Performance Evaluation of Compressed Earth Blocks Stabilized with STEIN Soil Hardener

Abstract

Compressed Earth Blocks (CEBs) offer a sustainable solution to housing challenges, but their mechanical and long-term properties often require enhancement through stabilization. STEIN soil hardener, a novel eco-friendly soil hardening agent made from a mixture of inorganic substances (containing silica and lime) and Portland cement, has been introduced as an alternative stabilizer. This study evaluates the performance of CEBs made using black cotton (expansive soil) and laterite soil stabilized with STEIN soil hardener.

The main objective of this study is to investigate the structural performance of compressed earth blocks stabilized with STEIN soil hardener. Specifically, it aims to evaluate the strength, durability, and optimal content of STEIN in black cotton and laterite soils while comparing its performance with Ordinary Portland Cement (OPC).

Blocks measuring 290 mm × 140 mm × 120 mm were prepared, cured, and tested at 7, 28, and 90 days for compression, flexural, water absorption, and abrasion resistance. The STEIN content was added and progressively increased by 2%, starting from 0% to 12% for Black Cotton Soil (BCS) and from 0% to 8% for laterite soil. Results from STEIN stabilization were compared with Ordinary Portland Cement (OPC) stabilized earth blocks.

 The finer particles in STEIN, with their greater surface area and composite structure, increase water demand, showing higher Maximum Dry Density (MDD). While surpassing the minimum compressive strength required by the Kenya Bureau of Standards (2.5 MPa at 28 days), STEIN achieves 2.906 MPa at 8% for BCS blocks and 5.115 MPa at 4% for laterite soil blocks, indicating suitability for real-life applications. At these percentages considered optimal, STEIN also demonstrates strong performance in enhancing the bending strength, water absorption, and abrasion resistance of CEBs, highlighting its potential as an eco-friendly alternative to ordinary cement in sustainable construction.

The study demonstrates that STEIN significantly outperforms Ordinary Portland Cement (OPC) as a soil hardening agent in both black cotton and laterite soils, particularly in terms of the mechanical and durability properties of Compressed Earth Blocks (CEBs). STEIN-stabilized blocks showed higher compressive and flexural strength, as well as improved durability, indicated by lower water absorption and higher abrasion resistance. STEIN promotes rapid strength development at early curing ages, making it ideal for quick strength gains. However, while the strength of STEIN-stabilized blocks continues to improve over time, its rate of improvement slows over time, leading to a lower strength gain at later curing ages compared to Ordinary Portland Cement (OPC), which continues to gain strength progressively. Additionally, laterite requires a lower stabilizer content compared to Black Cotton Soil (BCS), with a minimum of 4% for laterite, while BCS requires 8%, making laterite a more cost-effective and efficient option for CEBs. These findings highlight STEIN as a superior and more sustainable alternative to conventional cement stabilizers for compressed earth blocks.