The integrity of a structure is heavily reliant on its foundation, making it an essential component of any building. However, foundation structures are vulnerable to various types of attacks, including those from underground water and soil. As a result, it is crucial to take protective measures to safeguard the foundation against these threats.
Without a strong foundation, a structure cannot withstand the test of time. The foundation bears the weight of the entire building, providing stability and support to the structure. Any damage to the foundation can have catastrophic consequences for the building’s stability, making it essential to ensure that the foundation is adequately protected.
One of the most significant threats to foundation structures is the presence of water and soil. Water can cause the foundation to erode, weaken, and eventually collapse. Similarly, soil movements, such as landslides and earthquakes, can damage the foundation, leading to severe structural damage.
To prevent these threats from compromising the foundation’s structural integrity, protective measures must be implemented. Some of the common protective measures include waterproofing the foundation and installing drainage systems to channel water away from the foundation. Additionally, reinforcing the foundation with steel bars can help increase its strength and resistance to soil movements.
In conclusion, protecting the foundation of a structure is critical to its overall stability and longevity. By implementing protective measures, such as waterproofing and reinforcement, the foundation can be safeguarded against the various threats it faces from the surrounding environment.
How to Protect Foundation Structures from Soils and Ground Water Attacks?
The article addresses the issue of attacks on foundation structures caused by harmful elements in soils and ground water. The causes of such attacks are discussed, along with methods for exploring soil and groundwater to identify potential threats.
In order to protect concrete foundation structures from attacks in soil and ground water, the article provides guidance on effective protective measures that can be taken. Additionally, the article covers methods for protecting steel piles against corrosion, which can also be caused by exposure to harmful elements in the surrounding soil and groundwater.
Finally, the article provides information on protecting timber piles, which are particularly vulnerable to attacks from harmful elements in soil and groundwater. By following the guidance provided in the article, individuals and organizations can better safeguard their foundation structures against damage caused by soil and groundwater.
Causes of Attacks on Foundation Structures
Different types of foundations, such as concrete foundation, steel piles, and timber piles, may be vulnerable to various types of attacks that can cause damage. It is important to be aware of these causes of attacks to ensure that appropriate measures are taken to prevent or minimize the damage. For instance, concrete foundations can be susceptible to attacks from acid rain, sulfate attack, or freeze-thaw cycles. On the other hand, steel piles can be prone to corrosion caused by exposure to saltwater, which can weaken the structural integrity of the foundation. Similarly, timber piles may be at risk of decay caused by fungal or bacterial growth, which can compromise the strength of the foundation. Therefore, it is important to identify and address the specific causes of attacks that a foundation may be vulnerable to, to prevent costly and potentially dangerous damage.
Table-1: Types of foundation and causes of attacks
| Types of foundations | Causes of attacks |
| Concrete structure | Chemical wastes and sulfates in the ground, erosion, and mechanical abrasion, Figure-1 |
| Steel piles | Specific environmental conditions could lead to corrosion, Figure-2 |
| Timber piles | Organism in soil and water may lead to decaying of timber piles, ships or ice or other floating objects cause abrasion, serious damages may occur due to shingle movement in the case where the foundation exposed to wave action, Figure-3 and Figure-4 |
The extent of damage caused by attacks on soil cannot be solely attributed to the presence of hazardous substances in the soil. Other factors such as weather patterns and fluctuations in the groundwater level also play a crucial role.
Climatic conditions have a significant impact on the health of soil. For instance, heavy rainfall can cause soil erosion and wash away essential nutrients, leading to soil degradation. Similarly, droughts can cause soil to become dry and compacted, making it difficult for plants to grow. Extreme temperatures can also alter the chemical composition of the soil, making it more acidic or alkaline, which can affect the growth of plants and the survival of microorganisms.
