Research On The Application Of Dry Flue Gas Desulfurization Residue In Cement And Road Building Materials

Dry flue gas desulfurization technology was widely adopted in China because of its advantages such as low investment, less land occupation and less water consume. But the comprehensive utilization of byproduct-desulfurization residue was difficult due to its complex chemical and mineral composition. Address these issues, based on research of physical and chemical performance of different origin and batch desulfurization residue, the high-tech and value-added comprehensive utilization idea of desulfurization residue was advanced in this paper. First, the effect of desulfurization residue on the mechanical properties of slag cement was investigated. Then, according to the characteristics of retarding and slight expansion, a research on preparation of special purpose cement for road base using desulfurization residue and cement-desulfurization residue stabilized macadam materials has developed. The results show that:(1) The main chemical and mineral compositions of esulfurization slag discharged by different desulfurization process are similar. They all make up of byproduct of desulfurization, fly ash and residual desulfurization agent mainly, and their particle size is smaller than ordinary fly ash. Desulfurization residue has determinate potential activity for it contains some fly ash, and they also have many activation components, which can not only adjust the SO3 content of the material, but also activate the mixed materials fully.(2) Desulfurization residue can extend the setting time of desulfurization residue-slag composite cement obviously. It has shown a law that the compressive strength of the composite cement increased first and then decreased while the desulfurization residue content increased, the compressive strength peaked as the content of the desulfurization residue is 16.5%. Contrast with the slag cement without desulfurization residue, the initial and final setting times of the composite cement extended by 2h and 4h,3 days and 28d compressive strength increased by 20% and 18%. Furthermore, the expansion rate of the composite cement increased while the dry shrinkage reduced on the other hand.(3) By researching the influence of desulfurization residue content, clinker content and blending ratio of slag and fly ash on the performance of the special purpose cement, the ratio of the special purpose cement has been optimized. When the clinker content is 37%, desulfurization residue content is 8%, the slag content is equal to the fly ash as 26% and natural gypsum content is 3%, the performance of the special purpose cement with desulfurization residue for road base is the best. Compared with ordinary cement, the setting time of the special purpose cement is longer as its initial setting time is 444 minutes and final setting time reached 592 minutes, the early strength of the special purpose cement stabilize macadam is higher as its 7d unconfined compressive strength increased by 8% and 28d unconfined compressive strength increased by 17%, it also has less dry shrinkage and better anti-cracking properties as its 28d dry shrinkage index decreased and dry shrinkage anti-cracking coefficient increased by 78%.(4) The doping amounts of desulfurization residue effect obviously on the 7d, 28d unconfined compressive strength of cement-desulfuration residue stabilized crushed-stones. Results show that the 5% desulfurization residue content has the greatest effect. The mechanical strength of cement-desulfuration residue stabilized crushed-stones are much higher than that of the stones doped with same content of fly ash. Desulfurization residue can improve the shrinkage and crack resistance. SO3 which is up to 10% in it generate ettringite crystal to compensate part of the shrinkage. Combining with the interaction of active effect and micro-aggregate effect of fly ash grain among it, desulfurization residue decrease the dry shrinkage deformation of material and the crack resistance is improved.