Successful Application of New Composite Reinforcement in Sea Sand Concrete

CRCHI developed a 𝐜𝐨𝐦𝐩𝐨𝐬𝐢𝐭𝐞 𝐫𝐞𝐢𝐧𝐟𝐨𝐫𝐜𝐞𝐦𝐞𝐧𝐭 𝐢𝐧 𝐬𝐞𝐚 𝐬𝐚𝐧𝐝 𝐜𝐨𝐧𝐜𝐫𝐞𝐭𝐞 together with CRCC and Hunan University. The composite bar replacing traditional steel bar was used in a 𝐅𝐢𝐬𝐡𝐢𝐧𝐠 𝐏𝐨𝐫𝐭 𝐫𝐨𝐚𝐝 𝐩𝐫𝐨𝐣𝐞𝐜𝐭 in Ledong, Hainan.

The Yinggehai Primary fishing port road project is the first time that composite reinforcement – sea sand concrete is applied to the construction of coastal ports in China, which can fundamentally avoid the corrosion of reinforcement in sea sand concrete and improve the durability of sea sand concrete.

The new composite bar has 𝐚 𝐪𝐮𝐚𝐫𝐭𝐞𝐫 𝐨𝐟 𝐭𝐡𝐞 𝐝𝐞𝐧𝐬𝐢𝐭𝐲 of the steel bar, but achieves 2-3 𝐭𝐢𝐦𝐞𝐬 stronger 𝐭𝐞𝐧𝐬𝐢𝐥𝐞 𝐬𝐭𝐫𝐞𝐧𝐠𝐭𝐡. The product has a good quality of rust resistance and electrochemical corrosion resistance.

The Results of Application：

There is neither rust nor electrochemical corrosion in sea sand concrete due to the characteristics of the composite bar.
The project reduced the use of river sand, reduces the cost of raw materials, and effectively solves the problem of easy corrosion of steel bar on sea sand concrete pavement.

CRCHI has applied the innovative products in 𝐫𝐚𝐢𝐥 𝐭𝐫𝐚𝐧𝐬𝐢𝐭, marine 𝐞𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠, 𝐫𝐨𝐚𝐝 𝐞𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠 𝐚𝐧𝐝 𝐜𝐨𝐧𝐬𝐭𝐫𝐮𝐜𝐭𝐢𝐨𝐧 𝐞𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠 to meet the requirements of new construction methods and project needs.

The new technology for utilizing sea sand could potentially address the issue of limited river sand mining and provide an alternative raw material source for coastal construction projects.

If you are willing to know more about which exact problem CRCHI has solved and what innovation they’ve made, you can keep on reading. Let’s start with an important Civil Engineering Material — Reinforced Concrete.

Introduction to reinforced concrete

Reinforced concrete is made up of the following parts:

There are a few options of materials for civil construction in costal areas.

Option A: Ordinary reinforced concrete–which uses Steel bar as its reinforcement and River sand as its fine aggregate.

Two reasons for not using ordinary concrete in coastal projects:

It requires extra project costs for the long-distance transportation of those raw materials, owing to the local shortage of river sand and freshwater.

It brings negative impacts on river ecosystems, navigation and flood control by extracting massive amounts of river sand.

These have led to the use of the local sand source–sea sand.

Option B: Sea sand reinforced concrete–which use Steel bar as its reinforcement and Sea sand as its fine aggregate.

The alternative seems reasonable , but it has critical drawbacks:

Sea sand concrete tends to corrode steel reinforcement, which can cause structural problems.

–Why does corrosion occur?

The chemical theory behind the corrosion of steel in concrete due to sea sand involves the presence of chloride ions.

When sea sand is used as a component in concrete, it may contain chloride ions that can penetrate the concrete and reach the steel reinforcement. Chloride ions can break down the protective oxide layer on the surface of the steel, which exposes the bare metal and allows it to react with oxygen and water in the concrete.

This reaction forms iron oxide (rust), which can expand and cause cracks and spalling in the concrete, weakening the structure over time.

–How to solve the corrosion problem?

To prevent or reduce the corrosion of steel in concrete, it is important to limit the amount of chloride ions in the concrete mix.

And it should be noted that more stringent limits than the above would be required for concrete or for situations where chloride ingress can be expected (e.g. a marine or coastal environment). Otherwise, serious safety problems will emerge.

–How did CRCHI choose to solve the problem?

Other than desalination, the other way is to either use a protective coating on the steel reinforcement or develop a new material which is free of corrosion.

The project team got back to R&D and engineered with composite materials

Application of the New Composite Bar

CRCHI, together with CRCC and Hunan University, conducted in-depth research and trials. Finally, They found a solution by developing a good substitute composite bar and gained good application results.

The Results of Application：

A quarter of the density of ordinary steel bars, but 2-3 times its tensile strength.

Due to the characteristics of insulation and chloride corrosion resistance of the composite bar, there is neither rust nor electrochemical corrosion in sea sand concrete.

Solution： **Sea sand & Composite reinforcement**

Other industrial applications

The exploitation and utilization of sea sand and composite reinforcement is inevitable in coastal areas, once the technical problems are solved, more applications will emerge.

Other potential projects:

Bridges and tunnels near coastal areas
Beachfront buildings and infrastructure
Coastal erosion prevention projects
Artificial islands and land reclamation
Coastal flood control and disaster prevention projects.
……

Concerns and Further developments

–Will the massive exploitation of sea sand damage the ecosystem in a coastal area?

It can potentially harm the coastal ecosystem.

However, by taking a proactive approach, it’s possible to minimize the environmental impacts of sea sand exploitation.

Solutions:

Sustainable and responsible mining practices can be used, such as limiting the amount of sand that is extracted, avoiding sensitive areas, and restoring disturbed habitats.
Alternative materials, such as recycled or synthetic aggregates, can also be used.
Environmental impact assessments are important, as well as engagement with local communities and stakeholders.