Furthermore, the groundwater level is a vital component of soil health. Changes in the groundwater level can lead to the accumulation or dispersion of contaminants in the soil. For example, a rise in the groundwater level can increase the concentration of harmful chemicals in the soil, while a decrease in the groundwater level can cause the soil to become dry and arid, making it less habitable for plants and microorganisms.
In summary, the severity of soil attacks cannot be solely determined by the concentration of toxic substances in the soil. Climate and groundwater level are important factors that influence soil health and play a significant role in determining the extent of damage caused by soil attacks.
Fig.1: Sulfate attack on concrete foundation structure
Fig.2: Corrosion of steel piles
Fig.3: Timber piles used in the bridge construction
Fig.4: Decayed Timber Pile
Soil and Groundwater Exploration
Determining the groundwater table and fluctuations, as well as the presence of aggressive substances in the soil, is a crucial step in proposing proper protection measures for construction sites. To achieve this, chemical analysis of groundwater, disturbed and undisturbed soil samples is conducted. Stand pipes are also placed in boreholes for a sufficient period to gather the necessary data and determine the groundwater level. By doing this, not only can the groundwater fluctuations be identified, but the average groundwater level can also be determined.
Obtaining enough data to accurately specify the sulfate content and estimate changes in sulfate content with depth is essential. This is because inadequate data may lead to uneconomical protection measures being considered. Therefore, it is important to collect adequate data to ensure that the correct protection measures are proposed based on the site’s conditions where the foundation is to be constructed.
Protection of Concrete Foundation Structures against Soil and Ground Water Attacks
Concrete foundations can deteriorate due to various factors, with one of the primary causes being the aggressive nature of sulphate present in soil and ground water. Other factors that can contribute to concrete foundation damage include exposure to chemical waste, organic acids, specific deleterious aggregate, corrosion of reinforcement, and sea action.
To protect concrete foundation structures from these types of attacks, viable protection measures can be implemented. One such measure is to use materials with low permeability, such as dense concrete or coatings. Additionally, proper drainage and waterproofing techniques can be employed to prevent water and moisture from penetrating the foundation.
It is also important to carefully select the type of cement and aggregates used in the foundation, as certain types may be more susceptible to deterioration. Regular inspections and maintenance of the foundation can also help to detect and address any issues before they escalate.
Overall, implementing these protection measures can help to prolong the lifespan and ensure the durability of concrete foundation structures, even in environments with aggressive soil and ground water.
Protection Against Sulphate Attack
There are various methods that can be used to safeguard concrete foundation structures from attacks. The American Society for Testing and Materials (ASTM) has classified Type II Portland cement as providing reasonable resistance against sulphate attack, while Type V Portland cement offers excellent protection against such attacks. Super-sulphate and high alumina cement can be utilized to combat the most severe sulphate aggression from soil and ground water. However, high alumina cement can suffer from a sudden loss of concrete compressive strength, known as conversion. Nonetheless, this issue can be addressed and the concrete typically retains some residual strength after experiencing conversion. One indicator of high alumina conversion is the reduction in concrete sulphate resistance. To avoid high alumina conversion, it is recommended to avoid using a high percentage of cement, shield the concrete from heat and sun exposure, and steer clear of steam curing. Proper shading should be employed to protect concrete piles from the sun in stock yards. In high sulphate concentration areas, appropriate compaction of sulphate resistant cement may suffice for normal foundation construction, while a protective membrane should be used in harsher situations. For instance, plastic sheets or bituminous can be wrapped around concrete pad and strip foundations, while heavy duty plastic sheeting can be used to protect cast in place and driven concrete piles. However, this protection layer is susceptible to tearing from fastenings. As an alternative, galvanized corrugated cylindrical sheeting steel sheeting or rigid PVC tubing can be used, albeit at a higher cost.
