Process for producing improved building material and product thereof

• US 5,232,496 A
• Filed: 10/10/1989
• Issued: 08/03/1993
• Est. Priority Date: 08/19/1988
• Status: Expired due to Fees

• Current Assignee: E. Khashoggi Industries, LLC
• Original Assignee: E. Khashoggi Industries, LLC
• Inventors: Hodson, Simon K., Jennings, Hamlin M.
• Primary Examiner(s): Bell, Mark L.
• Assistant Examiner(s): Green, Anthony J.
• Application Number:
  US07/418,027
• Time in Patent Office: 1,393 Days
• Field of Search: 106/682, 106/638, 106/713, 106/814, 106/819
• US Class Current: 106/713
• CPC Class Codes: B01F 2025/91 Direction of flow or arrangement of feed and discharge openings
• CPC Class Codes: B01F 27/50 Pipe mixers, i.e. mixers wherein the materials to be mixed flow continuously through pipes, e.g. column mixers
• CPC Class Codes: B01F 27/80 with stirrers rotating about a substantially vertical axis
• CPC Class Codes: B01F 27/86 co-operating with deflectors or baffles fixed to the receptacle
• CPC Class Codes: B28B 11/24 for curing, setting or hardening processes for influencing or modifying the setting or hardening ability of mortars, concrete or artificial stone compositions, in general C04B40/00
• CPC Class Codes: B28B 11/245 Curing concrete articles B28B11/242 takes precedence
• CPC Class Codes: B28C 5/388 Methods
• CPC Class Codes: C04B 2103/0094 Agents for altering or buffering the pH; Ingredients characterised by their pH
• CPC Class Codes: C04B 22/002 Water
• CPC Class Codes: C04B 28/02 containing hydraulic cements other than calcium sulfates
• CPC Class Codes: C04B 40/00 Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability active ingredients C04B22/00 - C04B24/00; hardening of a well-defined composition C04B26/00 - C04B28/00; making porous, cellular or lightening C04B38/00; mechanical aspects B28, e.g. conditioning the materials prior to shaping B28B17/02
• CPC Class Codes: C04B 40/0028 Aspects relating to the mixing step of the mortar preparation
• CPC Class Codes: C04B 40/005 High shear mixing; Obtaining macro-defect free materials
• CPC Class Codes: C04B 40/0071 making use of a rise in pressure
• CPC Class Codes: C04B 40/0231 Carbon dioxide hardening
• CPC Class Codes: C04B 40/0616 preformed, e.g. bandages
• CPC Class Codes: C04B 7/527 obtaining cements characterised by fineness, e.g. by multi-modal particle size distribution

Abstract

The process for producing a paste of improved quality. In one aspect, the process comprises allowing hydraulic cement and water to mix sufficiently to reach early age equilibrium, exposing the mixing water and cementitious material to a carbon source selected from the group consisting of CO₂, CO, carbonate salts and mixtures thereof, and then allowing the resulting mixture to again reach early age equilibrium.

Claims

1. A process for producing a nonfoamed concrete building material, the process including the following steps:

(a) mixing a quantity of hydraulic cement and water to form a mixture of hydraulic cement and water, said mixing step continuing until a first occurrence of early age equilibrium is reached;

(b) controlling the exposure of a carbon source to the mixture of hydraulic cement and water such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixture of hydraulic cement and water in order to modify the workability of the mixture of hydraulic cement and water; and

(c) allowing the mixture of hydraulic cement and water from step (b) to reach a second occurrence of early age equilibrium,

wherein said steps (a), (b), and (c) occur during mixing, prior to initial set, such that the resulting cured nonfoamed concrete has sufficient strength for use as a building material.

2. The process of claim 1 wherein the carbon source is selected from the group consisting of CO₂, CO, carbonate salts, CO₂ enriched air, and mixtures thereof.

3. The process of claim 2 wherein the carbon source is selected from the group consisting of CO₂, CO and mixtures thereof.

4. The process of claim 3 wherein the carbon source is CO₂.

5. The process of claim 1 wherein the carbon source is exposed to the paste in the absence of foam-stabilizing agent.

6. The process of claim 1 wherein at a time at least 1 hour after exposing the carbon source to the mixture of hydraulic cement and water, the amount of carbon incorporated into the building material which chemically reacted with the hydraulic cement and water is increased by the process at least 1% over that present in the cement and water prior to processing.

7. The process of claim 1 wherein the ratio of cement to water in the mixture of hydraulic cement and water ranges from about 0.1 to about 20.

