Mechanical and microstructural characterization on novel flowable solidified soil from completely decomposed granite and bio-carbonated reactive magnesia cement

Abstract

Advancing sustainable infrastructure requires integrating biotechnological processes with geomaterial valorization. This study evaluates a novel flowable solidified soil (FSS) produced from completely decomposed granite (CDG) and bio-carbonated reactive magnesia cement (RMC), using polycarboxylate (PCE) and melamine water-reducing admixtures to optimize performance. Laboratory tests investigated the slump flow, density, unconfined compressive strength (UCS), secant modulus of elasticity (E₅₀), degree of carbonation (DC), composition and microstructure of bio-carbonated specimens (BC-specimens) with different bacterial solution (BS) and admixture contents. The results show that all BC-specimens met FSS flowability and strength requirements. Increasing BS content enhanced slump flow and DC but reduced density and UCS due to increased porosity. Both admixtures markedly enhanced flowability (maximum slump flow 30.60 cm at 55% BS and 1% melamine), while density and E₅₀ changed little. However, PCE reduced DC and UCS, whereas melamine enhanced both, achieving a maximum UCS of 1.47 MPa at 45% BS and 1% melamine. PCE induced air entrainment and inhibited the bio-carbonation through steric hindrance and Mg²⁺ complexation, while melamine improved particle dispersion and Mg²⁺ availability. Overall, the proposed FSS is feasible, and melamine is recommended for practice. These results provide guidance for developing more sustainable FSS.

Graphical abstract

Keywords

FSS / CDG / RMC / bio-carbonation / water-reducing admixture

References

[1] Lei B F , Pang S , Sun J C , Fan H H , Xie F H , Deng S , Chen S F . Rheological properties and freeze–thaw durability of fiber-reinforced flowable solidified soil incorporating multi-source waste. Results in Engineering, 2025, 28: 107892

[2] Zhou Y X , Zhang R J , Yang X G , Hou L . The design methodology for proportioning fluidized solidified soil. Journal of Building Engineering, 2025, 111(15): 113127

[3] T/BGEA 001-2019. Technical Standard for Backfilling Project by Using Premixed Fluidized Solidified Soil. Beijing: China Architecture & Building Press, 2019 (in Chinese)

[4] Akhtar A , Sarmah A K . Construction and demolition waste generation and properties of recycled aggregate concrete: A global perspective. Journal of Cleaner Production, 2018, 186: 262–281

[5] Luhar S , Cheng T W , Luhar I . Incorporation of natural waste from agricultural and aquacultural farming as supplementary materials with green concrete: A review. Composites Part B: Engineering, 2019, 175: 107076

[6] Ali M B , Saidur R , Hossain M S . A review on emission analysis in cement industries. Renewable and Sustainable Energy Reviews, 2011, 15(5): 2252–2261

[7] Hossain M A , Yin J H . Shear strength and dilative characteristics of an unsaturated compacted completely decomposed granite soil. Canadian Geotechnical Journal, 2010, 47(10): 1112–1126

[8] Dassekpo J B M , Zha X , Zhan J P . Compressive strength performance of geopolymer paste derived from completely decomposed granite (CDG) and partial fly ash replacement. Construction and Building Materials, 2017, 138: 195–203

[9] Zhan L T , Zhang Z , Chen Y M , Chen R , Zhang S , Liu J , Li A G . The 2015 Shenzhen catastrophic landslide in a construction waste dump: Reconstitution of dump structure and failure mechanisms via geotechnical investigations. Engineering Geology, 2018, 238: 15–26

[10] Yan S , Tang H , Wu Z J , Li S T , Li P F . Study on strength characteristics and microstructure of completely decomposed migmatitic granite. KSCE Journal of Civil Engineering, 2023, 27(1): 80–97

[11] Zhao Y R , Chen X S , Wen T D , Wang P H , Li W S . Experimental investigations of hydraulic and mechanical properties of granite residual soil improved with cement addition. Construction and Building Materials, 2022, 318: 126016

[12] Bahmani S H , Huat B B K , Asadi A , Farzadnia N . Stabilization of residual soil using SiO₂ nanoparticles and cement. Construction and Building Materials, 2014, 64: 350–359

[13] Kim Y S , Tran T Q , Kang G O , Do T M . Stabilization of a residual granitic soil using various new green binders. Construction and Building Materials, 2019, 223: 724–735

[14] Latifi N , Eisazadeh A , Marto A , Meehan C L . Tropical residual soil stabilization: A powder form material for increasing soil strength. Construction and Building Materials, 2017, 147: 827–836

[15] Soares E G , Castro-Gomes J . Carbonation curing influencing factors of carbonated reactive magnesia cements (CRMC)––A review. Journal of Cleaner Production, 2021, 305: 127210