Protection of Concrete Foundation Against Organic Acid Attacks in Soils and Groundwater
Peat soils and water may contain natural acids, and the oxidation of pyrite or marcasite can result in the formation of free Sulphuric acid. Impermeable concrete can provide protection against the less aggressive former type, while the latter is highly detrimental to concrete. A high sulphate content and pH values can indicate the presence of free Sulphuric acid, and the protection measures recommended depend on the pH value. If the pH value is 6 or greater, no measures are required, but if the pH value is lower, certain precautions should be taken. The use of sulphate resistance cement is advised, and a combination of rapid hardening cement with fly ash or ground granulated blast furnace slag can provide the desired protection.
Protection of Concrete Foundation Against Chemical and Industrial Wastes
Chemical works and dumped wastes can contain harmful substances, which can pose a challenge to deal with. The concentration of chemicals can vary, and their identification can be considerably difficult. When constructing a site that contains aggressive chemical substances such as acid waste, it is recommended to use pile foundation as a solution. The pile foundation is composed of a precast concrete shell with a hollow interior that contains a PVC pipe filled with concrete. The outer shell serves as a sacrificial layer over the length of the shaft in the ground that is contaminated with chemical waste. This solution helps to prevent the spread of harmful chemicals into the surrounding environment.
Protection of Steel Piles Against Corrosion
The management of hazardous waste from chemical works and dumping sites can be a challenging task, as the waste may contain harmful substances that pose a risk to human health and the environment. Moreover, the concentration and identification of these chemicals can be a difficult process. To address this issue, it is recommended to use pile foundations when constructing sites that contain aggressive chemical waste, such as acid waste.
Pile foundations are a type of foundation that consists of a precast concrete shell with a hollow interior. Inside the hollow interior, a PVC pipe filled with concrete is inserted. The outer concrete shell serves as a protective layer along the length of the shaft in the ground that is contaminated with chemical waste. This sacrificial layer prevents the harmful chemicals from spreading into the surrounding environment, thereby reducing the risk of contamination.
Using pile foundations as a solution is a reliable method to prevent the spread of harmful chemicals from contaminated sites. The outer concrete shell of the foundation acts as a barrier, which protects the surrounding environment from contamination. This method is particularly useful for sites that contain aggressive chemical substances such as acid waste, where the risk of contamination is high. Overall, the use of pile foundations is an effective solution to mitigate the environmental and health risks associated with chemical waste.
Steel Pile Paint Treatment Protection
Marine structures are exposed to harsh environments, and therefore, it is essential to protect them from corrosion. One way to protect these structures is through paint treatment. This technique involves several steps.
Firstly, the surface of the structure is prepared by using sand or grit blasting treatment until it achieves a white metal situation. This step is necessary to ensure that the surface is clean and free from contaminants.
Next, a layer of zinc silicate prime coat is applied to the clean metal surface. The thickness of this layer should be between 50-75 micrometers. The purpose of this layer is to provide an additional barrier against corrosion.
Lastly, a top coat of either epoxy or vinyl painting is applied. It is essential to ensure that the prime coat and top coat are compatible with each other. The top coat provides the final layer of protection against corrosion.
It is important to note that this paint treatment is only effective for areas of marine structures above the splash zone. For structures in the splash zone, the paint treatment may not provide long-term protection. In these cases, it is recommended to either introduce steel plates to protect the structure or increase the thickness of the steel piles.
Cathodic Protection of Steel Piles
Cathodic protection systems rely on the application of a metal’s characteristic electrochemical potential. The aim of this technique is to prevent the migration of metals from a structure into soils, groundwater, or any solution. To achieve this, the structure is turned into a cathode. There are two ways to implement cathodic protection: by using a power supply or sacrificial anode. In the former case, the anodes are usually carbon or scrap iron pieces, and a DC generator or similar device is employed to provide the necessary DC current for the flow from the anode to the cathode. It is important to keep the exposed surface of the structure to a minimum to reduce anode wastage and power supply requirements.
