Glossary 

HAMMER & CRUSHER/MILL:
The action of this crusher is the combination of shear and attrition as the material is worked against itself and against the sides of the crusher
    
HARDENING:
Bitumen undergoes hardening when it is heated excessively, it is actually an oxidation, and can therefore happen to mixed material which is stored in hot storage, in the presence of oxygen.
    
HARDSTONE:
Stone other than limestone. To class as a hardstone aggregate should have a PSV greater than 45.
     
HAULIER:
Owner or driver of one or more vehicles for transporting quarry products.
       
HEAVY DUTY:
Relatively new type of road base and base course, using harder binder and increased filler content.
    
HOGGIN:
Raw material won from a quarry for processing into sand and gravel.
  
HOT ROLLED ASPHALT:
Old name for "Rolled Asphalt".
    
HOT STORAGE:
Large insulated bins holding from 10 - 100 tonnes each, keeping hot coated materials, for up to 8 - 10 hours. Longer if the bins are airtight.
   
HYDRATION:
The chemical reaction between the water and cement in concrete manufacture. Creates heat and is aggressive to skin, hence the need to wear protective clothing when handling fresh concrete.
   
HYDROGEOLOGY:
The study of water levels in the ground.
   
HYDROLOGY:
The study of surface watercourses.
   
HYDROSEED:
A method of seeding very inaccessible areas.