Research On Method Of Synthesis Environment Estimation And Mechanism Of Strength For Pure Alkali Residue

Alkali residue is the industrial waste produced by ammonia soda process. If this waste cannot be dealt with properly, it will not only occupy a large amount of land resources but also cause serious pollution to our ecological environment. In this paper, the key problem to be solved urgently in the application of the alkali residue in engineering practice is studied. The objective of the study is to make the industrial waste alkali residue become a kind of resources which can be reused and doesn't pollute the environment.In order to investigate the engineering properties of alkali residue, a lot of laboratory tests are carried out on the basis of the analysis of previous studies and existing problems. The variation of the strength of in-place and compacted alkali residue with its water content, dry density and time is studied and the correspondence between the water content and the sensitivity is also revealed by the tests. In addition, the method to determine the bearing capacity of alkali residue is proposed and the relation between the water content and the characteristic root of the bearing capacity of alkali residue is obtained through the field tests. At the same time the chemical constitution and crystal structure of alkali residue is analyzed and how the strength of alkali residue forms is explained by the use of electron scanning technique and the corresponding chemistry analytical methods. On this basis, compressive environmental evaluation methods in the engineering application of alkali residue are investigated and the following conclusions can be drawn:1. Alkali residue is a kind of special soil which is different from natural soil. The unconfined shear strength of pure alkali residue is 48kPa whose optimum water content is 49.9%. While when w=90%, cu=71.5kPa. This indicates that the shear strength at the optimum water content isn't the maximum, which is significantly different from common soil in engineering practice.2.γdmax is got when the water content is wop for common clay and its shear strength is high when the saturation degree is about 80 percent. When the optimum water content of alkali residue is reached, Sr=57%,and the shear strength is not the maximum. But when w=90%, Sr=79%,and the strength of alkali residue reaches maximum, which is similar to common clay.3. Aragonite crystals in alkali residue are acicular, which makes it be the acicular cross structure. And acicular crystals cross reciprocally is the reason why the shear strength value is big for alkali residue with high water content4. When alkali residue is unsaturated, cement between natural alkali residue particles and aragonite crystals which are acicular or sinewy are destroyed by compaction. Therefore, shear strength of compacted alkali residue is higher than that of natural one.5. With time going on, acicular or sinewy aragonite crystals will overgrow on the calcite surfaces which are platelike or prismatic in alkali residue, which will make the particles to connect with each other and increase the rigidity of the structure of alkali residue. This is the fundamental reason why the strength of alkali residue increases with time.6. Alkali residue-water-electrolyte system is the main factor affecting the shear strength of alkali residue. When w=90%, ion concentration reaches the maximum value in the pores and the water cements between particles becomes the strongest, which makes the shear strength of alkali residue reach maximum when w=90%.7. The pollution to the environment can be avoided by adopting appropriate approaches in the application of alkali residue in engineering practices.The researches in this paper provide scientific data for the use of alkali residue as reclaimed resources, which is of vital importance for its engineering application.