Dr Lê Trung Thành, Director of the Department of Construction Materials at the Ministry of Construction. — Photo courtesy of Ministry of Construction

As the push to accelerate national key projects and various other developments gains momentum, the demand for sand has become increasingly urgent. In response, several studies in Việt Nam have explored the feasibility of using sea sand for construction and road bed filling. Preliminary findings suggest that sea sand largely meets the necessary requirements, positioning it as a viable alternative to river sand.

In an interview with Tài nguyên và Môi trường (Natural Resources and Environment) newspaper, Dr Lê Trung Thành, Director of the Department of Construction Materials at the Ministry of Construction, clarified the factors ensuring the safety and sustainability of using sea sand in place of river sand, as well as identifying long-term strategies to secure a stable supply for transportation projects in the southern region.

How do you assess the current situation of construction sand, where supply is falling short of demand?

Construction sand is broadly classified into two main types, sand for mortar and concrete in building projects and sand for filling in infrastructure and road construction.

Sand for mortar and concrete generally needs to be of higher quality, usually coarse-grained sand and must meet the technical standards set by Việt Nam. In contrast, filling sand used in road and infrastructure projects typically requires larger quantities with less stringent quality standards, often being finer-grained. Nevertheless, strict adherence to environmental regulations is essential in its use.

Estimates from localities suggest that the total reserves of sand and gravel suitable for concrete and mortar stand at around 700 million cubic metres, while reserves for filling sand exceed 2 billion cubic metres. The annual demand for construction sand for mortar and concrete is approximately 120 to 130 million cubic metres. However, current extraction and usage only meet 60 to 70 per cent of this demand, leading to the need for artificial crushed sand as a substitute.

Currently, the relatively high cost of artificial crushed sand makes it a feasible replacement primarily for sand used in concrete and mortar, but not for filling sand in road and infrastructure projects.

With many key transportation projects struggling with a shortage of sand for road bed filling, sea sand is being touted as the optimal substitute for river sand. What is your assessment?

In many meetings, the government leaders have emphasised the importance of replacing river sand with sea sand, particularly in key transportation projects. They have directed the Ministry of Transport, the Ministry of Natural Resources and Environment, the Ministry of Agriculture and Rural Development, and other relevant agencies to implement this policy. Following these directives, the Ministry of Transport was tasked to expand the pilot programme for using sea sand to address the shortage of river sand. This initiative includes providing clear and specific guidelines for local authorities, project investors and construction contractors on using sea sand as a filling material.

From a technical standpoint, this solution is sound. Both sea sand and river sand are granular materials with high density, making them entirely suitable for roadbed filling. On 11 March, the Ministry of Transport issued a document outlining key findings and main points from the pilot project on using sea sand for roadbed construction. The document also offers guidance to provincial and municipal People’s Committees on incorporating sea sand as a filling material in transportation projects.

A section of the North-South Expressway project. — VNA/VNS Photo

To use sea sand effectively while minimising its environmental impact, what regulations need to be followed?

Sea sand contains high levels of sea salt, mainly chloride salts, which can leach into the surrounding environment, affecting soil, groundwater and surface water. This can lead to corrosion of steel structures, including concrete reinforcement and may also impact soil quality.

To use sea sand effectively as a road bed material, it is crucial to establish clear regulations on allowable salinity levels for agricultural land, crops, aquaculture waters and related seafood.

Furthermore, it is vital to evaluate the environmental impacts of sea sand extraction, processing and transportation to minimise harm to marine environments, ecosystems and marine life.

Regarding the proposal to use 3.8 million cubic metres of fly ash from the Duyên Hải Thermal Power Plant in Trà Vinh Province as a sand substitute for filling applications, Deputy Prime Minister Trần Hồng Hà has instructed Trà Vinh Province to pilot this approach for local road or highway projects. What is your assessment of this proposal?

Although research has explored the use of fly ash from thermal power plants for lightweight road foundations and countries like the United States and Japan have developed technical guidelines for its use, no country currently employs fly ash from thermal power plants for highway embankments. Using fly ash as a substitute for soil in highway construction necessitates extensive research and evaluation of its load-bearing capacity over time, particularly under conditions of waterlogging.

In the short term, fly ash can be used in constructing concrete elements such as bridges and elevated roads within highway systems. Additional research should aim to expand the use of fly ash in transportation infrastructure projects, especially for lower-class roads.

What measures should be implemented to explore, manage, extract and use construction sand effectively, given the severe shortage of natural sand?

Efforts to explore, manage, extract and use construction sand must adhere strictly to planning and comply fully with technical regulations and standards. This will ensure that construction sand is used correctly for its intended purposes, such as in residential and industrial buildings, transportation infrastructure and irrigation projects.

Moreover, government bodies and relevant sectors should enhance policies, especially those concerning taxation and environmental impact, to promote the wider adoption of crushed sand and other alternatives to natural sand in construction projects. — VNS