Trust Does Not Preclude Control

For the first time, I encountered a statement under BOTAŞ security that read: "Trust is Not an Obstacle to Control," or in modern Turkish, "Confidence does not prevent inspection." Yes, although we trust people in many matters, as the proverb says, "To err is human," it is necessary to control the work, people and systems. However, this is such a delicate balance that one must not become too deeply involved in the work and complicate matters. Since waterproofing is applied to concrete, concrete must be properly inspected on site. Concrete inspection should not be left solely to the Building Inspection company, because concrete comprises more than just compressive strength. The ready-mixed concrete company is responsible for the concrete at the pump outlet. The remaining work—placing concrete in formwork, temperature control, shrinkage calculations, concrete pouring, concrete curing, etc.—falls under the responsibility of the client, project manager and site supervisor. Extra care must be taken with concrete that will come into contact with water. The waterproofing product to be used must be very carefully checked and selected based on documentation. An application method statement must be prepared describing how the product will be applied. Checklists must be created to verify that the product complies with its Technical Data Sheets and Safety Conditions. The most important matter here is the manufacturer's declarations. The manufacturer must clearly communicate to the end-user the method it has declared and recommended for application. Following application, how the material must be protected and when curing will be completed must also be clearly stated. Such quality controls should be used independently of personnel, without criticism of individuals, solely to measure the correctness of the work performed. This way, one must prevent the hollow remarks frequently heard on construction sites such as "it won't matter, never mind."   Although timber and steel structures exist, concrete is most widely used in construction in our country. Success in waterproofing encompasses the entire process from ordering the concrete, placing it properly, and completing curing. Even if the applied product is elastic and possesses crack-bridging properties, its performance still depends on the concrete itself. According to TS EN 206 (Concrete—specification, performance, production and conformity standard) and TS 13515 (complementary standard for its application), environmental exposure classes have now been defined for where concrete will be poured. Minimum cement quantities that can be used have also been specified. The standard, accounting for global warming, has set the maximum concrete pouring temperature at 35°C and classified concrete thicker than 90 cm as mass concrete, stipulating that the temperature of hardened concrete must not exceed 65°C. The ready-mixed concrete company produces and delivers the requested concrete according to order. However, the placement and maintenance of concrete fall to the client and contractor. Therefore, all measures that can be taken to prevent concrete cracking due to these factors fall to the client, contractor and building inspection. If the client does not demonstrate the necessary care in this matter, they must bear the consequences. If products that can be used during reinforced concrete construction are not used and precautions are not taken, rectification becomes both costly and technically yields negative results. For example, during construction, water-swelling strips used at concrete joints cost approximately EUR 4 per meter. If there is a waterproofing problem, the cost to remedy it is far higher. For instance, the material cost for 1 kg of polyurethane injection work is approximately EUR 40/kg. If the problem cannot be resolved, the extent of additional work required is unknown; it varies depending on the concrete condition, concrete quality, whether the concrete was properly compacted when placed in formwork, and other factors. Even if injection is done correctly and water is sealed off, water ingress can still occur in untreated areas and cannot prevent corrosion. You can change a building's doors, windows, taps and roof. If you dislike the color of a parquet floor, you can remove it and install a different-colored parquet in its place. However, you cannot change the structural framework—the skeleton holding the building upright. For a completed reinforced concrete structure, you cannot restore the concrete to its original state or remove the reinforcement and replace it with different reinforcement. This can be compared to bone loss disease found in humans. Once the disease begins, you cannot restore human bone to its previous condition. We can compare corrosion of reinforcing steel in reinforced concrete structures to human bone. It is possible to stop corrosion that has begun or slow its effects. However, reinforcing steel that has undergone corrosion, rusted and suffered cross-sectional loss cannot be restored to its original state. Concrete is not a completely impermeable building material. By using mineral and chemical additives in concrete, we can reduce concrete permeability. Concrete must be inspected especially in water-contact areas, water tanks, pools and wet spaces. Care must be taken from concrete pouring through curing. If cracks occur in concrete, it loses continuity. While varying by standard, the permissible crack width in reinforced concrete structures is 0.2 mm; some standards allow up to 0.4 mm. This is because it indicates the yield stress of the reinforcing steel has been exceeded and the rupture stress of the steel is approaching. For this reason, in large projects with costs exceeding USD 500 million, epoxy injection is generally applied if crack widths exceed standard limits. The locations in buildings where water ingress most frequently occurs are: 1) All horizontal and vertical concrete joints, 2) Tie-rod reinforcement, 3) Pipe entry and exit points, 4) Expansion joints (dilatation). In summary, since waterproofing is applied to concrete, every stage of concrete must be controlled. Waterproofing, thermal insulation, and if included in the project, green roof insulation details to be applied above should be similarly phased. It would be even better if a sample is prepared beforehand. After application, testing must be conducted with water tests, thickness determination and tensile testing. In areas where ceramic coating will be applied, such as wet spaces, water tanks and pools, water testing must be performed before grout application. Tile and ceramic grouting compounds are not waterproofing materials; they are building chemicals used to complete aesthetics and prevent ceramic damage during building movement. Cracks that may form in concrete should be minimized. Whether applied-type (bitumen, polyurethane, bitumen-polyurethane, MS polymer, hybrid, etc.) or sheet-type (PVC membrane, bituminous membrane, etc.) waterproofing is used, homogeneous and proper placement of concrete is quite important for waterproofing success. With an applied-type product, if problems occur during application, you can see where the problem originates and solve it with quick-setting grout or polyurethane-based injection materials. However, with sheet-type materials such as PVC membrane or bitumen-based membrane, you may not be able to determine the source of the problem. Water enters the waterproofing from one location and circulates. The location where water exits will not be where the problem is. Water will find its way through the weakest point in the concrete and seep through. All waterproofing and thermal insulation that has been applied must be removed and stripped away, after which waterproofing must be redone. Cem Ercan Civil Engineer M.Sc. Project and Technical Sales Manager Emülzer Asfaltevi Tecrit Maddeleri San. ve Tic. Ltd. Şti.