Document

This Ninth Supplemental Indenture (this “Supplemental Indenture”), dated as of April 1, 2026, between (a) Arcosa, Inc., a Delaware corporation (the “Issuer”) and (b) Computershare Trust Company, N.A., as successor to Wells Fargo Bank, National Association, as trustee (the “Trustee”).

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, the Sixth Supplemental Indenture, dated as of April 5, 2024, the Seventh Supplemental Indenture, dated as of October 1, 2024, and the Eighth Supplemental Indenture, dated as of October 31, 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, pursuant to Section 10.5(a)(1) of the Indenture, any Note Guarantee of a Guarantor shall be automatically and unconditionally released and discharged upon a sale, exchange, transfer or other disposition of the Capital Stock of such Guarantor, following which such Guarantor is no longer a Subsidiary of the Issuer;

WHEREAS, pursuant to the transactions contemplated by that certain Stock Purchase Agreement dated as of February 24, 2026 (the “Purchase Agreement”), among the Issuer, Arcosa Marine Products, Inc., a Delaware corporation (“Arcosa Marine Products”), and ACMP Buyer, LLC, a Delaware limited liability company (“Buyer”), Buyer agreed to buy from the Issuer all of the issued and outstanding shares of common stock of Arcosa Marine Products, a Guarantor under the Indenture, after which Arcosa Marine Products shall no longer be a Subsidiary of the Issuer;

WHEREAS, pursuant to Section 10.5(b) of the Indenture, upon delivery to the Trustee of an Officer’s Certificate to the effect that the transactions contemplated by the Purchase Agreement were made by the Issuer in accordance with the provisions of the Indenture, the Trustee shall execute any documents reasonably requested by the Issuer in order to evidence the release of Arcosa Marine Products from its obligations under its Note Guarantee;

WHEREAS, the Trustee has received an Officer’s Certificate and Opinion of Counsel in connection with the transactions contemplated by the Purchase Agreement and the Trustee’s execution of this Supplemental Indenture; and

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 to evidence the release of Arcosa Marine Products from its Note Guarantee.

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:

2. Release of Guarantor. In reliance on the Officer’s Certificate and the Opinion of Counsel delivered to the Trustee on the date hereof, the Trustee acknowledges and agrees that Arcosa Marine Products is hereby unconditionally, automatically and irrevocably released from its Note Guarantee, all of its obligations under the Note Documents, and as a Guarantor under the Indenture, and accordingly, that, without further action, Arcosa Marine Products is no longer party to the Indenture and the other Note Documents.

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., www.docusign.com, 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.