Sacrificial anodes, on the other hand, consist of significantly large masses of anode metals that corrode over time, providing protection during the structure’s service life. It is important to note that sacrificial anodes may need replacement after a while, particularly in a marine environment. The electromotive series of the sacrificial anode must be greater than that of the structure being protected. In marine structures, the use of sacrificial anodes is considered more feasible than the power supply approach since the latter requires cables that could be damaged by ships or other objects. However, the replacement of sacrificial anodes requires underwater replacement, which may not be easy to accomplish.
Fig.7: Cathodic protection of steel pile using power supply
Fig.8: Sacrificial anode used to protect steel pile in water
Protection of Timber Piles
In marine conditions, timber is commonly used for piles, bracing, and fences. However, these applications make it susceptible to decay caused by biological organisms. When timber is buried, it is less likely to be affected by such deteriorating factors as long as it remains wet. However, if the timber is exposed to partial wetting and drying, it will significantly deteriorate. This can occur when buried timber piles are used in areas where the water table fluctuates.
There are various protection measures that can be implemented to prevent timber pile damage. These measures include applying preservatives, using protective coatings, and wrapping the timber in a waterproof membrane. Another method involves using composite materials in place of timber. These protection measures can extend the lifespan of timber piles and reduce maintenance costs. It is important to consider these measures when using timber in marine conditions to ensure long-term durability and sustainability.
Preservation of timber piles by creosote
Timber foundations can be prone to deterioration from various biological and environmental factors. To prevent this, creosote is often used to impregnate the timber, which has been found to be an effective way of increasing the lifespan of the timber piles. In fact, it is considered to be the most favorable treatment among other liquids like water solvent and soluble types.
The effectiveness of creosote is greater for softwood compared to hardwood. This is because creosote can be impregnated to a greater depth in softwood, up to a depth of 75mm. However, hardwood cannot be impregnated properly and therefore needs to be subjected to maintained pressure for some time until adequate treatment is achieved.
If hardwood is being used, it is advised to creosote bolt holes properly since the wood cannot be treated as effectively as softwood. This will help to prevent any potential damage to the timber due to biological or other detrimental influences. Overall, the use of creosote for timber impregnation is a highly effective way of increasing the lifespan of timber foundations, particularly for softwood.
Fig.9: Impregnated timber with creosote
Protection of timber piles using concrete
In cases where the use of creosote is not suitable to achieve the desired final result, an alternative approach is considered. For instance, when the water table is subject to significant changes, creosote may not be a viable option. In such situations, a composite pile can be used, where the lower part of the pile, which is submerged in water, is made of timber, while the upper part is made of concrete. On the other hand, if the water table is relatively shallow, the pile can be cut and a pile cap can be placed at the level of the water table, using concrete to protect and extend the lifespan of the timber pile. Figure 7 provides an illustration of this approach, which utilizes concrete to preserve timber piles and increase their service life.
Fig.10: The use of concrete to prevent damage of timber pile. a is considered in the case deep water table level whereas b is practices in the case of shallow water table level
Protection of Timber Piles Against Marine Borer
It is advisable to choose timber that is naturally resistant to borers, rather than relying on timber piles and protective measures to mitigate the risk of borer infestation. Some types of timber, such as African padauk, Belian, Afrormosia, and many others, have inherent properties that make them resistant to borers (as shown in Figure 8 and Figure 9). By selecting these types of timber, one can proactively prevent the risk of borer damage without relying solely on additional protective measures.
Fig.11: African Padauk timber has the ability to withstand borer
Fig.12: Afromosia pile which can resist borer
It is important to note that if timbers with sapwood are used, the sapwood should be removed prior to treatment with creosote. This is because sapwood is vulnerable to borer attacks, which can compromise the structural integrity of the timber. The effectiveness of the treatment largely depends on maintaining a continuous treatment layer on the outer surface of the timber. Any damages to this treatment layer, such as piercing it with hooks, bolts, or saw cuts during lifting, can allow borers to penetrate and cause deterioration of the timber. Therefore, it is crucial to prevent any disruptions to the treatment layer to ensure the long-term effectiveness of the treatment.