تقييم فعالية طرق التثبيت الهجين لتحسين تربة الطبقة التحتية بشكل مستدام في نظام الطريق

Assessing the Effectiveness of Hybrid Stabilization Methods for Sustainable Subgrade Soil Improvement in Pavement Construction

Abstract

Roads are vital components of infrastructure, playing a crucial role in traffic flow and providing efficient transportation. One of the significant aspects of roads is the subgrade, which serves as the foundation. However, due to the heavy traffic loads it endures, even soils with strong engineering properties can fail, leading to complete road collapse. Consequently, researchers have sought to enhance subgrade properties through mechanical and chemical stabilization techniques that are widely employed. This research aimed to assess the effectiveness of a sustainable hybrid stabilization method for stabilizing weak sandy soils using recycled concrete aggregate and asphalt emulsion. The sandy soil was stabilized using four different grades of recycled concrete aggregate (RCA), divided into four grades (with gradations ranging from 19 mm to 0.0075 mm). Each grade comprised four percentages: 5%, 10%, 15%, and 20% of the dry soil weight. Asphalt emulsion (EA) was added at four ratios: 2.5%, 5%, 7.5%, and 10% as a chemical additive. A testing program was implemented to evaluate the properties of natural and stabilized soils in three stages: The first stage included a modified Proctor test and a California Bearing Ratio (CBR) test. The laboratory testing results showed that soil strength and bearing capacity improved significantly after the addition of RCA. The addition of RCA generally improves the maximum dry density, with a noticeable increase in density when 15% RCA is added, especially in zones 3 and 4, where the percentage increases were 6.15% and 4.62%, respectively.
Increasing the percentage of RCA in the natural soil mixture significantly enhances the CBR value in all four grades, determining the optimum 15% RCA ratio. The percentage increase in CBR values ranged from 30% to 125%. The second stage involved a CBR test of soil mixtures stabilized with RCA and supplemented with EA, revealing that the CBR values decreased as EA ratios increased. The third stage involved conducting three in-situ tests: the sand replacement method (SCM), lightweight deflectometer (LWD), and dynamic cone penetration test (DCP). All soil mixtures were stabilized with RCA and EA, and the results showed significant improvements in DCPI, surface deflection, dynamic modulus, and dry density due to the use of RCA and EA. The laboratory results served as input parameters in a theoretical model implemented in the KENPAVE program to assess the performance of natural and stabilized soils. Utilizing RCA increases compressive stress and Nd, while decreasing compressive strain and the damage rate.