Portland cement, process for preparing same, and compositions containing same

DETAILED DESCRIPTION I claim: 1.
A Portland cement composition comprising (1) dry powder of Portland cement, whose surface is coated with an asphalt film, and (2) particles of carbon black.
2.
A Portland cement composition as in claim 1, wherein said asphalt film comprises a film of straight asphalt or blown asphalt.
3.
A concrete composition comprising the Portland cement composition of claim 2, and aggregates.
4.
A Portland cement composition as in claim 2, wherein said asphalt has a softening point between 40.
degree.
-90.
degree.
C.
5.
A concrete composition comprising the Portland cement composition of claim 4, and aggregates.
6.
A Portland cement composition as in claim 4, wherein said asphalt is present in an amount of 0.
2 to 1% by weight.
7.
A concrete composition comprising the Portland cement composition of claim 6, and aggregates.
8.
A Portland cement composition as in claim 1, wherein said carbon black has a particle diameter of 70 millimicrons or less.
9.
A concrete composition comprising the Portland cement composition of claim 8, and aggregates.
10.
A Portland cement composition as in claim 5, wherein said carbon black is present in an amount of 0.
2 to 1.
5% by weight.
11.
A concrete composition comprising the Portland cement composition of claim 10, and aggregates.
12.
A Portland cement composition as in claim 1, wherein gypsum is present in said Portland cement in an amount of 2 to 5% by weight.
13.
A concrete composition comprising the Portland cement composition of claim 12, and aggregates.
14.
A concrete composition comprising the Portland cement composition of claim 1, and aggregates.
15.
A method for preparing a Portland cement composition comprising the steps of: (a) adding molten or powdered asphalt to a dry powder of Portland cement; (b) heating and agitating the mixture of step (a) at 100.
degree.
to 150.
degree.
C.
; (c) cooling the product of step (b) to room temperature; (d) admixing the resulting asphalt filmed Portland cement particles of step (c) with carbon black and agitating until a homogeneous mixture is produced