8. The process of claim 7 wherein the ratio of cement to water in the mixture of hydraulic cement and water ranges from about 0.2 to about 2.0.

39. The process according to claim 1, wherein the building material is nonfoamed concrete.

40. The process according to claim 39, wherein aggregate is added to the mixture of hydraulic cement and water after the second occurrence of early age equilibrium.

46. The product produced according to the process of claim 1.

47. The product produced according to the process of claim 2.

48. The product produced according to the process of claim 3.

49. The product produced according to the process of claim 4.

50. The product produced according to the process of claim 6.

64. The product produced according to the process of claim 40.

114. The process of claim 1 wherein a gaseous carbon source is exposed to the mixture of hydraulic cement and water.

119. The process of claim 6 wherein the quantity of carbon incorporated into the building material which chemically reacted with the hydraulic cement and water is increased by the process at least 10% over that present in the cement and water prior to processing.

120. The process of claim 6 wherein the quantity of carbon incorporated into the building material which chemically reacted with the hydraulic cement and water is increased by the process at least 100% over that present in the cement and water prior to processing.

9. A process for producing a nonfoamed building material, the process including the following steps:

(a) mixing a quantity of hydraulic cement and water to form a mixture of hydraulic cement and water, said mixing step continuing until early age equilibrium is reached;

(b) controlling the exposure of a carbon source to the mixture of hydraulic cement and water such that a quantity of carbon from the carbon source chemically reacts with the mixture of hydraulic cement and water in order to modify the workability of the mixture of hydraulic cement and water, said exposing step occurring during mixing, prior to initial set; and

(c) allowing the mixture of hydraulic cement and water from step (b) to form a gelled mixture of nonfoamed concrete, such that the resulting cured nonfoamed concrete has sufficient strength for use as a building material.

10. The process according to claim 9 further including the step of subjecting the gelled mixture to a localized stress.

11. The process of claim 9, wherein formation of the gelled mixture is induced by decreasing the pH of the mixture of hydraulic cement and water by at least 0.05 pH units.

12. The process according to claim 9 wherein the formation of the gelled mixture is induced by adding a weak acid to the mixture of hydraulic cement and water prior to initial set.

13. The process according to claim 12 wherein the weak acid is selected from the group consisting of carbonic acid, sulfuric acid, acetic acid, hydrochloric acid, and mixtures thereof.

14. The process according to claim 10, wherein the localized stress consists of extruding the gelled mixture.

15. The process according to claim 10, wherein the localized stress consists of cutting the gelled mixture with a sharp object.

16. The process according to claim 15, wherein the sharp object is a blade.

17. The process according to claim 10, wherein the localized stress is created by passing the gelled mixture through a screen.

18. The process according to claim 10, wherein the localized stress consists of adding aggregate to the gelled mixture.

51. The product produced according to the process of claim 9.

52. The product produced according to the process of claim 13.

53. The product produced according to the process of claim 18.

121. The process of claim 11 wherein formation of the gelled mixture is induced by decreasing the pH of the mixture of hydraulic cement and water by at least 0.1 pH units.

19. A process for producing a nonfoamed building material, the process including the following steps:

(a) combining hydraulic cement and water together to form a mixture;

(b) controlling the exposure of the mixture to a carbon dioxide source after a period of time such that a quantity of carbon from the carbon dioxide source is incorporated into and chemically reacts with the mixture in order to modify the workability of the mixture; and

(c) allowing the mixture to cure to a concrete building material without a significant volume of void defects sufficient to significantly reduce the strength of the cured concrete building material.

20. The process of claim 19 wherein the cement and water are mixed by a high shear energy mixing process.

54. The product produced according to the process of claim 19.

55. The product produced according to the process of claim 20.

21. A process for producing a nonfoamed building material, the process including the following steps:

mixing hydraulic cement and water in a distinct high shear energy volume flow pattern such that addition or removal of cement or water does not change the volume flow pattern, said mixing being performed in an atmosphere contiguous with the mixing cement and water which is enriched in carbon dioxide such that a quantity of carbon from the carbon dioxide is incorporated into and chemically reacts with the mixing of hydraulic cement and water in order to modify the workability of the flow volume.

22. The process according to claim 21, wherein the atmosphere contiguous with the mixing cement and water contains at least 1% by volume carbon dioxide.

23. The process according to claim 22, wherein the atmosphere contiguous with the mixing cement and water contains from 5% to 100% carbon dioxide.

