STATEMENT OF THE PROBLEM

Description

1.2    Statement of the Problem

There are always compromises that have to be made when it comes to construction sites. You might get a great location, but the soil may be poor and unusable as fill material.  Excavating the entire site, hauling the bad soil away and replacing it with better soil is not only expensive and time-consuming, but also unnecessary.  Soil stabilization techniques are much less expensive than excavation, undercutting, and replacing the poor soil with stone material.  Modern technologies allow us to modify existing soil to your specifications, providing quality fill material for your project (Jameson et al., 2013).

Primarily, the problem that arises with regard to expansive oils is that their deformations are significantly greater than the elastic deformations and therefore cannot be predicted by classical, elastic or plastic theory. Movement is usually in an uneven pattern and of such a magnitude as to cause extensive damage to the structures and pavements resting on them(James et al., 2012).

Problematic soils pose great threat and dangers to engineering structures because of their expansive characteristics. Expansive soils cause more damage to structures, particularly light buildings and pavements, than any other natural hazards, including earth quakes and floods(Rogers  et al., 2013).

Because of the above mentioned problems, there is need to further investigate cost-effective ways of stabilizing them – which the use of rice husk is one of them.

Therefore, the possible use of other locally available industrial and agricultural wastes (such as rice husk) as possible substitutes or as a mixtures to main stabilizers to stabilizes oil, will considerably reduce the cost of construction and as well as reduce or eliminate the environmental hazards caused by such wastes.

1.3        Significance of Study

The rising cost of traditional additives such as cement and lime has motivated the search for cheaper and locally available materials for improving problematic or deficient soils to meet geotechnical engineering requirements in the construction industry. The safe disposal of industrial and agricultural waste products demands urgent and cost effective solutions because of the debilitating effect of these materials on the environment and to the health hazards that these wastes constitute (Thompson,2010).

This study serves as a means of providing useful information about cheap and locally available materials such as agricultural waste as stabilizing agents for the purpose of full or partial replacement of traditional stabilizers.

The study will make the reader to become conversant with popular earth-based construction material.

 

EARTH BLOCK

Earth blocks are a building material made primarily from an appropriate mix of fairly dry inorganic subsoil, non-expansive clay, sand, and aggregate. Forming earth blocks requires dampening, mechanically pressing at high pressure, and then drying the resulting material. If the blocks are stabilized with a chemical binder such as Portland cement they are called compressed stabilized earth block (CSEB) or stabilized earth block (SEB). Typically, around 3,000 psi (21 MPa) of pressure is applied in compression, and the original material volume is reduced by about half(Bredenoord, 2023).

Creating CEBs differs from rammed earth in that the latter uses a larger form work into which earth is poured and manually tamped down, creating larger forms such as a whole wall or more at one time, rather than building blocks. CEBs differ from mud bricks in that the latter are not compressed, but solidify through chemical changes that take place as they air dry. The compression strength of properly made CEB usually exceeds that of typical mud brick. Building standards have been developed for CEB.

CEBs are assembled onto walls using standard bricklaying and masonry techniques. The mortar may be a simple slurry made of the same soil/clay mix without aggregate, spread or brushed very thinly between the blocks for bonding, or cement mortar may also be used for high strength, or when construction during freeze-thaw cycles causes stability issues. Hydra form blocks are shaped to be interlocking.

CEB technology has been developed for low-cost construction, as an alternative to adobe, and with some advantages. A commercial industry has been advanced by eco-friendly contractors, manufacturers of the mechanical presses, and by cultural acceptance of the method. In the United States, most general contractors building with CEB are in the Southwestern states: New Mexico, Colorado, Arizona, California, and to a lesser extent in Texas. The methods and presses have been used for many years in Mexico, and in developing countries.

The South African Department of Water Affairs and Forestry considers that CEB, locally called “Dutch brick”, is an appropriate technology for a developing country, as are adobe, rammed earth and cob. All use natural building materials (Bredenoord, 2023). In 2002 the International Institute for Energy Conservation was one of the winners of a World Bank Development Marketplace Award for a project to make an energy-efficient Dutch brick-making machine for home construction in South Africa. By making cheaper bricks that use earth, the project would reduce housing costs while stimulating the building industry.The machine would be mobile, allowing bricks to be made locally from earth (Jayasinghe, 2017).

Various types of CEB production machines exist, from manual to semi-automated and fully automated, with increasing capital-investment and production rates, and decreased labor. Automated machines are more common in the developed world, and manual machines in the developing world.

An abnormal result of a compressive strength of 45 MPa (6,500 psi) was obtained in one sample.The authors of this paper intended to show, with the abnormal test result, that earth responds differently from brittle masonry, and perhaps should be tested using different methods than those used for traditional brittle masonry(Jayasinghe, 2017).

Advantages of earth block

• Minimal or no need for mortar, thus reducing both the labor and materials costs.
• Transport cost: Suitable soils are often available at or near the construction site.
• Strengths might exceed the ASTM standard for concrete blocks (1900 psi) in some instances. In India, the observed compressive strength and flexural strength of CSEB at 28 days of aging with 9% cement stabilization has been observed to be 3.2 MPa (464 psi) and 1 MPa (145 psi) respectively.With 7% cement and sandy soil 3-4 MPa (435 – 580 psi) compressive strength has resulted(Jayasinghe, 2017).
• Non-toxic: like bricks, materials are completely natural, non-toxic, and do not out-gas(with the possible exception of chemically inert noble gases like helium or radon if naturally occurring radioactive material is present)
• Sound resistant: an important feature in high-density neighborhoods, residential areas adjacent to industrial zones
• Fire resistant: like bricks, earthen walls do not burn
• Insect resistant: like bricks, insects are discouraged because the walls are solid and very dense, and have no food value
• No need for process heat in production or for calcination of calcium carbonate (unless cement is used) therefore the material is inherently low-carbon and can be made carbon neutral quite easily (by employing carbon neutral power to the compression machines)

 

Disadvantages of earth block

• There is a wait-time required with this construction technique because after the blocks are pressed, materials must dry.
• The mixture of the interlocking blocks must be consistent and just moist enough. If the mixture is too dry, it will collapse after it has been hydraulically pressed; but if the mixture has too much water, it cannot be solidified.
• There is also the risk of erosion from weather conditions such as wind or rain that could threaten the stability of the blocks.Reinforcement using plaster might be required to ensure that the wall is durable in weather conditions such as rain and wind.
• Power is needed on-site for the compressing machines(Garg et al., 2010). In off-grid applications this is quite often supplied by a diesel generator, thus worsening the carbon balance
• Workforce trained to produce and construct interlocking blocks is limited(Garg et al., 2010).
• Being understudied, the durability of these blocks has not been seen in environments other than rural developments (Garg et al., 2010).
• Like most reinforced masonry, the tensile strength is orders of magnitude lower than the compression strength; this limits the architectural options.
• Earth blocks tend to lose strength and dimensional stability when coming in contact with water for a long period of time. In some cases, it may lead to the complete disintegration of the block(Garg et al., 2010).