Heavy concrete: more weight, less volume

Standard concrete has a density of 2.4 tons per cubic meter. In some situations it may be interesting to apply heavy concrete. By (partially) replacing sand and gravel with MagnaDense, concrete with a density as high as 4 to 3 can be produced. Leon Hendriks of LKAB Minerals explains the advantages of more weight and less volume for infrastructure applications.

Conventional concrete already has a relatively high weight. "In 99% of cases it is not necessary to make concrete even heavier," Hendriks outlines. "Yet there are exceptions to the rule and it is indeed desirable to achieve a higher weight with less volume. Think of applications such as counterweights for lock gates, movable bridges and excavators. But also coastal protection elements to combat erosion or breakwaters to protect structures. In addition, heavy concrete also offers added value for underground structures, such as parking garages or tunnels, to parry groundwater pressure. The underwater floor can be less thick and does not need to have tension piles because of its high weight. It can provide substantial savings in time, cost and volume. In addition, it also reduces the risk of thermal cracking."

Heavy concrete is easily pumped

MagnaDense

LKAB Minerals supplies the aggregate MagnaDense to produce heavy concrete. "It is a material of natural origin and is made from the mineral magnetite, an iron oxide," explains Hendriks. "The aggregate is mined and produced in Sweden at our parent company LKAB, which has the largest iron ore mines in Europe. In Moerdijk, we keep different grades of MagnaDense in stock. Depending on the requirement, all or part of the sand and gravel are replaced with MagnaDense to obtain the required density of the concrete. We can supply mixture proposals to achieve any density between 2.4 and 4 t/m3."

According to Hendriks, it is a misconception that heavy concrete does not handle well. "It is easily pumped. For example, we delivered a mixture for the London Underground that was pumped as much as 1 kilometer. You do have to take into account a higher weight. A boom that is fully suspended is often calculated for conventional concrete. All other technical properties can also be influenced by playing with the amount of water and cement. Think low or just high strength, a very stiff or just fluid mixture, it is all comparable to conventional concrete. The only thing that changes is the volumetric mass."