56. The product produced according to the process of claim 21.

57. The product produced according to the process of claim 22.

58. The product produced according to the process of claim 23.

24. A process for producing a nonfoamed cement paste, comprising the steps of:

(a) generating water enriched with CO₂ ;

(b) combining hydraulic cement with said water such that a quantity of carbon from the water enriched with CO₂ is incorporated into and chemically reacts with the combined hydraulic cement and water to form a cement paste in which the workability of the cement paste can be controlled; and

(c) allowing the cement paste to cure to form a cementitious matrix without significant void defects in the cementitious matrix.

25. The process of claim 24, wherein carbonated water is generated by agitating the water to entrain carbon dioxide from air.

26. The process of claim 24, wherein carbonated water is generated by bubbling carbon dioxide-containing air through the water.

27. The process of claim 24, wherein the hydraulic cement is Portland cement.

28. The paste produced using the process of claim 24.

29. A process for increasing the compressive strength of a nonfoamed concrete product, the process comprising the step of:

(a) mixing water and hydraulic cement to produce a paste;

(b) controlling exposure of said mixing water and hydraulic cement to an atmosphere contiguous with the mixing hydraulic cement and water, said atmosphere being enriched with carbon dioxide, such that a quantity of carbon from said atmosphere is incorporated into and chemically reacts with the mixture of hydraulic cement and water in order to modify the workability of the mixing hydraulic cement and water such that the mixture of the hydraulic cement and water can be readily worked into a shape; and

(c) allowing the mixture to cure into a concrete product of a shape such that the concrete product has increased strength.

30. The process of claim 29, wherein the paste is allowed to gel and a localized stress is applied to the paste prior to initial set of the paste.

31. The process of claim 30, wherein the localized stress is induced by adding aggregate to the paste.

59. The product produced according to the process of claim 29.

60. The product produced according to the process of claim 30.

32. A process for producing a nonfoamed concrete building material including the steps of:

(a) mixing a quantity of hydraulic cement and water for a period of time, thereby forming a mixture of hydraulic cement and water;

(b) controlling the exposure of the mixing hydraulic cement and water to an atmosphere enriched with a gaseous carbon source selected from the group consisting of CO₂, CO and mixtures thereof such that a quantity of carbon from the carbon source is incorporated into the mixture of hydraulic cement and water during mixing, and prior to initial set in order to modify the workability of the mixing hydraulic cement and water, such that the resultant concrete building material has a matrix containing a minimal volume of voids.

33. The process according to claim 32 wherein the carbon source is CO.

34. The process according to claim 32 wherein the carbon source is an enriched CO₂ atmosphere.

35. The process according to claim 32 wherein the quantity of carbon incorporated into the mixture of hydraulic cement and water is increased at least 1% above that present in the hydraulic cement, water and unenriched atmosphere prior to processing.

36. The process according to claim 32 wherein the mixture of hydraulic cement and water is exposed to the carbon source for at least 30 seconds before mixing ends.

61. The product produced according to the process of claim 32.

62. The product produced according to the process of claim 34.

63. The product produced according to the process of claim 35.

122. The process according to claim 32 further comprising the step of allowing the mixture of hydraulic cement and water to cure and wherein the quantity of carbon from the carbon source incorporated into the cured mixture which chemically reacted with the hydraulic cement and water is increased at least 10%.

123. The process according to claim 32 further comprising the step of allowing the mixture of hydraulic cement and water to cure and wherein the quantity of carbon from the carbon source incorporated into the cured mixture which chemically reacted with the hydraulic cement and water is increased at least 100%.

37. A nonfoamed cementitious material manufactured according to the process of:

(a) first, combining hydraulic cement and water;

(b) and second, increasing the carbon content of the combined hydraulic cement and water by greater than 1% at an age at least 1 hour after initially combining the hydraulic cement and water in order to modify the workability of the combining hydraulic cement and water, said greater than 1% increase in carbon content arising from carbon incorporated into the cementitious material originating from at least one carbon source selected from the group consisting of CO₂, CO₂ enriched air, CO and mixtures thereof.

38. The cementitious material produced according to the process of claim 37.

41. A process for producing a nonfoamed concrete building material, the process comprising the steps of:

(a) mixing a quantity of hydraulic cement and water so as to form a mixture; and

(b) controlling the exposure of the mixture to a carbon source, said exposure occurring during mixing, prior to initial set, in order to modify the workability of the mixture, wherein at a time greater than one hour after mixing of the hydraulic cement and water the mixture has an increased carbon content of at least 1% over the carbon present in the hydraulic cement and water which were mixed, such that the resultant nonfoamed concrete control has sufficient strength for use as a building material.