[16] Mo L W , Panesar D K . Effects of accelerated carbonation on the microstructure of Portland cement pastes containing reactive MgO. Cement and Concrete Research, 2012, 42(6): 769–777

[17] Dung N T , Unluer C . Performance of reactive MgO concrete under increased CO₂ dissolution. Cement and Concrete Research, 2019, 118: 92–101

[18] Yang Y , Ruan S Q , Wu S F , Chu J , Unluer C , Liu H L , Cheng L . Biocarbonation of reactive magnesia for soil improvement. Acta Geotechnica, 2021, 16(4): 1113–1125

[19] Ruan S Q , Qiu J S , Weng Y W , Yang Y , Yang E H , Chu J , Unluer C . The use of microbial induced carbonate precipitation in healing cracks within reactive magnesia cement-based blends. Cement and Concrete Research, 2019, 115: 176–188

[20] Hoang T , Dung N T , Unluer C , Chu J . Use of microbial carbonation process to enable self-carbonation of reactive MgO cement mixes. Cement and Concrete Research, 2021, 143: 106391

[21] Chen Z , Fang X W , Long K Q , Shen C N , Yang Y , Liu J L . Using the biocarbonization of reactive magnesia to cure electrolytic manganese residue. Geomicrobiology Journal, 2021, 38(8): 709–718

[22] Wang R , Tang C S , Pan X H , Wang D L , Dong Z H , Zhang X Y , Lu X C . Efficient stabilization of dredged sludge with high water content using an improved bio-carbonation of reactive magnesia cement method. Journal of Rock Mechanics and Geotechnical Engineering, 2024, 16(9): 3760–3771

[23] Wang D L , Tang C S , Pan X H , Dong Z H , Wang R , Zhang J Z , Ji X L , Hu H C , Shi B . Construction and demolition waste stabilization through biocarbonation of reactive magnesia cement: Effect of urea concentration. Journal of Materials in Civil Engineering, 2025, 37(1): 04024450

[24] Shi J Q , Xiao Z H , Xiao Y , Liu H L . Bio-molding of lunar regolith with bio-carbonized magnesium oxide. Biogeotechnics, 2025, 3(4): 100159

[25] Xiao Y , Zhang Z C , Stuedlein A W , Evans T M . Liquefaction modeling for biocemented calcareous sand. Journal of Geotechnical and Geoenvironmental Engineering, 2021, 147(12): 04021149

[26] Zhang J X , Yang X , Liu H L , Chu J . Role of bacteria on bio-induced calcium carbonate formation: insights from droplet microfluidic experiments. Géotechnique, 2024, 75(6): 787–799

[27] Xiao Y , He X , Stuedlein A W , Chu J , Evans T M , van Paassen L A . Crystal growth of MICP through microfluidic chip tests. Journal of Geotechnical and Geoenvironmental Engineering, 2022, 148(5): 06022002

[28] Liu H L , Xiao Y , Shi J Q , Cao B F , Sun J B. . 3D printing lunar regolith simulant with microbial-carbonated magnesium oxide.. Biogeotechnics, 2025, 100197

[29] Zhao C , Xiao Y , Liu H L , Chu J . Effects of urease and cementing solution concentrations on micro-scale enzymatic mineralisation characteristics. Géotechnique, 2024, 75(6): 732–746

[30] Rajasekar A , Wilkinson S , Moy C K S . MICP as a potential sustainable technique to treat or entrap contaminants in the natural environment: A review. Environmental Science and Ecotechnology, 2021, 6: 100096

[31] Wang H X , Tong T Z , Sun X H , Miao L C , Chu J , Wang D L , Shi J Q , Wang Y . Low-carbon and highly efficient sand solidification based on the combined bio-carbonation of reactive magnesia and enzymatically induced carbonate precipitation. Journal of Environmental Chemical Engineering, 2025, 13(2): 115670

[32] Lei L , Hirata T , Plank J . 40 years of PCE superplasticizers—History, current state-of-the-art and an outlook. Cement and Concrete Research, 2022, 157: 106826

[33] Khayat K H . Viscosity-enhancing admixtures for cement-based materials—An overview. Cement and Concrete Composites, 1998, 20(2–3): 171–188

[34] Liu J , Yu C , Shu X , Ran Q , Yang Y . Recent advance of chemical admixtures in concrete. Cement and Concrete Research, 2019, 124: 105834

[35] Hay R , Khalil A , Otchere C , Alanis S , Celik K . Proportioning, carbonation, performance assessment, and application of reactive magnesium oxide cement-based composites with superplasticizers. Journal of Materials in Civil Engineering, 2023, 35(2): 04022405

[36] ASTM D2487-11. Standard Practices for Classification of Soils for Engineering Purposes (Unified Soil Classification System). West Conshohocken, PA: ASTM, 2011

