Investigating the Beneficial Effects of Alternate Fines in Concrete

Carson, Matthew Glenn (2020) Investigating the Beneficial Effects of Alternate Fines in Concrete. [USQ Project]


Abstract

The supply of concrete contributes about 8% of the world's Co2 greenhouse gas emissions. Concrete is the second most used substance on earth after water.

The research attempts to address two problems in the construction industry, the greenhouse gas emissions from producing cement and the build-up of waste materials in quarries and recycle centres. The research will look at the potential for the waste materials from quarries and recycle centres to be used as a partial replacement for cement in concrete.

Six different recycled materials were sampled from different quarries and recycling centres. The physical properties of the materials were analysed before they were added to concrete trial mixes partially replacing cement at different percentages by weight. In the first set of trials only the strength of the hardened concrete was taken to determine how much cement could be replaced before the trial mix no longer achieved the target strength. Once the optimum percentage was found further testing was conducted on the concrete. These tests included workability, the set time, bleed, compressive strength, flexural strength, shrinkage, the sulphates and chlorides of each of the mixes and then were compared to a standard concrete mix with the same amount of cement replaced with fly ash.

From the results the intial trials found that the limestone dust when partially replaceing cement did not make strength at any percent. The Scotchy Pocket Quarry Andesite dust made strength up to 20% replacement of cement. The Calcium Quarry Marble dust made strength up to 20% replacement of cement, but the results showed that there is variation in the material. The Coominya Quarry Sandstone dust made strength up to 10% replacement of cement. The Enviro-sands glass dust made strength up to 10%. Finally the Enviro-Sands Glass fine sand all made strength with 50% replacement of natural sand being chosen to continue testing on.

The results from the second trial found that the Scotchy Pocket Quarry Andesite Dust had an entrapped air percentage of 1.4% the same as the control fly ash mix. Had a set time of 6 hours and 25 minutes which is 1 hour and 5 minutes longer than the control fly ash mix. Had more bleed than the fly ash control at 34.2ml over 3 hours with a bleed ratio of 2.3%. For the testing on the harden concrete density was 10 kg/m3 less than the fly ash control. The flexural strength went 5.7 MPa after 56 days which is 0.6 MPa more than the control. The shrinkage was 690 microstrain which is 20 microstrain less than the fly ash control, and the sulphates was less than the control at 19.9 g/kg and the chlorides were the same as the control at 0.8 kg/m3. The cost of the mix was $2 less than the fly ash control at $122.02 and the tons of Co2 per cubic meter of concrete was slightly more than the fly ash control at 0.384 tons/m3.

The results from the second trial found that the Calcium Quarry Marble Dust had an entrapped air percentage of 1.4% the same as the control fly ash mix. Had a set time of 5 hours and 55 minutes which is 35minutes longer than the control fly ash mix. Had more bleed than the fly ash control at 25.8ml over 2.5 hours with a bleed ratio of 1.5%. For the testing on the harden concrete density was 11 kg/m3 more than the fly ash control. The flexural strength went 4 MPa after 56 days which is 1.1 MPa less than the control. The shrinkage was 720 microstrain which is 10 microstrain more than the fly ash control, and the sulphates was less than the control at 19.3 g/kg but the chlorides were more than the control at 1.0 kg/m3. The cost of the mix was $2 less than the fly ash control at $122.02 and the tons of Co2 per cubic meter of concrete was slightly more than the fly ash control at 0.384 tons/m3.

The results from the second trial found that the Enviro-Sands Glass Fine Sand had an entrapped air percentage of 2.4% which is 1% more than the control fly ash mix. Had a set time of 5 hours and 30 minutes which is 10 minutes more than the control fly ash mix. Had more bleed than the fly ash control at 39.2ml over 3.5 hours with a bleed ratio of 2.4%. For the testing on the harden concrete density was 4 kg/m3 less than the fly ash control. The flexural strength went 5.8 MPa after 56 days which is 0.7 MPa more than the control. The shrinkage was 540 microstrain which is 170 microstrain less than the fly ash control, and the sulphates was less than the control at 18.2 g/kg and the chlorides were less than the control at 0.6 kg/m3. The cost of the mix was $55.64 more than the fly ash control at $180.04 and the tons of Co2 per cubic meter of concrete was not able to be determine.

The results from the second trial found that the Coominya Quarry Sandstone Dust had an entrapped air percentage of 1.3% the same as the control fly ash mix. Had a set time of 4 hours and 45 minutes which is 5 minutes longer than the control fly ash mix. Had less bleed than the fly ash control at 13.4 ml over 2 hours with a bleed ratio of 0.7%. For the testing on the harden concrete density was 28 kg/m3 less than the fly ash control. The flexural strength went 4 MPa after 56 days which is 0.9 MPa less than the control. The shrinkage was 750 microstrain which is 100 microstrain more than the fly ash control, and the sulphates was more than the control at 25.2 g/kg and the chlorides were more than the control at 0.9 kg/m3. The cost of the mix was $1.20 less than the fly ash control at $126.28 and the tons of Co2 per cubic meter of concrete was slightly more than the fly ash control at 0.421 tons/m3.

The results from the second trial found that the Enviro-sands Glass Dust had an entrapped air percentage of 4.0% which is 2.7% more than the control fly ash mix. Had a set time of 5 hours and 35 minutes which is 55 minutes longer than the control fly ash mix. Had more bleed than the fly ash control at 25.4 ml over 2.5 hours with a bleed ratio of 1.7%. For the testing on the harden concrete density was 39 kg/m3 less than the fly ash control. The flexural strength went 3.4 MPa after 56 days which is 1.5 MPa less than the control. The shrinkage was 770 microstrain which is 120 microstrain more than the fly ash control, and the sulphates was more than the control at 24.0 g/kg and the chlorides were the same as the control at 0.8 kg/m3. The cost of the mix was $13.99 more than the fly ash control at $141.27 and the tons of Co2 per cubic meter of concrete was not able to be calculated.

The future works on the project should look into the possibility of the alternate materials causing an ASR reaction in the concrete this would need to be known before the materials could be used in the industry.

The alternate materials could be utilised in the industry as they can perform like standard mixes or even better than the standard mix. However, a few items would have to happen before these materials could really be utilised, the mixes are required optimised and then pushed to see where the limits of the materials are. The prices of the materials especially the glass product would have to decrease to compete with the conventional materials, and finally further research would have to be done to fully understand how these materials react in the concrete mixes.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours)(Civil)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Supervisors: Elks, Gary
Date Deposited: 25 Aug 2021 22:40
Last Modified: 25 Aug 2021 22:40
URI: http://eprints.usq.edu.au/id/eprint/43077

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