43. The process according to claim 41, wherein the ratio of the quantity of water to hydraulic cement is in the range from about 0.2 to about 0.5, and wherein the carbon source exposure occurs within ten minutes after mixing begins.

44. The process according to claim 43, wherein the carbon source exposure occurs less than two minutes after mixing begins.

45. The process according to claim 41, wherein the mixture is allowed to rest after carbon source exposure for a period of time in the range from about 30 seconds to about an hour.

42. The process according to claim 42, wherein the carbon content increase is at least 10%.

65. A process for regulating the rate of hydration of a nonfoamed hydraulic cement paste formed by first, mixing water and hydraulic cement and second, controlling the exposure of the mixing water and hydraulic cement to a carbon source selected from the group consisting of CO₂, CO, air enriched by a carbon source, and mixtures thereof prior to initial set such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixing water and hydraulic cement in order to modify the workability of the paste and regulate the rate of hydration of the hydraulic cement paste.

66. A process for reducing the shrinkage of cured nonfoamed hydraulic cement paste formed by first, mixing water and hydraulic cement and second, controlling the exposure of the mixing water and hydraulic cement to a carbon source selected from the group consisting of CO₂, CO and mixtures thereof prior to initial set such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixing water and hydraulic cement in order to modify the workability of the mixing water and hydraulic cement so as to reduce the shrinkage of the cured hydraulic cement paste.

67. A process for reducing the bleeding of nonfoamed hydraulic cement paste formed by first, mixing water and hydraulic cement and second, controlling the exposure of the mixing water and hydraulic cement to a carbon source selected from the group consisting of CO₂, CO and mixtures thereof prior to initial set such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixing water and hydraulic cement in order to modify the workability of the mixing water and hydraulic cement and to reduce the bleeding of the hydraulic cement paste during a curing process.

68. A process for producing a nonfoamed concrete building material, the process including the following steps:

(a) mixing hydraulic cement and water together by a high shear energy mixing process; and

(b) controlling the exposure of the mixing hydraulic cement and water to a carbon source selected from the group consisting of carbon dioxide, carbon monoxide, carbonate salts, and mixtures thereof such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixing hydraulic cement and water in order to modify the workability of the hydraulic cement and water and to increase the strength of the resulting nonfoamed concrete building material.

69. The process of claim 68 wherein the carbon source is carbon dioxide.

70. The process of claim 68 wherein the carbon source is an atmosphere contiguous with the mixing cement and water enriched in carbon dioxide.

88. The nonfoamed concrete building material produced according to the process of claim 68.

89. The nonfoamed concrete building material produced according to the process of claim 69.

90. The nonfoamed concrete building material produced according to the process of claim 70.

71. A process for producing a nonfoamed concrete building material, the process including the following steps:

(a) mixing a quantity of hydraulic cement and water together to form a mixture of hydraulic cement and water;

(b) controlling the exposure of a carbon source to the mixing hydraulic cement and water such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixture of hydraulic cement and water in order to modify the workability of the mixture of hydraulic cement and water, the carbon source selected from the group consisting of carbon dioxide, carbon monoxide and mixtures thereof; and

(c) allowing the mixture of hydraulic cement and water from step (b) to reach early age equilibrium,

wherein said steps occur prior to initial set.

72. The process of claim 71 wherein the carbon source includes carbon dioxide.

73. The process of claim 71 wherein the carbon source is exposed to the water and cement by flowing the carbon source over the cement and water mixture.

74. The process of claim 71 wherein the quantity of carbon incorporated into the nonfoamed concrete building material which chemically reacted with the hydraulic cement and water is increased by at lest 1% over that present in the cement and water prior to mixing.

75. The process of claim 71 wherein the ratio of hydraulic cement to water in the mixture ranges from about 0.1 to about 20.

91. The nonfoamed concrete building material produced according to the process of claim 71.

92. The nonfoamed concrete buildingmaterial produced according to the process of claim 72.

93. The nonfoamed concrete building material produced according to the process of claim 73.

94. The nonfoamed concrete building material produced according to the process of claim 74.

95. The nonfoamed concrete building material produced according to the process of claim 75.

128. The process of claim 71 wherein the quantity of carbon incorporated into the building material is increased by at least 10% over that present in the quantity of hydraulic cement and water prior to mixing.

129. The process of claim 71 wherein the quantity of carbon incorporated into the building material is increased by at least 100% over that present in the quantity of hydraulic cement and water prior to mixing.

