Particle Gradation Design Research About Limestone Powder Composite Gelled Powder Materials

As a kind of common and cheap waste material, Limestone powder's reasonable application in composite gelled material not only can effectively alleviate the current situation that the increasingly shortage of traditional admixture such as fly ash, and even can be a functional components to solve some problems of the flow property, etc when local admixture single doped. Therefore, studying the composite application characteristics of the limestone powder in different cement-based gelled system from the aspect of particle size distribution which was paid more and more attention in these years, and then universality and greatly realizing the effective utilization of limestone powder, is of great significance.Taking the powder particle size distribution as the main focus, this paper attempts to use limestone powder as functional components and study the characteristics and effect mechanism in the application of several kinds of composite gelled system. Combined with the actual project, we select natural pozzolan and self-igniting coal gangue which have a wide distribution as the composite component,and attempt to maximize the performance characteristics of limestone powder from the aspect of particle size distribution, in order to solve the problems when these local admixture single doped, and finally achieved good results. On the other hand, we use limestone powder in combination with ultra-fine fly ash and silica fume, relying on the Fuller model to design grading curve, through the best packing density to maximize play the particle packing advantages of limestone powder, and finally managed to get the high-performance composite admixture with good strength, flow property and economy. The results of the study are as follows:1)In the limestone powder- natural pozzolan composite system, getting plenty of fine limestone powder to increase the content of particle packing density is very important. The results of particle gradation design show that the composite of natural pozzolan with essentially the same particle size distribution of cement and limestone powder with higher levels of fine particles is the most appropriate, it can improve the performance of the system with large degree of increase, and ensure the grinding energy consumption cost efficiency at the same time.2)Compositing limestone powder with appropriate particle size distribution can well solve the problem of the flow property when self-igniting coal gangue singledoped. The closer to Fuller curve grading requirements by mixing limestone powder with higher levels of fine particles, the better the performance of the flow. according to the results of particle gradation design, composite self-igniting coal gangue with particle size D50 of 0.75 times of benchmark cement and limestone powder with D50 of 0.348 times, can better play to the physical grain filling effect, and improves the performance of the composite mortar system with larger degree of optimization.3)In limestone powder- ultra-fine fly ash- silica fume composite system, due to the smaller water adsorption of limestone powder, its effect on filling in grading system is more important than its material characteristics, so after quantifying some materials components which have larger influence by their material characteristics such as silica fume, we can identify the powder composite proportion which is most close to the best packing density relying on the Fuller curve and according to the particle size distribution of limestone powder. This design method for limestone powder in the application of the composite system is quite feasible.4)From the aspect of the particle size distribution, compositing with limestone powder which is used as functional component to solve problems when some kind of local admixture single doped or to replace part of active components which have a higher price is very feasible. It more should be for the purpose of making powder system achieve the best packing density as much as possible, and take the particle gradation design as the key to practical application.