Roadbed material production method

Patent metadata

Field	Value
Publication number	US-2024092693-A1
Application number	US-202218263157-A
Country	US
Kind code	A1
Filing date	Mar 16, 2022
Priority date	Mar 23, 2021
Publication date	Mar 21, 2024
Grant date	—

Abstract

Provided is a method of producing a roadbed material from which less hexavalent chromium leaches out through use of a crushed product of a cementitious hardened body containing hexavalent chromium as a raw material. The method includes a carbonation treatment step of subjecting the crushed product of the cementitious hardened body to carbonation treatment with a carbon dioxide-containing gas having a temperature of 50° C. to 140° C. and a water content of 1.5% or more to obtain the roadbed material from which less hexavalent chromium leaches out than before the treatment. Preferably, the method includes, before the carbonation treatment step, a crushing step of crushing the cementitious hardened body to obtain a crushed product consisting of grains having a grain size of 100 mm or less at a ratio of 50 mass % or more and a grain size of 2.36 mm or less at a ratio of 1 mass % or more.

First claim

1 . A method of producing a roadbed material through use of a crushed product of a cementitious hardened body containing hexavalent chromium as a raw material,
the method comprising a carbonation treatment step of subjecting the crushed product of the cementitious hardened body to carbonation treatment with a carbon dioxide-containing gas having a temperature of from 50° C. to 140° C. and a water content of 1.5% or more to obtain the roadbed material from which less hexavalent chromium leaches out than before the treatment.

2 . The method of producing a roadbed material according to claim 1 , further comprising, before the carbonation treatment step, a crushing step of crushing the cementitious hardened body containing hexavalent chromium to obtain the crushed product, wherein the crushed product consists of grains having a grain size of 100 mm or less at a ratio of 50 mass % or more and having a grain size of 2.36 mm or less at a ratio of 1 mass % or more.

3 . The method of producing a roadbed material according to claim 5 , further comprising, between the crushing step and the carbonation treatment step, a classification step of classifying the crushed product obtained in the crushing step to obtain the crushed product, which is for being subjected to the carbonation treatment step, consisting of grains having a grain size of 100 mm or less at a ratio of 80 mass % or more and having a grain size of 2.36 mm or less at a ratio of 5 mass % or more.

4 . The method of producing a roadbed material according to claim 1 , wherein the cementitious hardened body is a waste material made of concrete or a waste material made of mortar.

5 . The method of producing a roadbed material according to claim 1 , further comprising, before the carbonation treatment step, a crushing step of crushing the cementitious hardened body containing hexavalent chromium to obtain a crushed product consisting of grains having a grain size of 100 mm or less at a ratio of 50 mass % or more and having a grain size of 2.36 mm or less at a ratio of 1 mass % or more.

6 . The method of producing a roadbed material according to claim 1 , the crushed product, which is for being subjected to the carbonation treatment step, consists of grains having a grain size of 100 mm or less at a ratio of 80 mass % or more and having a grain size of 2.36 mm or less at a ratio of 30 mass % or more.

7 . The method of producing a roadbed material according to claim 1 , a period of time for which the carbon dioxide-containing gas is brought into contact with the crushed product in the carbonation treatment step is 5 minutes or more.

8 . The method of producing a roadbed material according to claim 1 , a ratio of a carbon dioxide gas in the carbon dioxide-containing gas in terms of a volume fraction value is 5% or more.

Assignees

• Taiheiyo Cement Corp
• Univ Tokyo

Inventors

• Nozaki Takahito
• FUKUOKA Aoi
• Ichitsubo Kouki
• Hayakawa Takayuki
• Noguchi Takafumi
• Wang Dianchao

Classifications

• C04B20/023 Primary

  Chemical treatment · CPC title

• C04B20/0232

  with carbon dioxide · CPC title

• C04B2111/00017

  Aspects relating to the protection of the environment · CPC title

• C04B18/167

  Recycled materials, i.e. waste materials reused in the production of the same materials · CPC title

• C04B20/026

  Comminuting, e.g. by grinding or breaking; Defibrillating fibres other than asbestos · CPC title