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Making concrete from sand and sea water
Does salt water have been adhesive to concrete or not? How can this technology make concrete from sand and seawater?

14:30 this afternoon (14-3), in HCMC there was a transfer of technology in production of concrete by beach sand and sea between building material producers and the Defense Ministry.

If this technology is put into production, the construction of breakwater embankment, the road, the storm shelter ... in Truong Sa and other islands will be received an advantage because we are longer have to carry sand and fresh water from the mainland to the island to make concrete.

Concrete specially donated Truong Sa

Mr. Tran Minh Chi, the chairperson of Thach Anh Construction Investment Stock Company, told. On May, 2011 when launching Youth program "Contribution stone Truong Sa", the engineers at Thach Anh were thinking an idea "why not use sea sand, sea water to make concrete?", which will help a lot of funding, time transport materials from the mainland to the islands. This idea has been supporting by the generals of the Ministry of Defense, Thach Anh has studied ordered the technology of concrete production made by beach sand and seawater.

After more than six months of research and trial production, bricks from sand and seawater were brought to the Technical Centre of Standards and Quality 3. The results show that the average compressive strength of concrete reached 89.9 MPa (TCVN 6476:1999 method), water absorption 3.1% (TCVN 6355:1998 part 3), deep abrasion 215mm3 (BSEN 1338:2003 test method). Thach Anh has registered technological patent and prepare to conduct transfer their invented technology to the Ministry of Defense.

Engineer Nguyen Minh Luan - deputy technical director- author of the theme - said that the main raw material for production of concrete are gravel, sand, coral, P40 cement, water and additives to create sticky. If compared to conventional concrete, to produce 1m3 of concrete with compressive strength of 30Mpa, it needs to use 472kg of cement P40, but with sand and sea, it will take 350kg cement compressive strength of 50MPa. With the additional adhesive used by Thach Anh, concrete products are not only high compressive strength, water absorption, low abrasive outside but also are not water repellent inside, results in leading to greater longevity of concrete.

"Concrete made ​​from sand and seawater of Thach Anh’s technology can be frozen for four hours, while the concrete generally takes 24 hours, this feature is convenient for casting concrete right on the beach. Pouring concrete into the mold in tide receding period until the concrete has hardened "- Mr. Luan said.

According to Luan, additive concentration is around 1% weight of cement in concrete mixtures. Additives for concrete have a large slump, so that the capable of creeping into every corner of côppha is excellent and it is not necessary to use awls and easy to implement construction.

The trick is additives used in the technology. Thach Anh’s additives used in sea- sand concrete of  production effects compression of partial elements together, pushing most of the salt water out of concrete block surface, minimizing the amount of salt remaining in the block concrete, fixing the inner corrosion mechanism, prolonging the life of concrete blocks. On the other hand, using this type of cement with sustainable sulfate will support reduction process of the ion corrosion. It is also increasing the life of concrete. Therefore, observing that concrete blocks, we can see a layer of white gloss paint the bottom bricks.

Manually done reliability

Looking back to the process of research, said Mr. Tran Minh Chi, at first, Thach Anh collected sand seawater in Con Dao for some experiments, during the experiments also added salt into water to have a high salinity. The result of the first period was very good, but the High Command of Navy was not satisfied and recommended to test those experiments with sand and sea from the Truong Sa. Sand and water were sealed and signed carefully by the navy. On concrete mixer day, there were officials of the navy came to watch the process of mixing, pouring concrete into the mold, the mold was sealed by Admiral Nguyen Van Hien - Deputy Minister of Defense, the Navy commander – and he tested the concrete dry.

According to Mr. Tran Minh Chi, after the technology had transferred, the Ministry of Defense used the technology to produce concrete bricks from sand and seawater to insert into breakwater embankments, to make bricks for building storm shelter, schools, freshwater reservoirs, roads on the island. There is not necessary to build machinery line, it could be mixed, molded manually by human power, no heat, no pollution, the cost of production on the island is less than 1/3 of that as using normal and freshwater to make concrete. Thach Anh Company will continue to support the manufacturing process instructions, train employees.

Afternoon 13-3, exchanging information with Youth News, Admiral Nguyen Van Hien said: "We welcome the transfer technology and consider this as an act of “stone contributing to Truong Sa". As being the construction work, civil or military also need to use those concrete bricks, so that the technology is very significant for no transport water and sand from land to island”

According to Admiral Hien, this type of transferred technology can be applied immediately and now there are some related and adjusted issues to deploy. Regarding to the evaluation of the technical elements of concrete technology transferred, Mr. Hien said: "Before received, we had the test and evaluated. This was done very carefully”

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