Structural Performance of Adobe Blocks Stabilized with Parkia Biglobosa Seeds Wastewater

Abstract

Adobe blocks construction remains an essential housing solution in many regions due to its affordability and accessibility. However, traditional adobe blocks face limitations, including low compressive strength and vulnerability to moisture, which restrict their durability and broader use This study explores the potential of Parkia biglobosa wastewater (PBWW) as a sustainable stabilizer for adobe blocks, addressing the limitations of traditional adobe. Red clay soil from Juja, Kenya, was combined with PBWW, whose high calcium and potassium content promotes pozzolanic reactions, forming durable calcium silicate and aluminate hydrates.

The primary objective of this study was to assess the potential of Parkia biglobosa wastewater (PBWW) as an environmentally friendly stabilizer for adobe blocks. Specially, it aimed to assess the compressive strength, water absorption, and abrasion resistance of blocks stabilized with different PBWW percentages (0, 5%, 10%, 15%, and 25%). The study also aimed to evaluate the mechanical strength, durability, and sustainability of PBWW-stabilized adobe bricks to those stabilized with conventional and organic methods.

The red clay soil was sieved through 5 mm screen to remove larger particles, ensuring uniformity, and combined with Parkia biglobosa wastewater (PBWW) obtained by boiling the seeds for six hours, which was used as a stabilizer in varying the percentages. Adobe blocks measuring 12 × 14 × 29 cm³ were molded from this mixture and cured in shaded conditions for 7, 14, 28, and 56 days to optimize stabilization. The blocks were then tested for compressive strength, water absorption, and abrasion resistance, following British, African Regulatory and Kenyan standards to ensure reliable results.

Results revealed that 10% PBWW achieved optimal compressive strength, surpassing the Kenyan Standard (2.5 MPa, KS 02-1070:1993) and the British Standard for clay bricks (2.8 MPa, BS 3921:1985) at 28 days, while 25% PBWW provided the highest water resistance and durability. The improvement of compressive strength at 10% PBWW is attributed to effective particle bonding and optimal mineral interaction, which enhanced the cohesion of soil particles. These results demonstrated the effectiveness of Parkia Biglobosa wastewater in improving the compressive strength and water resistance of soil blocks. However, beyond 10%, diminishing returns were observed, as excess organic material disrupted the soil particle matrix, leading to reduced compressive strength. Similarly, water resistance and durability increased significantly at higher PBWW concentrations, with 25% delivering the best performance by reducing porosity and improving cohesiveness.

The use of Parkia biglobosa wastewater (PBWW) as a stabilizer for adobe blocks improves the compressive strength, water absorption, and abrasion resistance. This is due to PBWW's unique mineral composition, particularly its high CaO and K₂O content, enhances pozzolanic reactions more effectively than traditional organic stabilizers. The use of PBWW also demonstrates significant environmental advantages over conventional stabilizers like cement and lime by reducing the carbon footprint while utilizing a locally available by-product.