تاثير سيمان و آهك بر تغيير شكل هاي دائمي مخلوط هاي آسفالت بازيافتي به روش سرد با امولسيون قير

Effect of Portland cement and Lime Additives on permanent Deformation of Cold in-Place Recycled Mixtures with Asphalt Emulsion

Cold in-Place recycling (CIR) has been effective at rehabilitating the aged pavements, and many agencies have used asphalt emulsions for CIR in their projects with good results. However, some emulsion CIR projects exhibited rutting, thermal cracking and asphalt stripping problems, leading agencies to use Portland cement, lime and class C fly ash as additives to prevent early rutting and stripping problems. Due to lack of previous studies on applying additives in CIR mixes, in this study we used Portland cement and lime as additives. The Portland cement was introduced in powder form and lime was utilized as hydrated lime in powder form and lime slurry, and the effects of each additive on permanent deformation of CIR mixtures have been evaluated. The objectives of this study were to evaluate the effects of lime and Portland cement on permanent deformation of CIR mixtures with asphalt emulsion and comparing the effects of these two additives. A laboratory study was undertaken to evaluate the effect of Portland cement and lime on permanent deformation of CIR mixes. The mixtures were tested for Marshall Test (ASTM D 1559), resilient modulus (ASTM D4123), and Dynamic creep test: BS-DD226, Wheel track test: BS 598:Partl 10:1996. The results showed that: 1. Addition of Portland cement and lime increases the Marshall Stability and bulk specific gravity and reduces void content and flow of the recycled mixtures. The use of Portland cement resulted highest stability values. 2. The use of HLS, HL, and Portland cement result in significantly increase in resilient modulus values. Use of HLS and Portland cement resulted in more resilient modulus values than HL. The use of 2% Portland cement resulted highest resilient modulus value since Portland cement stiffens the binder. 3. The results of dynamic creep test show that the use of Portland cement and lime resulted decreased rut depth. The use of Portland cement, HLS and HL resulted in a reduction in rut depth of 40, 30 and 26% as compared to sample without additives respectively. 4. The results of wheel track test show that the samples without additives have the most rutting potential. The addition of 2% Portland cement, 2% HLS and 2% HL resulted in a reduction in rut depth of 58, 50 and 38 as compared to sample without additives respectively. 5. Both dynamic creep and wheel track tests show that addition of Portland cement and lime can reduce the permanent deformation of recycled mixtures. The best additive for reducing permanent deformation proved to be Portland cement. Cement acts as a secondary binder in cold mix. Hydration is necessary to activate the cement and this can only occur in the cold mix material in which water is available. In the absence of water, cement merely acts as an inert filer. It is also well known that the hydration reaction of cement can cause a noticeable temperature rise in concrete mixtures. The effect of heat of cement hydration on bituminous emulsion mixtures may also be significant. A rise in temperature would increase the rate of reaction between aggregate and emulsion and, if large, could increase the rate of water evaporation from a mixture. Both of these effects could increase the breaking rate of the emulsion and the curing rate of the mixture. 6. Use of Portland cement and lime slurry had better results than hydrated lime but due to the difficulties in producing lime slurry in practice, the use of Portland cement is recommended.