76. A process for producing a nonfoamed concrete building material, the process including the following steps:

(a) mixing a quantity of hydraulic cement and water together to form a mixture of hydraulic cement and water;

(b) controlling the exposure of a carbon source to the mixing cement and water such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixing cement and water in order to modify the workability of the mixing cement and water, the carbon source selected from the group consisting of CO₂, CO, air enriched by a carbon source, and mixtures thereof; and

(c) allowing the mixture from step (b) to form a gelled mixture.

77. The process of claim 76 further including the step of subjecting the gelled mixture to a localized stress.

78. The process of claim 76, wherein formation of the gelled mixture is induced by decreasing the pH of the mixture of hydraulic cement and water by at lest 0.05 pH units.

79. The process according to claim 76 wherein the formation of the gelled mixture is induced by adding a weak acid to the mixture of hydraulic cement and water prior to initial set.

80. The process according to claim 79 wherein the weak acid is selected from the group consisting of carbonic acid, sulfuric acid, acetic acid, hydrochloric acid, and mixtures thereof.

81. The process according to claim 77, wherein the localized stress consists of extruding the gelled mixture.

82. The process according to claim 77, wherein the localized stress consists of cutting the gelled mixtures with a sharp object.

83. The process according to claim 82, wherein the sharp object is a blade.

84. The process according to claim 77, wherein the localized stress is created by passing the gelled mixture through a screen.

85. The process according to claim 77, wherein the localized stress consists of adding aggregate to the gelled mixture.

86. The process of claim 76, wherein the mixing step is performed in an atmosphere contiguous with the mixing hydraulic cement and water, and wherein the atmosphere contains at least 1% by volume carbon dioxide.

87. The process according to claim 86, wherein the mixing step is performed in an atmosphere contiguous to the mixing hydraulic cement and water, and wherein the atmosphere contains from about 5%-100% by volume carbon dioxide.

96. The nonfoamed concrete building material produced according to the process of claim 76.

97. The nonfoamed concrete building material produced according to the process of claim 77.

98. The nonfoamed concrete building material produced according to the process of claim 78.

99. The nonfoamed concrete building material produced according to the process of claim 79.

100. The nonfoamed concrete building material produced according to the process of claim 80.

101. The nonfoamed concrete building material produced according to the process of claim 81.

102. The nonfoamed concrete building material produced according to the process of claim 82.

103. The nonfoamed concrete building material produced according to the process of claim 83.

104. The nonfoamed concrete building material produced according to the process of claim 84.

105. The nonfoamed concrete building material produced according to the process of claim 85.

106. The nonfoamed concrete building material produced according to the process of claim 86.

107. The nonfoamed concrete building material produced according to the process of claim 87.

130. The process of claim 76, wherein formation of the gelled mixture is induced by decreasing the pH of the mixture of hydraulic cement and water by at least 0.1 pH units.

108. A process for producing a nonfoamed builing material, the process including the following steps:

(a) mixing hydraulic cement and water to form a mixture, said mixing being performed by high shear agitation so as to increase the pH of the aqueous phase formed during the mixing step; and

(b) adding a quantity of reactive silica to said mixture.

109. The process according to claim 108 wherein the hydraulic cement and water are mixed using an HEM Mixer.

110. The process according to claim 108 wherein the reactive silica is selected from the group consisting of fly ash, silica fume, slag cement, glass and mixtures thereof.

111. The process according to claim 108 wherein from about 0.25% to about 100% of reactive silica, by weight of hydraulic cement, is added.

112. The process according to claim 111 wherein from about 10% to about 40% of reactive silica, by weight of hydraulic cement, is added.

113. The product produced according to the process of claim 108.

135. The process according to claim 111, wherein from about 5% to about 60% of reactive silica, by weight of hydraulic cement, is added.

136. The process according to claim 111, wherein from about 10% to about 40% of reactive silica, by weight of hydraulic cement, is added.

115. A process for producing a nonfoamed cementitious product comprising the steps of:

(a) mixing a quantity of hydraulic cement, water, and CO₂ provided by a carbon dioxide source, such that a quantity of carbon from the carbon dioxide source is incorporated into and chemically reacts with the mixture of hydraulic cement and water in order to modify the workability of the mixture of hydraulic cement and water, to form a cement paste; and

(b) allowing the cement paste to cure into a cementitious product having no void defects so as to create a substantial reduction in strength of the cementitious product.

