Nanozeolite-modified green concrete

1. A dry concrete composition, comprising:

10 to 30 wt. % of natural pozzolan;

0.25 to 10 wt. % of a zeolite particles having an average longest dimension of 25 to 45 nm;

20 to 50 wt. % of a fine aggregate having an average longest dimension of less than 9.55 mm;

35 to 60 wt. % of a coarse aggregate having an average longest dimension of 9.55 to 100 mm; and

2.5 to 12.5 wt. % of an alkali activator comprising sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3 ),

wherein the amounts of the natural pozzolan, the zeolite particles, the fine aggregate, the coarse aggregate and the alkali activator are 100 wt. % of the dry concrete composition,

wherein the composition comprises no more than 15 wt. % hydraulic cement, and

wherein the composition is suitable, when set, to provide a concrete of a compressive strength of at least 14 MPa, as determined by ASTM C109.

2. The composition of claim 1 , wherein the zeolite particles have a specific surface area in a range of from 50 to 120 m 2 /g.

3. The composition of claim 1 , wherein the zeolite particles have a bulk density of 1.2 to 1.8 g/cm 3 .

4. The composition of claim 1 , wherein the zeolite particles have a pH in a range of from 8 to 11, when suspended in water.

5. The composition of claim 1 , wherein a weight ratio of the natural pozzolan to the zeolite nanoparticles is in a range of from 15:1 to 35:1.

6. The composition of claim 1 , wherein a weight ratio of the coarse aggregate to the fine aggregate is in a range of 1.5:1 to 2.3:1.

7. The composition of claim 1 , wherein a weight ratio of a total weight of the fine and coarse aggregates to a total weight of the natural pozzolan and the zeolite nanoparticles is in a range of 4:1 to 5:1.

8. The composition of claim 1 , wherein a weight ratio of the alkali activator to the natural pozzolan is in a range of 0.5:1 to 0.6:1.

9. The composition of claim 1 , wherein a weight ratio of the sodium silicate to the sodium hydroxide is in a range of 1.5:1 to 4:1.

10. The composition of claim 1 , wherein the natural pozzolan comprises, relative to a total weight of the natural pozzolan:

35 to 45 wt. % of SiO 2 ;

8 to 16 wt. % of Al 2 O 3 ;

12 to 25 wt. % of Fe 2 O 3 ;

6 to 15 wt. % of CaO;

5 to 12 wt. % of MgO;

1 to 3 wt. % of K 2 O;

2 to 7 wt. % of Na 2 O; and/or

0.3 to 1.5 wt. % of TiO 2 .

11. The composition of claim 1 , comprising no more than 1 wt. % hydraulic cement.

12. The composition of claim 1 , which is sufficient to provide a solid having a compressive strength in a range of from 30 MPa to 70 MPa, when set, as determined by ASTM C109.

13. The composition of claim 1 , wherein the fine aggregate comprises at least 75 wt. % dune sand, relative to total fine aggregate weight.

14. The composition of claim 1 , wherein the coarse aggregate comprises at least 75 wt. % of crushed limestone, relative to total coarse aggregate weight.

15. A wet concrete slurry, comprising:

the composition of claim 1 ; and

no more than 5 wt. % water,

wherein the slurry is sufficiently fluid to pour under gravity in ambient conditions.

16. A pozzolan concrete, comprising a cured form of the slurry of claim 3 .

17. The concrete of claim 16 , which has a compressive strength of 20 to 50 MPa after curing at a temperature of 21 to 25° C. for 28 days, and a compressive strength of 30 to 75 MPa after curing at a temperature of 50 to 70° C. for 7 days, as determined by ASTM C109.

18. The concrete of claim 16 , cured at a temperature in a range of from 15 to 40° C.

19. The concrete of claim 16 , cured at a temperature above 40° C.

20. A building, comprising the concrete of claim 16 as a structural element.