Organosilane and Lignosulfonate Stabilization of Roads Unbound: Performance during a Two-Year Time Span

The construction of the new Norwegian E39 highway comprises the excavation of extended tunnelling systems, which lead to a tremendous amount of blasted rocks. Among others, a sustainable cost-benefit application of these resources is represented by their local use as construction material in the unbound layers of the roads. Two types of nontraditional additives are investigated to improve the mechanical properties of aggregates; this is particularly useful for those rocks that do not fulfil the design requirements in their natural status. This work focuses on the field application of two innovative stabilizing technologies based on organosilane and lignosulfonate. The performance of these additive agents is characterized by considering three typical road base layer sections built on purpose according to real practice and added with water (no treatment), organosilane, and lignosulfonate. The test sections are subjected to climatic actions only as neither traffic nor surface courses are applied. With the investigation covering two years, the layers’ stiffness, deformation, and resistance to penetration are evaluated by employing a light-weight deflectometer and dynamic cone penetrometer. Both organosilane and lignosulfonate significantly enhance the mechanical properties of the treated base layers.

Using the Light Weight Deflectometer for Performance-Based Quality Assurance Testing of Cement Modified Subgrades

This report documents the findings from SPR-4230 (Alternative Quality Assurance Methods for Compacted Subgrade). The main objective of SPR-4230 involved establishing performance-related quality assurance (QA) test methods for pavement subgrade construction. Because INDOT generally prefers specifying subgrade treatment type IBC (i.e., 14-in. cement modified subgrade), this study focused on performance-based QA test methods for constructing cement modified subgrade. Moreover, INDOT prefers using light weight deflectometer (LWD) for chemically modified subgrade construction acceptance, so this study aimed to use LWD deflection measurements as performance-related construction acceptance criteria. A laboratory study was performed to relate LWD deflections with resilient modulus that is the key subgrade performance-related parameter in pavement design. In addition, LWD deflections were related with unconfined compressive strength increase that is the key parameter in chemical soil modification mix design. A rigorous field study consisting of LWD testing and falling weight deflectometer (FWD) testing at INDOT new pavement construction sites was conducted to verify the laboratory developed relationship. Recommendations for implementing results of this study into cement modified subgrade construction acceptance is provided, as are recommendations for future research.

Field investigation of shallow soft-soil highway subgrade treated by mass carbonation technology

The innovative carbonation technique based on reactive MgO and CO2 has been identified as an environmentally friendly and efficient method in the improvement of weak soils. Previous laboratory studies have indicated that carbonated MgO-admixed soils had significant improvement in mechanical properties. However, there are to date limited investigations on the soft-soil field application of this technique. In this study, a field trial was conducted to ascertain the feasibility of the MgO mass carbonation technique in improving shallow soft-soil subgrades. A series of field tests, including temperature, dynamic cone penetrometer, and light-weight deflectometer tests, were undertaken. The results indicated that compared with uncarbonated soil layers, there was two to three times increase in dynamic resilient moduli and soil resistances of carbonated MgO-admixed soils. The outcomes of this field investigation will contribute to the utilization of the combined stabilizer of MgO and CO2 and the mass carbonation technology in subgrade improvement.