How to Protect Foundation Structures from Soils and Groundwater Attacks?

Foundation is an essential part of structures and it greatly affects structural integrity of the structure. Foundation structures are commonly subjected to different forms of attacks from underground water and soils and hence necessary protection measures are required to be undertaken.

How to Protect Foundation Structures from Soils and Ground Water Attacks?

In this article, consideration regarding the attacks on foundation structures caused by harmful elements in soils and ground water are discussed as follows:

• Causes of attacks
• Soil and groundwater exploration
• Protection of concrete foundation structures against attacks in soil and ground water
• Protection of steel piles against corrosion
• Protection of timber piles

Causes of Attacks on Foundation Structures

There are different types of attacks that various types of foundation may suffer from. The following states various causes of attacks that different types of foundations namely concrete foundation, steel piles, and timber piles may suffer from and consequently damaged.

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 degree of the attacks is not only based on the concentration of harmful elements in soil but it is also dependent on climatic conditions and the changes in levels of groundwater table.

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

It is substantially significant to determine groundwater table and fluctuation and existence of aggression substances in the soil since proper protection measures can be proposed based on the site condition on which the foundation is constructed on.

Usually, ground water, disturbed and undisturbed soil samples are taken for chemical analysis. Stand pipes may be placed in boreholes for adequate time so as to take necessary data and determine groundwater level. In this way, not only does the groundwater fluctuation can be determined but also average groundwater level can be obtained.

It is necessary to achieve enough data to specify sulfate content correctly and estimate sulfate content changes as the depth is increased. This is because uneconomical protection measures might be considered based on inadequate data.

Fig.5: Groundwater level determination

Protection of Concrete Foundation Structures against Soil and Ground Water Attacks

The major factor that lead to concrete foundation deterioration is the aggression of sulphate that present in soil and ground water. Apart from sulphate attack, chemical wastes, organic acids, specific deleterious aggregate, corrosion of reinforcement, and sea action could cause concrete foundation damages.

In the following sections, viable protection measure that can be used to protect concrete foundation structure against attacks of soil and ground water will be explained.

Protection Against Sulphate Attack

There are several techniques that may be employed to protect concrete foundation structure form attacks. According to ASTM classification, Type II Portland cement can provide a fair resistance against sulphate attack, and Type V Portland cement possess great resistance against sulphate attacks.

The most serious sulphate aggression from soil and ground water can be dealt with using super-sulphate and high alumina cement. Despite the fact that high alumina cement could suffer from conversion, which is a sudden decline of concrete compressive strength, but this issue may be tackled and there is residual strength in such concrete when it experiences conversion. An indication of high alumina conversion is the reduction of concrete sulphate resistance.

Measure to avoid high alumina conversion involves avoiding application of high percentage of cement, protect the concrete from heat, avoid steam curing, and protect concrete piles from sun in stock yards using proper shading.

For normal foundation construction, suitable compaction of sulphate resistant cement may be adequate in high sulphate concentration areas whereas protective membrane should be used in harsh situations.

It is recommended to employ and wrap plastic sheets or bituminous around concrete pad and strip foundation.

Heavy duty plastic sheeting can be used to protect cast in place and driven concrete piles and this protection layer is possible to be teared by fastenings. So, galvanized corrugated cylindrical sheeting steel sheeting or rigid PVC tubing can be used instead but it would be more expensive.

Protection of Concrete Foundation Against Organic Acid Attacks in Soils and Groundwater

Natural acids may present in peat soils and water, and free Sulphuric acid may formed as a result of oxidation of pyrite or marcasite. The former type is less aggressive if impermeable concrete is provided whereas the latter is greatly harmful for concrete.

High sulphate content and pH values are used as a sign of the occurrence of free Sulphuric and based on the pH values protection considerations are recommended. For example, if the value of pH is equal to 6 of greater, no measure is needed to consider but smaller values would require the use of sulphate resistance cement, rapid hardening cement in combination with fly ash or ground granulated blast furnace slag would provide desired protection.

Protection of Concrete Foundation Against Chemical and Industrial Wastes

Harmful chemical substances could be present in chemical works and dumped wastes. This material is difficult to deal with since concentration of chemical would vary and their identification is considerably difficult.

Therefore, if the construction site contained aggressive chemical substances such as acid waste, then it is advised to employ pile foundation that made up of precast concrete shell, hollow interior having a PVC pipe placed and filled with concrete and the outer shell work as a sacrificial over the length of the shaft in the ground that contaminated with chemical wastes.

