Granular materials experience grain breakage under high stress, resulting in increased compressibility and reduced mechanical performance. Such behavior also occurs under current stresses when grains have a low individual strength. This study investigates the mitigation of such degradation through a grading-based strategy in a Lightweight Expanded Clay Aggregates (LECA). A series of single-particle crushing and oedometer compression tests were performed on mono- and bidisperse LECA samples, with and without gravel inclusions. The experimental program examined the stress-strain behavior, compressibility, and breakage evolution. The results confirmed that grain size and grading significantly affect grain breakage probability and deformation. Gap-graded mixtures exhibited lower compressibility, higher yield stress, and reduced breakage indexes. Notably, introducing a smaller grain fraction—either homogeneously or heterogeneously via top-down percolation—delayed the onset of breakage and improved the material’s performance. The effectiveness of gravel inclusion was particularly pronounced, reducing vertical strain by up to 18% and breakage by over 40% at 5000 kPa. These findings suggest that gap-grading offers a practical and sustainable alternative to chemical reinforcement techniques, with potential for in-situ application in geotechnical projects.