Method and apparatus for continuous production of quick-setting foamed cement grout with selectively adjustable proportions

A method for forming a flow of quick-setting foamed cement grout, said method comprising the steps of:

• providing a flow of finished foam material at a metered rate;
• mixing said flow of finished foam material in a pump means with a flow of cement slurry at a metered rate so as to entrain air therein and thereby form a flow of viscous, low shear-strength foamed cement grout which is discharged from said pump means, said finished foam being added to said flow of cement slurry in an amount sufficient to provide said foamed cement grout with a viscosity which is sufficiently high to minimize flow of said grout through and out of a void prior to a predetermined initial set time of said grout;
• and
• adding a flow of sodium silicate solution to said flow of foamed cement grout downstream of said pump means so as to form said quick-setting foamed cement grout, said sodium silicate solution being added at a metered rate selected to accelerate hardening of said quick-setting foamed cement grout to said predetermined initial set time.

Apparatus for forming a flow of quick-setting foamed cement grout, said apparatus comprising:

• foam supply means for providing a finished foam material at a metered rate of flow;
• a positive displacement mixing pump connected to said foam supply means for receiving said finished foam material therefrom at said metered rate of flow, said pump having a delivery rate which is directly proportional to an operating rate thereof and an intake port for receiving a flow of cement slurry, so that by controlling said operating rate of said pump said cement slurry is drawn through said intake port at a metered rate of flow and mixed with said finished foam material in said pump so as to entrain air therein and thereby form a viscous, low shear-strength foamed cement grout which is discharged from said pump, said finished foam being added to said cement slurry in an amount sufficient to provide said grout with a viscosity which is sufficiently high to minimize flow of said grout through and out of a void prior to a predetermined initial set time of said grout;
• and
• a positive displacement solution pump connected to a supply of sodium silicate solution, said solution pump having a delivery rate which is directly proportional to an operating rate thereof and a discharge for adding said sodium silicate solution to said foamed cement grout downstream of said mixing pump so as to form said quick-setting foamed cement grout, so that by selectively controlling said operating rate of said solution pump said sodium silicate solution is added at a metered rate of flow which is selected relative to said metered rates of flow of said cement slurry and finished foam so as to accelerate hardening of said quick-setting foamed cement grout to said predetermined initial set time.

A method for forming a quick setting foamed cement grout said method comprising the steps of:

• providing a flow of fluid cement slurry site to a positive displacement mixing pump and operating said positive displacement pump so that said cement slurry is drawn into said pump at a metered rate of flow;
• supplying a finished foam material to said mixing pump at a metered rate of flow so that said finished foam material is mixed with said slurry in said pump so as to entrain air therein and thereby form a viscous, low shear-strength foamed cement grout which is discharged from said pump, said finished foam being added to said cement slurry in an amount sufficient to provide said foamed cement grout with a viscosity which is sufficiently high to minimize flow of said grout through and out of a void prior to a predetermined initial set time of said grout;
• and
• adding a sodium silicate solution to said foamed cement grout downstream of said mixing pump, said sodium silicate solution being added at a metered rate of flow which is selected relative to said metered rates of flow of said cement slurry and finished foam so as to accelerate hardening of said quick-setting foamed cement grout to said predetermined initial set time.