Sea Sand Vs River Sand and Its Application in Concrete

Why do you need to know the way to identify sea sand vs river sand? With the increasing efforts of environmental protection policies to strengthen the ecological balance. This has led to the closure of a large number of mines and the banning of sand from lakes and inland rivers, resulting in a shortage as the main material for concrete. Some businessmen then use sea sand to fill the market. In order to distinguish the composition and nature of sea sand vs river sand, we kindly remind concrete companies that they should identify sand carefully when purchasing it.

The following is a specific introduction to the impact of sea sand on the quality of concrete and a simple way to identify sea sand and river sand.

Characteristics of sea sand vs river sand

Sea sand

Sea sand is the sand produced in the ocean (including beach sand and submarine sand) and near the mouth of the sea. Sea sand is affected by seawater, and sea sand without desalination treatment has the following 2 characteristics.

High salt content

The salt contained in sea sand is mainly chloride salt and sulfate. The content of chlorine salt is 10 times that of sulfate (abbreviated as Cl- for chlorine salt and SO42- for sulfate), so the sea sand is mainly high in chlorine salt. There is information that the salt content of sea sand reaches 0.1% to 1% (light sand mass percentage, converted to Cl- is about 0.06% to 0.6%). JGJ206-2010 “Technical Specification for the Application of Sea Sand Concrete” stipulates that the maximum content of water-soluble chloride ions is 0.03%.

High shell content

The main component of the shell is CaCO3, which is characterized by a thin flaky shape, smooth surface, low strength, and easy to destroy along the direction of decomposition.

River sand

River sand is produced by the natural stone in its natural state by the force of water repeatedly ramming and rubbing for a long time. Its composition is more complex, the surface has a certain smoothness, and the impurity content is more. River sand has no taste, while sea sand has a salt taste. River sand has round and smooth particles and is relatively clean and widely available.

The root cause of the hazards of sea sand house

A sea sand house is a house built with concrete prepared by using sea sand that has not been desalinated. After a certain period of time (usually several years) the reinforcement inside the concrete is severely corroded. The structure is damaged and the load capacity of the house is drastically reduced. In case of serious geological disasters, such as earthquakes, the house will easily collapse, and even some buildings will collapse on their own without natural disasters. It can be seen that the danger of “sea sand house” is extremely serious and should not be taken lightly. The following discusses the root cause of the hazard.

The hazard of chloride ions

The corrosion of reinforcement in sea sand concrete is an extremely complex process. It is related to many factors such as chloride ion content, pore characteristics, hydration effect, temperature and humidity, carbonation characteristics, PH value, thickness of the protective layer, etc. It is the result of the interaction between various factors.

The chloride ion plays the role of a catalyst in the corrosion process of reinforcing steel. The chemical reaction is caused by local acidification (e.g. carbonization, etc.), and the surface passivation film is destroyed after the PH value drops to a certain level to reach the critical concentration of chloride ions. This creates a potential difference between the unbroken passivation film and the nearby broken passivation film – forming a rust primary cell.

Chlorine ions are in the process of cyclic participation, until the rust phenomenon is more and more serious, resulting in concrete cracking and deterioration. The chloride ion is involved in the above reaction, forming intermediate products, but also in the electrochemical reaction solution plays the role of lubricant. It reduces the resistance of the electrochemical solution, lowers the PH value, and accelerates the process of rusting reaction.

The adverse effect of shell material

The shells are easy to break down due to the deconstruction, and the cement paste is poorly combined. When it is in large quantity, it will make the concrete poor in compatibility, and also make the concrete tensile, flexural, and compressive strength decrease, and wear resistance, and impermeability deteriorates.

The difference between sea sand vs river sand

Sea Sand Vs River Sand

Sand can be divided into sea sand, river sand, and mountain sand from the source.

Although sea sand is clean, sea sand without desalination treatment is strictly prohibited as a construction material. Because of the high salt content of sea sand, it is very easy to make the construction work of chloride ion corrosion of steel, causing safety hazards. To distinguish whether it is sea sand, mainly to see whether the sand contains marine fine shells inside.

Mountain sand has a good cement adhesion effect because of its rough surface, but the composition of mountain sand is complicated, and most of it contains mud and other organic impurities.

The genesis of sea sand and river sand are all basically the same, are granite, and sandstone accept the residual minerals of strong weathering. Mainly quartz, but also contains a small amount of feldspar and white mica. Sand deserts are ancient river rocks or lakes that have dried up. Therefore, the two do not look very different.

River sand is recently deposited fluvial sand, which is widely distributed in the river rocks of large rivers and small rivers, and will be cleaner and is the best sand for construction. Sea sand is poorer for construction because it has more salt and other impurities.

The method of identifying sea sand vs river sand

The main component of sea sand is quartz particles. It has fewer feldspar and rock chip particles, very fine particle size, better rounding, and fewer mica flakes. Sea sand has sodium, magnesium, and salt in it, so it cannot be used in construction.

You can distinguish river sand from sea sand by the following methods.

Color: Blackish is sea sand, and yellowish is river sand.

First of all, we should see whether there are marine tiny shells in the sand, which is sea sand.

The white crystals (salt) in the sun are sea sand.

Grab a handful of dipping water, not too much water, and taste the water, salty is the sea sand, and light is the river sand.

First, from the appearance, the sea sand particles are large, containing many shell fragments. The real river sand is very uniform and very fine, and the river sand has different sizes of pebbles.

Sticky hand feeling, grab a handful of sand forceful grip down, and then shoot off, found sticky hand shot not clean for the sea sand, not sticky hand basic can shoot clean for the river sand.

Sea sand mixed with more shellfish shells, large particles, and gravel between the compactness is very low, so the feeling in the hand is very rough. River sand particles are small, and the compactness between gravel is high, so the feeling in the hand is very fine.

Use the chloride ion concentration in concrete quick test strip (ECT chlorine test strip) detection. The quick test strip is easy to use, simple to operate and has instant results.

Also to read:

Six Factors Affecting the Capacity of Sand Making Machine

The Basic Principles of Using Fine Sand to Prepare Concrete

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