Research progress of cementless binders in controlled low-strength material: a review on mix proportion design, performance and application

Controlled Low-Strength Material (CLSM) with cementless binder has emerged as a sustainable alternative to traditional cement-based CLSM, offering environmental, economic, and performance advantages. This review explores the various aspects of cementless CLSM such as reaction mechanisms, mix design methodologies, properties, practical applications, and cost and environmental impacts. Key factors influencing the performance of cementless CLSM, including binder composition, activator type and dosage, and water-to-binder ratio, are critically analyzed. The review also identifies challenges and limitations associated with cementless CLSM, such as material variability, slow early-age reaction kinetics, and the absence of standardized mix designs. Potential applications are highlighted across utility trench backfill, void filling, pavement subbase, erosion control, and thermal insulation. The findings demonstrate that cementless CLSM is a viable construction material capable of meeting performance requirements while significantly reducing carbon footprint and promoting industrial by-product utilization. Finally, the review identifies critical research gaps and proposes prioritized future directions, including durability characterization, field validation, and standardization efforts, to enhance the feasibility and adoption of cementless CLSM in the construction industry. This comprehensive review serves as a resource for researchers, practitioners, and stakeholders committed to sustainable construction, enabling informed decision-making in the development and application of cementless CLSM.