined as per British Standard (BS 812). Flakiness index (FI) is a measure of the percentage weight of particles whose least dimension is less than 0.6 times the mean dimension and Elongation Index (EI) is the percentage weight of particles whose longer dimension is more than 1.8 times the mean dimension. The values of FI and EI of aggregates obtained from Azad Kashmir are presented graphically in Fig. 4. It is observed that FI and EI values of aggregates under investigation are within the limits prescribed by BS Standards.
Mechanical Properties of Aggregates: Following mechanical properties of aggregates were studied as per British Standards:
* Aggregate Impact Value
* Aggregate Crushing Value
Aggregate Impact Value (AIV): It is a relative measure of resistance to crushing of an aggregate when it is subjected to repetitive and impact loads and is calculated using Equation 1. To determine AIV of aggregates, Where M1 = Mass of the test specimen and M2 = Mass of the test specimen passing 2.36 mm test sieve after impact loading The comparison of AIV of Azad Kashmir crush aggregates with Margalla and Sargodha is shown in Fig.5. It is observed that AIV of Arja aggregates is similar to that of Sargodha aggregates. However, aggregates obtained from Kamser quarries exhibited AIV lesser than that of both Marghalla and Sargodha aggregates.
Aggregate Crushing Value (ACV): It is a relative measure of resistance of an aggregate to crushing when it is subjected to compressive forces and is calculated using Eq.2. British Standard (BS 812-110) is followed to determine ACV. The comparison of ACV of Azad Kashmir aggregates with Marghallah and Sargodha is shown in Fig.6. It is observed that the ACV of aggregates obtained from Azad Kashmir is close to values of Margallah and Sargodha crush commonly used in Pakistan.
Where, A = Mass of sample placed in three layers in 150mm hardened steel cylinder and B = Fraction passing through 2.36mm sieve after the loading.
Mechanical Properties of Hardened Concrete Concrete Composition: For all types of concrete, locally available Ordinary Portland Cement (OPC) was used.
Lawrencepur sand was used as fine aggregates in all compositions of concrete. Different coarse aggregates used to make concrete were Hajira, Kamser, Arja, Sargodha and Marghallah. Maximum size of coarse aggregate used in concrete was 19mm. Water cement ratio for all concrete mixes was kept as 0.55. Composition of the concrete is given in Table 1.
Table 1: Concrete Composition
Concrete Constituent###Quantity (kg/m3)
Compressive Strength of Concrete: The specimens of concrete cylinders were tested at 28 days age in saturated surface dry condition for determination of compressive strength. Cylinders were tested following the procedure of ASTM C 39-86. Test specimens were capped before testing. For each concrete type, three cylinders were tested. Compressive strength values of each tested sample are given in table 2. Compressive strength values (average of three specimens) of concrete made using three aggregate samples available in Azad Kashmir (Hajira, Kamser and Arja aggregates) and two commonly used aggregates in Pakistan are graphically presented in Fig.7. Regarding the nomenclature of different concretes tested in this study, 'Conc' stands for concrete and the second word represents the aggregate type. For example, "Conc-Hajira" means concrete made using Hajira aggregates.
Among the three aggregates obtained from Azad Kashmir, Arja aggregates when used in concrete yielded maximum compressive strength which is even higher than the concrete containing Marghallah and Sargodha aggregates.
Table 2: Compressive and indirect tensile strength
###Strength, Mpa###Strength, MPa
Indirect Tensile Strength of Concrete: The splitting tensile strength is determined according to ASTM-C496 at 28 days using cylinders measuring 150 mm (diameter) x 300 mm (height) and cured in water till the date of test.
For each composition of concrete, three cylindrical specimens were tested. The value of each sample is given in table 2. Average indirect tensile (i.e. splitting) strength values of five different concretes tested in this study are presented in Fig.8. Among five different concretes, concrete containing Hajira aggregates exhibited maximum value of splitting tensile strength. The results clearly depict that aggregates obtained from Azad Kashmir performed satisfactorily in terms of splitting tensile strength when compared to Marghalla and Sargodha aggregates.
