Study on the Properties and Microstructure of Multi-Solid Waste Ultra-High Performance Concrete
In order to improve the comprehensive utilization rate of solid waste such as lithium slag and phosphorus slag,ultra-high performance concrete(UHPC)was prepared by using lithium slag and phosphorus slag as composite admixtures instead of partial cement.The effect of changing the amount of composite admixtures on the compressive strength and microstructure of UHPC was studied.The results showed that compared with the reference group,the 3 d compressive strength of UHPC gradually decreased with the increase of the composite admixture content.Although the composite admixture was unfavorable for the early strength of UHPC,it had a significant enhancement effect on the later compressive strength.When the content of the composite admixture was 25%,the 28 d compressive strength of UHPC reached the maximum value of 145.78 MPa.Microscopic analysis showed that with the increase of age,the activity of the composite admixture was fully utilized,and its active SiO2 and Al2O3 would react with Ca(OH)2 to generate a large number of C-S-H,AFt and other hydration products.Ca2+ consumption further promoted the hydration of phosphorus slag,solid-waste synergistic coupling hydration,and promoted the later strength increase of UHPC.
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