Document:

Exhibit 4.2

 

[Form of Warrant Certificate]

 

[FACE]

 

Number

 

Warrants 

 

THIS WARRANT SHALL BE VOID IF NOT EXERCISED
PRIOR TO

THE EXPIRATION OF THE EXERCISE PERIOD
PROVIDED FOR

IN THE WARRANT AGREEMENT DESCRIBED BELOW

 

CONCRETE PUMPING HOLDINGS, INC.

Incorporated Under the Laws of the State
of Delaware

 

CUSIP [_]

 

Warrant Certificate

 

This Warrant Certificate certifies
that                     ,
or registered assigns, is the registered holder of warrant(s) evidenced hereby (the “Warrants” and
each, a “Warrant”) to purchase shares of common stock, $0.0001 par value (“Common Stock”),
of Concrete Pumping Holdings, Inc., a Delaware corporation (the “Company”). Each Warrant entitles
the holder, upon exercise during the period set forth in the Warrant Agreement referred to below, to receive from the Company that
number of fully paid and non-assessable shares of Common Stock as set forth below, at the exercise price (the “Exercise
Price”) as determined pursuant to the Warrant Agreement, payable in lawful money (or through “cashless
exercise” as provided for in the Warrant Agreement) of the United States of America upon surrender of this Warrant
Certificate and payment of the Exercise Price at the office or agency of the Warrant Agent referred to below, subject to the conditions
set forth herein and in the Warrant Agreement. Defined terms used in this Warrant Certificate but not defined herein shall have
the meanings given to them in the Warrant Agreement.

 

Each Warrant is initially exercisable for
one fully paid and non-assessable share of Common Stock. The number of shares of Common Stock issuable upon exercise of the Warrants
is subject to adjustment upon the occurrence of certain events set forth in the Warrant Agreement.

 

The initial Exercise Price per share of
Common Stock for any Warrant is equal to $11.50 per share. The Exercise Price is subject to adjustment upon the occurrence of certain
events set forth in the Warrant Agreement.

 

Subject to the conditions set forth in the
Warrant Agreement, the Warrants may be exercised only during the Exercise Period and to the extent not exercised by the end of
such Exercise Period, such Warrants shall become void.

 

Reference is hereby made to the further
provisions of this Warrant Certificate set forth on the reverse hereof and such further provisions shall for all purposes have
the same effect as though fully set forth at this place.

 

This Warrant Certificate shall not be valid
unless countersigned by the Warrant Agent, as such term is used in the Warrant Agreement.

 

This Warrant Certificate shall be governed
by and construed in accordance with the internal laws of the State of New York, without regard to conflicts of laws principles
thereof.

 

     

     

    

 

	 	CONCRETE PUMPING HOLDINGS, INC.
	 	 	 
	 	By:	            
	 	Name:	 
	 	Title:	 
	 	 
	 	CONTINENTAL STOCK TRANSFER &
    TRUST COMPANY, as Warrant Agent
	 	 	 
	 	By:	 
	 	Name:	 
	 	Title:	 

 

     

     

    

 

[Form of Warrant Certificate]

 

[Reverse]

 

The Warrants evidenced by this Warrant Certificate
are part of a duly authorized issue of Warrants entitling the holder on exercise to receive shares of Common Stock and are issued
or to be issued pursuant to a Warrant Agreement dated as of July 27, 2017 (the “Warrant Agreement”),
duly executed and delivered by Industrea Acquisition Corp. (“Industrea”) to Continental Stock Transfer &
Trust Company, a New York corporation, as warrant agent (the “Warrant Agent”), as assigned to the Company
pursuant to an Assignment and Assumption Agreement, dated as of December 6, 2018, duly executed and delivered by the Company, Industrea
and the Warrant Agent, which Warrant Agreement is hereby incorporated by reference in and made a part of this instrument and is
hereby referred to for a description of the rights, limitation of rights, obligations, duties and immunities thereunder of the
Warrant Agent, the Company and the holders (the words “holders” or “holder”
meaning the Registered Holders or Registered Holder) of the Warrants. A copy of the Warrant Agreement may be obtained by the
holder hereof upon written request to the Company. Defined terms used in this Warrant Certificate but not defined herein shall
have the meanings given to them in the Warrant Agreement.

 

Warrants may be exercised at any time during
the Exercise Period set forth in the Warrant Agreement. The holder of Warrants evidenced by this Warrant Certificate may exercise
them by surrendering this Warrant Certificate, with the form of election to purchase set forth hereon properly completed and executed,
together with payment of the Exercise Price as specified in the Warrant Agreement (or through “cashless exercise” as
provided for in the Warrant Agreement) at the principal corporate trust office of the Warrant Agent. In the event that upon
any exercise of Warrants evidenced hereby the number of Warrants exercised shall be less than the total number of Warrants evidenced
hereby, there shall be issued to the holder hereof or his, her or its assignee, a new Warrant Certificate evidencing the number
of Warrants not exercised.

