Study On Preparation Of Ferronickel Slag Cementitious Material And Its Application For Rapid Repair Of Cement Concrete Pavement

Ferronickel slag cementitious material is a new type of magnesium oxychloride cement prepared by ferronickel slag,hydrochloric acid,light burned magnesia powder and water.The material has the advantages of fast hardening and early strength,good adhesion and good wear resistance,but its application is limited by poor water resistance and brittleness.As a kind of metallurgical solid waste,ferronickel slag has a high magnesium content.In this paper,ferronickel slag cementitious material was prepared by using ferronickel slag with high magnesium content.Water resistance modification and toughening modification were carried out by adding modifier and polypropylene fiber respectively,and then used as rapid repair material to repair pavement diseases such as cracks and holes in cement concrete pavement.It can not only achieve the purpose of solid waste utilization,but also meet the requirements of open traffic in a short time after the completion of pavement repair,which is of great significance to extend the service life of the road.The main research contents of this paper were as follows:(1)Firstly,the chemical composition and mineral composition of ferronickel slag were analyzed.The preparation process parameters such as filler sequence,stirring times and stirring time during the preparation of ferronickel slag cementitious materials were determined by laboratory tests,and the preparation process and precautions were obtained.The orthogonal test method was used to study the influence of three factors on the early compressive strength,flexural strength,fluidity and water resistance of each group of specimens by orthogonal test of three factors and three levels of ferronickel slag and hydrochloric acid mass ratio,light burned magnesia powder content and water consumption.The benchmark mix ratio of sequent water resistance modification and fiber toughening test was determined,and the microstructure of the benchmark mix ratio sample was analyzed.(2)The effects of single-doped phosphoric acid,citric acid,styrene-acrylic emulsion and compound-doped phosphoric acid and styrene-acrylic emulsion on the setting time,compressive strength and water resistance of ferronickel slag cementitious materials were studied.The phase composition and microstructure of the samples were analyzed by XRD and SEM microscopic test to determine the appropriate dosage of each admixture.Studies showed that single-doped phosphoric acid and citric acid can significantly improve the water resistance of the specimen and prolong the setting time.The styrene-acrylic emulsion had no obvious modification effect on the water resistance of each group of specimens.The water resistance modification effect of mixed phosphoric acid and styrene-acrylic emulsion was better than that of single-doped phosphoric acid.The four admixtures could all reduce the early strength.The comprehensive performance of 1% phosphoric acid and 3% styrene-acrylic emulsion was the best,and the softening coefficient reached 0.96.(3)Based on the optimal mixture ratio of water resistance modification,the effects of different lengths and different contents of polypropylene fiber on the fluidity,compressive strength,flexural strength and impact resistance of ferronickel slag cementitious materials were studied.The results showed that with the increase of polypropylene fiber content,the fluidity decreased gradually,the compressive and flexural strength of the specimens at each age increased gradually,and the number of initial and final cracks increased significantly.The addition of polypropylene fiber effectively improved the impact resistance of the material.On the basis of the optimal mix ratio of the above test,the bond strength test was carried out.(4)The pavement damage was investigated and the causes of the damage were analyzed.The suitable test section was selected to carry out the pavement disease repair test.After the pavement repair was completed,the requirements of open traffic could be achieved in a short time.According to the characteristics of ferronickel slag cementitious material,the construction technology and precautions of the repair material were summarized.