[37] GB/T 50123-2019. Standard for Geotechnical Testing Method. Beijing: China Planning Press, 2019 (in Chinese)

[38] YB/T 4019-2020. Determination of Chemical Activity of Light Calcined Magnesia. Beijing: Metallurgical Industry Press, 2020 (in Chinese)

[39] Whiffin V S. Microbial CaCO₃ Precipitation for the Production of Biocement. Dissertation for the Doctoral Degree. Perth: Murdoch University, 2004

[40] ASTM D2166/D2166M-18. Standard Test Method for Unconfined Compressive Strength of Cohesive Soil. West Conshohocken, PA: ASTM, 2018

[41] Wang D L , Tang C S , Pan X H , Wang R , Shi M , Dong Z H , Zhang Y C , Shi B . A novel bio-carbonation method of reactive magnesia with urea pre-hydrolysis for geomaterial stabilisation. Géotechnique, 2023, 74(13): 1634–1648

[42] Wu J , Liu L , Deng Y F , Zhang G P , Zhou N , Xiao H L . Use of recycled gypsum in the cement-based stabilization of very soft clays and its micro-mechanism. Journal of Rock Mechanics and Geotechnical Engineering, 2022, 14(3): 909–921

[43] Criado M , Fernández-Jiménez A , Palomo A , Sobrados I , Sans J . Effect of the SiO₂/Na₂O ratio on the alkali activation of fly ash. Part II: ²⁹Si MAS-NMR survey. Microporous and Mesoporous Materials, 2008, 109(1–3): 525–534

[44] Silva R V , Neves R , De Brito J , Dhir R K . Carbonation behaviour of recycled aggregate concrete. Cement and Concrete Composites, 2015, 62: 22–32

[45] Weinstein L , McDonald A . The effect of urea, urethane and other carbamates on bacterial growth. Science, 1945, 101(2611): 44–45

[46] Dong Z H , Pan X H , Tang C S , Wang D L , Wang R , Shi B . An efficient microbial sealing of rock weathering cracks using bio-carbonation of reactive magnesia cement. Construction and Building Materials, 2023, 366: 130038

[47] Zhang C , Sun Y J , Yang Y . Bio-carbonation of reactive magnesia cement in geotechnical engineering practice: A state-of-the-art review. Journal of Sustainable Cement-Based Materials, 2024, 13(11): 1567–1581

[48] Yamada K , Takahashi T , Hanehara S , Matsuhisa M . Effects of the chemical structure on the properties of polycarboxylate-type superplasticizer. Cement and Concrete Research, 2000, 30(2): 197–207

[49] Tayebi M , Ilango N K , Nguyen H , Lori A R , Ranjbar N , Carvelli V , Kinnunen P . New insights into hydration of MgO in the presence of polycarboxylate ether superplasticizers. Cement and Concrete Composites, 2025, 162: 106153

[50] Kjeldsen A M , Flatt R J , Bergström L . Relating the molecular structure of comb-type superplasticizers to the compression rheology of MgO suspensions. Cement and Concrete Research, 2006, 36(7): 1231–1239

[51] Zhu Y Q , Li Y J , Sun X Y , Guo Z , Rui S J , Zheng D Q . A one-phase injection method to improve the strength and uniformity in MICP with polycarboxylic acid added. Acta Geotechnica, 2025, 20(5): 2279–2291

[52] Mangi H N , Ma L Q , Sajib M H , Yan D T , Ahmad Q A , Ngo I , Yang X H . CO₂ carbonation process of cemented paste backfill material using polycarboxylate ether (PCE) and MgCl₂. Results in Engineering, 2025, 28: 107742

[53] Zhu J F , Hui J , Luo H J , Zhang B , Wei X H , Wang F , Li Y F . Effects of polycarboxylate superplasticizer on rheological properties and early hydration of natural hydraulic lime. Cement and Concrete Composites, 2021, 122: 104052

[54] Lei L , Zhang L . Synthesis and performance of a non-air entraining polycarboxylate superplasticizer. Cement and Concrete Research, 2022, 159: 106853

[55] Grabiec A M . Contribution to the knowledge of melamine superplasticizer effect on some characteristics of concrete after long periods of hardening. Cement and Concrete Research, 1999, 29(5): 699–704

[56] Li H , Wang Z H , Zhang Y W , Zhang G F , Zhu H M . Composite application of naphthalene and melamine-based superplasticizers in alkali activated fly ash (AAFA). Construction and Building Materials, 2021, 297: 123651

[57] Tekin İ , Pekgöz M , Saleh N K , Kiamahalleh M V , Gholampour A , Gencel O , Ozbakkaloglu T . Compatibility of melamine formaldehyde- and polycarboxylate-based superplasticizers on slag/sintering ash-based geopolymer paste. Construction and Building Materials, 2025, 458: 139681

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