Cementitious compositions
View Patent ↗The invention provides a method of preparing a blast hole which method comprises the steps of: drilling a blast hole; placing explosives in the blast hole; filling the blast hole with a stemming material comprising a cement composition and water wherein the weight ratio of water to solids content of the stemming material is at least about 1:1.
1. A method of preparing a blast hole which method comprises the steps of:
drilling a blast hole;
placing explosives in the blast hole;
filling the blast hole with a stemming material comprising a cement composition and water wherein the weight ratio of water to solids content of the stemming material is at least about 1:1.
2. A method as defined in claim 1 wherein the stemming material is pumpable.
3. A method as defined in claim 1 wherein the cement composition comprises a cement comprising calcium oxide, calcium hydroxide, Portland cement and/or a high alumina cement; and optionally one or more of the following ingredients:
(a) a calcium sulphate source;
(b) a reactive silica source;
(c) a suspension agent;
(d) a retarding agent; and/or
(e) an additive.
4. A method as defined in claim 1 wherein the cement composition comprises a reactive silica source and an activator.
5. A method as defined in claim 4 wherein the reactive silica source is a pozzolan; and/or wherein the activator is an alkali.
6. A method as defined in claim 1 wherein after the placing step, the method comprises a step of preparing a stemming material by mixing the cement composition with the water.
7. A method as defined in claim 6 wherein the cement composition is a two part cement composition comprising a first component and a second component and wherein the preparing step comprises mixing the first component with the second component wherein the first and/or the second cement components contain the water.
8. A method as defined in claim 7 wherein the first component comprises a cement, water, optionally a reactive silica source, optionally a retarding agent and optionally a suspension agent.
9. A method as defined in claim 7 wherein the second component comprises a reactive silica source, a calcium sulphate source, water and/or a cement.
10. A method as defined in claim 7 wherein the two part cement composition is ettringite-forming.
11. A method as defined in claim 10 wherein a first part of the two part ettringite-forming cement composition comprises water, a reactive silica source, and a high alumina cement and wherein a second part of the two part ettringite-forming cement composition comprises water, a calcium sulphate source and calcium oxide and/or calcium hydroxide.
12. A method as defined in claim 11 wherein the high alumina cement has a C:A molar ratio of greater than 1:1.
13. A method as defined in claim 7 wherein the two part cement composition has a first part comprising Portland cement, water, optionally a retarding agent and optionally a suspension agent and a second part comprising an aqueous solution of a reactive silica source.
14. A method defined in claim 6 wherein the preparing step is carried out in the blast hole or in a mixer placed near or above the blast hole.
15. A method as defined in claim 1 wherein the cement composition is a one part cement composition which is ettringite forming.
16. A method as defined in claim 15 wherein the ettringite-forming cement composition comprises a high alumina cement, a calcium sulphate source and optionally calcium oxide and/or calcium hydroxide.
17. A method as defined in claim 16 wherein the ettringite-forming cement composition comprises high alumina cement and the calcium sulphate source in a weight ratio of from 3:7 to 4:1.
18. A method as defined in claim 1 wherein the weight ratio of water to solids is at least about 1.5 to 1.
19. A method as defined in claim 1 wherein the blast hole contains water and the filling step comprises use of a tremie method.
20. A method as defined in claim 1 wherein the method comprises the sequential steps of:
(i) drilling a blast hole;
(ii) filling the blast hole with a stemming material comprising a cement composition and water wherein the weight ratio of water to solids content of the stemming material is at least about 1:1; and
(iii) placing explosives in the blast hole.
21. A method as defined in claim 20 wherein the blast hole contains water and the filling step comprises use of a tremie method.
22. A blast hole having a proximal end at ground level and a distal end wherein the blast hole has an explosive at its distal end and wherein the blast hole is filled with a stemming material comprising a cement composition and water wherein the weight ratio of water to solids content of the stemming material is at least about 1:1.