Shrinkage of Cold Recycled Cement-Treated Mixtures of Asphalt Pavement Materials

Abstract

As with other chemically stabilized materials, cold recycled cement-treated mixtures inherently shrink. Shrinkage cracks might accelerate the rate of pavement deterioration. The research reported here aimed at studying variables that may affect the shrinkage of recycled mixtures. An experimental plan was set to evaluate the effects of cement and reclaimed asphalt pavement (RAP) contents and curing time on the shrinkage of such mixtures with different recycled base course materials (namely cement-treated base [CTB], soil-cement [SC], and lateritic soil [LS]). Previously studied recycled mixtures with graded crushed stone (GCS) base course material were also considered in the analysis. From test results and statistical analysis, it was concluded that the finer the recycled mixture (with SC and LS base course materials), the higher the shrinkage potential. Conversely, coarser mixtures (with CTB and GCS as base materials) tend to shrink less. Accordingly, increasing RAP contents might help to reduce the shrinkage of finer mixtures because of coarser RAP gradation. Shrinkage increases with time and shows higher increasing rates at the early stages. Statistics showed that a stronger curing time effect occurs by the third week, and because of that, it is important to avoid moisture loss at the early stages. For the levels considered (1–7 %), cement content did not greatly impact the shrinkage, although it was statistically significant in most cases. Statistical analysis confirmed this, contradicting the practice of often adopting low cement contents to reduce shrinkage hazards.

Microstructure in Adhesion Development Process and Strength Formation Mechanism in Early Stage of Cold Recycled Mixture with Emulsified Asphalt

“…Other cement that does not react with water would be used as filler to adjust the gradation of CRME [15]. Although studies have shown that cement content did not greatly impact the shrinkage [31,32], it is traditionally believed that excessive cement dosage can lead to material shrinkage and cracking.…”

“…Although it could spread more stresses under the wheel loading, it would become more like cementstabilized materials and give rise to shrinkage cracking, resulting in reflection cracking on the pavement surface. Although there was research indicating that increasing the cement content would not cause the abovementioned issues [31,32], the specifications still limited the amount of cement used. For instance, in Chinese Technical Specifications for Highway Asphalt Pavement Recycling (JTG/T 5521-2019), it is advisable the cement dosage does not exceed 1.5%, and the amount of cement added in CRME should not exceed 1.8% [40].…”

Effect of Asphalt Pavement Base Layers on Transverse Shrinkage Cracking Characteristics

“…With respect to pavement transverse shrinkage cracking, it is more beneficial to simply reverse whether the overall pavement still belongs to the category of linear temperature shrinkage according to the material temperature shrinkage coefficient formula (Formula (2)), and then judge the overall pavement dry shrinkage state as follows [35][36][37].…”