Frost Resilience of Stabilized Earth Building Materials

Sustainable utilization of biopolymers as green adhesive in soil improvement: a review

Throughout history, soil improvement has relied on various additives, from ancient practices using lime and other traditional compounds to modern methods employing geosynthetics and microbial treatments. However, conventional soil admixtures, while effective, often carry significant environmental drawbacks, especially in the case of additives like cement. In response to these environmental concerns, there has been a growing interest in the use of biopolymers as a sustainable alternative for ground improvement. This literature review centers on the properties and performance of biopolymers, addressing their increasing adoption in soil enhancement endeavors. It explores the historical context of soil improvement practices, highlights the contemporary environmental challenges posed by traditional additives, and underscores the emerging trend toward biopolymers as a green adhesive solution. The review further probes into specific biopolymers, examining their characteristics and elucidating how biopolymer-treated soils achieve the desired improvements. In essence, this review provides a comprehensive understanding of the historical evolution of soil improvement practices, the current environmental imperatives, and the promising role that biopolymers play in achieving sustainable soil enhancement. It serves as a valuable resource for researchers and practitioners seeking environmentally friendly alternatives in geotechnical engineering.

Moisture content and material density affects severity of frost damage in earthen heritage

Successful conservation of earthen heritage requires an understanding of interactions between environmental and climatic conditions, soil-based materials and human interventions. Frost cycling is likely to be an important contributor to the deterioration of earthen heritage, with frost damage known to cause deterioration features such as flaking and granular disintegration. However, it is not clear how important a contribution frost cycling makes in comparison with other agents. Previous earthen heritage studies have focused on other agents of deterioration, such as wind and rain, or investigated the role of freeze-thaw cycles under conditions unrepresentative of many earthen sites. We investigate how density and moisture content affect the severity of frost damage on earthen heritage using materials and conditions informed by those found at earthen sites in NW China. We prepared rammed earth cubes (5 × 5 × 5 cm) at two densities (1.65 and 1.75 g cm^-3) and with five moisture content levels between 0.46 and 8%. Samples were subjected to 80 freeze-thaw temperature cycles (+7 to -15 °C) in an environmental cabinet. Deterioration was recorded using visual assessment, measurements of surface roughness, ultrasonic pulse velocities, a Vicat needle test and mass loss. Results showed frost damage was dependent on moisture content and density of rammed earth samples. Samples with <2% moisture content showed no visible frost damage. Samples with higher moisture contents (>6%) and higher densities exhibited the greatest deterioration with surface granulation, salt efflorescence and flakes detaching from the parent cubes. This suggests that frost damage to rammed earth is likely to be focused in periods when rainfall or snowmelt is followed by freeze-thaw temperature cycling. In addition, results suggest that if higher density earthen materials are used for repairs or restoration for sites in dryland environments, these could be more vulnerable to frost damage than lower density materials.

Biopolymers as Green Binders for Soil Improvement in Geotechnical Applications: A Review

Soil improvement using biopolymers has attracted considerable attention in recent years, with the aim to reduce the harmful environmental effects of traditional materials, such as cement. This paper aims to provide a review on the environmental assessment of using biopolymers as binders in soil improvement, biopolymer-treated soil characteristics, as well as the most important factors affecting the behavior of the treated soil. In more detail, environmental benefits and concerns about the use of biopolymers in soil improvement as well as biopolymer–soil interaction are discussed. Various geotechnical properties are evaluated and compared, including the unconfined compressive strength, shear strength, erosion resistance, physical properties, and durability of biopolymer-treated soils. The influential factors and soil and environmental conditions affecting various geotechnical characteristics of biopolymer-treated soils are also discussed. These factors include biopolymer concentration in the biopolymer–soil mixture, moisture condition, temperature, and dehydration time. Potential opportunities for biopolymers in geotechnical engineering and the challenges are also presented.

The Effect of Soil Mineral Composition on the Compressive Strength of Cement Stabilized Rammed Earth

Cemented stabilized rammed earth (CSRE) is a building material used to build load bearing walls from locally available soil. The article analyzes the influence of soil mineral composition on CSRE compressive strength. Compression tests of CSRE samples of various mineral compositions, but the same particle size distribution, water content, and cement content were conducted. Based on the compression strength results and analyzed SEM images, it was observed that even small changes in the mineral composition significantly affected the CSRE compressive strength. From the comparison of CSRE compressive strength result sets, one can draw general qualitative conclusions that montmorillonite lowered the compressive strength the most; beidellite also lowered it, but to a lesser extent. Kaolinite lightly increased the compressive strength.