Ceramic Dust as Construction Material in Rigid Pavement

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Table 1. Chemical properties of Ceramic dust

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The other ingredient OPC 53 Grade cement confirming to IS 12269-1987 and fine aggregate of Sp.gr. 2.66 and finesses modulus 2.65 confirming to IS 383-1970 was used along with coarse aggregate ^{[21, 22]}. The physical properties of coarse aggregate such as aggregate impact test, Los Angeles Abrasion test, water absorption test etc. were performed in Transportation Engineering Laboratory, CED, SVNIT, and presented in Table 2.

Table 2. Properties of Coarse Aggregate and Fine Aggregate observed in Laboratory Test

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3. Experimental Investigation

Based on physical strength requirements of DLC and PQC layers for concrete road, different experimental tests were conducted on the given samples. Potable water was used to mix with different ingredient to make concrete in ceramic as well as in conventional mix. The mix design methodology was developed based upon absolute volume method by conducting several trail mix and proportion of these mixes were used to find an optimum mix proportion. The different water content ratios (0.40, 0.42, 0.44, 0.46, 0.48 and 0.50) were used in different initial trails. For respective w-c ratio, volume of each concrete ingredient was same except cement, however, total volume was kept same in ceramic dust concrete mix and conventional concrete mix. With the control concrete environment, the cement was replaced in mix with 10%, 20% and 30% ceramics dust and mix content is given in Table 3.

Table 3. Proportion for Compressive Strength

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The concrete cube samples were cast in the mould of size 150x150x150 mm as shown in Figure 2 and placed on a level and rigid base. The filled moulds were kept in moist closet or moist room for 24 ± 1 hour after completion of vibration. The moulds were then removed and immediately submerged in clean fresh water and kept there until taken out just prior to breaking. The water was renewed every 7 days and was maintained at a temperature of 27 ± 2ºC. The slump of the fresh concrete was determined to ensure that it would be within the designing value and to study the effect of ceramic waste replacement on the workability of concrete and lies between 75 to 100 mm. The specimens were de-mould after 24 hours, cured in water and then tested at room temperature at the required age as shown in Figure 3.

The workability of mix proportion in this work was determined by slump cone test. Flow table was used to filled the mould and mixed was tampered. Slum test shows that maximum slum was observed in between 70 to 100 mm. If ceramic waste mixes increase up to 20% ceramic waste, results shows no detrimental effect on slump value. The physical and chemical properties of ceramic wastes resembles with the cement. So, it can replace the cement in concrete. In this study, ceramic waste was added in the ratios of 10%, 20% and 30%. All the cubes were tested on digital compression testing machine of capacity 2000 kN compressive load. The load was applied without shock and increased continuously at rate of approximately 140 kg/cm²/min until the resistance of the specimen to the increasing load broke down and no greater load could be sustained.

Figure 2. Sample prepared for test

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Figure 3. Cube compressision test

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Table 4. Proportion for Tensile Strength and Modulus of Strength

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To determine the split tensile strength, cylinder moulds of diameter 150mm and length 300mm were casted. Totally, 18 cylindrical specimens were casted with different proportions of ceramic dust and mix content as shown in Table 4.

The crude black oil was applied as seen earlier along the inner surfaces of the mould for the easy removal of casted cylinder from the mould. To determine the flexural strength concrete was poured throughout its length of mould of size 1000 x150 x150mm and compacted well. The size of beam specimens is 1000 x150 x150mm. The beam specimens were cast and tested with and without ceramic waste for normal conditions.

Figure 4. Flexural testing on samples

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Load cell was placed on the beam top and corrected to its centre by using plumb bob. Load cell was connected by the load indicator; three deflectometers were placed on the bottom side of the beam. Two point loading system was adopted for the test. Finally for the flexural strength 06 samples were prepared with the mix content as shown in the Table 5.

Table 5. Proportion for Flexural Strength

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4. Results and Discussion

The experimental investigation was done to determine Compressive strength, Flexural strength, Split Tensile strength and Modulus of Elasticity of concrete mixed with different ratios of 10%, 20% and 30% ceramic dust for DLC and PQC concrete.

