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Strength of RC Beam Using Geopolymer Concrete and Adopting Bubble Technology


Published on Feb 27, 2019

Abstract

The Bubble Deck technology developed in Europe makes use of high-density polyethylene hollow spheres to replace the ineffective concrete in the centre of the slab, thus decreasing the dead weight and increasing the efficiency of the floor. This method is used in the concrete floor system. Concrete is good in compression and hence is more useful in the compression region than in the tension region. The reduction in concrete can be done by replacing the tension zone concrete. Keeping the same idea in mind, an attempt has been made to find out the effectiveness of plastic bubbles by replacing concrete in the tension zone of Ordinary Portland Cement Concrete (OPCC) and Geopolymer Concrete(GPC) beam. Geopolymer Concrete does not form calcium- silicate-hydrates (CSHs) for matrix formation and strength like OPCC but utilizes the polycondensation of silica and alumina precursors to attain structural strength. In this project, M25 concrete mix is used to prepare both OPCC and GPC beams. The trial mix is tested for compressive strength. Flexure test is done is done for 28 days of curing of the beams.

The procedure is repeated for beam samples with bubble mesh and bubble mesh along with shear reinforcement. Comparative analysis of the OPCC and GPC beams are done to observe the percentage reduction in self-weight and cost effectiveness. Analysis of behavior of GPC beam in comparison with that of OPCC beam is also carried out.

Keywords : Bubble technology, Geopolymer concrete, Ordinary Portland Cement Concrete, Sodium hydroxide, GGBS, Glass powder

Objectives:

1. To compare and analyse the behaviour of geopolymer concrete (GPC) beam with that of Ordinary Portland Cement Concrete(OPCC) beam.

2. To analyse the behaviour of geopolymer concrete beam by replacement of tension zone concrete with non-conventional materials like plastic balls.

3. Cost effective analysis by partial replacement of tension zone concrete in beam by the plastic balls.

Methodology:

1. Study of Mix Design of M25 concrete and selection of ingredients of concrete mix as per the Mix Design (both OPCC and GPC). Ingredients selected are cement, sand and coarse aggregate for OPCC and for GPC cement is completely replaced with 70% flyash, 15% GGBS and 15% glass powder. NaOH solution of 12M is added in place of water for GPC.

2. Preparation of beam samples with conventional concrete and geopolymer concrete.

3. Testing of RC beam (750mm x 150mm x 150mm) for bending and deflection.

4. Preparation of test samples of Ordinary Portland cement and geopolymer cement concrete beam with plastic balls as partial tension zone replacement.

5. Testing of samples for bending and deflection.

6. Preparation of sample beams with replacement of tension zone concrete with bubble mesh and provision of shear reinforcement.

7. Comparing the results of OPCC and GPC beams to draw conclusions.

Results:

Concrete beam of size 750mm x 150mm x 150mm with replacement of concrete below neutral axis with bubble mesh and shear reinforcement were tested for OPCC and GPC beams. Based on the test results, the following conclusions are made. The replacement of tension zone concrete with bubble mesh has caused a decrease in flexural strength for both OPCC and GPC beams. However, the strength has been maintained for beams with bubble mesh replacement with shear reinforcement.

Conclusion

It is observed that the placement of bubble mesh in concrete beam does not require any additional time. However, accurate placement of the mesh without displacement while pouring the concrete is a challenge. Another challenge is allowing for sufficient concrete to be present between lower portion of bubble mesh and tension zone reinforcement to enable maximum transfer of tensile forces from concrete to reinforcement. Economy and reduction of weight is upto 15% in OPCC and 13% in GPC beams. GPC beams can be used for sustainable and environment friendly construction work as it reduces the emission of carbon dioxide during the production of cement. However, hand mix of concrete does not provide the required compressive strength.

1. 28 days compressive strength for conventional concrete obtained was about 54.44 MPa and for GPC 12 MPa.

2. After adopting bubble technology flexural strength of beam remains almost same.

3. Saving in concrete is about 15% by weight.

Future Scope:

The following could be some of the areas for future work:

1) Analysis may be carried out considering cracking load instead at breaking load to get the exact behaviour of concrete.

2) Optimum mix proportions for geopolymer concrete can be developed to achieve higher strength.

3) Geopolymer concrete beams with optimum molarity may give better results.

4) Durability test may help in long term effect on strength.

Project Done By Ms. Ankitha Shanbhogue, Mr. C.Vaibhav, Mr. Darshan M.P, Mr. Anand Kumar






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