READY MIXED CONCRETE USING MANUFACTURED SAND AS FINE AGGREGATE

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1 READY MIXED CONCRETE USING MANUFACTURED SAND AS FINE AGGREGATE V. Syam Prakash*, College of Engineering, Trivandrum, Kerala, India 32nd Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 2007, Singapore Article Online Id: The online version of this article can be found at: This article is brought to you with the support of Singapore Concrete Institute All Rights reserved for CI Premier PTE LTD You are not Allowed to re distribute or re sale the article in any format without written approval of CI Premier PTE LTD Visit Our Website for more information

2 32 nd Conference on OUR WORLD IN CONCRETE & STRUCTURES: August 2007, Singapore READY MIXED CONCRETE USING MANUFACTURED SAND AS FINE AGGREGATE V. Syam Prakash*, College of Engineering, Trivandrum, Kerala, India Abstract Concrete is the most widely used composite construction material. Ready mixed concrete can enhance the speed of construction and improve the quality of concrete components. The constituent materials of Ready Mixed Concrete (RMC), especially the fine aggregate, play a very important role for imparting better properties of concrete in its fresh and hardened state. In Kerala, river sand was used as fine aggregate for construction. Due to the continuous mining of sand from river led to the depletion of river sand and it became a scarce material. Also, since sand mining from river caused a lot of environmental issues. Hence the Government has banned mining of the same. As a substitute to river sand, Manufactured sand (MSand) has been produced by crushing stone. This paper presents the physical and mechanical properties of MSand and ready mixed concrete prepared using MSand. Experimental results shows that the quality of MSand is better than the river sand in many respects, such as cleanliness, grading, strength, angularity, flakiness, elongation etc. Design of RMC and its experimental investigation reveals that the use of MSand in RMC imparts better properties for RMC in its fresh state and hardened state. Test results on RMC in its fresh and hardened state are also presented in this paper. The study concludes that MSand is a suitable and viable substitute to river sand and could be effectively used in RMC which provides adequate strength and durability for the concrete. 1. Introduction Quality of construction is the most important aspect under consideration in the construction sector. Factory manufactured items always play a vital role in the quality of products. There comes the importance of Ready mixed concrete (RMC) and Manufactured sand (MSand). RMC consist of cement, fine and coarse aggregate, water and admixture. Of this cement and admixture is factory made, water is naturally available, coarse aggregate is naturally available and factory crushed. Hence these components normally maintain a standard quality. Fine aggregate is quite often obtained from river beds. This became very scarce as the Government of Kerala has imposed ban on the mining of the same due to the environmental hazards. The quality of the river sand normally depends on its source and most of the time it varies quite a lot. As the use of fine aggregate in concrete is more than 30% of the composite, its mechanical properties affect the quality of RMC. Hence manufactured sand has been identified as a substitute for river sand thereby solving the issue of mining of sand from river beds and improving the quality of fine aggregate. This paper presents the result of experimental investigations carried out on MSand and the details of RMC designed using MSand.