 

Notwithstanding anything else in this Warrant
Certificate or the Warrant Agreement, no Warrant may be exercised unless at the time of exercise (i) a registration statement
covering the shares of Common Stock to be issued upon exercise is effective under the Securities Act and (ii) a prospectus
thereunder relating to the shares of Common Stock is current, except through “cashless exercise” as provided for in
the Warrant Agreement.

 

The Warrant Agreement provides that upon
the occurrence of certain events the number of shares of Common Stock issuable upon exercise of the Warrants set forth on the face
hereof may, subject to certain conditions, be adjusted. 

 

Warrant Certificates, when surrendered at
the principal corporate trust office of the Warrant Agent by the Registered Holder thereof in person or by legal representative
or attorney duly authorized in writing, may be exchanged, in the manner and subject to the limitations provided in the Warrant
Agreement, but without payment of any service charge, for another Warrant Certificate or Warrant Certificates of like tenor evidencing
in the aggregate a like number of Warrants.

 

Upon due presentation for registration of
transfer of this Warrant Certificate at the office of the Warrant Agent a new Warrant Certificate or Warrant Certificates of like
tenor and evidencing in the aggregate a like number of Warrants shall be issued to the transferee(s) in exchange for this
Warrant Certificate, subject to the limitations provided in the Warrant Agreement, without charge except for any tax or other governmental
charge imposed in connection therewith.

 

The Company and the Warrant Agent may deem
and treat the Registered Holder(s) hereof as the absolute owner(s) of this Warrant Certificate (notwithstanding any notation
of ownership or other writing hereon made by anyone), for the purpose of any exercise hereof, of any distribution to the holder(s) hereof,
and for all other purposes, and neither the Company nor the Warrant Agent shall be affected by any notice to the contrary. Neither
the Warrants nor this Warrant Certificate entitles any holder hereof to any rights of a stockholder of the Company.

 

     

     

    

 

Election to Purchase

 

(To Be Executed Upon Exercise of Warrant)

 

The undersigned hereby irrevocably elects
to exercise the right, represented by this Warrant Certificate, to receive ___________ shares of Common Stock and herewith tenders
payment for such shares of Common Stock to the order of Concrete Pumping Holdings, Inc. (the “Company”)
in the amount of $___________ in accordance with the terms hereof. The undersigned requests that a certificate for such
shares of Common Stock be registered in the name of _____________________, whose address is ____________________ and that such
shares of Common Stock be delivered to ____________________ whose address is ____________________. If said number
of shares of Common Stock is less than all of the shares of Common Stock purchasable hereunder, the undersigned requests that a
new Warrant Certificate representing the remaining balance of such shares of Common Stock be registered in the name of ____________________,
whose address is ____________________ and that such Warrant Certificate be delivered to ____________________, whose address
is ____________________.

 

In the event that the Warrant has been called
for redemption by the Company pursuant to Section 6 of the Warrant Agreement and the Company has required
cashless exercise pursuant to Section 6.3 of the Warrant Agreement, the number of shares of Common Stock
that this Warrant is exercisable for shall be determined in accordance with subsection 3.3.1(b) and Section 6.3 of
the Warrant Agreement.

 

In the event that the Warrant is a Private
Placement Warrant that is to be exercised on a “cashless” basis pursuant to subsection 3.3.1(c) of
the Warrant Agreement, the number of shares of Common Stock that this Warrant is exercisable for shall be determined in accordance
with subsection 3.3.1(c) of the Warrant Agreement.

 

In the event that the Warrant is to be exercised
on a “cashless” basis pursuant to Section 7.4 of the Warrant Agreement, the number of shares
of Common Stock that this Warrant is exercisable for shall be determined in accordance with Section 7.4 of
the Warrant Agreement.

 

In the event that the Warrant may be exercised,
to the extent allowed by the Warrant Agreement, through cashless exercise (i) the number of shares of Common Stock that this
Warrant is exercisable for would be determined in accordance with the relevant section of the Warrant Agreement which allows for
such cashless exercise and (ii) the holder hereof shall complete the following: The undersigned hereby irrevocably elects
to exercise the right, represented by this Warrant Certificate, through the cashless exercise provisions of the Warrant Agreement,
to receive shares of Common Stock. If said number of shares is less than all of the shares of Common Stock purchasable hereunder
(after giving effect to the cashless exercise), the undersigned requests that a new Warrant Certificate representing the remaining
balance of such shares of Common Stock be registered in the name of ____________________, whose address is ____________________
and that such Warrant Certificate be delivered to ____________________, whose address is ____________________.

 

[Signature Page Follows]

 

     

     

    

 

	Date:              , 20	 	 
	 	 	(Signature)
	 	 	 
	 	 	 
	 	 	 
	 	 	 
	 	 	(Address)
	 	 	 
	 	 	 
	 	 	(Tax Identification Number)
	Signature Guaranteed:	 	 
	 	 	 
	 	 	 

THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR
INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE
MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15 (OR ANY SUCCESSOR RULE)).Exhibit 4.4

 

ASSIGNMENT AND ASSUMPTION AGREEMENT

 

THIS ASSIGNMENT AND ASSUMPTION AGREEMENT (the
“Agreement”) is entered into and effective as of December 6, 2018 by and among Industrea Acquisition Corp.,
a Delaware corporation (“Industrea”), Concrete Pumping Holdings Acquisition Corp. (to be renamed “Concrete
Pumping Holdings, Inc.” effective as the Closing (as defined below)) (“Newco”), and Continental Stock
Transfer & Trust Company, a New York corporation (“Continental”).

