DATA ANALYSIS
Chapter 4: Results, Analysis, and Discussions
4.1 Introduction
This chapter presents, interprets, and analyzes the findings of the study, which aimed to compare rammed earth construction with traditionally burned clay bricks.
4.2 Sample Characteristics
Figure 20: Particle Size Distribution
Figure 4.1 illustrates the Particle Size Distribution that was assessed prior to stabilizing the material. The analysis was conducted at the Arab Contractors Laboratory in Pallisa District. The results indicate that over 95% of the material passed through a 10mm sieve, suggesting that the material was not excessively coarse. Furthermore, the percentage passing through a 0.075mm sieve indicates that the material contained a sufficient amount of fines for stabilization. Coarse material tends to increase voids, which negatively impacts bonding.
Figure 21: Determination of Liquid, Plastic, and Linear Shrinkage Limits
Soils with significant clay content are typically associated with low compressive strength and excessive settlement. The reduction in strength is often due to high moisture content, which can also lead to excessive shrinkage upon drying. Cement stabilization is used to mitigate these effects, as demonstrated in the results obtained after stabilization. The liquid limit, which is the moisture content at which soil transitions from a liquid to a plastic state, was determined using a cone penetrometer. The plastic limit, which is the moisture content at which soil becomes too dry to remain plastic, was also measured. The plasticity index, representing the range of moisture content where the soil remains plastic, is the difference between the liquid limit and plastic limit.
4.3 Correlation Between Density and Strength
In rammed earth construction, density is believed to correlate with strength and durability. Densification through ramming enhances the contact between soil particles, generally leading to higher frictional strength, although the relationship between density and strength is not perfectly linear.
4.4 Effect of Particle Size on Strength
One key factor in this analysis is the impact of voids on the sample’s surface, which result from a lack of fines among larger particles. In rammed earth construction, some researchers recommend sieving out materials coarser than 5-10mm. Previous experiments have shown that increasing gravel size reduces the compressive strength of rammed earth structures. The presence of large particles without sufficient fines can be detrimental, making it crucial to minimize voids.
Chapter 5: Conclusion and Recommendations
5.1 Conclusions
Overall, rammed earth construction is an affordable and environmentally friendly alternative to traditionally burned clay bricks in Uganda. The quality of soil across different regions in Uganda makes this construction method viable, and it provides a traditional architectural aesthetic.
5.2 Recommendations
a. Despite significant research over the past 60 years, the current understanding of rammed earth material properties and design procedures is still less developed compared to other civil engineering materials like steel, concrete, and timber.
b. Professional inexperience in designing and constructing with earth leads to several challenges, including inconsistent material quality, moisture sensitivity, potential shrinkage and cracking, and slow or expensive construction processes.
c. The presence of contaminants negatively impacts the strength of rammed earth, as soil homogeneity is crucial for structural integrity. Organic materials, in particular, can interfere with cement stabilization, leading to lower strength outcomes. Ensuring soil homogeneity is essential to minimize localized failures in rammed earth structures.
5.2.1 For Possible Application
Although height restrictions and land value comparisons limit its use, rammed earth can still serve as a viable building material. The lack of recognized standards and codes of practice in many countries, however, hinders the further development and widespread adoption of earthen construction methods.
5.2.2 For Further Research
There is a need to reconsider rammed earth building technology to enhance construction speed and cost-effectiveness. Due to the scarcity of natural resources, increasing demand for raw materials, and challenges posed by construction and demolition waste, investigating new applications for recycled aggregates has become a critical area of study in civil engineering.
