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A method of using carbon dioxide to strengthen recycled concrete fine aggregate

A technology of recycled concrete and recycled fine aggregates, applied in the direction of climate sustainability, sustainable waste treatment, solid waste management, etc. The effect of reducing the water absorption rate of the aggregate, reducing the crushing value of the aggregate, and improving the compressive strength

Active Publication Date: 2017-05-10
SOUTHEAST UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Among them, the acid cleaning method has a limited effect and will also introduce acid radical ions, which will affect the pH value of the attached mortar; the polymer treatment method can effectively reduce the water absorption of recycled concrete aggregates, but the strength improvement is limited; Aggregate grading requirements, such as screening out recycled fine powder particles, and this undoubtedly increases the process complexity and cost burden of strengthening recycled fine aggregates, and also reduces the utilization rate of recycled aggregates
[0004] In addition, there are existing studies on the use of CO 2 Research reports and patents on carbonization treatment to strengthen the performance of recycled aggregates, but these published documents use recycled aggregates from waste concrete test blocks, which are relatively young (not more than 12 months) and contain more carbonizable substances, making Good effect of carbonization modification
However, the concrete in the construction demolition waste has been used for decades, and the recycled aggregate prepared from it has a low content of carbonizable substances, and the existing literature methods are not suitable for it

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] This embodiment includes the following steps:

[0028] (1) Ca(OH) 2 Solution treatment: spread the recycled fine aggregate on the tray, and spray Ca(OH) whose parameter C is 0.01 mol / kg 2 Aqueous solution and stir evenly, control its water content to 5%.

[0029] (2) CO 2 Strengthening treatment: will be treated with Ca(OH) 2 The regenerated fine aggregate after aqueous solution treatment was placed in a closed carbonization box, the temperature was controlled at 30 °C, the relative humidity was 50%, and the CO 2 The concentration is 75%, carbonization treatment until the surface carbonization is complete.

[0030] (3) Preparation of recycled mortar: The treated recycled fine aggregate was used to prepare recycled mortar with a replacement rate of 100%.

[0031] Refer to the standard GB / T25176-2010 "Recycled Fine Aggregate for Concrete and Mortar" and GB / T14684-2011 "Sand for Construction" to investigate the basic properties of aggregates before and after carboniza...

Embodiment 2

[0038] This embodiment includes the following steps:

[0039] (1) Ca(OH) 2 Solution treatment: spread the regenerated fine aggregate on the tray, and spray Ca(OH) whose parameter C is 0.05 mol / kg 2 Aqueous solution and stir evenly, control its water content to 0.2%.

[0040] (2) CO 2 Strengthening treatment: will be treated with Ca(OH) 2 The regenerated fine aggregate after aqueous solution treatment was placed in a closed carbonization box, and the temperature was controlled at 10 °C, CO 2 The concentration is 100%, carbonization treatment until the surface carbonization is complete.

[0041] (3) Preparation of recycled mortar: The treated recycled fine aggregate was used to prepare recycled mortar with a replacement rate of 100%.

[0042] The results show that carbonation treatment after adding calcium can effectively reduce the water absorption and crushing value indicators of recycled concrete fine aggregate, as shown in Table 3.

[0043] Table 3 Properties of recycl...

Embodiment 3

[0049] This embodiment includes the following steps:

[0050](1) Calcium chloride solution treatment: spread the recycled fine aggregate on the tray, spray the calcium chloride aqueous solution with parameter C of 0.01 mol / kg and stir evenly, and control the moisture content of the recycled aggregate to 10%.

[0051] (2) CO 2 Strengthening treatment: place the regenerated fine aggregate treated with calcium chloride aqueous solution in a closed carbonization box, control the temperature at 50°C, relative humidity at 20%, CO 2 The concentration is 20%, carbonization treatment until the surface carbonization is complete.

[0052] (3) Preparation of recycled mortar: The treated recycled fine aggregate was used to prepare recycled mortar with a replacement rate of 100%. As shown in Table 5.

[0053] Table 5 Properties of recycled aggregates before and after carbonization

[0054] name Fineness modulus Water absorption / % Crushing Index / % Powder content / % Appa...

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Abstract

The invention discloses a method for reinforcing recycled concrete fine aggregate by using carbon dioxide, which comprises the following steps: (1) calcium hydroxide solution or calcium salt calcification treatment: spreading recycled fine aggregate prepared from construction waste on a tray, spraying a calcium hydroxide or calcium salt solution, and stirring uniformly; (2) CO2 curing: putting the recycled fine aggregate subjected to calcium hydroxide solution or calcium salt calcification treatment in a closed carbonization box, and carrying out carbonization curing until the surface is completely carbonized; and (3) recycled mortar preparation: preparing recycled mortar with the substitution rate of 100% by using the treated recycled fine aggregate. Compared with the unreinforced recycled aggregate, the crushing value of the recycled fine aggregate prepared by the method is lowered by nearly 45%, and the water absorptivity is lowered by nearly 53%. Compared with the recycled mortar prepared from the unreinforced recycled aggregate, the consistency of the recycled mortar prepared by the method is enhanced by 42% or so, the 7d strength of the mortar is enhanced by 15-26%, and the 28d strength can be enhanced by 17-24%.

Description

technical field [0001] The present invention relates to a method using CO 2 The invention discloses a method for intensifying treatment of recycled concrete fine aggregate, which belongs to the technical field of recycling of construction waste and production of building materials. Background technique [0002] Processing waste concrete into recycled aggregate for the preparation of recycled concrete not only solves the problem of environmental pollution, but also realizes the reuse of resources and reduces the waste of resources and energy. However, compared with natural aggregates, recycled aggregates have a large number of fine cracks inside, high crushing index value, and high water absorption rate. The working performance, mechanical properties and durability of recycled cement products prepared by using recycled aggregates are also difficult to meet engineering requirements. Therefore, strengthening recycled fine aggregate to improve the performance of recycled mortar...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B18/16
CPCY02W30/91
Inventor 潘钢华陆小军付明华
Owner SOUTHEAST UNIV
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