硅酸盐学报

赤泥基高强度免烧透水砖制备及影响因素与构效机制

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金盛垚 ¹ , 娄向阳 ¹ , 胡健 ¹ , 朱健 ² , 陈洪 ¹

硅酸盐学报 | 环境矿物材料专题—研究论文 2024,52(10): 3159-3169

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硅酸盐学报 |环境矿物材料专题—研究论文 2024 , 52 (10) : 3159 -3169

赤泥基高强度免烧透水砖制备及影响因素与构效机制

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金盛垚¹, 娄向阳¹, 胡健¹, 朱健², 陈洪¹

作者信息

^1．南方科技大学环境科学与工程学院，广东省土壤与地下水污染防控及修复重点实验室，广东深圳 518055

^2．贵州大学资源与环境工程学院，贵阳 550025

通讯作者:

陈洪（1986—），男，博士，研究员；

朱健（1981—），男，博士，教授。

作者简介:

金盛垚（2001—），男，博士研究生。

Preparation of High-Strength Permeable Bricks with Red Mud: Influencing Factors and Structure-Performance Mechanism

Shengyao JIN¹, Xiangyang LOU¹, Jian HU¹, Jian ZHU², Hong CHEN¹

Affiliations

^1.Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China

^2.College of Resources and Environmental Engineering, Guizhou University, Guiyang 550025, China

Corresponding Author:

CHEN Hong (1986-), male, Ph.D., Professor; E-mail: chenh3@sustech.edu.cn;

ZHU Jian (1981-), male, Ph.D., Professor. jzhu@gzu.edu.cn

JIN Shengyao (2001-), male, Doctoral candidate. E-mail: 12331312@mail.sustech.edu.cn

出版时间: 2024-10-20 doi: 10.14062/j.issn.0454-5648.20240154

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摘要

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随着赤泥堆存量不断增加和城市化进程加快，赤泥资源化利用和低碳透水砖开发，成为协同解决2大问题的关键。基于赤泥和透水砖材料基因共性，以赤泥为原料，采用造粒工艺将赤泥制成免烧骨料，结合混料、成型、养护等步骤，成功制备了高强度免烧透水砖。为系统阐明透水砖制备过程中材料性能的影响因素与构效关系，进一步探究了水灰比、目标孔隙率以及发泡剂占比对透水砖性能的影响，发现水灰比和目标孔隙率主要通过改变砖体内部浆料的流动性，以及连通孔隙数量来显著影响砖体的性能。在发泡剂添加量低于4%（质量分数）时，可以有效提升砖体内部的孔隙率，但是过高的添加量会使透水砖的水灰比增大，弱化了发泡剂本身的造孔作用。采用X射线粉末衍射仪、扫描电子显微镜研究透水砖制备过程中的强度形成机理，发现在砖体制备过程中，赤泥以及水泥反应形成了硅酸钙凝胶，可以有效凝结骨料，赋予透水砖强度以及透水性能。本工作体现了“变废为宝”的资源化利用理念，为赤泥的资源化利用与海绵城市建设对高端建材的需求，提供了新的思路和方法。

关键词

赤泥 / 免烧透水砖 / 水灰比 / 孔隙率 / 发泡剂

Abstract

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Introduction

Red mud is a solid waste generated from alumina production, its massive accumulation occupying extensive land areas and leaching alkalis and heavy metals, leading to significant environmental issues such as soil alkalization and groundwater pollution. This study responds to the current demand for sponge city construction via innovatively utilizing red mud as a raw material to produce un-sintered aggregates through a novel pelletization process that leverages similarities between red mud and permeable brick materials. High-strength un-sintered permeable bricks were prepared via integrating mixing, molding, and curing techniques. These bricks improve overall compressive strength and permeability, while drastically reducing energy consumption and environmental impact during production. This approach presents a fresh perspective on red mud utilization and sponge city development, promising the environmental and economic benefits.

Methods

The preparation of red mud-based unsintered permeable bricks involved: 1) pelletization, the aged red mud chunks were crushed, then mixed uniformly with P·O 42.5 ordinary Portland cement and water, and fed into a pelletizer for pelletization. The aggregated particles were removed and naturally cured for one week; 2) mixing, different proportions were designed based on a volumetric method, with red mud-based un-sintered aggregates, cement, water, and additives calculated and weighed according to these proportions, then added to a basin and mixed uniformly; 3) pressing, the uniformly mixed slurry was placed and pressed into a mold with the dimensions of 20 cm×15 cm×10 cm by a semi-automatic brick machine; 4) curing, the pressed permeable bricks were demolded and naturally cured for 1-2 d, then placed in a standard curing box for 28 d.

The phase structure and micro-morphology of the material were analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The heavy metal leaching performance of the permeable bricks was analyzed according to the national standards (HJ557-2010). The concentrations of ten metal elements in the leachate were determined inductively coupled plasma mass spectrometry (ICP-MS). In addition, the environmental risk of heavy metal elements in the leachate was evaluated according to the national standards (GB/T 5085.3-2007).

