INTRODUCTION:

Coarse aggregate occupies major part in the concrete mix. So the aggregate content should be in a form of limited quantity of supplying of concrete materials. Therefore there is a need to search for an alternative material for aggregate which has similar properties. Bethamcherla waste stone (BWS) is a flaggy lime stone occurring in the crystalline form. It is naturally split, yielding compact slabs and tiles. Kurnool district of Andhra Pradesh has been gifted by nature with huge deposit of Bethamcherla stone. It is an excellent flooring stone having unique geo-mechanical properties ideally suitable for usage as flooring stone. For M20 grade of concrete, the coarse aggregate (C.A.) is replaced with the Bethamcherla waste stone aggregate (BWS) in the proportion of 0, 25, 50, 75 and 100% along with incorporation of steel fibers (0%, 1% & 2% by volume) in all mixes. Six cube specimens are prepared in the size of 150mmX150mmX150mm to be tested in compression and six cylindrical specimens of 150mmX300mm are prepared to be tested in tension. This work is primarily aimed at determining the first hand properties of aggregate replaced fiber concrete in the fresh and hardened stages. To fulfill this purpose tests of workability specified by the Indian codes are conducted on the different mixes of concrete and evaluated to determine the ease of casting and placing. The hardened strength parameters in compression and tension are determined to establish the maximum replacement ratio.

LITERATURE:

The use of recycled waste aggregate opens possibilities in the ways in which recycled materials can be used for structural applications; indeed, it may be an important breakthrough towards sustainable development. The utilization of waste aggregate is an effective solution to the problem of possessing excess waste materials while simultaneously maintaining satisfactory concrete quality. The utilization of waste construction materials should be related to the application of quality guarantee systems to achieve suitable product properties. Recycled waste aggregate has been employed for a long time, and is in limited use of roadwork, earth work and non-structural applications. The use of recycled aggregate in concrete construction or structural applications is scarcely reported. The recycling process for different waste materials can be conducted in which concrete and masonry waste can be recycled by sorting, crushing and sieving into recycled aggregates that can be used to make concrete for road construction and building material. The past reviews on introduction of fibers into the concrete gives the greater strengths and durable properties. The most recent improvement in the material properties of fiber reinforced concrete was being achieved with a combination of different fiber types, a fiber cocktail called hybrid fiber reinforced concrete. In fiber reinforced concrete, fibers can be effective in restraining cracks at both micro and macro levels. The use of two or more types of fibers in a suitable combination may potentially not only improve the properties of concrete over a wide range of deformation, but may also result in performance synergy. HanifiBiniciet.al (2007) studied the mechanical properties of concrete containing marble and lime dust. The results compared with conventional concrete. The results showed that marble and lime dust concrete increase workability and abrasion resistance is comparable to that of conventional concrete. The conclusion of the work is use of marble and lime dust gives durable for the concrete production.

Hebhoud (2011) conducted the experimentation on concrete. He used the marble aggregate as coarse aggregate. The results showed that use of marble aggregate up to 70% of any formulation is beneficial for the concrete resistance. Joseph (2012) conducted the experimental work on the structural characteristics of concrete using lateritic sand and quarry dust as fine aggregate. The results revealed that there is a considerable increase in both flexural and tensile strengths with increase in late rite. Shirulee et.al (2012) studied the replacement of cement with marble dust powder in concrete. The results showed that the 10% replacement by weight of cement increased the compressive strength of cube and also reported that replacement beyond 10% is ineffective on the compressive strength. V. Venkatalakshmi et.al (2012) studied the performance of fiber reinforced concrete using low grade limestone as a replacement for conventional aggregate under tension and compression which concluded that the control specimen (100 % granite) mix specimen had the maximum cube compressive and split tensile strength compared to the other aggregate replaced mixes and further the inclusion of fibers enhanced the strength of concrete in compression and Tension was also reported. S.A. Mahadik (2014) conducted the experimentation on incorporation of steel fibers to the concrete. He found that the compressive strength of fiber reinforced concrete was gradually increased when compared to the conventional concrete. He concluded that the steel fibers can be used up to the 0.75% by volume of concrete for structural purposes.

MATERIALS AND METHODOLOGY:

Cement:

Ordinary Portland cement of grade 53 of specific gravity 3.05 has been used in this work

Fine Aggregate:

Locally available river sand confirming to zone-II is used as fine aggregate. The specific gravity of the sand is 2.68. Percentage of bulking was found to be 27.53%.

