AN EXPERIMENTAL STUDY ON PARTIAL REPLACEMENT OF CEMENT BY GGBS

- Concrete is the most world widely used construction material with about 6 billion tones being produced every year. In terms of per capita consumption, it comes next to water. The extraction of raw materials and emission of CO 2 during manufacturing of cement cause great damage to the environmental sustainability. So, it becomes the need to reduce cement consumption. of the concrete, it be by the cement by supplementary materials. These materials may be naturally occurring, industrial wastes or by-products that are less energy extensive. These pozzolanic materials when combined with calcium hydroxide, exhibits cementitious properties. Most commonly used pozzolanic materials are fly ash, metakaolin, silica ground granulated blast furnce slag (GGBS). It needs to examine the admixtures performance when blended with concrete so as to ensure required strength, durability and reduced lifecycle cost. The present paper focuses on investigating characteristics of M35 grade concrete with partial replacement of cement by GGBS with 30%, 40% and 50%. The cubes and beams are tested for compressive strength and flexural strength respectively. From the experimental investigation, it was found that as the GGBS replacement level increased the workability increased. Also, both compressive strength and flexural strength of concrete increased as the GGBS content increased up to 40% but they decreased as the GGBS content increased above 40%. It was also found that both maximum compressive strength and maximum flexural strength of the concrete were achieved at 40% GGBS replacement. So, the optimum content of GGBS for compressive strength and flexural strength is 40%.

Abstract-Concrete is the most world widely used construction material with about 6 billion tones being produced every year. In terms of per capita consumption, it comes next to water. The extraction of raw materials and emission of CO2 during manufacturing of cement cause great damage to the environmental sustainability. So, it becomes the need to reduce cement consumption. Without compromising with strength and durability characteristics of the concrete, it can be done by partially replacing the cement by supplementary materials. These materials may be naturally occurring, industrial wastes or byproducts that are less energy extensive. These pozzolanic materials when combined with calcium hydroxide, exhibits cementitious properties. Most commonly used pozzolanic materials are fly ash, metakaolin, silica fume and ground granulated blast furnce slag (GGBS). It needs to examine the admixtures performance when blended with concrete so as to ensure required strength, durability and reduced lifecycle cost. The present paper focuses on investigating characteristics of M35 grade concrete with partial replacement of cement by GGBS with 30%, 40% and 50%. The cubes and beams are tested for compressive strength and flexural strength respectively. From the experimental investigation, it was found that as the GGBS replacement level increased the workability increased. Also, both compressive strength and flexural strength of concrete increased as the GGBS content increased up to 40% but they decreased as the GGBS content increased above 40%. It was also found that both maximum compressive strength and maximum flexural strength of the concrete were achieved at 40% GGBS replacement. So, the optimum content of GGBS for compressive strength and flexural strength is 40%.

I INTRODUCTION
Concrete has been the major instrument for providing stable and reliable infrastructure since the days of Greek and roman civilization. Concrete is the most world widely used construction material with about 6 billion tons being produced every year. It is the only next to water in terms of per-capita consumption. Concrete is a mixture of cement, water and aggregates (fine and coarse) with or without chemical admixtures. The

Plan of Experimentation
The experimental investigation is planned as follows:

Properties of ingredients of concrete
The materials used in the experimental work namely cement, GGBS, fine aggregate and coarse aggregate (20 mm and 10 mm) have been tested in laboratory for use in mix designs. The details are as follows: CEMENT Ordinary Portland cement of 43 grade was used in this investigation. The properties of cement are as follows:

Mix Design (as per IS 10262: 2009)
The following specifications were considered for Mix design:

Replacement of Cement by GGBS
The mix proportions with partial replacement of OPC by GGBS with 0%, 30%, 40% and 50% are shown in Table 3.

Casting and curing of test specimens
3 specimens of standard cubes (150 mm × 150 mm × 150 mm) and 3 specimens of standard beams (500 mm × 100 mm × 100 mm) were casted for each concrete mix. 4 different concrete mixes of M35 grade were prepared in which cement was partially replaced by GGBS with 0%, 30%, 40% and 50% respectively. In all 12 specimens of cubes and 12 specimens of beams were casted. These specimens were cured for 7, 14 and 28 days.

Curing
After 24 hours of casting the test specimens, cubes and beams, were de-moulded and immediately immersed in clean and fresh water for curing for 7, 14 and 28 days.

Tests for Workability
The results on tests for workability are shown in Table 4.

Compressive Strength of Concrete
CTM of 2000 kN capacity was used. The cube specimen was placed in the machine in such a manner that the load was applied to the opposite sides of the cube cast. The specimen was aligned centrally on the base plate of the machine. The load was applied gradually without shock and continuously at the rate of approximately 140 kg/cm 2 /min until failure. The test results for compressive strength are shown in Table 5 for 0%, 30%, 40% and 50% GGBS concrete of M35 grade at room temperature for 7, 14 and 28 days respectively.

S.
No.

Flexural strength of concrete
The beam specimen was placed in the machine in such a manner that the load was applied along two lines spaced 13.33 cm apart. The axis of the specimen was carefully aligned with the axis of the loading device. The load was applied through two similar steel rollers, 38 mm in diameter, mounted at the third points of the supporting span that is spaced at 13.33 cm centre to centre. The load was applied without shock and increased continuously at a rate of 180 kg/min until the specimen failed. The test results for flexural strength are shown in Table 6 for 0%, 30%, 40% and 50% GGBS concrete of M35 grade at room temperature for 7, 14 and 28 days respectively.

Effect of variation of GGBS on Compaction Factor
The values of compaction factor for 0%, 30%, 40% and 50% GGBS concrete are shown in Figure  5.

Effect of variation of GGBS on Slump
The values of slump for 0%, 30%, 40% and 50% GGBS concrete are shown in Figure 6.

Effect of variation of GGBS on compressive strength
The values of compressive strength for 0%, 30%, 40% and 50% GGBS concrete for 7, 14 and 28 days are shown in Figure 7.

Effect of variation of GGBS on flexural strength
The values of flexural strength for 0%, 30%, 40% and 50% GGBS concrete for 7, 14 and 28 days are shown in Figure 8.