Exhibit
      4.5.1

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CONFORMED
      COPY



LAFARGE
    (VENEZUELA) HOLDINGS

AMENDMENT
    TO THE AGREEMENT AND ARTICLES OF TRUST

DATED
    AS OF MAY, 2003



|PADOCS01/2254077.2 | Lafarge
        (Venezuela) HoldingsFirst
      Amendment to Trust Agreement | Conformed
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1

AMENDMENT
      NUMBER 1 TO THE AGREEMENT AND ARTICLES OF TRUST (this Amendment)
      made, delivered and accepted as of this day of May, 2003, among Lafarge
      Asland S.A. (Settlor) a Spanish corporation and an indirect
      subsidiary of Lafarge S.A. (Lafarge), a French société anonyme,
      and Alfred J. Ross of New York, New York, John H.F. Haskell, Jr. of New
      York, New York and The Bank of New York, a New York banking corporation,
      as trustees (such individuals and corporations and their successors as
      trustees are herein, the Trustees).


WHEREAS
      Lafarge and the Trustees entered into an agreement and articles of trust
      dated as of August 1, 2000 (the Trust Agreement; capitalized
      terms used herein and not defined herein shall have the meanings ascribed
      thereto in the Trust Agreement), which provided for the creation of Lafarge
      (Venezuela) Holdings (Venezuela Holdings or the Trust)
      and the transfer to Venezuelan Holdings of Lafarges shares in C.A.
      Fabrica Nacional de Cementos S.A.C.A., a corporation organized under the
      laws of Venezuela (Venezuelan Corp.);


WHEREAS
      Lafarge intended that the terms of the Trust Agreement would provide an
      inducement for a person making a tender offer or exchange offer for Lafarges
      shares to make a comparable tender offer for Venezuelan Corp.s public
      shares;


WHEREAS
      Section 1.5(c) of the Trust Agreement provides that prior to a Commencement
      Date Lafarge may amend the Trust Agreement; provided, however, that any
      amendment to the Trust Agreement which alters the powers, duties, liabilities
      or rights to indemnification of the Trustees may only be made with the
      consent of the Trustees and that no amendment is permitted which (i) materially
      adversely affects the intent, purposes or effectiveness of Article VI of
      the Trust Agreement or (ii) affects Section 1.5 of the Trust Agreement,
      except an amendment which further restricts Lafarges ability under
      the Trust Agreement to withdraw or transfer the whole or any part of the
      Trust corpus;


WHEREAS
        Section 6.4(g) of the Trust Agreement provides that during a period other
        than an Operative Period or a Five Year Period the Settlor and the Trustees
        may by mutual consent declare that the Trust be construed, regulated
        and governed by the laws of any country or subdivision thereof;


WHEREAS
      No Operative Period or Five Year Period has begun and this Amendment is
      made prior to a Commencement Date;


WHEREAS
        Pursuant to Section 1.5(c) of the Trust Agreement and for the benefit
        of the beneficiaries of the Trust, Lafarge and the Trustees wish to enter
        into this Amendment in order to clarify the beneficial interests created
        by the Trust and to provide that the situs of the Trust will be England
        and that the Trust Agreement shall be governed by English law.


NOW, THEREFORE,
      the parties hereto agree as follows:


1.Amendment
          to the Recitals.
          Pursuant to and in accordance with Section1.5(c)
          of the Trust Agreement, the second paragraph of the recitals to the
          Trust Agreement is amended by:




|PADOCS01/2254077.2 | Lafarge
        (Venezuela) HoldingsFirst
      Amendment to Trust Agreement | Conformed
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2



(a) adding
      a new sub-paragraph (ii) which shall read in its entirety as follows:


(ii)
      to extend to Venezuelan Corp., and U.S. Corp., LCI and Swiss Corp., for
      a period of ten years from the date hereof, in the event of a tender or
      exchange offer under French law for Lafarges shares, (A) an assurance
      that the strategy and policies of Venezuelan Corp., and U.S. Corp., LCI
      and Swiss Corp., will not be substantially modified as a result of a successful
      tender offer or exchange offer for Lafarges shares and (B) an opportunity
      to protect the interests of all of the equity holders of Venezuelan Corp.,
      and U.S. Corp., LCI and Swiss Corp.;; and


(b) renumbering
      sub-paragraphs (ii) through (vi) so that they shall now be sub-paragraphs
      (iii) through (vii) respectively.