4.1. Effect of Ceramic Dust on Compressive Strength of Concrete

The compressive strength was obtained at 7-days and 28 days of different samples of concrete. The results show that differences were wider in early age than after 28 days strength. The mechanical strength decreases considerably after ceramic dust percentage increases beyond 20%. Since, concrete pavement is become operational after 28 days, so this will not pose any problem in DLC and PQC quality.

As shown in Figure 5, The average 28 days compressive strength for different proportions of concrete result show that strength of concrete is increased, as ceramic waste quantity increases up to 20 %. Beyond, 20 % mix, it was reduces mainly. The 7-days compressive strength mix decreases by 28% and 17% with respect to conventional concrete mix. However, 28 days strength was having no significant change. The compressive strength significantly decreases due to excessive free water content in the mixes with ceramic waste content causes the bleeding and segregation in concrete. Therefore, it leads reduction in the concrete strength. For dry lean concrete, 7-day compressive strength required in between 6.5 Mpa to 10 Mpa. Less strength concrete is preferred in DLC as high strength concrete tends to develop crack. Therefore, less early age strength in ceramic waste concrete is beneficial in constriction of DLC. Regarding PQC the characteristic strength, 35 N/mm² is required after 28 days and traffic also get open after 28 days curing of PQC. This will also increase the debate as Indian specification makes it mandatory to achieve quantity of cement and quality of strength. As contractors are of the opinion that only required strength should be made mandatory and quantity of cement should be made optional. Required strength was achieved by using 280 Kg/m³ for the given 20% ceramic waste in place of 350 Kg/m³. Extra cement than required, only gives rise to increased CO₂ emission and leads to shrinkage cracks. Even minimum, 260 Kg/m³ cement is also recommended for flyash mix concrete. Therefore, using 280 Kg/m³ for ceramic waste mix concrete to achieve characteristic strength of M35 is may be useful saving.

Figure 5. Test Result of Compressive Strength

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4.2. Effect of Ceramic Dust on Flexural Strength of Concrete

Flexural strength of the concrete mix decreases as the percentage of ceramic waste in concrete increases. It is also noted that reduction in flexural strength decreases after every 10% addition of ceramic waste. It decreases by 0.12 Mpa on 10% addition of ceramic waste in concrete. The flexural strength decreases by 0.15 Mpa on further 10% addition of ceramic waste and by 0.18 Mpa on even further 10% addition of ceramic waste as shown in Figure 6. The decrease in flexural strength is not as significant as it satisfy the minimum flexural strength for PQC i.e. 4.5 Mpa. This criterion is also passed to use ceramic based concrete to construct rigid pavement.

In concrete road construction, flexural strengths are considered one of the important strength parameters. The results shows that cermic waste proportion uo to 20% is feable to use in DLC and PQC.

Figuer 6. Flexural Strenght (Mpa) after 28 days

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4.3. Effect of Ceramic Dust on Split Tensile Strength of Concrete

The splitting tensile strength value varies from 0.89 Mpa to 1.28 Mpa at 7 days. It is observed that split tensile strength of the PQC decreases as the percentage of ceramic waste in concrete is increased up to 20 %. It decreases by approximately 0.037 Mpa on every 10% addition of ceramic waste. The loose bond of the matrix might have led to the decreasing values of split tensile strength as shown in Figure 7. However, results shows that splitting tensile strength will also have under limits and can be use in DLC and PQC.

Figure 7. Spit Tensile Strength

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4.4. Effect of Ceramic Dust on Modulus of Elasticity of Concrete

Recently, changes are made in Indian concrete road construction specification, IRC-58-2012, that strength based design should be followed rather than empirical methods. The results reveal that modulus of elasticity of the sample strength decreases as the percentage of ceramic waste in concrete is increased. It decreases by 2.2 % on 10% addition of ceramic waste in concrete. It decreases by 0.85 GPa as compared to control specimen on 20% addition of ceramic waste in mix as shown in Figure 8.

All of the beams tested failed in flexure with crushing of concrete in the compression zone at the failure stage after the development of flexural cracks. The first visible cracks formed between the locations of the two point loads in the region of maximum bending moment. Thereafter, as the load was increased more cracks started to form over the shear span on both sides of the beam. Flexural beams replaced with copper slag gives more flexural strength compared to the control specimens. Hence, it is concluded that 20% replacement of ceramic waste may be for PQC and DLC may be used with proper quality control and assurance.

Figure 8. Elastic Modulus of ceramic based concrete

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