Development of Interlocking Blocks for Landscape Work from Crumb Rubber

Abstract

Thailand’s industrial use of natural rubber generates substantial waste, especially end-of-life tyres that can be processed into crumb rubber. This study develops non-load-bearing interlocking blocks for practical landscape applications with two objectives: (1) to reduce block weight and density while maintaining compressive strength in accordance with TIS 3411-2565 (≥ 3.45 MPa), and (2) to establish practical mix guidelines for real-world landscape use. Thirteen mix designs were tested by varying proportions of cement, laterite soil, crumb rubber, and binder type (water or polyurethane). Tests included density, compressive strength, production economic, and an expert evaluation across seven-dimension. The results indicate that Mix 4 (1:2:1 with water as binder) is the most promising, achieving a density of 1,571.20 kg/m³ and a compressive strength of 3.92 MPa (meeting the standard), with a cost of THB 14.95 per block and a production rate of 20 blocks per day. In contrast, polyurethane-bonded mixes showed high viscosity, poor formability, and no improvement in performance or cost-effectiveness compared with water. Expert evaluation highlighted strengths in environmental friendliness and safety, while surface finish and design were identified as areas needing improvement. A practical guideline is therefore proposed: cement, laterite soil, and water 75–80% v/v and crumb rubber 20–25% v/v, as a baseline mix for non-load-bearing interlocking blocks in landscape applications.