3 2. Materials The materials used for the study are Portland cement, MSand, coarse aggregate, water and admixture. These materials were tested as per the relevant Indian standards and are discussed in the following sections. 2.1 Cement Ordinary Portland Cement of 43grade was used in the study. The properties of cement have been determined by the standard tests conducted according to IS 4031/1968. It conforms to IS specifications and the test results are given below. (i) Standard consistency : 28.6 % (ii) Initial setting time : 260 minutes (iii) Final setting time : 435 minutes (iv) Compressive strength at 3 days : 22.08N/mm 2 (v) Compressive strength at 7 days : N/mm 2 (vi) Compressive strength at 28 days : N/mm Fine Aggregate M Sand was used as fine aggregate. It is manufactured in a central plant by crushing stone making use of the Vertical Shaft Impact (VSI) crusher. Due to the use of this technology the sand particles can be shaped very similar to that of the naturally available fine aggregate. During the process of manufacturing, sieving is done using water jet and the fine separation by screw classifiers. The sand obtained by means of this method is clean, durable and has the desired particle size distribution. Using this method sand falling in any Zone can be manufactured according to our requirement. MSand used for the present study was manufactured as fine aggregate falling under Zone II. Report of sieve analysis is given in Table 1. and the grading curve in Figure 1. On testing, the specific gravity was obtained as 2.59 and had shown 50.50% bulking at 6% water content. In order to check the strength properties of MSand, standard mortar cubes were cast using MSand and river sand. The average compressive strength of these standard cubes at the age of 28 days was obtained as 45.5 MPa and MPa respectively. Also, mm cubes cast using concrete of nominal mix 1:2:4 with MSand and river sand as fine aggregate. The average compressive strength at the age of 28 days was observed as 19 MPa and MPa respectively. Table 1. Sieve Analysis of Fine Aggregate Sample Sieve size (mm) Weight Retained (gm) % weight Retained Cumulative % weight Retained % passing Pan

4 % passing Log Sieve Opening Fig. 1. Grading Curve of Fine Aggregate 2.3 Coarse Aggregate Coarse aggregate has been obtained by blending aggregates of nominal size 20 mm, 12.5mm, & 6mm. These three types were mixed by trial and error to get the appropriate gradation, which has been obtained as 1:1:1.33. The result of the sieve analysis of this graded coarse aggregate sample is given in Table 2. and the grading curve shown in Fig 2. The particles of fine aggregate were angular satisfying the IS requirements. Other properties of the material are as follows. 1. Specific Gravity : Flakiness Index : % 3. Elongation Index : % 4. Grading (Fig 2.) : Corresponds to recommended grading as per IS 383/1970 Table 2. Sieve Analysis of Coarse Aggregate Sample Sieve size Weight Retained (gm) % weight Retained Cumulative % weight Retained % passing 40 mm mm mm mm

5 % passing Log Sieve Opening (mm) 2.4 Water Fig. 2. Grading Curve of Coarse Aggregate Potable water has been used for the concrete. 2.5 Admixture Admixtures supplied by three firms, viz., FOSROC, CERAPLAST and SIKAMENT were used. Details of super plasticizer supplied by these firms are as follows. FOSROC : Super plasticizer - Conplast SP 430 NE1 Plasticizer - Conplast SP 430 NL1 CERAPLAST : Super plasticizer - Ceraplast 300-RS(G) Plasticizer - Ceraplast 300 SIKAMENT : Super plasticizer - Sikament 581(s)/2 3. Mix Design The mix design has been carried out according to the recommended guidelines given in SP 23 of the Bureau of Indian Standards and IS The target strength for M 20 and M 25 mixes were calculated as MPa and MPa respectively with the respective standard deviations of 4.6 MPa and 5.3 MPa. The mix proportions were arrived at by preparing number of trial mixes and testing each mix for its workability and its strength. The mixes needed adjustments in respect of water content and ratio of coarse to fine aggregates to get the required slump. The final mixes were arrived at by trying different mixes by varying the water cement ratio and quantity of super plasticizer so as to get the specified workability and required strength at the minimum possible cement content. The dosage of admixtures has been done based on the guidance of the chemist of manufacturers. It has been observed that, a post dose of plasticizer might also be required after 2hours for obtaining adequate workability for pumping of concrete. The relevant details regarding the mixes are given in Table 3. and the details of dosage of admixtures and the corresponding slump obtained are given in Table 4. Using the final mix proportion of the designed RMC of M 20 and M 25 mix, 36 cubes (150x150x150 mm size) were cast using each admixture and well cured. Cubes were tested to find 7 th and 28 th day compressive strength. Casting and testing of cubes were done strictly accordingly to the procedures laid down in Indian Standard specifications.

