硅酸盐学报2026，Vol.54Issue(5)：1555-1563,9.DOI:10.14062/j.issn.0454-5648.20250251
膨胀珍珠岩对水镁石基磷酸镁防火涂料性能的影响
Effect of Expanded Perlite on Properties of Brucite-Based Magnesium Phosphate Fire Retardant Coating
摘要
Abstract
Introduction As a type of energy-saving and environmental protection building system,steel structure building is widely used in engineering construction in recent years,and its fire protection measures are particularly important.At present,the commonly used fire retardant coatings are mainly divided into two categories,i.e.,organic intumescent and inorganic non-intumescent coatings.Although organic intumescent coatings exhibit a good fire resistance in the initial stage,their duration of protection is relatively short,and they may release toxic and corrosive gases during combustion,posing certain safety risks.In contrast,inorganic non-intumescent fireproof coatings have advantages such as high thermal resistance,strong durability,good wear resistance,and low cost,making them considered as an ideal fire protection material for steel structures.However,some issues such as insufficient adhesion and poor overall durability seriously limit its widespread application in practical engineering.Magnesium phosphate cement(MPC)is regarded as a fireproof material with an application potential due to its high strength,high-temperature resistance and excellent interfacial bonding performance with steel.However,the conventional raw material for MPC like dead-burned magnesia has a high density and carbon emissions,which is unfavorable for its green and sustainable development.To address the above issues,this study was to select a low-grade natural brucite powder as a complete substitute for dead-burned magnesia to prepare magnesium phosphate cement,and optimize the physical,mechanical,and fire insulation properties of brucite-based magnesium phosphate steel structure fireproof coatings(BMPC)via introducing modified expanded perlite. Methods The raw materials for the preparation of BMPC included natural brucite powder,ammonium dihydrogen phosphate,analytical grade borax,and expanded perlite.Expanded perlite was divided into two types,i.e.,untreated(EP)and water absorption pretreatment(HEP)according to different treatment methods.Under the condition of fixed process parameters(i.e.,M/P mass ratio of 2.5,borax content of 15%,water-cement ratio of 0.17,and expanded perlite content of 0-20%of the total mass of brucite powder and ammonium dihydrogen phosphate),the BMPC slurry was prepared. The dry density and surface drying time of the BMPC coating under natural curing conditions were tested in accordance with the standard GB 14907-2018.The compressive strength and adhesive strength tests were conducted on the specimens after 3-d,7-d and 28-d curing,respectively.The thermal conductivity of BMPC was determined by a transient plane source method.The fire resistance limit was tested according to the standard GB/T 9978.1-2008.The internal pore structure of BMPC samples was analyzed by an industrial computed tomography system,and its microstructure was analyzed by field emission scanning electron microscopy.The phase change of BMPC coating before and after fire test was analyzed by X-ray diffractometry,and its thermal stability in the range of 30-1000℃was analyzed by thermogravimetric analysis. Results and discussion The expanded perlite(HEP)after water absorption treatment has a more open pore structure and a higher surface roughness rather than the untreated expanded perlite(EP).In the BMPC system,the HEP has a relatively small effect on the mechanical properties,especially under low density conditions,it can still maintain high compressive strength and adhesive strength.At the HEP content of 20%,the microporous structure inside the material significantly reduces the thermal conductivity and thermal diffusion coefficient.This is mainly since the HEP acts as a low thermal conductivity filler,and the air layer retained in its pores(i.e.,thermal conductivity of 0.026 W/(m·K))effectively blocks heat transfer.Also,the introduction of HEP optimizes the pore structure,reduces the proportion of large pores,makes the heat conduction path more complex,delays the diffusion process of heat into the substrate,and significantly slows down the flame propagation rate and thermal decomposition process.The results of fire resistance test and pore structure show that the porosity of BMPC-HEP sample is higher than that of the control group,and the standard deviation of pore fluctuation increases from 4.0%to 5.1%,indicating that HEP forms a lightweight porous structure at a high temperature,further improving the thermal insulation performance and thermal stability of the material.The addition of HEP has a significant effect on the microstructure of BMPC at a high temperature.Some struvite and unreacted raw materials absorb a large amount of heat during pyrolysis,which plays a role in delaying temperature rise and enhancing thermal buffering,and provides an important support for the thermal insulation protection mechanism of fire retardant coatings. Conclusions The expanded perlite after water absorption treatment had little effect on the mechanical properties of BMPC system.When the density reduced from 1062 kg/m3 to 647 kg/m3,the 28-d compressive strength and adhesive strength were only reduced by 26.5%and 17.7%,respectively.At the content of HEP of 20%,the thermal conductivity and thermal diffusivity of BMPC were 49.3%and 44.0%lower than those of BMPC without HEP,respectively.The significant improvement of this thermal performance could be mainly attributed to the fact that HEP itself had low density and low thermal diffusion characteristics,effectively slowing down the heat transfer rate in the process of temperature change,and thereby improving the thermal insulation performance of the material.The fire resistance limit of BMPC-HEP system reached 206 min,which was significantly better than that of the control sample.Its excellent fire resistance was mainly attributed to the synergistic effect of porous structure,low thermal conductivity filler and microstructure stability at a high temperature,indicating that it could have a promising application potential in the field of fire retardant coatings for steel structures.关键词
水镁石/磷酸镁防火涂料/膨胀珍珠岩/导热系数/耐火性能Key words
brucite/magnesium phosphate fireproof coating/expanded perlite/thermal conductivity/fire resistance分类
建筑与水利引用本文复制引用
王楠,李悦,龙世儒,林辉,刘雄飞..膨胀珍珠岩对水镁石基磷酸镁防火涂料性能的影响[J].硅酸盐学报,2026,54(5):1555-1563,9.基金项目
国家重点研发计划(2022YFC3803103) （2022YFC3803103）
国家自然科学基金(52308229,52278252). （52308229,52278252）
