SEVENTH SUPPLEMENTAL INDENTURE

EXHIBIT 4.3

Execution Version

SEVENTH SUPPLEMENTAL INDENTURE

This Seventh Supplemental Indenture (this “Supplemental Indenture”), dated as of October 1, 2024, among (a) East SM, LLC, a Delaware limited liability company (the “New Guarantor”), (b) Arcosa, Inc., a Delaware corporation (the “Issuer”) and (c) Computershare Trust Company, N.A., as successor to Xxxxx Fargo Bank, National Association, as trustee (the “Trustee”).

W I T N E S S E T H

WHEREAS, each of the Issuer and the existing Guarantors (as defined in the Indenture referred to below) has heretofore executed and delivered to the Trustee an indenture (as amended by the First Supplemental Indenture, dated as of September 30, 2021, the Second Supplemental Indenture, dated May 17, 2022, the Third Supplemental Indenture, dated as of October 3, 2022, the Fourth Supplemental Indenture, dated as of January 4, 2023, the Fifth Supplemental Indenture, dated as of August 23, 2023, and the Sixth Supplemental Indenture, dated as of April 5, 2024, the “Indenture”), dated as of April 6, 2021, providing for the issuance of an unlimited aggregate principal amount of 4.375% Senior Notes due 2029 (the “Notes”);

WHEREAS, the Indenture provides that under certain circumstances the New Guarantor shall execute and deliver to the Trustee a supplemental indenture pursuant to which the New Guarantor shall unconditionally Guarantee all of the Issuer’s Obligations under the Notes and the Indenture on the terms and conditions set forth herein and under the Indenture;

WHEREAS, pursuant to Section 9.1(i) of the Indenture, the Trustee is authorized to execute and deliver this Supplemental Indenture without notice to or the consent of any Holder of the Notes.

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the parties mutually covenant and agree for the equal and ratable benefit of the Holders as follows:

1.    Capitalized Terms.    Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2.    Guarantor.     The New Guarantor hereby agrees to be a Guarantor under the Indenture and to be bound by the terms of the Indenture applicable to Guarantors, including Article X thereof.

3.    Governing Law. THIS SUPPLEMENTAL INDENTURE WILL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

4.    Waiver of Jury Trial. EACH OF THE PARTIES HERETO HEREBY IRREVOCABLY WAIVE, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING DIRECTLY OR INDIRECTLY ARISING OUT OF UNDER OR IN CONNECTION WITH, THE INDENTURE, THE NOTES, THE NOTE GUARANTEES OR THE TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY.

5.    Counterparts. This Supplemental Indenture may be executed in two or more counterparts, which when so executed shall constitute one and the same agreement. The exchange of

copies of this Supplemental Indenture and of signature pages by facsimile, PDF or other electronic transmission, or any electronic signature complying with the U.S. federal ESIGN Act of 2000, Uniform Electronic Transaction Act or other applicable law, e.g., xxx.xxxxxxxx.xxx, shall constitute effective execution and delivery of this Supplemental Indenture as to the parties hereto and may be used in lieu of the original Supplemental Indenture for all purposes.

6.    Headings. The headings of the Sections of this Supplemental Indenture have been inserted for convenience of reference only, are not to be considered a part of this Supplemental Indenture and shall in no way modify or restrict any of the terms or provisions hereof.

7.    The Trustee. The Trustee makes no representation or warranty as to the validity or sufficiency of this Supplemental Indenture or with respect to the recitals contained herein, all of which recitals are made solely by the other parties hereto.

[Signatures on the following pages.]

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed, all as of the date first above written.

NEW GUARANTOR:

EAST SM, LLC

/s/ Xxxxx Xxxxx

Name: Xxxxx Xxxxx

Title: Treasurer

Signature Page to Seventh Supplemental Indenture

ISSUER:

ARCOSA, INC.
By:			/s/ Xxxxx Xxxxx
			Name: Xxxxx Xxxxx
			Title: Treasurer

Signature Page to Seventh Supplemental Indenture

TRUSTEE:

COMPUTERSHARE TRUST COMPANY, N.A., as Trustee
By:			/s/ Xxx Xxxxxxxx
			Name: Xxx Xxxxxxxx
			Title: Vice President

Signature Page to Seventh Supplemental Indenture