Patent Application
20080000391
The properties of two cement slurries prepared according to the invention are compared to a conventional cement system:
Slurry A (Invention)
A mixture of powders comprising: 55% by volume of Portland Class G, 20% by volume of a mixture of Portland micro-cement and slag having a mean size of about 1.5 μm, and 25% by volume of fume silica is prepared. Water and additives (anti-foaming agent at 0.03 gallons per sack of powder (0.0025 l/kg), and a super-plasticizer based on polynaphthalene sulfonate at 0.4 gallons per sack of powder (0.0334 l/kg)) are mixed with this powder so as to ensure that the volume percentage of liquid in the slurry is 40%. A sack of powder is defined by analogy with sacks of cement as being a sack containing 45.359 kg of mixture, in other words 1 gps=0.0834 litres of additive per kg of mixture.
A mixture of powders comprising 55% by volume of Portland Class G, 20% by volume of glass microspheres having a density of 380 kg/m3, and 25% by volume of fume silica is prepared. Water and additives (anti-foaming agent at 0.03 gallons per sack of powder (0.0025 l/kg), and a super-plasticizer based on polynaphthalene sulfonate at 0.3 gallons per sack of powder (0.0250 l/kg) are mixed with this powder so as to ensure that the volume percentage of liquid in the slurry was 40%.
Portland cement Class G cement is mixed with fresh water, 0.03 gps (0.0025 l/kg) of antifoam, and 0.04 gps (0.0033 l/kg) of dispersant so that the density of the slurry is 15.8 ppg (1900 kg/m3) (porosity 59%)
The densities are expressed in kg/m3 (and in pounds per gallon in parentheses). CS means compressive strength after 6 days for cement set at ambient pressure and 60 C, and it is expressed in MPa (and in pounds per square inches in parentheses).
It can be seen that for the slurries A and B, compressive strengths are much higher than for slurry C due lower water to cement ratios.
The properties of foamed cement slurries prepared according to the invention are compared to conventional foamed cement systems:
Base Slurry A (Invention)
A mixture of powders comprising 55% by volume of Portland Class G, 20% by volume of glass microspheres having a density of 380 kg/m3, and 25% by volume of fume silica is prepared. Water and a super-plasticizer based on polynaphthalene sulfonate at 0.3 gallons per sack of powder (0.0250 l/kg)) are mixed with this powder so as to ensure that the volume percentage of liquid in the slurry was 40%.
The slurry is foamed with various quantities of foam to obtain slurries whose final densities are 1440 kg/m3, 1278 kg/m3 and 1150 kg/m3.
Portland cement Class G cement is mixed with fresh water and 0.04 gps (0.0033 l/kg) of dispersant so that the density of the slurry is 15.8 ppg (1900 kg/m3)(porosity 59%).
The slurry is foamed with various quantities of foam to obtain slurries whose final densities are 1440 kg/m3, 1278 kg/m3 and 1150 kg/m3.
The densities are expressed in kg/m3 (and in pounds per gallon in parentheses). CS means compressive strength after 10 days for cement set at ambient pressure and temperature, and it is expressed in MPa (and in pounds per square inches in parentheses).
It can be seen that for the slurries prepared in accordance with the invention, compressive strengths are significantly higher than conventional foamed systems for the same slurry density due a lower water to cement ratio.
The properties of three cement slurries prepared according to the invention are shown in Table 3 below. They show the wide range of slurry densities that can be covered by the concept and the remarkable mechanical properties of the set materials.
A mixture of powders comprising 35% by volume of Portland Class G, 40% by volume of glass microspheres having a density of 380 kg/m3, 25% by volume of fume silica is prepared. Water and a super-plasticizer based on polynaphthalene sulfonate at 0.2 gallons per bag of powder (0.0167 l/kg)) are mixed with this powder so as to ensure that the volume percentage of liquid in the slurry is 40%.
A slurry similar to slurry A is prepared but without antifoam agent. This base slurry is then foamed with a quantity of foam to obtain a slurry whose final density is 970 kg/m3.
A mixture of powders comprising 50% by volume of Portland Class G, 25% by volume of glass microspheres having a density of 380 kg/m3, 25% by volume of fume silica is prepared. Water and an anti-foaming agent at 0.03 gallons per sack of powder (0.0025 l/kg) are mixed with this powder so as to ensure that the volume percentage of liquid in the slurry is 60%.
The densities are expressed in kg/m3 (and in pounds per gallon in parentheses). CS means compressive strength after 10 days for cement set at ambient pressure and temperature, and it is expressed in MPa (and in pounds per square inches in parentheses).
As can be seen from the preceding examples, considerable changes can be made to the slurries according to the invention while still remaining within the scope of the inventive concept. Other changes than those described can also be made.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06291087.2 | Jun 2006 | EP | regional |