Results and discussion

The bulk density (ρ_bv) of red mud-based aggregates is 1 078.50 kg/m³, with an apparent density (ρ_ap) of 1 724.14 kg/m³ and a porosity (v) of 37.45%. The analysis of the water-cement ratio (w_c) on permeable brick performance reveals that increasing w_c from 0.20 to 0.35 gradually enhances the compressive strength. This improvement stems from the increased fluidity and adhesive properties of the cement paste at a higher w_c, facilitating a better aggregate encapsulation and thereby improving the connectivity. However, increasing w_c beyond 0.35 to 0.40 results in a significant decrease in the compressive strength likely due to excessive fluidity causing settling of the cement paste.

The results of target porosity effect on permeable bricks demonstrate a negative correlation with the compressive strength and a positive correlation with the permeability coefficient. A greater porosity leads to increased interconnected pores within the bricks, enhancing water infiltration but reducing contact points crucial for stress transmission. This leads to localized increases in pressure and higher susceptibility to fracturing, thereby impacting the mechanical properties.

The results of foaming agent content effect on permeable brick performance indicate that increasing the foaming agent from 0% (in mass fraction) to 4% slightly increases the permeability coefficient, while marginally decreasing compressive strength. This effect results from hydrogen peroxide decomposition, creating additional pores within the bricks that weaken aggregate bonding and increase porosity. A further increase in foaming agent content reduces the permeability coefficient, while gradually enhancing compressive strength.

The XRD analysis confirms CaCO₃ as a common component in red mud, cement, aggregates, and permeable bricks. The characteristic peaks of red mud and aggregates remain unchanged, indicating no alteration in primary phases of red mud under the un-sintered process. In the permeable bricks, the characteristic peaks of 3CaO·SiO₂ are absent, whereas the peaks of Ca₅(Si₆O₁₆)(OH)₂ appear. This indicates that 3CaO·SiO₂ undergoes a reaction with water under high alkalinity conditions to produce Ca₅(Si₆O₁₆)(OH)₂, consequently boosting the bricks' strength. The microstructural observation of cross-sections and vertical sections reveals abundant micro-voids crucial for permeability. The cross-sections display flaky hydration gels distributed along aggregate surfaces, while the vertical sections exhibit thinner hydration products and flocculent gels.

The results of heavy metal leaching experiments reveal chromium (Cr) as the maximum concentration metal in leachates from red mud-based un-sintered permeable bricks, exceeding 40 μg/L, while other metals are below 10 μg/L. Leachate toxicity is well below the values of the national standards (GB/T 5085.3-2007), confirming compliance with environmental safety standards and minimal environmental risk for red mud-based un-sintered permeable bricks.

Conclusions

Red mud-based un-sintered permeable bricks were prepared through pelletization, mixing, pressing, and curing. The water-cement ratio affected brick's performance. An increase in the water-cement ratio enhanced the fluidity of the slurry and increased compressive strength, but when the ratio exceeded 0.35, the mechanical properties deteriorated. Increasing the target porosity improved permeability but reduced compressive strength. Adding hydrogen peroxide as a foaming agent effectively increased porosity at levels below 4%, but excessive addition led to the reduced performance. The XRD analysis showed that a high alkalinity of red mud promoted the formation of C-S-H gel, enhancing compressive strength. The SEM images of the cross and vertical sections of the permeable brick revealed flaky and flocculent hydration gel products attached to the surfaces of the aggregates. The results of heavy metal leaching experiments indicated that the leaching risk of heavy metals from the permeable bricks was extremely low. This work could provide an effective approach to simultaneously address the challenges of red mud resource utilization and sponge city construction.

Key words

red mud / un-sintered permeable bricks / water-cement ratio / porosity / foaming agent

引用本文

金盛垚, 娄向阳, 胡健, 朱健, 陈洪. 赤泥基高强度免烧透水砖制备及影响因素与构效机制. 硅酸盐学报, 2024 , 52 (10) : 3159 -3169 . DOI: 10.14062/j.issn.0454-5648.20240154

Shengyao JIN, Xiangyang LOU, Jian HU, Jian ZHU, Hong CHEN. Preparation of High-Strength Permeable Bricks with Red Mud: Influencing Factors and Structure-Performance Mechanism[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (10) : 3159 -3169 . DOI: 10.14062/j.issn.0454-5648.20240154

基金

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广东省杰出青年基金(2020B1515020022)

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2024年第52卷第10期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240154

接收时间：2024-02-28
首发时间：2026-10-22
出版时间：2024-10-20

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收稿日期：2024-02-28
修回日期：2024-04-19

基金

广东省杰出青年基金(2020B1515020022)

作者信息

^1．南方科技大学环境科学与工程学院，广东省土壤与地下水污染防控及修复重点实验室，广东深圳 518055

^2．贵州大学资源与环境工程学院，贵阳 550025

通讯作者:

陈洪（1986—），男，博士，研究员；

朱健（1981—），男，博士，教授。

参考文献

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240154

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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