RESULTS AND DISCUSSION
To control the economy of any construction project, availability of local construction materials to make concrete of required properties plays major role. Capital required for the transportation of constructing materials form one site to another remote site may raise the cost of the project significantly. Moreover, for the management of any construction project, time spent in transportation of construction materials is also important. At present, in most of the construction project in Azad Kashmir area, aggregates from Sargodha (450 km away from Azad Kashmir) and aggregates from Marghallah (150 km away from Azad Kashmir) are transported and used. The time and cost involved in the transportation of these aggregates always cause significant increase in the overall cost of the construction project.
Physical tests on concrete, like grading, Flakiness and Elongation Index, performed on the locally available aggregates in Azad Kashmir as per American and British standards have shown that these aggregates are suitable to make concrete of required properties. Comparison of specific gravity values of aggregates from Azad Kashmir with commonly used aggregates in Pakistan has shown that specific gravity of Hajira and Arja aggregates is similar to that of Sargodha crush while specific gravity of Kamser aggregate is similar to that of Marghallah crush. Among the three aggregates from Azad Kashmir, Kamser aggregate exhibited the lowest value of water absorption which was 75.7 (Percent) and 68.6 (Percent) of the Sargodha and Marghallah aggregates, respectively.
Similarly, maximum value of water absorption was obtained with Hajira aggregate which was 14.6 (Percent) greater than the water absorption of Marghallah crush and 26.4 (Percent) greater than the value of Sargodha crush.
Aggregate Impact value (AIV) and Aggregate Crushing value (ACV) of coarse aggregates play major role in development of resistance in hardened concrete against impact and compressive loads, respectively. In case of ultra high strength concrete, the failure in compression is always due to breakage of coarse aggregate particles (Zhou et al. 1991; Wu et al. 2001; Ghaffar et al. 2001; Ghaffar, 2012) and aggregate crushing value has great importance; greater is the ACV, more is the strength of concrete. The results of this study concerning AIV and ACV of aggregates obtained from Azad Kashmir and commonly used aggregates in Pakistan indicate that aggregates from Azad Kashmir can be used in concrete with confidence. The AIV exhibited by Hajira aggregate was close to the value of Marghallah aggregate. Out of three aggregates from Azad Kashmir, the lowest value of AIV was yielded by Kamser aggregate. AIV of Arja aggregates was found to be almost similar to that of Sargodha crush.
The minor variations in physical properties of Azad Kashmir and commonly used aggregates in Pakistan are due to different characteristics of their parent rocks and different method of crushing.
Three basic mechanical tests were performed on concrete made using five aggregates investigated under the scope of this study. The properties of hardened concrete which were determined include compressive strength, tensile strength and modulus of rupture (MOR). Among three different aggregates from Azad Kashmir, the maximum compressive strength was exhibited by concrete containing Arja aggregates and the value was even greater than compressive strength of concrete made using Marghallah and Sargodha crush. Compressive strength values of concretes containing Hajira and Kamser aggregates were also close to the value of concretes containing Sargodha and Marghallah crush.
It is obvious that all three aggregates obtained from three quarries in Azad Kashmir may be employed to produce concrete of required compressive strength.
From the results of indirect tensile strength, it is observed that concretes made using Hajira and Arja aggregates developed tensile strength greater than concrete containing Sargodha and Marghallah crush. The lowest value of indirect tensile strength was exhibited by concrete containing Kamser aggregates.
Conclusions: The results of some basic physical and mechanical tests on aggregates obtained from Hajira, Kamser and Arja quarries of Azad Kashmir indicate that aggregates locally available in Azad Kashmir region of Pakistan may be used with confidence to make concrete of required properties. Furthermore, concrete made from all three aggregates (i.e., Hajira, Kamser and Arja aggregates) have the potential to develop similar compressive strength, indirect tensile strength and modulus of rupture as that obtained with concrete containing commonly used Marghalla and Sargodha aggregates in Pakistan. The use of Hajira, Kamser and Arja aggregates in local projects in Azad Kashmir will reduce the cost of the project appreciably. The future research work in the same area will focus on the creep and shrinkage properties of concrete made using aggregates from the same three quarries (Hajira, Kamser and Arja) of Azad Kashmir.
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Civil Engineering Department, University of Engineering and Technology Lahore, Pakistan Corresponding Author, E-mail: firstname.lastname@example.org, cell no. +92-322-3064000
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|Publication:||Pakistan Journal of Science|
|Date:||Mar 31, 2013|
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