LIU Fengli¹ ，LUO Na¹ ，XIE Huang² ，WANG Wenhui¹ ，WANG Yagung¹ ,SHUI Zhetao³

1. School of Civil Engineering and Architecture， Henan University， Kaifeng，475004， China；2. CCCCSHEC Chengdu Urban Construction Engineering Co.， Ltd.， Chengdu 610218， China；3. Faculty of Engineering， The University of Sydney， New South Wales， Sydney 2006，Australia

Abstract

Objective The production of autoclaved aerated concrete requires large quantities of siliceous raw materials. Due to the gradual restriction of natural river sand and the escalating cost of fly ash， it is essential to find new siliceous raw materials. At the same time， there are huge reserves of solid wastes in our country， which damage the ecological environment and cause problems such as utilization difficulties. Therefore， the resource utilization of solid wastes has become a research hotspot. Granite powder is a byproduct generatedduring cutting ang grinding processes of granite stone. Given that quartz is the primary mineral constituent of granite powder， it theoretically holds potential as a substitute material for siliceous raw materials. The use of granite powder instead of natural sand to prepare autoclaved aerated concrete holds significant importance in developing AAC raw material sources， reducing production costs， and efficiently utilizing solid waste in bulk， thereby offering notable social and economic benefits. Moreover， investigating the mechanistic influence of granite powder on the properties of autoclaved aerated concrete holds considerable research value.

Methods Most of the literature primarily focuses on optimizing product properties and studying the influence of macroscopic properties， such as mechanical properties， with limited attention paid to microscopic mechanisms. In this paper， firstly， the effects of different dosages of granite stone powder on autoclaved aerated concrete slurry aerating， fluidity， compressive strength and dry density were investigated to determine the optimal dosage ratio. Secondly， for exploring the effect of granite stone powder on the physical and mechanical properties and microscopic properties of autoclaved aerated concrete， the products were characterized by X-ray diffraction， Scanning Electron Microscope and Fourier Transform Infrared. This paper not only studies the influence of granite powder content on the macroscopic properties of AAC， but also analyzes its microscopic properties through XRD， FTIR， SEM and other characterization methods. This approach reveals the microscopic mechanism underlying the influence of large granite powder content on AAC properties， with the research results offering insights into the resource utilization of significant granite powder content in AAC production and serving as a reference for future studies in this field.

Results and Discussion Slurry fluidity decreased with an increasing replacement rate of granite powder. However， there is no significant effect on the slurry gassing process. Calculations revealed that all slurries completed gassing approximately 50 minutes into the process. The amount of gassing in the slurries at five minutes and the total gassing volume decreased by only 3. 57% and 3. 04%， respectively. Besides， the compressive strength and specific strength of autoclaved aerated concrete exhibited a decreasing trend with the increase of granite powder， while the dry density showed minimal change. For replacement rates of granite powder at 60% or lower， the compressive strength and specific strength of the products decreased slowly. For replacement rates of granite powder exceeding 60%， the compressive strength and specific strength of the products decreased significantly. When the substitution rate of granite powder is 60%， the compressive strength of the product is 3. 02 MPa， and the dry density is 523 kg/m³， which meets the performance requirements of A 2. 5 and B 05. This finding provides a reference for the preparation of autoclaved aerated concrete with large dosage of low-grade siliceous solid waste. Under autoclave curing conditions， Ca（OH）₂ formed by the hydration of calcareous materials reacts with SiO₂ provided by siliceous raw materials to form tobermorite. The crystal clusters of the hydration products are interwoven with the unreacted mineral aggregate to form a good network dense structure， which has a positive effect on improving the strength of the product. The content of SiO₂ in granite stone powder is lower than that of Yellow River superfine sand， with the increase of granite powder mixing， the tobermorite content in the products decreases after autoclave reaction decreases， the crystallinity of tobermorite also decreases， which is the main reason for the decrease of the compressive strength of the products.

Conclusion In this paper， AAC was prepared by granite powder instead of natural sand， and the influence mechanism of granite powder on AAC properties was discussed. With an increase in granite powder content， both the compressive strength and specific strength of the product decreased， while the dry density remained relatively stable. When the replacement rate was below 60%， the compressive strength and specific strength of the product decline slowly， whereas rates exceeding 60% resulted in a significant decrease in both parameters. The Results show that the optimal mixing amount of granite powder is 60%. Microscopic analysis revealed thatthe SiO₂ content of granite stone powder is lower than that of Yellow River super fine sand. Furthermore， an increase in granite stone powder content led to a reduction in tobermorite content and crystallinity in the products after autoclave reaction， primarily responsible for the observed decrease in compressive strength. At this time， the performance of autoclaved aerated concrete can meet the national standards. This research not only broadens the way of stone processing waste re-resourcing， but also provides reference for the production of AAC by using granite stone powder in large admixture.

Keywords：granite stone powder； autoclaved aerated concrete； mechanical properties； microstructure