Research On The Composition, Design And Mechanism Of A Special Purpose Cement Based On Road Base Stabilizing

Aimed at the problem of short setting time and large shrinkage of ordinary cement while they used for road base stabilizing, and based on fully analyze the characters of the structure and composition of the cement stabilized materials, this paper discussed the rule of different SO3 contents effects on cement stabilized road base materials, on this basis, we have developed a new type of special purpose cement with rereading and slight expandability, and then we conducted a series of studies on the formation principle of the special cement and its road performance. The results indicate that:(1) When clinker content is 40%, the setting time of the cement increases with the content of gypsum, when the content of SO3 is 4.28%, the final setting time reaches 6h. In cement mortar system, when the SO3 content is around 3.38%, the mechanical performance of the material is the best, and in the cement stabilized material system, the maximum SO3 content increases to around 4.28%. The ettringite generation has direct ratio with the SO3 content, with the proper increasing of SO3 content, the activity of mixing materials has been further stimulated, and the alternation and expansion effect of the large number of ettringite can compact the structure of the material, so as to improve the mechanical properties of the material.(2) By researching the influence of clinker content, SO3 content and blending ratio of slag and fly ash on the setting time and mechanical performance of the special purpose cement and its stabilized crushed stone, and taking the economic factors into consideration, the formation principle of the cement has been determined as the clinker content is about 40%, the slag content is equal to the fly ash and the SO3 content is about 4.2%, it would be better to use low calcium fly ash with high activity and gypsum which the main crystalline phase is dihydrate calcium sulphate.(3) The final setting time of the special purpose cement for road base stabilizing is 402 minutes, it benefits the delayed construction of the cement stabilized crushed stone. The expansion effect of this cement is roughly equal to ordinary composite cement mixing expansive agent, its net expansion is large in later period and its dry shrinkage is less than composite cement system, all of these ensure to improve the mechanical and anti-cracking properties of the road base material. The 7d compressive strength of P.C32.5 and RBC stabilized crushed stone is similar, but the increase rate of compressive strength of RBC system is about two times higher than P.C32.5 system, such as the 28d increase rate of RBC system is 75.6% and the 90d is 117%. The dry shrinkage energy anti-cracking coefficient of RBC system is 4.99%, and relative to P.C32.5 system, the coefficient of RBC system increases by 302%, while the P.C32.5+UEA system increases by 202%, thus the anti-cracking performance of RBC system is the best.(4) The main hydration products of the cement for road base stabilizing are amorphous C-S-H gel with large particle size and needle like AFt, the AFt needle interlocks among the C-S-H and other products, the generation of AFt results in large volume expansion, the expansion can compensate the shrinkage of the road base course. With the extension of hydration ages, the activity of mixing materials gradually enhances under the stimulation of Ca (OH)2, it causes the RBC cement has a high later age strength.