Density-Strength Decoupling in Compressed Earth Blocks: Insights from Mechanical, Ultrasonic, and Microstructural Characterisation

Amine Bouslihim; Hamid Bouabid; Mohammed Cherraj; Amine Bennis

doi:10.48084/etasr.18168

Authors

Amine Bouslihim Laboratory of Mechanics and Materials, Faculty of Sciences, Mohammed V University, Rabat, Morocco | HESTIM Engineering & Business School, Center for Studies and Research in Engineering and Management (CERIM), Casablanca, Morocco
Hamid Bouabid Laboratory of Mechanics and Materials, Faculty of Sciences, Mohammed V University, Rabat, Morocco
Mohammed Cherraj Team of Modelling and Simulating in Mechanics and Energetics, Faculty of Sciences, Mohammed V University, Rabat, Morocco
Amine Bennis HESTIM Engineering & Business School, Center for Studies and Research in Engineering and Management (CERIM), Casablanca, Morocco

Volume: 16 | Issue: 3 | Pages: 35555-35561 | June 2026 | https://doi.org/10.48084/etasr.18168

Received: 14 February 2026 | Revised: 17 March 2026 | Accepted: 26 March 2026 | Online: 22 April 2026

Corresponding author: Amine Bouslihim

Abstract

This study investigates the effect of coarse sand grain correction on the coupled evolution of dry density, compressive strength, Ultrasonic Pulse Velocity (UPV), and microstructure of Compressed Earth Blocks (CEBs). Granular correction increased the Maximum Dry Density (MDD) from 1965 kg.m^-3 to 2032 kg.m^-3 (+3.4%); however, compressive strength decreased from 1.5 MPa to 1.25 MPa (-17%) and UPV from 0.873 km·s^-1 to 0.737 km·s^-1 (-16%). Conversely, a clay-rich soil exhibited the highest strength (2.42 MPa) and UPV (0.964 km·s^-1) despite the lowest density (1890 kg·m^-3). Scanning Electron Microscopy (SEM) and X-Ray Fluorescence (XRF) analyses revealed that strength evolution is governed primarily by the continuity of fines bonding rather than by density alone. A linear relationship between UPV and compressive strength was obtained with an R² = 0.803. These findings demonstrate a density-strength decoupling induced by physical particle size correction and highlight microstructural bonding as the controlling mechanism for low-carbon CEB optimization.

Keywords:

compressed earth blocks, density-strength decoupling, particle-size distribution correction, ultrasonic pulse velocity, microstructural bonding, sustainable earthen materials

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