 

WHEREAS, Industrea and Continental
have previously entered into a warrant agreement, dated as of July 27, 2017 (the “Warrant Agreement”) governing
the terms of Industrea’s 34,100,000 outstanding warrants to purchase shares of common stock of Industrea (the “Warrants”);
and

 

WHEREAS, Industrea has entered into
an Agreement and Plan of Merger, dated as of September 7, 2018, (as amended, the “Merger Agreement”), with Newco,
Concrete Pumping Holdings, Inc. (“CPH”), Concrete Pumping Intermediate Acquisition Corp., Concrete Pumping Merger
Sub Inc. (“Concrete Merger Sub”), Industrea Acquisition Merger Sub Inc. (“Industrea Merger Sub”)
and PGP Investors, LLC, solely in its capacity as the initial Holder Representative, pursuant to which (a) Concrete Merger Sub
will merge with and into CPH, with CPH surviving the merger as a wholly owned indirect subsidiary of Newco, and (b) Industrea Merger
Sub will be merged with and into Industrea, with Industrea surviving the merger as a wholly owned subsidiary of Newco (the “Business
Combination”); and

 

WHEREAS, effective upon the Business
Combination, holders of the common stock, par value $0.0001 per share, of Industrea (“Industrea common stock”)
will receive common stock, par value $0.0001 per share, of Newco (“Newco common stock”) in exchange for the
Industrea common stock; and

 

WHEREAS, pursuant to Section 4.4
of the Warrant Agreement, upon the closing of the Business Combination (the “Closing”), the Warrants will represent
the right of the holders thereof to purchase shares of Newco common stock; and

 

WHEREAS, as a result of the foregoing,
the parties hereto wish for Industrea to assign to Newco all of Industrea’s rights and interests and obligations in and under
the Warrant Agreement and for Newco to accept such assignment, and assume all of Industrea’s obligations thereunder, in each
case, effective upon the Closing.

 

NOW, THEREFORE, for good
and valuable consideration, receipt of which is hereby acknowledged, the parties hereby agree as follows:

  

1.          Assignment
and Assumption of Warrant Agreement. Industrea hereby assigns, and Newco hereby agrees to accept and assume, effective as of
the Closing, all of Industrea’s rights, interests and obligations in, and under the Warrant Agreement and Warrants. Unless
the context otherwise requires, from and after the Closing, any references in the Warrant Agreement or the Warrants to: (i) the
“Company” shall mean Newco; (ii) “Common Stock” shall mean the shares of Newco common stock; and (iii)
the “Board of Directors” or the “Board” or any committee thereof shall mean the board of directors of Newco
or any committee thereof.

 

2.          Replacement
Instruments. Following the Closing, upon request by any holder of a Warrant, Newco shall issue a new instrument for such Warrant
reflecting the adjustment to the terms and conditions described herein and in Section 4.4 of the Warrant Agreement.

 

3.          Amendment
to Warrant Agreement. To the extent required by this Agreement, the Warrant Agreement is hereby deemed amended pursuant to
Section 9.8 thereof to reflect the subject matter contained herein, effective as of the Closing.

 

4.          Governing
Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of New York, as such laws
are applied to contracts entered into and performed in such State without resort to that State’s conflict-of-laws rules.

 

     

     

    

 

5.          Counterpart.
This Agreement may be executed in counterparts, each of which shall be deemed to be an original, but all of which together shall
constitute one and the same instrument. Execution and delivery of this Agreement by email or exchange of facsimile copies bearing
the facsimile signature of a party hereto shall constitute a valid and binding execution and delivery of this Agreement by such
party.

 

6.          Successors
and Assigns. All the covenants and provisions of this Agreement shall bind and inure to the benefit of each party’s respective
successors and assigns.

 

[Signature Pages Follow] 

 

     

     

    

 

IN WITNESS WHEREOF, the parties hereto have
signed this Agreement as of the date and year first written above.

 

	 	INDUSTREA ACQUISITION CORP.
	 	 	 
	 	By:	 /s/ Tariq Osman
	 	 	Name: Tariq Osman
	 	 	Title:   Executive Vice President

 

 

     

     

    

 

	 	CONCRETE PUMPING HOLDINGS ACQUISITION CORP.
	 	 	 
	 	By:	 /s/ Tariq Osman
	 	 	Name: Tariq Osman
	 	 	Title:   President

 

 

     

     

    

 

	 	CONTINENTAL STOCK TRANSFER & TRUST COMPANY
	 	 	 
	 	By:	 /s/ Erika Young
	 	 	Name: Erika Young
	 	 	Title:   Vice President

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