Mix Design And Road Performance Of Cement And Flyash Stabilized Crushed-stones Roadbases

In recent years the roadbase of cement and fly ash stabilized crushed-stones is being used in some provinces. It is testified that this material has better working properties and application perspective. But the 《Technical Specifications for Construction of Highway Roadbases》 has no technical specifications, and available research conclusions are deficient in systematization, so the department of highway design and construction has few restrictions When applying this material. In order to supply scientific method for prospective departments, this paper cam's out the following five research works in details: (1) the mix design research of cement and fly ash stabilized crushed-stones; (2)reaction theory research of cement and flyash; (3)working properties research of cement and flyash stabilized crushed-stones;(4)mechanics analysis of cement and fly ash stabilized crushed-stones; (5)mix design method research of cement and flyash stabilized crushed-stones .1. Fly ash stabilized crushed-stones mix design includes aggregate's grading envelope,the proportion of bound materials to aggregate and the proportion of cement to flyash.(1) The research of aggregate's grading envelope includes three aspects: continuous gradation envelope research based upon theory of maximum density curve; gap gradation envelope research based upon 25mmNMNS of American's AASHTO. which points out that dense framework structure's mix design method adds percentage of cement and flyash to fine-grained material below 2.36mm, and VCAmix of coarse-grained material above 4.75mm must be below VCAdrc; on the basis of appreciation of popular dense framework structure's mix design methods, thoroughly new structure named suspended frame work dense structure is put forward, which not only maintains traditional characteristics of dense framework structure, but also solve the problem of fine-grained material's separation from coarse-grained material.(2) Among the research of the best proportion of bound materials to aggregate, firstly, volume computing method of the best bound material percentage is introduced, secondly, based upon maintaining the proportion of cement to flyash, this paper gets a curve graph which shows the variation of bound material and the greatest dry density through the greatest dry density teat of different bound material percentage, the greatest dry density's climax determines the best proportion of bound material to aggregate for bound material fill up wholly the void of aggregate, then mixture makes up framework dense structure. It is proved that this structure has a series of good road properties. At last, we determine the best proportion limit of bound material to aggregate when aggregate changes.(3) when cement and flyash's physical and chemical effects which contribute toroad properties is fully excavated, the proportion of cement to flyash is the best. For velocity of flyash's pozzolanic Reaction is slow, but velocity of cement-water system hydration reaction is fast, the degree of later strength development can judge the value of proportion, higher the degree is , better the proportion is. Because cement and flyash's properties vary from one region to another, the proportion of cement to flyash isn't identical which is influenced by relative considerations.2. The hydration reactions theory research of cement and flyash includes following five aspects: (1) particular hydration reaction development of cement and flyash's system; (2) reciprocal influence of cement and flyash's reaction; (3) special intersection between aggregate and bound material which is composed of cement and flyash; (4) research of pozzolanic reaction thermodynamics and dynamic.3. Tests show that the strength of 90d age's cement stabilized crushed-stones has reached 80 percent of its 180d age's, the strength of 120d age's cement and flyash stabilized crushed-stones has also reached 80 percent of its 180d age's, for the design age of cement stabilized crushed-stones is 90d age, it is scientific to take 120d as design age of cement and flyash stabilized crushed-stones. After that, through varying aggregate gradation and cement percent, we determine material's 7 day age's compressive strength standard, design age's cleavage strength limit and resilience modulus limit.4. In research of mechnics analysis of cement and flyash stabilized crushed-stones,the road surface deflect,every layer's tensile stress and temperature stress of three semi-rigid roadbase have bee computed. The results indicate that anti-fatigue of cement and flyash stabilized crushed-stones is the best, and its temperature stress is lower than cement stabilized crushed-stones,but higher than lime and fly ash stabilized crushed-stones.5. Based upon system engineering's relative theory, cement and flyash stabilized crushed-stones'mix design method is introduced which has four characteristics: (1) good crack resistance property, (2) good erosion resistance property; (3) covering 7 day age's compressive strength standard; (4) low investment...