Cementation methods
View Patent ↗The present invention provides methods for mineral precipitation and/or cementation of permeable or fractured non-porous materials using isolated urease.
1. A cementation method, comprising combining a column of a permeable starting material or a column of a non-porous but fractured starting material with a mixture comprising:
(a) isolated urease;
(b) urea;
(c) a source of divalent cations; and
(d) an organic additive,
wherein (a), (b), (c) and (d) are provided in amounts effective and the combining is carried out under conditions suitable to cause carbonate precipitation and/or cementation of the starting material within the column, and
wherein the combining comprises:
(i) mixing the urease with the starting material; and
(ii) injecting into the column of starting material, under pressure and via an injection tube, a solution comprising the urea and the source of divalent cations.
2. The method of claim 1 , wherein the method is used for one or more of improving bearing capacity of foundations; reducing settlement potential of foundations or embankments; increasing lateral resistance of foundations; enhancing stability of slopes or embankments; or reducing lateral earth pressures on retaining walls.
3. The method of claim 1 wherein the starting material comprises at least one of sand, silt, soil, clay, sediments, sawdust, fractured crystalline rocks, cracked concrete or sedimentary rocks.
4. The method of claim 1 , wherein the isolated urease comprises jack bean urease.
5. The method of claim 1 , wherein the source of divalent cations comprises a source of divalent calcium ions.
6. The method of claim 1 , wherein the combining step is carried out more than once.
7. The method of claim 1 , wherein the combining step is carried out once.
8. The method of claim 1 , wherein the permeable starting material comprises sand.
9. The method of claim 1 wherein the injecting is carried out two or more times.
10. The method of claim 1 wherein the urease is mixed with starting material in only a portion of the column prior to the injecting step.
11. The method of claim 1 , wherein the organic additive is water soluble.
12. The method of claim 1 , wherein the organic additive is powdered milk.
13. The method of claim 1 , wherein the organic additive is present in the mixture at a concentration of 1-10 g/L.
14. The method of claim 13 , wherein the organic additive is present in the mixture at a concentration of 3-5 g/L.
15. The method of claim 13 , wherein the organic additive is present in the mixture at a concentration of about 4 g/L.