The results suggest that mixing concrete with fresh water before curing in seawater increases its compressive strength. For varying cement concentrations, the compressive strengths at 7 and 14 days rise by around 3–15 percent and 1–4 percent, respectively, for concrete mixes made and cured in saltwater. The increase in strength is likely due to an increased calcium concentration in the hydration products caused by the presence of sodium carbonate (a component of saltwater) which results in higher-quality concrete.
Concrete that is mixed with sea water has been used for various purposes including building roads and bridges, since it can be worked more easily than normal concrete. It also tends to be less expensive than normal concrete.
In addition, concrete that has been mixed with seawater has been shown to have improved durability compared to normal concrete. This is probably because the salt in the seawater causes the calcium hydroxide in the concrete to calcine or turn into calcium oxide and calcium hydroxide compounds which improve the resistance of the concrete to acid attack and freezing/thawing damage.
There are several types of concretes with different properties designed for different applications. Concrete that is used in structures such as buildings or bridges should have enough compressive strength after curing for any additional loading that it will experience during its lifetime.
The study found that when sea water is used for mixing or curing, it changes the rate of strength growth in concrete. At 90 days, the strength of concrete formed using sea water was found to be roughly 15% lower than that of equivalent concrete specimens prepared and cured with fresh water. However, this reduction in strength is not considered a problem for most applications.
These findings are important because they show that using sea water instead of fresh water reduces the initial strength of the concrete but has no effect on its long-term durability. This means that concrete made with sea water can still achieve its full potential strength after 90 days if it is kept out of contact with air and sunlight. The reduced early strength of concrete made with sea water is likely due to the effects of salt on the cement paste. When mixed with water, cement powder absorbs some of that water, which causes the powder to expand as it dries. If there is no place for this water to go, it will cause the mixture to become stiffer and less workable. Salt in particular reacts with the calcium hydroxide in portland cement, forming calcium chloride and sodium carbonate. Both of these substances are white and very fine, which may explain why using sea water tends to make the concrete look like it has more sand in it than normal concrete.
The Effect of Saline Water in Concrete Mixing and Curing on Strength Concrete is currently the most often used building material due to its high compressive strength and durability. Concrete's strength and durability will be completely established only when it has been cured. The key to a strong concrete structure is the use of sufficient curing time and temperature. The development of an adequate curing system was one of the major advances in concrete technology. Today, concrete that is mixed and placed in the field and not stirred until it reaches optimum age is usually sufficiently cured by leaving it undisturbed over the course of a year or more.
In general, saline water can be used as a replacement for fresh water in concrete mixes provided that certain criteria are met. First, the sodium chloride content of the water needs to be within certain limits for the hydration process to occur at a reasonable rate. Second, the pH of the water should be maintained within the range of 6.5 to 9.0 to ensure proper formation of the calcium-carbonate matrix that gives concrete its strength.
Concrete that does not have enough time to cure properly tends to be weak and may even be dangerous to human health. If you need to mix concrete quickly, it is recommended that you add chemical admixtures to speed up the setting process. These admixtures include accelerators such as sodium carbonate or potassium hydroxide and retarders such as sulfite or phosphate.
In concrete, seawater promotes both chemical and physical damage. Using a high-strength, low-permeability concrete mix extends the concrete's service life in a maritime environment. For concrete exposed to seawater, the maximum water-to-c e m e n t ratio is 0.40. Concrete that is not allowed to dry out becomes more vulnerable to oxidation and attack by sodium carbonate in seawater.
Concrete that has been exposed to moisture (e.g., from rain or melted snow) and heat can become embrittled or "soft". This condition usually occurs before the concrete begins to show signs of wear. Embrittlement may occur anywhere in the concrete structure where there is heat and moisture, such as at the bottom of an air-conditioning unit or under the floorboards of a house. As long as the concrete remains in contact with this heat and moisture, it will remain susceptible to embrittlement. Once begun, the process of embrittlement can lead to major problems for your concrete structure.
If you are considering building a new home or remodeling an existing one, consider using concrete with polymer additives to prevent it from breaking down in marine environments. These materials can also be used to create durable outdoor furniture that will last for years without needing to be re-stained or repaired.
I am a painter. When salt is added to concrete (usually by mixing with sea water), the cured concrete has increased compressive, tensile, and flexural strengths (of probably the 1.4X scale that you mention). After a few months, however, salt crystal development leads the concrete to become 8% weaker than conventional concrete. This loss in strength can be offset by the use of more concrete or higher-quality cement.
Salt has a very high electrical conductivity. When salt mixes with water, small electric currents are created as sodium ions flow toward less salty regions of the puddle. These currents increase the rate at which the cement protein molecules cross-link and harden, making the concrete stronger. However, this advantage comes with a cost: as the salt content increases, so does the risk of a premature chemical attack on the concrete's steel reinforcement. If this occurs, the concrete must be removed and replaced before it cures completely.
Concrete that has been mixed with seawater is called "salted" concrete. The term "cement" refers to a mixture of limestone, clay, sand, and other materials used to create a solid material that will harden into a rock-like substance when exposed to air and heat. Concrete is a mixture of cement and water; therefore, concrete is a type of salted concrete.
The addition of salt to concrete prevents the formation of ettings in the cement matrix.