Protection of Steel Piles Against Corrosion

Steel piles may suffer from corrosion in soils and ground water since both air and water are basic requirements for the occurrence of steel pile corrosion. Commonly, certain regions of the steel pile will act as anode areas and other areas as cathode. Consequently, rust will be formed in cathode areas whereas pitting will be created in anode regions.

Corrosion of steel piles in soil and ground water is a serious problem and it needs to be tackled properly. In the following sections, measures recommended to protect steel pile in soil and ground water from corrosion will be explored briefly.

Steel Pile Paint Treatment Protection

In this technique, sand or grit blasting treatment is initially utilized for the structure so as to achieve white metal situation. After that, a thickness of 50-75 micrometer of zinc silicate prime coat is applied on the clean metal surface. Lastly, epoxy or vinyl painting is provided as a top coat. It should be remembered that the prime coat should be in harmony with top coat.

Protection by paint treatment is used for regions of marine structures above the splash zone.

Lastly, it should be bore in mind that paint treatment is not applicable for long service life of the structure in splash zone. So, it is advised to introduce either steel plates to protect the structure or increase the thickness of the steel piles.

Fig.6: Corrosion of steel pile in marine condition

Cathodic Protection of Steel Piles

The application of characteristic electrochemical potential of metals is the basis of cathodic protection system. In this technique, the structure is turned to cathodic which avoid the migration of metals from the structure to soils or groundwater or any solution.

Power supply supplied system or sacrificial anode may be used in cathodic protection method. In the former case, anodes take the form of sizable lump carbon or scrap iron pieces. A D.C generator or other suitable means is employed to provide D.C current which is needed for the flow from the anode to the cathode.

It should be noted that by keeping the exposed surface of the structure as minimum as possible the wastage of anode will be decline and the requirements of power supply will be eased.

As far as the application of sacrificial anode is concerned, it composed of considerably large masses of anode metals that corrode while it offers protection during the service life of the structure.

Therefore, sacrificial anodes might need replacement after a while especially in marine environment. Moreover, electromotive series of sacrificial anode should be greater than that of structure that intended to be protected.

Lastly, it is believed that the use of sacrificial anode in marine structures is more feasible compare to power supply approach since the latter need cables which might be damaged by ships or other objects. However, the replacement of sacrificial anode need underwater replacement that may not be conducted easily.

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

Timber used as a pile, bracing, and fences in marine conditions, so the timber decaying due to biological organism is highly possible. However, when the timber is buried, it would rarely affect by such deteriorated factors provided that it is being kept wet.

Moreover, if the timber is subjected to partial wetting and drying, then it would seriously deteriorate. Such situation may come across when buried timber piles is used in regions where water table changes.

Lastly, there are number of protection measures that may be employed to avoid pile timber damages. In the following sections, these measures will be explained.

Preservation of timber piles by creosote

It is reported that, the use of creosote to impregnate timber foundation is considerably effective way to prevent timber from deterioration due to biological and other detrimental influences.

Creosote impregnation will increase the ability of timber piles to stand for longer time and this liquid is claimed to be the most favorable among all other types of liquids used to protect timber for example water solvent and soluble types.

The effectiveness of creosote is greater in the case of softwood compare with hardwood. This is because the creosote can be impregnated to a greater depth in former case in comparison with the latter case.

It is reported that, the impregnation depth of 75mm can be obtained in the case of softwood whereas hardwood cannot be impregnated properly so it would be set under maintained pressure for a while until reasonable treatment is achieved.

Lastly, due to the fact that hardwood cannot be treated adequately, so it is advised to creosote bolt holes suitably.

Fig.9: Impregnated timber with creosote

Protection of timber piles using concrete

This approach is considered in the case where the use of creosote would not generate required final result. For example, creosote cannot be used in conditions where the level of water table changes.

If the water table is considerably deep, then it is recommended to use composite pile which means the lower part of the pile is completely submerged which is timber whereas the upper part would be concrete.

However, when the depth of water table is reasonably shallow, then the pile is cut and the pile cap is placed at this water table level. Figure 7 illustrates the use of concrete to preserve timber pile and increase its life service.

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 recommended to employ timber that can withstand borers at first place rather than using timber piles and providing protections against such risk. There are several timbers that naturally resist borer for example African padauk (Figure 8), Belian, Afrormosia (Figure 9), and many other types of timber piles.

