HE Xiao^1a， ZHOU Wenjuan¹， LIU Yang²， DUAN Zhenhua³

1a. School of Civil and Transportation Engineering， 1b. Technology Innovation Centre for Construction Waste Resource Utilization Project，Ministry of Housing and Urban-Rural Development，Beijing University of Civil Engineering and Architecture， Beijing 100044， China；

2.Dandong Natural Resources Affairs Service Center， Dandong 118000， China；

3.College of Civil Engineering，Tongji University，Shanghai 200092， China

Abstract

Objective Raw soil has low strength and poor durability， but it offers advantages such as recyclability， good thermal performance， and ease of construction. The strength and durability of raw soil can be improved through chemical modification by active materials such as cement， gypsum， lime， and fly ash. The strength of raw soil can be improved through physical modification by recycled aggregates made from crushed and screened waste concrete， bricks，etc.Therefore， to fully utilize raw soil in modern construction industry， lime and fly ash are needed to blend into recycled aggregate-raw soil composite to improve durability.

Methods The mass fractions of raw soil， recycled fine aggregates， and recycled coarse aggregates were set at 60%，10%， and  30%， respectively. The mass of water was set to 14% of the total mass of the three raw materials. After mixing the three raw materials， water was added to produce the initial specimen of recycled aggregate-raw soil composite. Chemical modification was carried out by adding different dosages of lime and fly ash，with lime mass fractions set at 6%，7%，7%，8%，and 8%，and fly ash mass fractions set at 12%，12%，13%，13%， and 14%，respectively. Through water resistance， erosion， wet-dry cycling，and freeze-thaw cycling tests，the water resistance，erosion resistance，wet-dry cycling resistance，and freeze-thaw resistance of the recycled aggregate-raw soil composite were analyzed. X-ray diffraction and scanning electron microscopy were used to characterize the hydration products and microstructure of the recycled aggregate-raw soil composite.

Results and Discussion With the increase in lime and fly ash dosage，the softening coefficient of the specimens increased，and the water resistance was gradually enhanced. When the lime mass fraction was 8% and the fly ash mass fraction was 14%，the recycled aggregate-raw soil composite specimen exhibited the highest softening coefficient and the best water resistance. Its erosion resistance was significantly improved with an erosion resistance time of up to 60 minutes. The specimen had the smallest mass loss rate. After 15 wet-dry cycles， both the mass loss rate and compressive strength loss rate were at their minimum values，showing the best resistance to wet-dry cycles. After 25 freeze-thaw cycles，the mass loss rate of the specimen was less than 5% and the compressive strength loss rate was less than 25%，demonstrating the best freeze-thaw resistance of the recycled aggregate-raw soil composite specimen.

Conclusion The alkaline effect of lime activates the reactive substances（SiO₂，Al₂O₃）in the raw soil， fly ash， and recycled micro powder， participating in the hydration reactions to generate C-S-H gel，C-A-S-H gel，Ca（OH）₂ crystals， and calcium vanadate crystals. These hydration products fill the cracks and pores within the recycled aggregate-raw soil composite， enhancing the adhesion between the particles and improving the durability of the recycled aggregate-raw soil composite.

Keywords：recycled aggregate-raw soil composite； lime； fly ash； durability； microstructure

Get Citation: HE Xiao，ZHOU Wenjuan，LIU Yang，et al. Effects of lime and fly ash dosage on durability of recycled aggregate - raw soil composite［J］.China Powder Science and Technology，2025，31（5）：1−10.

Received: 2024-09-03,Revised: 2024-12-31,Online: 2025-03-01.

Funding Project: 国家重点研发计划项目，编号：2022YFC3803403。

First Author: 何晓（2000—），女，硕士生，研究方向为固体废弃物的资源化利用。E-mail：hexiaoya0222@163.com。

Corresponding Author: 周文娟（1977—），女，副教授，硕士，硕士生导师，研究方向为固体废弃物的资源化利用。E-mail：zhouwenjuan@bucea.edu.cn

DOI：10.13732/j.issn.1008-5548.2025.05.012

CLC No:TB4； TU521             Type Code:A

Serial No:1008-5548（2025）05-0001-10