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Method for improving performances of recycled concrete by utilizing carbon dioxide

A technology for recycling concrete and carbon dioxide, which is applied in the fields of climate sustainability, sustainable waste treatment, solid waste management, etc., can solve the problems of difficult diffusion of CO2 and slow diffusion speed, and achieves important theoretical value and the effect of expanding the scope of application.

Active Publication Date: 2019-12-20
HUNAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

But the rate of carbonization remains a major hurdle for this technology
This is because the carbonation rate of early concrete depends on the diffusion of carbon dioxide into the concrete matrix, and the diffusion rate is very slow
In addition, the carbonization product CaCO 3 The particles can fill the pores in the concrete matrix, allowing CO 2 Diffusion is more difficult

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0013] A method for improving the performance of self-compacting recycled concrete by utilizing carbon dioxide, comprising the following steps: 2 The powder is mixed with water to form a calcium hydroxide solution. Then, carbon dioxide was bubbled through the solution to complete carbonation, as measured by a pH meter. The second step is to add cement and mix with the solution produced in the first step for 60s. Then, the recycled coarse aggregate was added and stirred for 60 s, then sand and natural coarse aggregate were poured in, and the concrete mixture was obtained by fully stirring for 120 s.

[0014] The compressive strength and flexural strength of the self-compacting concrete 28d made by this example increased by 13.4% and 14.4%, respectively, and the water absorption and porosity decreased by 15% and 14%.

Embodiment 2

[0016] A method for improving concrete properties by utilizing carbon dioxide, comprising the following steps: 2 The powder is mixed with water to form calcium hydroxide solution, and the solution concentration is 0.14mol / L. Then, carbon dioxide was passed into the solution at 2 L / min, and the slurry was stirred at 800 rpm using a magnetic stirrer for about 10 minutes. Then, cement, coarse aggregate, and sand were added, and the mixture was fully stirred for 120 s to obtain a mixture.

[0017] The compressive strengths of concretes 7d and 28d made by this example were both increased by 16%, and the flexural strengths of 7d and 28d were increased by 7% and 5%, respectively. This method has little effect on the drying shrinkage of concrete.

Embodiment 3

[0019] A method for improving concrete properties by utilizing carbon dioxide, comprising the following steps: 2 The powder is mixed with water to form calcium hydroxide solution, and the solution concentration is 0.52mol / L. Then, carbon dioxide was passed into the solution at 2 L / min, and the slurry was stirred at 800 rpm using a magnetic stirrer for about 15 minutes. Then, cement, coarse aggregate, and sand were added, and the mixture was fully stirred for 120 s to obtain a mixture.

[0020] The compressive strengths of concretes 7d and 28d made by this example were increased by 10% and 13%, respectively, and the flexural strengths of 7d and 28d were increased by 8% and 5%, respectively. This method has little effect on the drying shrinkage of concrete.

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Abstract

An objective of the invention is to provide a method for improving performances of recycled concrete by utilizing carbon dioxide. The method comprises the following steps: mixing Ca(OH)2 powder rich in calcium with water so as to form a calcium hydroxide solution; then introducing carbon dioxide gas into the calcium hydroxide solution until the calcium hydroxide solution is completely carbonized,then adding cement, mixing the cement with the solution produced in the first step under stirring for 60 s, then adding recycled coarse aggregate, carrying out stirring for 60 s, pouring sands and natural coarse aggregate, and carrying out complete mixing under stirring for 120 s so as to obtain a concrete mixture. The recycled concrete prepared by using the method provided by the invention is improved in compressive strength and flexural strength to a certain extent; meanwhile, the method can fix carbon dioxide in the atmosphere. The method provided by the invention provides a direction for promotion and application of CO2 and recycled aggregates, expands the application range of the CO2 and the recycled aggregates, has important theoretical value and significant economic benefits and environmental protection benefits, and has great significance for development of concrete.

Description

technical field [0001] The invention relates to the fields of resource recycling and building materials, in particular to a method for improving the performance of recycled concrete by utilizing carbon dioxide. Background technique [0002] With the rapid development of China's economy, the shortage of natural resources and the problems of environmental pollution are becoming more and more serious. As a high consumption industry, the construction industry consumes a lot of natural resources every year. According to data, China's current annual consumption of sand and gravel aggregates exceeds 20 billion tons, which is the largest mineral resource currently mined. At the same time, with the continuous advancement of urbanization, the amount of new urban construction, the demolition of old urban areas, and the reconstruction of urban villages are all increasing rapidly, resulting in more and more construction waste. At present, my country produces more than 2 billion tons of...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B28/00C04B40/00
CPCC04B28/00C04B40/0028C04B14/28C04B22/106C04B14/06C04B14/00C04B18/16C04B2103/0067Y02W30/91
Inventor 林忠财
Owner HUNAN UNIV
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