LUO Jiebo1a，PENG Xiaotong1a，LIU Zhaolei2，WANG Zhongqing2，ZHANG Xiuzhi1b
1a.School of Civil Engineering and Architecture，1b.School of Materials Science and Engineering，University of Jinan，Jinan 250022，China；2.China Railway Tenth Bureau Group Co.，Ltd.，Yantai 264001，China
Abstract
Objective An innovative non-autoclaved aerated concrete（NAAC）is developed to achieve an optimal balance between thermal insulation and mechanical properties，addressing the demand for energy efficiency and environmental sustainability in construction.Traditionally，the production of aerated concrete relies on autoclaving to enhance material strength，which is highly energy-consuming and has stringent re-quirements on equipment.To overcome these limitations，the study focuses on the non-autoclaved process，systematically optimizingraw mat-erials ratios to enhance material performance.By refining silica fume dosing and cement grade，the optimal test ratios for strength enha-ncement are determined without significantly increasing thermal conductivity.
Methods This study used a single-factor test method to optimize the composition in aerated concrete.By designing tests with varying si-lica fume substitution rates，the dry density and compressive strength of each specimen were analyzed.Based on these results，the cement grade was varied to determine the optimal silica fume admixture and cement grade.Firstly，a small amount of silica fume was used to addr-ess the insufficient strength of traditional autoclaved aerated concrete while ensuring minimal impact on thermal conductivity.The effec-ts of silica fume content on material performance were assessed to determine the optimal substitution rate.Subsequently，the effects of different cement grades on NAAC performance were explored through additional tests.Finally，the microstructure of the optimal NAAC was analyzed using a scanning electron microscope（SEM）.
Results and Discussion Optimizing silica fume content and cement grade proved effective in improving the strength of NAAC，while mai-ntaining the ideal thermal conductivity for self-insulated wall panels.Increasing silica fume content improved the dry density and compr-essive strength of the material.At a silica fume substitution rate of 2%，the dry density was the smallest，while at a substitution rate of 10%，the compressive strength was the highest.A 4% substitution rate was proved to strike the best balance：the dry density increased minimally by 0.92%，and compressive strength increased significantly by 4.17%，with an increase of only 7% in thermal conductivity compa-red to the benchmark group.These findings demonstrated that the material is both lightweight and high-strength.The addition of silica fu- me，which had a lower density and higher reactive silica content compared to fly ash，resulted in lighter wall panels.Changing the cement grade also influenced material properties.Specimens made with P.O 52.5 silicate cement exhibited higher compressive strength and lower dry density than those made with P.O 42.5 silicate cement. However，the thermal conductivity of the P.O 52.5 specimens increased by 5.43% at the same mix ratio.Microstructural analysis revealed that silica fume’s pore structure did not significantly change thermal conductivity，and the fibres could be pulled out from the matrix，enhancing compressive strength. Moreover，the use of silica fume and P.O 52.5
cement promoted the distribution of the acicular hydrated calcium silicate（C-S-H）and hexagonal flake or plate calcium hydroxide（CH） along the inner side of the pore walls.These hydration products intertwined to form a mesh-like structure，which enhanced the overall st-rength and stability of the material.
Conclusion The optimal silica fume content for non-autoclaved self-insulating aerated concrete is determined to be 4%（mass fraction）. Compared to fly ash，silica fume’s lower density and higher reactive silica content effectively reduce the weight of the wall panel mat-erials when used as an admixture.As self-insulated wall panels are mainly self-supporting，their compressive strength requirements are relatively low.Specimens prepared with P.O 52.5 silicate cement demonstrate superior performance in engineering practice，achieving a dry density of 798 kg/m3 ，a compressive strength of 3.9 MPa，and a thermal conductivity coefficient of 0.095 53 W/（m·K）.These values meet the A2.5 B06 grade specifications for aerated concrete，ensuring both performance and compliance.
Keywords： non-autoclavedaeratedconcrete；dry density；compressive strength；silica fume；microstructure
Get Citation:LUO Jiebo，PENG Xiaotong，LIU Zhaolei，et al.Effect of silica fume and cement on the properties of non⁃autoclaved aerated concrete and microanalysis［J］.China Powder Science and Technology，2025，31（2）：1−9.
Received:2024-10-22，Revised:2024-11-23，Online:2025-01-20.
Funding Project:国家自然科学基金项目，编号：52178211。
First Author:罗杰波（2000—），男，硕士生，研究方向为新材料结构。E-mail：1151579328@qq.com。
Corresponding Author:彭晓彤（1973—），男，教授，博士，硕士生导师，研究方向为新材料结构。E-mail：pengxito@163.com。
DOI：10.13732/j.issn.1008-5548.2025.02.014
CLC No:TU528；TB4 Type Code:A
Serial No:1008-5548（2025）02-0001-09