Fig.11: African Padauk timber has the ability to withstand borer

Fig.12: Afromosia pile which can resist borer

It should be said that the sapwood of such timbers should be removed otherwise treatments by creosote need to be introduced. This is because sapwood of such timbers is susceptible to borer aggression.

The continuity of the treat on the surface of the timber out layer is greatly influence the treatment effectiveness. Damages of treatment by any means for example piercing the treatment layer with hooks, which may be used during lifting, or bolts or saw cut would permit the penetration or borer and cause deterioration of the timber.

Openings in Concrete Beams – Effects on Strength and Serviceability

Transverse openings in concrete beams could be different in shapes and sizes as shown in Figure 1. Even though large number of transverse openings with various shapes and sizes might employ, but it is better to use circular shape to make rooms for service pipes, for example electrical supply and plumping, and using rectangular transverse opening through for accommodating rectangular ducts of air conditioners.

Figure 1 different shapes and sizes of transverse openings in concrete beams

In existing structures and buildings, creating transverse openings through beams for better utilization and services above beam soffit other than dead spaces could be detrimental potentially.

Problems related to transversal openings through beams can be avoided provided that placements of utility services is planned and taken into account previously but this is not the case most of the times.

Generally, there are two most common situations when drilling holes are required which are during utility installation of recently constructed buildings and in existing structures.

In the former case because of contractor request who want to save money by rearrangement of pipe services that is not accounted for carefully in the design stage.

These types of requests would endanger serviceability and safety of buildings. The latter is when structural performance of an old building is needed to be assessed. In this circumstances core sample of concrete is taken out for testing purposes after that the opening is filled with grouts that are non-shrinking.

The effects of openings in concrete beams on serviceability and strength of the structure are discussed in this article.

Effects of Openings in Concrete Beams on Serviceability

Effects on Cracks and Crack Width

It is demonstrated that beams with opening near center stub showed similar crack pattern. Generally, flexural cracks are appeared ahead of shear cracks but this pattern is reversed in beams with openings. If opening size is increased, Loads that cause diagonal cracks and crack width will decline.

Moreover, it can be claimed that crack width is larger in beams with openings than solid beams and exceed limitations of crack width irrespective of location and size of holes. From this it becomes quite clear that serviceability of cracks could extremely influenced by openings.

Moreover, there are various techniques that are used to repair beams which are drilled for assessment purposes such as filling holes with unshrinking grouts and externally bonded fiber reinforced polymer plate. The latter method proved to be much more effective compare with the former.

Beams improved with externally bonded method provide much higher crack control compare with grouting and even better than solid beams. Furthermore, opening locations in beams affect the diagonal cracks and changing locations could lead to narrowing crack width when openings are close to center stub.

Effects on Stiffness and Deflection

The stiffness of beams after cracking is considerably affected by openings and any increase in the size of holes will directly decline beam stiffness. In contrary, there are no obvious or clear influences of the opening location on the beam’s stiffness.

Openings in beams will lead to increase deflection without considering size and location of openings. Consequently, this could be detrimental for serviceability of the beams.

It should be said that beam strengthened with externally bonded plate method entirely remove weaknesses that arise from openings. Additionally, grouting improvement might make some improvement but it is not near from the desired result.

Effects of Openings in Concrete Beams on Strength

Effects on Ultimate Strength

Increasing opening sizes and changing their locations from the center stub of the beam are obviously decreasing the ultimate strength of the beams.

When the openings are located close to the beam supports to skip failure plane, the ultimate strength decreases compared with beams without openings by more than ten percent. This could be resulted from cutting one or more stirrups which decrease capacity to carry considerable amount of applied shear.

In circumstances where the openings are drilled for estimating performance of old buildings, different methods for example externally bonded fiber reinforced polymer plate, grouting by using non-shrinking cement or any other way can be employed to regain the ultimate strength of the elements.

Grouting might regain the beam strength to an extent, but it is around twenty percent less than original strength. Externally bonded FRP plate will be beneficial to regain the strength that has been lost as a consequent of openings.

Finally, it is recommended to adopt a considerably large safety factor in the original design or utilizing a promising technique such as externally bonded FRP plate for regaining strength when an opening is made in an existing beam.

How to be Successful in your Civil Engineering Career?

Achieving Effectiveness as a Young Civil Engineer

Civil engineers spend four or more years in the institution being persuaded that if they solve the technical problems properly they will be rewarded with high grades.