Coarse Aggregate:

Granite aggregate of local origin confirming to the grading and technical specifications as per IS 2386 is used in this work with the maximum size of aggregate being limited to 20mm

Replacement Aggregate:

Flaggy limestone aggregate of specific gravity 2.59 obtained by manual hammering of flaggy limestone slabs and screened through 20mm and 10mm sieves are particularly used in this work

Fibers:

In this study, galvanized steel fibers with aspect ratio of 30 have been used. Diameter of steel fiber is 1mm having the length of 30mm is used.

The design stipulations for the mix and summary of the mix proportions arrived from these specifications are tabulated below.

Design stipulations:

The following table shows the design stipulations adopted for design of the concrete mix.

S.NO	Particulars	Proportion
1.	Maximum size of aggregate	20mm
2.	Characteristic compressive strength (28 days)	20 N/mm²
3.	Degree of quality control	Good
4.	Degree of Workability	25-50mm (slump value)
5.	Cement used	OPC-53 grade cement
6.	Specific gravity a) Cement b) Fine aggregate c) Coarse aggregate	3.05 2.61 2.47
7.	Grading of sand	Zone-II
8.	Water absorption of coarse aggregate	0.5%
9.	Water content	186 lits

Fig 1: Materials used in the experimental work

M20 grade concrete mix design carried out by using the IS 10262 : 2009 codes. Here it is mentioned mix proportion as cement : fine aggregate : coarse aggregate of w/c ratio 0.5.

Cement : F.A. : C.A. (Kg/m³) = 372 : 687.32 : 1061.26 (Kg/m³)

= 1 : 1.84 : 2.85

Mixing of materials:

The materials are weighed and are mixed manually for the various concrete mixes having different aggregate replacements along with varying fiber dosages.

Determination of fresh properties of concrete:

Fresh properties of concrete are determined by conducting workability tests like slump, compaction factor and vee-bee and the variation of these values for incremental replacements of flaggy limestone and effect of fiber inclusion are studied and examined further.

Placing and curing of concrete:

The filling of fresh concrete in to the cube and cylindrical moulds is done in three layers with adequate compaction effort. Concrete is left undisturbed in the moulds and hardened specimen are remolded after allowing a time period of 12 hours for the final setting of concrete.

Details of specimen:

Totally 6 cube and 6 cylindrical specimens are prepared for each mix. 15 mixes of varying aggregate replacement proportions 0, 25, 50 75, and 100 percentage by weight of conventional aggregate are studied in this experimental work along with the inclusion of steel fibers at 0%, 1% and 2% of concrete volume.

Tests on hardened concrete:

The compressive strength and split tensile strength tests are conducted in accordance with IS 1828-1 (2005) after a curing period of 7days 28 days with 3 representative samples for each concrete mix.

The results of slump test from the above graph shows that the 0% replacement aggregate concrete with 0% steel fibers has the slump value as 52 and the 100% replacement aggregate concrete as 98. The slump values for 0% replacement aggregate with 1% and 2% steel fibers were obtained as 37 and 28. Whereas the 100% replacement aggregate with 1% and 2% steel fibers were obtained as 73 and 56. The graph shows the increasing trend with the replacement of aggregate. That is the slump value has increased with the increase of percentage replacement whereas slump value decreased with the addition of steel fibers.

The results of compaction factor test from the graph shows that the 0% replacement aggregate concrete with 0% steel fibers has the compaction factor value as 0.872 and the 100% replacement aggregate concrete as 0.954. The compaction factor values for 0% replacement aggregate with 1% and 2% steel fibers were obtained as 0.853 and 0.827. Whereas the 100% replacement aggregate with 1% and 2% steel fibers were obtained as 0.927 and 0.908. A graph is plotted between the percentage replacement of waste stone aggregate and compaction factor values of concrete. The graph shows the increasing trend with the replacement of aggregate. That is the compaction factor value has increased with the increase of percentage replacement whereas compaction factor value decreased with the addition of steel fibers.

