高镁磷尾矿作为矿物掺合料应用于混凝土性能研究

Study on performance of concrete with high-Mg phosphate tailing as mineral admixture

高镁磷尾矿是磷矿反浮选过程产生的固体废弃物,主要矿物相为白云石、少量氟磷灰石和石英。将磷尾矿烘干粉磨后制成磷尾矿粉,分析了磷尾矿粉粒径分布、毒害性,参照GB/T51003—2014《矿物掺合料应用技术规范》测定了磷尾矿粉相关性能指标。以水泥、磷尾矿粉、粉煤灰为凝胶材料,制备了不同强度等级C30、C40、C50及C60混凝土,测定了混凝土工作性能、力学性能,并分析了掺磷尾矿粉水泥浆不同水化龄期的矿物组成。结果表明,经过烘干粉磨后,磷尾矿粒径D_(90)由133.1μm降至63.4μm,烧失量为39%、28d活性指数为70%、亚甲蓝值小于1.4、流动度比大于100%。当磷尾矿粉占总凝胶材料10%时配制的C60混凝土,坍落度为230mm、28d强度为64.1MPa、90 d强度为78.6 MPa;在养护龄期为90 d时,磷尾矿粉水泥硬化体中出现新矿物相水滑石,有利于混凝土后期强度增长。磷尾矿粉可作为矿物掺合料用于制备混凝土。

High-Mg phosphate tailing is a solid waste produced in the reverse flotation process of phosphate rock.The main mineral phase is dolomite,containing a small amount of fluorapatite and quartz.The phosphate tailing was dried and ground to produce phosphate tailing powder.The particle size distribution and toxicity of phosphate tailing powder were analyzed,and the related performance indexes were determined according to GB/T 51003—2014“Technical Specification for Applica⁃tion of Mineral Admixtures.”Concretes with different strength grades of C30,C40,C50 and C60 were prepared using ce⁃ment,phosphate tailing powder and fly ash as gel materials.Working and mechanical properties of concrete were measured,and mineral composition of cement slurry with phosphate tailing powder at different hydration ages was analyzed.The results showed that the average particle size D_(90)of the phosphate tailing was decreased from 133.1μm to 63.4μm after drying.The firing loss of phosphate tailing powder was 39%,the 28 d activity index was 70%,and the methylene blue value was less than 1.4.The fluidity ratio of colloidal sand was greater than 100%.When 10%of the total gel material was added with phos⁃phate tailing powder,the slump of C60 concrete was 230 mm,the strength of 28 d was 64.1 MPa,and the strength of 90 d was 78.6 MPa.At the curing age of 90 d,the new mineral phase hydrotalcite appeared in the cement hardening body mixed with phosphate tailing powder,which was conducive to the strength growth of concrete in the later stage.Phosphorus tail powder could be used as mineral admixture to prepare concrete.