Not surprisingly, when they get to work, many civil engineers still expect that all they have to do to succeed is to apply effectively the technical and analytical skills they have been taught to the engineering assignments given to them. This is necessary, but not sufficient.

Successful Civil Engineers learn to manage their careers with the same skill and care they apply to their technical assignments, and with a sufficient priority.

Get Off to A Right Start

In Civil Engineering education, you have to work hard to survive a demanding curriculum and to build an academic record you can be proud of. The chances are that you landed your first job because the employer came looking for you.

Although, more or less than 10% of university graduates are engineers, they receive about half of all on-campus job offers. Civil Engineering employment has traditionally been reasonably secure, and most industries were less likely to lay off engineers than other workers.

However, nowadays, jobs held by civil engineers are growing increasingly vulnerable due to structural changes in economic situation which affect the work environment that confront engineers resulting in corporate downsizing, reduced long-term research expenditures, automation and globalization.

A perverse consequence of the increase in productivity of individual civil engineers using computer-aided design (CAD) is the elimination of the jobs of other civil engineers!

Regard Your Work

Since having a secure job is not satisfying for most professional civil engineers, you must begin to build for yourself a personal reputation on which your future career success will depend. Several decades later, you may come to reflect on the actions and decisions in your early career that made you successful, or that might have made you more successful: perhaps then you will be willing to share your hard-earned wisdom with young civil engineers who are following in your footsteps.

The new graduate usually makes his or her mark within the first few years in the organization depending on his or her technical ability which is complemented by his managerial ability to command, plan, organize and control people.

You will be judged not on what you know but on what you do and the engineer accomplishes but little without other people’s assistance. This makes it essential to give your best efforts to your early assignments, regardless of how trivial they may appear.

Doing an exceptional job on a minor assignment is the best way to be recognized and assigned more important, more challenging, more satisfying work since executives are continually searching for competent people to move up into more responsible positions.

Don’t wait for others – Get Things Done

Just because you have asked a foreman, a vendor, or a colleague to provide something you need does not mean that it’s going to happen in a timely fashion. Keep a tickler file and call (and call again if need be) to check on progress. Find another way to get it done or work two techniques in parallel if necessary.

Go the Extra Miles – and Hours

Reputations are not made on a 40-hour week, and to be an effective professional you will at least have to do your professional studies largely on your own time; as you increase in responsibility you will also find that you need uninterrupted blocks of time that never seem to be available during the day for planning and thinking problems through.

The fastest promotions generally go to those who put forth the extra effort and meet deadlines. This must be balanced against other values – time spent raising our families, recreation time to keep us whole and renewed, service to our community and other time invested on things that are important to us.

These balances can be particularly difficult for married female professionals, unless they are fortunate enough to marry someone who truly does his share in home and family choices.

Look for Visibility

You can do a good job every day, but you need to be seen to be recognized as a “rising star”. Look for opportunities to make a presentation, to take leadership role in a professional society chapter, to give a talk in a symposium or to organize a seminar for skill empowerment.

Learning the dividing line between making your capabilities visible and “brown nosing” takes maturity, but it is maturity that leads to greater responsibility.

Learn the Corporate Culture

Keep your eyes and ears open. Notice how successful civil engineers dress, and do likewise (but perhaps with a touch of style); save your expressions of independence for more important things. Notice how your colleagues interact and how they get things accomplished. If you cannot be comfortable and effective in your company’s culture, perhaps you’d better go somewhere else!

Regard Your Boss

Long before the days of universities and textbooks, craftsmen in all the arts absorbed their skills by apprenticeship to master craftsmen. By observing the master engineer, you can learn much more quickly the art of being an effective civil engineering professional.

Understand the boss to the point that the decisions you make are the same ones he or she would make. Strive to become his or her alter ego because not only will you learn the art, but you will become so trusted and valuable that when this paragon is promoted, he or she will not want to tackle a bigger job without taking you along to help. If, on the other hand, your boss is not of this caliber, you still owe him or her your best while you are looking for a transfer.

Keep up the “Old School” ties

Always stay in touch with your past school friends, professors, old colleagues and bosses. Someday, you may need help in finding a new job, getting a recommendation or some other venture. Also, you may need outside sources of information on people and business or some other vital resources needed to solve a problem.

You will be measured not just by what you know but by what you can find out when needed. Networking is the modern term for such a web of mutually supportive relationships.