# US 10,870,603 B2 · Hemp straw ash as a supplementary cementitious material

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- Number: US 10,870,603 B2
- Document ID: US10870603B2
- Status: Granted
- Kind: B2
- Application number: 16/537,850
- Filed: 2019-08-12
- Published: 2020-11-12
- Granted: 2020-12-22
- Earliest claimed: 2019-05-09
- Assignees: Nextleaf Solutions Ltd.
- Applicants: Nextleaf Solutions Ltd.
- Inventors: Sudip Talukdar; Spencer Behn; Kumayl Aarifali Rashid; Farhad Pargar; Cristina Zanotti
- Web page: https://patentgrep.com/patent/US10870603B2

## CPC

- C04B 18/101: {Burned rice husks or other burned vegetable material}
- C04B 28/02: containing hydraulic cements other than calcium sulfates
- C04B 28/04: Portland cements
- C04B 2111/00017: {Aspects relating to the protection of the environment}
- Y02W 30/91: Use of waste materials as fillers for mortars or concrete
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

Hemp straw is ground and burnt to result in hemp straw ash for making concrete. The hemp straw ash is mixed with water, cement, fine aggregate, coarse aggregate and superplasticizer using a two-step addition process to form a concrete mixture. The two-step addition process follows a specific order for the addition of the materials to a concrete mixer drum. Concrete made using the hemp straw ash is useful for lower-strength applications.

## Claims

### Claim 1

A process for making concrete comprising:
grinding hemp straw to result in ground hemp straw;
burning the ground hemp straw to result in hemp straw ash;
mixing superplasticizer, fine aggregate, coarse aggregate, cement, water and the hemp straw ash to result in a concrete mixture, wherein the concrete mixture comprises, by weight:
10-11% water;
37-41% coarse aggregate;
29-36% fine aggregate;
superplasticizer up to 0.08%;
hemp straw ash up to 5%; and
14 to 19% cement.

### Claim 2 (depends on 1)

The process of claim 1, wherein the fine aggregate and coarse aggregate combined form 70-73% of the concrete mixture.

### Claim 3 (depends on 1)

The process of claim 1, wherein the cement and hemp straw ash are a binder, and the concrete mixture has a water to binder ratio, by weight, of between 0.50 and 0.55.

### Claim 4 (depends on 1)

The process of claim 1, wherein the concrete mixture comprises, by weight:
10-11% water;
37-41% of coarse aggregate;
30-36% of fine aggregate;
superplasticizer up to 0.03%;
hemp straw ash up to 3%; and
16 to 19% cement.

### Claim 5 (depends on 1)

The process of claim 1, wherein the mixing step is split into two stages and a first stage of the mixing step comprises, in order:
placing half of the fine aggregate in a concrete mixer drum;
adding half of the cement to the concrete mixer drum
adding all of the hemp straw to the concrete mixer drum;
adding half of the coarse aggregate to the concrete mixer drum; and
adding three quarters of the water and all of the superplasticizer to the concrete mixer drum;
thereby resulting in an intermediate mixture.

### Claim 6 (depends on 5)

The process of claim 5, wherein a second stage of the mixing step comprises, in order:
adding the other half of the fine aggregate to the concrete mixer drum;
adding the other half of the cement to the concrete mixer drum;
adding the other half of the coarse aggregate to the concrete mixer drum; and
adding the remaining quarter of the water to the concrete mixer drum;
thereby resulting in the concrete mixture.

### Claim 7 (depends on 6)

The process of claim 6, comprising:
mixing the intermediate mixture for 4 minutes; and
mixing the concrete mixture for 3 minutes.

### Claim 8 (depends on 1)

The process of claim 1, wherein burning the ground hemp straw occurs in an incinerator set at a temperature of 500-900° C., for a duration of 1-24 hrs.

### Claim 9 (depends on 1)

The process of claim 1, comprising soaking the ground hemp straw in a solution of HCl 6 M for 5 hours.

### Claim 10 (depends on 9)

The process of claim 9, comprising treating the ground hemp straw in ethanol and/or acetone using a solvent exchange method after soaking the ground hemp straw in the HCl 6 M solution.

### Claim 11 (depends on 10)

The process of claim 10, comprising heating the ground hemp straw at a temperature of 105° C. in an oven after treating the ground hemp straw in ethanol and/or acetone.

### Claim 12

A concrete mixture comprising, by weight:
10-11% water;
37-41% coarse aggregate;
29-36% fine aggregate;
superplasticizer up to 0.08%;
hemp straw ash up to 5%; and
14 to 19% cement.

### Claim 13 (depends on 12)

The concrete mixture of claim 12, wherein:
the fine aggregate is sand;
the cement has a particle size of 5 μm to 45 μm; and
the coarse aggregate is gravel with a particle size of 12 mm or more.

### Claim 14 (depends on 12)

The concrete mixture of claim 12, comprising a supplementary cementitious material that induces a pozzolanic reaction in the mixture.

### Claim 15 (depends on 12)

The concrete mixture of claim 12, wherein the cement and hemp straw ash are a binder, and the mixture has a water to binder ratio, by weight, of between 0.50 and 0.55.

### Claim 16 (depends on 12)

The concrete mixture of claim 12, comprising, by weight:
10-11% water;
37-41% coarse aggregate;
30-36% fine aggregate;
superplasticizer up to 0.03%;
hemp straw ash up to 3%; and
16 to 19% cement.

### Claim 17

Concrete solidified from a concrete mixture, the concrete mixture comprising, by weight:
10-11% water;
37-41% coarse aggregate;
29-36% fine aggregate;
superplasticizer up to 0.08%;
hemp straw ash up to 5%; and
14 to 19% cement.