The results of Vee-Bee test from the above graph shows that the 0% replacement aggregate concrete with 0% steel fibers has the vee bee time as 5.7 and the 100% replacement aggregate concrete as 3.15. The vee bee time for 0% replacement aggregate with 1% and 2% steel fibers were obtained as 6.12 and 8.25. Whereas the 100% replacement aggregate with 1% and 2% steel fibers were obtained as 3.46 and 3.93. The graph shows the decreasing trend with the replacement of aggregate. That is the vee-bee value has decreased with the increase of percentage replacement whereas vee-bee value increased with the addition of steel fibers.

The above figure shows that the compressive strength for 0% replacement with zero percent fiber is 9.87 and for 100% replacement is 5.85. The compressive strengths for zero percent replacement with 1% and 2% fibers are 10.68 and 11.88. And for 100% replacement with 1%, 2% fibers are 6.54 and 7.32. From the graph it is observed that the compressive strength has increased when we replace the natural aggregate with Bethamcherla waste stone aggregate up to 25% after that it gradually declined up to 100%. At the same time, the compressive strength improved with the addition of steel fibers.

The above figure shows that the compressive strength for 0% replacement with zero percent fiber is 30.24 and for 100% replacement is 19.41. The compressive strengths for zero percent replacement with 1% and 2% fibers are 32.68 and 35.73. And for 100% replacement with 1%, 2% fibers are 21.45 and 23.43. From the graph it is observed that the compressive strength has increased when we replace the natural aggregate with Bethamcherla waste stone aggregate up to 25% after that it gradually declined up to 100%. At the same time, the compressive strength improved with the addition of steel fibers. The figure shows that the compressive strength value obtained at 28 days has increased when we replace the natural aggregate with Bethamcherla waste stone aggregate up to 25% after that it gradually declined up to 100%. At the same time, the compressive strength improves with the addition of steel fibers

The graph shows the variation of split tensile strength obtained at 7 days with the aggregate replacement. The split tensile strength obtained for 0% replacement aggregate with 0% steel fiber is 3.21 and for 100% replacement aggregate is 1.8. The split tensile strength for 0% replacement with 1%, 2% fiber is 3.48 and 3.98. For 100% replacement with 1% and 2% fiber is 2.11 and 2.407. From the graph it is observed that the increase in the percentage of replacement results the decrease in the split tensile strength and the split tensile strength has increased with the addition of steel fibers.

The graph shows the variation of split tensile strength obtained at 28 days with the aggregate replacement. The split tensile strength obtained for 0% replacement aggregate with 0% steel fiber is 3.99 and for 100% replacement aggregate is 2.40. The split tensile strength for 0% replacement with 1%, 2% fiber is 4.357 and 4.908. For 100% replacement with 1% and 2% fiber is 2.82 and 3.21. From the graph it is observed that the increase in the percentage of replacement results the decrease in the split tensile strength and the split tensile strength has increased with the addition of steel fibers.

CONCLUSION:

1. The workability of concrete increased with the increase of flaggy limestone fraction whereas increase in the fiber content decreases the workability of the mix.

2. The compressive strength of the mix increased up to 25% replacement of the flaggy limestone aggregate with the 25% specimen attaining maximum value further replacement of limestone shows the decline in the strength values, the least value exhibited by the 100% flaggy limestone specimen.

3. The value of split tensile strength approached a maximum value for 100% granite specimen and shows a declining trend with increase in the flaggy limestone aggregate content.

4. Fibers produced a favorable effect on the overall increase of strength parameters.

REFERENCES:

1. Hanifi Biniciet, “Durability of concrete made with granite and marble as recycle aggregates”, a Journal of Material Processing Technology. Vol-208, 2007,pp. 299-308.

2. Joseph (2012), “Flexural and Tensile Strength Properties of concrete using Lateritic Sand and Quarry Dust as Fine aggregate”. ARPN Journal of Engineering and Applied Sciences, Vol. 7, No. 3, March 2012.

3. S. A. Mahadik (2014), “Effect of Steel Fibers on Compressive and Flexural Strength of Concrete”. International Journal of Advanced structures and Geotechnical Engineering ISSN 2319-5347, Vol. 03, No.04, October 2014.

4. Hebhoud, “use of waste marble aggregates in concrete”, Construction and Building materials, Vol. 25-2011 pp.1167-1171.

Received on 10.11.2015 Accepted on 20.12.2015

Int. J. Tech. 5(2): July-Dec., 2015; Page 257-262

DOI: 10.5958/2231-3915.2015.00032.2