Microstructure and mechanical properties of cement-based composites doped with silica manganese slag and desert sand

LAN Yongjun; ZHANG Zhe; ZHOU Zhiyao; WANG Zi; MENG Songsong; LI Hongbo

doi:10.13732/j.issn.1008-5548.2025.02.006

Abstract：Objective The microstructures and mechanical properties of cement-based composites were studied by using silica manganese slag and desert sand as admixtures,and the feasibility of preparing cement-based composites instead of cement was analyzed. Methods Using Portland cement and standard sand cement as control groups,silicon manganese slag and desert sand cement-based samples were prepared.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)were employed to analyze the microstructure and hydration products of four different groups of cement-based composites.Flexural and compressive strength tests were conducted to evaluate the mechanical properties of the samples.Microstructural illustrations of the microcementation surface were drawn to analyze the impact of microstructure on mechanical properties. Results and Discussion XRD spectra revealed the presence of calcium hydroxide Ca(OH)2 and ettringite(AFt)diffraction peaks in all four groups.The silicon manganese slag particles in samples S1exhibited hydration activity,accelerating the hydra-tion reaction of tricalcium silicate C3S in the later curing stages,resulting in the production of a significant amount of AFt,cal-cium silicate hydrate gel(C-S-H),and Ca(OH)2 crystals.SEM analysis showed that samples S0 and S1 had a higher quantity of hydration products and a denser,stable structure.Conversely,samples S2 and S3 had fewer hydration products and exhibited numerous pores and cracks,indicating structural instability.The flexural and compressive strengths of all four groups increased with the curing period.The order of flexural and compressive strength from highest to lowest was S0,S1,S2,and S3.At 28 days of curing,the flexural strengths of samples S0,S1,S2,and S3 were 2.8,2.6,2.4,and 1.6 MPa,respectively,while the com-pressive strengths were 58.8,57.6,41.7,and 24.1 MPa,respectively.Samples S0 and S1 had similar compressive strengths,both higher than those of S2 and S3,indicating that silicon manganese slag was more suitable to substitute cement for cement-based materials.Illustrations of the microcementation surface for samples S0,S1,and S2 were drawn.In sample S1,the silicon manganese slag was in close contact with the cement particles,forming a denser microstructure.Sample S2's large standard sand particles led to more pores in the microstructure.In sample S3,the presence of cluster accumulation in some desert sand reduced the overall structural stability. Conclusion When the mass fraction of silicon manganese slag is 15％and the curing period is 28 days,the microstructure of the silicon manganese slag cement-based sample is dense,with mechanical properties close to those of the Portland cement sample.Compared to desert sand,silicon manganese slag is more suitable to substitute cement for the preparation of cement-based com-posite materials.