An evaluation of the procedure and results of laboratory crushing in quality assessment of rock aggregate raw materials

Quality estimation of rock aggregate raw materials is often performed with mechanical tests on aggregates crushed with laboratory crushers. However, standardised mechanical tests are intended for testing products, not raw materials. Different laboratory crushers produce aggregates with varying shape properties [flakiness index (FI), shape index and surface roughness], and this has a distinctive impact on the results from mechanical tests. Setting of crushers also plays an important role in laboratory crushing of aggregates and it should be adjusted according to required particle size. Four laboratory crushers and three apparati to measure resistance to wear by abrasion from a studded tyres test (A _N test) from three laboratories were compared and studied. The A _N test was carried out according to the EN standard and on bar-sieved samples in order to find how FI or surface roughness affects the A _N value.