Metallurgical Slag Aggregate: Roadbed Strengthening on Weak Base Soil
Frost heave on roads is one of the common causes of pavement deformation and asphalt concrete failure. It occurs mainly in winter and spring due to freezing of moisture in heaving soils, which leads to its uneven volume change and triggers bulging, bumps, and cracks.
Repairing such sections requires partial replacement of weak soils with crushed stone of various origins, including slag-based materials. NLMK’s blast-furnace slag aggregate has proven to be an optimal alternative to natural stone in these applications. Its performance has been confirmed by industrial trials on roads in the Lipetsk Region.
Properties and advantages of blast-furnace aggregate
BF crushed stone (aggregate) is a construction material produced by crushing and screening of steelmaking by-products. It is available in various size fractions and as a crushed stone-sand mix. It is characterized by high strength, excellent adhesion, and low cost, and compacts well in different structural layers.
Heaving repair trials
In spring 2026, 0/63 fraction crushed stone-sand mix (0/63 CSM) supplied by NLMK was used to partially replace the crushed-stone base on one of the main roads in the village of Dolgorukovo, Lipetsk Region.
Industrial tests under the GOST 32860-2014 specification have validated:
· Grain size distribution. The granulometric composition of 0/63 CSM showed higher effectiveness in eliminating frost heave compared with natural fractional crushed stone. No racked-in chipping was required, i.e., no need to procure and use additional stone fractions.
· Compaction. 0/63-2 CSM compacted more easily than natural 40–70 mm crushed stone. Achieving the required degree of compaction took 20% fewer roller passes.
· Effectiveness. Thanks to its hydraulic activity, BF slag aggregate is particularly effective for frost-heave repairs.* Over time the base gains additional strength due to self-cementing and the formation of a monolithic layer.
· Safety. BF slag aggregate is classified as a Class I construction material and can be used for all types of construction, including frost-heave remediation.
Thanks to its size composition and physico-mechanical properties, NLMK’s crushed stone-sand mix is a proven solution for eliminating frost heaves.