^{Yan Mengru， Jiang Chengshuai， Zhang Xiuzhi}

School of Materials Science and Engineering， University of Jinan， Jinan 250022， China

Abstract

Objective Foamed concrete （FC） has high porosity， strong permeability and water absorption， and exhibits significantly lower durability than ordinary concrete. During long-term service， degradation problems such as freeze-thaw damage and carbonation erosion severely restrict its engineering application. Using recycled micro-powder （RMP） to partially replace cement in preparing recycled micro-powder foamed concrete （RMFC） not only substantially facilitates efficient carbon emission reduction for energy-saving buildings， but also aligns with the strategic orientation of green and sustainable development in the building materials industry. Nevertheless， most existing studies focus on FC with a single density grade， and the regulation mechanism of RMP dosage on the mechanical properties and durability of FC with multiple density grades remains unclear. Therefore， this study adopts the control variable method to conduct comparative experiments to analyze the effects of RMP dosage on the mechanical properties and durability of FC with three densities （500 kg/m³， 600 kg/m³， and 700 kg/m³）. The research methods and findings can provide a theoretical basis and technical reference for the practical engineering application of RMFC.

Methods In this study， the control variable method was adopted for the test scheme. Four cement replacement ratios of RMP， namely 0%， 10%， 20%， and 30%， were designed. FC with dry densities of 500 kg/m³， 600 kg/m³， and 700 kg/m³ were selected as research objects， and a total of 12 mix proportion specimens were prepared. Corresponding FC specimens were prepared according to each RMP dosage. The experimental procedure consisted of multiple stages. First， tests on mechanical strength， water absorption， thermal insulation performance， drying shrinkage， frost resistance， and carbonation durability were conducted on the 12 groups of specimens. Then， the evolution patterns of various properties of FC under different RMP dosages and matrix densities were compared and analyzed. The optimal RMP dosage for each density grade was identified. Afterwards， X-ray diffraction （XRD） and scanning electron microscopy （SEM） were utilized to reveal the intrinsic mechanism by which RMP improved the performance of FC.

Results and Discussion The experimental results indicated that the compressive strength of FC increased significantly and water absorption decreased markedly with the increase of density. As the dosage of RMP increased， the compressive strength of FC at each density grade increased first and then decreased， while water absorption rate showed an opposite trend of first decreasing and then increasing. The mass water absorption and volumetric water absorption of FC followed the same variation trend. The thermal conductivity of FC with a density of 500 kg/m³ decreased with increasing RMP dosage， whereas the thermal conductivity of FC with densities of 600 kg/m³ and 700 kg/m³ first increased and then decreased. Under the same RMP dosage， FC with higher density possessed larger thermal conductivity. At a fixed density， the drying shrinkage value of FC increased remarkably with the growth of RMP dosage. The compressive strength loss rate decreased first and then increased， and the carbonation coefficient increased first and then decreased as RMP dosage increased. At an identical RMP dosage， raising the density of FC reduced drying shrinkage and compressive strength loss rate， while the carbonation coefficient increased with density. Combined analysis of XRD patterns and SEM images demonstrated that the improvement effect of RMP on FC originated from the synergy of pozzolanic activity and micro-aggregate filling effect， and the effectiveness of these two effects was strongly dependent on the controlled dosage of RMP.

Conclusion When the mass fraction of RMP is 10%， the compressive strength of FC with all density grades can be effectively improved and its water absorption rate can be reduced. Increasing the density of FC can also increase compressive strength and reduce water absorption rate. Although FC achieves the optimal thermal insulation performance at an RMP mass fraction of 30%， the matrix has high porosity at this dosage， which impairs other properties including compressive strength and water absorption rate. FC exhibits the best frost resistance and carbonation resistance at 10% RMP by mass， yet the incorporation of RMP increases the drying shrinkage of FC. Increasing the density of FC can not only mitigate drying shrinkage， but also further enhance frost resistance and carbonation resistance. FC with a density of 700 kg/m³ exhibits the best durability. The performance improvement mechanism of FC at 10% RMP mass fraction originates from the micro-aggregate effect and pozzolanic effect of RMP. At low RMP dosages， the two effects work synergistically to enhance the compressive strength and durability of FC. At high RMP dosages， insufficient inherent pozzolanic activity of RMP， together with the dilution effect of excess RMP， leads to declines in compressive strength and durability of FC. Taking overall performances such as compressive strength， water absorption， and durability into comprehensive consideration， the optimal mass fraction of RMP is determined to be 10%， and the optimal density of FC is 700 kg/m³.

Keywords： recycled micro-powder； foamed concrete； compressive strength； water absorption rate； durability

Get Citation:Yan Mengru， Jiang Chengshuai， Zhang Xiuzhi. Effects of recycled micro-powder on properties of foamed concrete with multiple density grades［J］. China Powder Science and Technology， 2026， 32（6）： 1-13.

Received:  2026-03-18， Revised： 2026-06-25， Online： 2026-10-12。

Funding： The research was supported by the National Natural Science Foundation of China (Grant No. 52178211).

DOI：10.13732/j.issn.1008-5548.2026.06.017

CLC No.:  TU528.2； TB44

Type Code:  A

Serial No.:  1008-5548（2026）06-0001-13