PAN Wenhao，MIAO Chaoyang，TANG Ning，LI Fajing，CUI Zhiyuan

Abstract

Objective Steel slag， generated at a rate of 10%~15% of crude steel production in China， has been accumulating in large quantities due to less efficient processing compared to developed countries. This stockpiling results in ecological risks， threatens human and animal health， and occupies valuable land resources. Although steel slag shares chemical similarities with Portland cement clinker and exhibits potential hydraulic and alkali-activated properties， its utilization remains limited. This is mainly due to its high content of inert phases such as iron oxides and RO phases， its dense crystalline structure， and poor grindability. Additionally， the presence of free calcium oxide （f-CaO） and magnesium oxide （f-MgO） in steel slag leads to volume instability. Existing grinding aids for steel slag are primarily adapted from cement additives and are not specifically designed to address the unique properties of steel slag. This study aims to develop a novel polymer-based composite grinding aid to enhance the grindability of steel slag， improve its cementitious activity， and mitigate volume instability， thereby promoting its large-scale and efficient utilization.

Methods A polymer-based composite grinding aid was synthesized through a two-step process. First， ester monomers were produced by the esterification of methacrylic acid and ethylene glycol， followed by free radical polymerization with isopentanol polyoxyethylene ether （TPEG） to form the polymer component. The esterification reaction conditions （acid-alcohol molar ratio： 1∶1.1~1∶1.3； reaction time： 3~5 h； temperature： 90~130 ℃） were optimized using a three-factor and three-level orthogonal experimental design， with the esterification rate as the evaluation metric. Methanesulfonic acid was employed as the catalyst， combined with a binary inhibitor system （methoxyphenol-phenothiazine） to prevent self-polymerization of methacrylic acid. The synthesized polymer was then mixed with sodium sulfate （71%）， sodium carbonate （15%）， and calcium chloride （4%） to prepare the composite grinding aid. Steel slag powder prepared with 3.8% of the grinding aid was evaluated according to GB/T 20491—2017 standards. Key parameters， including specific surface area （503 m²/kg）， density （3.39 g/cm³）， free CaO content （3.12%）， and activity indices （7 d，80.28%； 28 d，83.42%）， were determined. Laser particle size analysis and scanning electron microscopy （SEM） were used to assess grindability and hydration product morphology. Fourier-transform infrared spectroscopy （FTIR） confirmed the structural integrity of the ester monomers and polymers， with characteristic adsorption peaks for ester carbonyl groups （1 718 cm^-1）， hydroxyl groups （3 115~3 655 cm^-1）， and ether bonds （1 107 cm^-1）.

Results and Discussion Orthogonal experiments revealed that reaction time had the strongest influence on the esterification rate （R=3.78）， followed by the acid-alcohol ratio （R=3.48） and temperature （R=3.23）. The optimal conditions—an acid-alcohol ratio of 1：1.3， reaction time of 6 h， and temperature of 110 ℃—produced high-purity ester monomers， confirmed by sharp ester carbonyl peaks （1 718 cm^-1） and retained C═C double bond signals （1 638 cm^-1） in the FTIR spectra. Subsequent polymer synthesis via free radical polymerization successfully integrated hydroxyl， ester， and ether functional groups， aligning with the intended molecular design. The composite grinding aid significantly improved the grinding efficiency of steel slag. Laser diffraction analysis demonstrated a 66.77% cumulative distribution of 0-30 μm particles in the treated group， compared to 54.36% for the control group. This enhancement was attributed to the polymer’s hydroxyl groups neutralizing surface charges on fractured slag particles， reducing agglomeration， while its long side chains provided steric hindrance to help disperse fine particles. SEM analysis showed that the treated group developed denser microstructures with abundant ettringite crystals interwoven with calcium hydroxide and calcium silicate hydrate （C-S-H） gels， filling pore spaces and reducing porosity. In contrast， the control group exhibited sparse ettringite formation and higher porosity， which corresponded with lower mechanical strength. Performance testing confirmed that the prepared steel slag powder complied with Grade I steel slag powder standards， with a specific surface area of 503 m²/kg， a 28-day activity index of 83.42%， a fluidity ratio of 98%， and stable volume stability （2.0 mm expansion in the boiling test）. The polymer’s dual functionality—stabilizing particle surfaces through chemical bonds and promoting particle dispersion via steric effects—effectively addressed the challenges of poor grindability and low hydration activity in steel slag.

Conclusion This study proposes a systematic approach for synthesizing a high-efficiency polymer-based composite grinding aid tailored for steel slag. The optimized esterification conditions （1∶1.3 acid-alcohol ratio， 6 h reaction time， 110 ℃） maximize ester monomer yield while maintaining key double bonds. Subsequent free radical polymerization successfully integrates hydroxyl， ester， and ether functional groups into the polymer backbone， enabling synergistic effects of charge neutralization and steric stabilization. The resulting composite grinding aid （10% polymer， 71% Na₂SO₄， 15% Na₂CO₃， 4% CaCl₂） enhances the grinding efficiency of steel slag， increasing the 0~30 μm particle fraction by 12.41% compared to untreated slag. It meets the Grade I standards， with improved specific surface area， activity indices， and volume stability. Microstructural analyses validate the formation of dense hydration products with reduced porosity， attributed to higher ettringite and calcium hydroxide content. Overall， this study provides a technically viable and economically feasible solution for the valorization of steel slag， addressing both environmental concerns and resource utilization challenges in the steel industry.

Keywords： slag grinding aid； slag grinding； free radical polymerization； steel slag powder

Get Citation: PAN Wenhao， MIAO Chaoyang， TANG Ning， et al. Copolymerization and application of steel slag-based grinding aids［J］. China Powder Science and Technology， 2026， 32（3）： 1-10.

Received: 2025-04-26 .Revised: 2025-06-05,Online: 2025-09-17.

Funding Project: 国家自然科学基金项目，编号：52278453；辽宁省科技计划联合计划自然基金面上项目，编号：2024011941-JH4/4800；沈阳市科技局自然科学基金项目，编号：24-213-3-16。

First Author: 潘文浩（1979—），男，副教授，博士，硕士生导师，研究方向为固体废弃物资源化利用，绿色建筑材料应用。E-mail：pwh@sjzu.edu.cn。

Corresponding Author: 唐宁（1984—），男，教授，博士，硕士生导师，香江学者、“兴辽英才计划”青年拔尖人才、辽宁省“百千万人才工程”千人层次人才、辽宁省高等学校创新人才，研究生导师，研究方向为高性能沥青混凝土的制备与应用，低品位原料和固体废弃物制备建筑材料。E-mail：tangning@sjzu.edu.cn。

DOI：10.13732/j.issn.1008-5548.2026.03.007

CLC No: TQ172.463； TB4               Type Code: A

Serial No: 1008-5548（2026）03-0001-10