6 Table 3. Details of Final Mix Proportion Details of mix Designed mix proportion by weight (Cement: Fine aggregate: Coarse aggregate) Grade of mix M 20 M 25 1:2.35:3.63 1:2.02:3.39 Proportion of 20mm, 12.5mm and 6mm aggregate 1:1:1.33 1:1:1.33 Cement content in kg/m Sand content 41% 39% Water-cement ratio Table 4. Dosage of Admixtures in the Final Mix Type of admixture Dosage of admixture M 20 M 25 FOSROC: (Litres/kg cement) Pre dose: Super plasticizer Conplast SP430NE1 (Expected slump after 2hours is +80mm) Post dose: Plasticizer Conplast SP430NL1 (Expected slump on addition is +125mm) CERAPLAST: (Percentage by weight of cement) Pre dose: Super plasticizer Ceraplast 300-RS(G) (Expected slump after 2hours is +80mm) Post dose: Plasticizer Ceraplast-300 (Expected slump on addition is +125mm) SIKAMENT: (Percentage by weight of cement) Pre dose: Super plasticizer Sikament 581(S)/2 (Expected slump after 2hours is +80mm) Test Results The materials used in this study satisfied the standard requirements. Test results of MSand were satisfactory in respect of its physical properties and mechanical properties. Comparison of the test result of standard mortar cubes cast using M Sand and river sand indicate that the former is comparable with the later. This result was again supported by the test result on nominal mix concrete. The concrete cubes cast using the RMC were tested following the standard procedure. Average values of compressive strength obtained on the 7 th day and 28 th day and the calculated values of standard deviation are given in Table 5. Test results shows that the characteristic compressive strength has been obtained for all mixes with the standard deviation within the permissible limit. It could also be noticed that the minimum quantity of cement has been used for all the mixes. This ensures that the use of M Sand is quite appropriate for making RMC satisfying workability, transportability and pumpability of concrete in its fresh stage leading to a strong and durable concrete in its hardened stage.

7 Table 5. Test results of Designed Mixes. Mix M 20 Admixture Average Compressive Strength (MPa) 7 th day 28 th day Standard Deviation of 28 th day strength FOSROC M 25 CERAPLAST SECAMENT FOSROC CERAPLAST SECAMENT Conclusions Following are the conclusions derived from the study 1. M Sand is satisfying the requirements of fine aggregate such as strength, gradation, shape, angularity etc. 2. The VSI technology adopted for the manufacture of M Sand assures the quality of fine aggregate. 3. MSand can be produced to fall in the desired Zone according to our requirement. This can definitely ensure the quality of concrete. 4. The mechanical properties of MSand depend on the source of its raw material. Hence selection of quarry is very important for obtaining quality fine aggregate. 5. The workability of RMC has been maintained by the quality of M Sand used in this study. This enabled the transportability and pumpability. 6. Compressive strength obtained for standard mortar cubes, nominal mix concrete and RMC indicates that the strength properties of M Sand are adequate. 7. The requirement of cement has been observed to be very reasonable for all the mixes. The same content of cement was adequate for the same grade of mix with different admixtures. 8. RMC prepared using all the three admixtures gave satisfactory results in terms of its workability and compressive strength. References [1] J.D. Dewar and R. Anderson, Manual of Ready Mix Concrete, Blakie Academic Professional, an imprint of Chapmen and Hell, UK. [2] Collis L. and Fox R.A., Aggregates, Sand, Gravel and Crushed Rock Aggregates for Construction Purposes, The Geological Society, London, 1985, 220pp. [3] Concrete Technology, A.M. Neville and J.J. brooks, Pearson Education, Edinburdg Gate Harlow, Essex, Cm20, 2JE, England. [4] IS 4926 : 2003, Ready Mix Concrete, Code of practice [5] IS 2383 : 1963 (Part1 to Part 8), Methods of Test for Aggregates for Concrete [6] IS 383 : 1970 Specification for Coarse and Fine Aggregate from Natural Sources for Concrete [7] SP 23 : 1982, Hand Book on Concrete Mixes.