Effect of very fine aggregate on concrete strength

The effect of very fine aggregate on the water requirement and strength evolution of superplasticized concrete was studied. The maximum aggregate size was 6 mm, fine aggregate content 0–15% of the total aggregate, binder (OPC and silica) content 80–800 kg m⁻³, and specific surface area of the finest aggregate material 18–1000 m² kg⁻¹. The water requirement for constant workability fell sharply with increasing amount and fineness of the very fine aggregate due to improved particle packing. At constant, relatively small binder contents of 80–250 kg m⁻³, modifying the aggregate distribution increased the 91-day strength of 6 mm concrete as much as threefold, e.g. from 20 to 65 MPa at 200 kg m⁻³. This effect was less significant the greater the binder content. The correlation between strength and porosity was similar regardless of concrete composition. The stress-strain behaviour was more dependent on strength than on composition.