Spherical cement particles are produced by (a) grinding cement clinker particles by a high speed impact treatment in apparatus of Fig. 1 wherein the particles are rotated and scattered by blades on a rotating plate and multiply impacted until (Fig. 6) the particles are spherical, or (b) by mechanochemical surface fusion.

The sphered cement may be encapsulated (Fig. 3) by attaching fine cement powder, silica-fume or other powder to its surface.

These sphered particles preferably have at least 60 wt% thereof of diameter 3.9 to 30 µm.

Before the particles have been completely sphered, the powder formed therefrom can be attached (Fig. 5) to fill the recesses in the particles, thus rounding them.

Alternatively (Fig. 4), silica fume particles are coated with ultrafine particles of cement clinker.

Cement mortar is made from the cements, or low-hydration concrete using the sphered cement, aggregate and water in a proportion of 1:2.5 to 8.0:0.17 to 0.75. The resultant cured concrete is of high strength.

A spherical hydraulic substance comprising a hydraulic powder based on CaO, SiO₂, Al₂O₃ and Fe₂O₃, wherein at least the surface of the powder is melted for smoothening and then cooled and the powder has a particle diameter of 500 µm or less and a means circularity of 0.7 or above. This substance is produced either by melting the starting material mainly comprising the above oxides, followed by splashing to effect cooling for solidification, or melting at least the surface of the hydraulic substance, followed by cooling for solidification. Alternatively it is produced by mixing a hot substance such as iron making slag in a state molten or heated above 500°C with a dried, calcined, sintered or molten starting material based on at least one oxide selected among CaO, SiO₂, Al₂O₃ and Fe₂O₃ and splashing the molten mixture to effect cooling for solidification. Since this substance is a minute spherical particle having a smooth surface and a shape close to a true sphere, it is remarkably excellent in fluidity and strength when kneaded with water.

Spherical cement particles are produced by (a) grinding cement clinker particles by a high speed impact treatment in apparatus of Fig. 1 wherein the particles are rotated and scattered by blades on a rotating plate and multiply impacted until (Fig. 6) the particles are spherical, or (b) by mechanochemical surface fusion.

The sphered cement may be encapsulated (Fig. 3) by attaching fine cement powder, silica-fume or other powder to its surface.

These sphered particles preferably have at least 60 wt% thereof of diameter 3.9 to 30 µm.

Before the particles have been completely sphered, the powder formed therefrom can be attached (Fig. 5) to fill the recesses in the particles, thus rounding them.

Alternatively (Fig. 4), silica fume particles are coated with ultrafine particles of cement clinker.

Cement mortar is made from the cements, or low-hydration concrete using the sphered cement, aggregate and water in a proportion of 1:2.5 to 8.0:0.17 to 0.75. The resultant cured concrete is of high strength.

An apparatus for producing a spherical hydraulic material comprises a melting furnace (1) for melting raw materials of a hydraulic material and/or the hydraulic material, fine granulation means for finely granulating the molten material (2) such as a nozzle (4) or a high speed rotary member, a chamber (5) for accepting the finely granulated material, cooling it and converting it into spherical fine powder, and means (6, 7) for recovering the spherical fine powder. When the material molten in the melting furnace enters the chamber and is finely granulated, the molten material is immediately formed into a complete sphere because its surface tension is relatively great, and is cooled and recovered as the spherical fine powder. The resulting spherical hydraulic material is highly fluidized by a small amount of water, and turns to a molded article having high strength and high durability, and moreover, having an excellent dimensional accuracy. Spherical hydraulic material which is approximately in the form of a complete sphere, is extremely smooth on the particle surface and exhibits high fluidity can be obtained by using this apparatus. This hydraulic material can be produced without limiting the blend ratio of the starting components, and various ashes of an incinerator can be utilized as the hydraulic material. Moreover, maintenance becomes easy.