Expansive cement and its method of manufacture

Claim 2

The method of claim 2 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the composition.

Claim 3

The method of claim 1 wherein the calcium sulfate is added in the form of gypsum.

Claim 4

The method of claim 1 wherein the expansive cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent, and the excess of S03 is about 3 to 11 weight percent of the Portland cement.

Claim 5

The method of claim 1 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement or clinker is about 3.5 to 17 weight percent and the excess of S03 is about 6 to 24 weight percent of the Portland cement or clinker.

Claim 6

The method of claim 1 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement or clinker is about 6 to 17 weight percent, and the excess of S03 is about 9 to 24 weight percent of the Portland cement or clinker.

Claim 7

The method of claim 1 wherein calcium sulfate is added as gypsum up to about 10 weight percent of the total composition and the remainder of the calcium sulfate required to give said excess of S03 over the optimum S03 is added as anhydrous calcium sulfate.

Claim 9

The method of claim 9 wherein about 2 to 8 weight percent of the expansive cement composition is CaS04. 1/2 H20.

Claim 10

The method of claim 10 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the composition.

Claim 11

The method of claim 9 wherein the expansive cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent and the excess S03 is about 3 to 11 weight percent of the Portland cement.

Claim 12

The method of claim 9 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent and the excess S03 is about 6 to 24 weight percent of the Portland cement.

Claim 13

The method of claim 9 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent and the excess S03 is about 9 to 24 weight percent of the Portland cement.

Claim 14

The method of claim 9 wherein the calcium sulfate is added as gypsum.

Claim 15

The method of claim 9 wherein the components are combined before grinding to final size, in which the calcium sulfate is added as gypsum to a maximum of about 10 weight percent of the total composition and the remainder of the calcium sulfate required to give the determined excess of S03 over the optimum S03 is added as anhydrous calcium sulfate.

Claim 16

The process for preparing a cement having controlled expansive properties consisting essentially of Portland cement, calcium aluminate cement in the amount from about 2 to 17 weight percent of the Portland cement, and calcium sulfate to provide excess S03 over the optimum S03 of about 2 to 24 weight percent of the Portland cement, said optimum being determined by ASTM Standard C563-70 comprising: a. determining the optimum S03 for the Portland cement, b. grinding the Portland cement constituent to an average minimum Wagner surface of at least 1,600 cm2/gm, c. grinding the calcium aluminate cement constituent to an average minimum Wagner surface of at least 1,350 cm2/gm, d. grinding the calcium sulfate so that at least 70 percent passes through a No. 100 sieve, and e. blending to homogeneity the Portland cement and the calcium aluminate cement with a sufficient excess of S03 over the optimum S03 determined in step (a). added as calcium sulfate to give a cement having the desired expansion level.

Claim 17

The process of claim 17 wherein the calcium sulfate is ground so that at least 85 percent passes through a No. 100 sieve.

Claim 18

The process of claim 17 wherein the calcium sulfate is added in the form of gypsum.

Claim 19

The process of claim 17 wherein the cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent of the Portland cement and the excess S03 is about 3 to 11 weight peRcent of the Portland cement.

Claim 20

The process of claim 17 wherein the cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent of the Portland cement and the excess S03 is about 6 to 24 weight percent of the Portland cement.

Claim 21

The process of claim 17 wherein the cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent of the Portland cement and the excess S03 is about 9 to 24 weight percent of the Portland cement.

Claim 22

The process of claim 17 wherein 2 to 8 weight percent of the cement is CaS04. 1/2 H20.

Claim 23

The process of claim 23 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.

Claim 24

The process of claim 17 wherein the Portland cement is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.

Claim 25

The process for preparing a cement having controlled expansive properties consisting essentially of Portland cement clinker, calcium aluminate cement clinker in the amount from about 2 to 17 weight percent of the Portland cement clinker, and calcium sulfate to provide excess SO3 over the optimum SO3 of about 2 to 24 weight percent of the Portland cement clinker, said optimum being determined by ASTM Standard C563-70 comprising: a. determining the optimum SO3 for the Portland cement clinker, b. mixing the Portland cement clinker and calcium aluminate cement clinker with a sufficient excess of SO3 over the optimum S03 determined in step a. added as calcium sulfate to give a cement having the desired expansion level, and c. grinding the mixture to an average minimum Wagner surface of 1,600 cm2/gm.

Claim 26

The process of claim 26 in which the calcium sulfate is added as gypsum to a maximum of about 10 weight percent of the total composition and the remainder of the calcium sulfate required to provide the determined excess of SO3 over the optimum SO3 is added as anhydrous calcium sulfate.

Claim 27

The process of claim 26 wherein 2 to 8 weight percent of the cement is CaS04. 1/2 H2O.

Claim 28

The process of claim 28 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.

Claim 29

The process of claim 26 wherein the cement is a shrinkage-compensating cement, the calcium aluminate cement clinker is about 2 to 9 weight percent of the Portland cement clinker and the excess SO3 is about 3 to 11 weight percent of the Portland cement clinker.

Claim 30

The process of claim 26 wherein the cement is a self-stressing cement, the calcium aluminate cement clinker is about 6 to 17 weight percent of the Portland cement clinker and the excess SO3 is about 9 to 24 weight percent of the Portland cement clinker.

Claim 31

The process of claim 26 wherein the Portland cement clinker is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.

Claim 32

An expansive cement having controlled expansive properties consisting essentially of Portland cement, calcium aluminate cement in an amount from about 2 to 17 weight percent of the Portland cement, and calcium sulfate to provide excess SO3 over the optimum SO3 of about 2 to 24 weight percent of the Portland cement, said optimum being determined by ASTM Standard C563-70.

Claim 33

The expansive cement of claim 33 wherein the calcium sulfate is added in the form of gypsum.

Claim 34

The expansive cement of clAim 33 wherein about 2 to 8 weight percent of the cement is CaS04. 1/2 H2O.

Claim 35

The expansive cement of claim 35 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.

Claim 36

The expansive cement of claim 33 wherein said cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent of the Portland cement and the excess SO3 is about 3 to 11 weight percent of the Portland cement.

Claim 37

The expansive cement of claim 33 wherein said cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent of the Portland cement and the excess SO3 is about 6 to 24 weight percent of the Portland cement.

Claim 38

The expansive cement of claim 33 wherein said cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent of the Portland cement and the excess SO3 is about 9 to 24 weight percent of the Portland cement.

Claim 39

The expansive cement of claim 33 wherein the Portland cement is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.