116. A process according to claim 115 wherein the carbon dioxide source includes a carbon dioxide enriched atmosphere contiguous to the mixing hydraulic cement and water, said atmosphere including at least 1% by volume CO₂.

117. A process according to claim 115 wherein the carbon dioxide source includes a carbon dioxide enriched atmosphere contiguous to the mixing hydraulic cement and water, said atmosphere including at least 5% by volume CO₂.

118. A process according to claim 115 wherein the carbon dioxide source includes a carbon dioxide enriched atmosphere contiguous to the mixing hydraulic cement and water, said atmosphere including at least 75% by volume CO₂.

124. A nonfoamed cementitious material prepared by first, combining hydraulic cement and water and second, increasing the carbon content of the combining hydraulic cement and water by greater than 10% at an age at least 1 hour after combining the hydraulic cement and water, said greater than 10% increase in carbon content arising from carbon incorporated into and chemically reacted with the hydraulic cement and water which originated from at least one carbon source selected from the group consisting of CO₂, CO, air enriched by a carbon source, and mixtures thereof in order to modify the workability of the cementitious material.

125. A nonfoamed cementitious material prepared by first, combining hydraulic cement and water to form a mixture and second, increasing the carbon content of the mixture of hydraulic cement and water by greater than 100% at an age at least 1 hour after combining the hydraulic cement and water, said greater than 100% increase in carbon content arising from carbon incorporated into and chemically reacted with the hydraulic cement and water which originated from at least one carbon source selected from the group consisting of CO₂, CO, air enriched by a carbon source, and mixtures thereof, in order to control the workability of the cementitious material.

126. A process for producing a nonfoamed concrete building material from cementitious materials, the process comprising the steps of:

mixing a quantity of hydraulic cement and water to form a mixture of hydraulic cement and water; and

exposing a carbon source to the mixture prior to initial set, wherein at the one hour age the mixture of hydraulic cement and water has an increased carbon content of at least 10% over the carbon present in the quantity of hydraulic cement and water in order to increase the strength of the nonfoamed building material.

127. A process for producing a nonfoamed concrete building material from cementitious materials, the process comprising the steps of:

mixing a quantity of hydraulic cement and water to form a mixture of hydraulic cement and water; and

exposing a carbon source to the resulting mixture prior to initial set, wherein at the one hour age the mixture of hydraulic cement and water has an increased carbon content of at least 100% over the carbon present in the quantity of hydraulic cement and water in order to increase the strength of the nonfoamed concrete building material.

131. A process for producing an improved nonfoamed concrete building material comprising the steps of:

(a) mixing a quantity of hydraulic cement and water;

(b) adding a weak acid to the mixture of hydraulic cement and water, prior to initial set; and

(c) allowing the mixture of hydraulic cement and water in order to control the workability of the mixture from step (b) to form a gelled mixture.

132. The process of claim 131 further including the step of subjecting the gelled mixture to a localized stress.

133. The process of claim 131, wherein formation of the gelled mixture is induced by decreasing the pH of the mixture of hydraulic cement and water by at least 0.1 pH units.

134. The process according to claim 131 wherein the weak acid is selected from the group consisting of carbonic acid, sulfuric acid, acetic acid, hydrochloric acid, and mixtures thereof.

137. A process for producing an improved nonfoamed building material, the process comprising:

combining a quantity of hydraulic cement, water, and a gaseous carbon source such that a quantity of carbon from the carbon source contacts and reacts with a substantial quantity of an aqueous phase formed by combining the hydraulic cement and water prior to initial set in a high shear energy mixing process.

138. A process for accelerating the rate of cure and hydration of a nonfoamed hydraulic cement paste formed by first, mixing water and a quantity of hydraulic cement and second, exposing mixing water and hydraulic cement to a carbon source selected from the group consisting of CO₂, CO and mixtures thereof prior to initial set such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixture of hydraulic cement and water so as to accelerate the rate of cure and hydration of the hydraulic cement paste.

139. A process for producing nonfoamed concrete building material, the process comprising:

(a) mixing hydraulic cement and water by a high shear energy mixing process to form a cement paste;

(b) exposing a carbon source to the mixing hydraulic cement and water while mixing the cement paste by a high shear energy mixing process in order to increase the exposure of the cement paste to the carbon source such that a quantity of carbon from the carbon source is incorporated into and chemically reacts with the mixing hydraulic cement and water, the carbon source selected from the group consisting of CO₂, CO, CO₂ enriched air, and mixtures thereof,

wherein said steps (a) and (b) occur during mixing, prior to initial set.