(c) amending
      and restating in its entirety the third paragraph of the recitals to the
      Trust Agreement as follows:


WHEREAS
      the Settlor requests and the Board accepts the Settlors request to
      hold the Shares for the benefit of the Settlor and Venezuelan Corp. as
      the beneficiaries of the Trust and as hereinafter set forth.


2.Amendment
          to SECTION 1.8.
          Pursuant to and in accordance with Section1.5(c)
          of the Trust Agreement, Section 1.8 of the Trust Agreement is amended
          and restated in its entirety as follows:


SECTION
          1.8 Governing Law; Exclusive Jurisdiction.


(a)Governing
          Law.
          This Trust Agreement, the Trust created hereunder and any cause of
          action arising out of or related to this Trust Agreement or the Trust
          shall be governed by, and construed under, the laws of England applicable
          to contracts and instruments in and to be performed entirely in such
          country.


(b)Exclusive
          Jurisdiction.
          All litigation with respect to any claims, disputes or causes of action
          arising out of or related to this Trust Agreement or the Trust shall
          be commenced exclusively in the courts of England.


3.Amendment
          to SECTION 6.2.
          Pursuant to and in accordance with Section1.5(c)
          of the Trust Agreement, Section 6.2 of the Trust Agreement is amended
          and restated in its entirety as follows:


SECTION
      6.2Statement
      of Intent.It
      is the intent of the Settlor:


to
        extend to the public shareholders of Venezuelan Corp., for a period of
        ten years from the date hereof, in the event of a tender or exchange
        offer under French law for Lafarges shares:


|PADOCS01/2254077.2 | Lafarge
        (Venezuela) HoldingsFirst
      Amendment to Trust Agreement | Conformed
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3

(A)an
      opportunity, comparable to that presently enjoyed under French law and
      regulations by public shareholders of French subsidiaries of French corporations,
      to receive a tender offer for their shares, or alternatively,


(B)an
      assurance that the strategy and policies of Venezuelan Corp. will not be
      substantially modified as a result of a successful tender or exchange offer
      for Lafarges shares;


if at such
    time Lafarge's Beneficial Ownership of Voting Shares of Venezuelan Corp.
    comprises 20% or more of the voting power represented by the outstanding
    Voting Shares of Venezuelan Corp. (assuming that at such time Lafarges
    20% or more Beneficial Ownership of Voting Shares of such corporation is
    greater than the Beneficial Ownership of Voting Shares of such corporation
    owned by any other Person);

to extend
      to Venezuelan Corp. for a period of ten years from the date hereof, in
      the event of a tender or exchange offer under French law for Lafarges
      shares, (i) an assurance that the strategy and policies of Venezuelan Corp.
      will not be substantially modified as a result of a successful tender or
      exchange offer for Lafarges shares and (ii) an opportunity to protect
      the interests of all equity holders of Venezuelan Corp.;


to provide
      in this Trust Agreement inducements for a person making a tender or exchange
      offer for Lafarge's shares to make the Venezuelan Tender Offer, failing
      which Lafarge shall make such Venezuelan Tender Offer; and


to provide
      in this Trust Agreement, if the Venezuelan Tender Offer is not made and
      consummated, for a five-year exercise by the Trustees, for the protection
      of the public equity holders of Venezuelan Corp., of the voting rights
      with respect to the Venezuelan Corp. securities held in the Trust on the
      terms and conditions herein provided.


It is the
      further intent of the Settlor to benefit the shareholders of Venezuelan
      Corp. by making them beneficiaries of the Trust to the extent that the
      provisions of the Trust provide them an opportunity to (i) obtain a premium
      for their Equity Securities comparable to the premium offered by a Bidder
      for the Voting Shares of Lafarge, or (ii) see the strategy and policies
      of Venezuelan Corp. unchanged by a successful tender or exchange offer
      for Lafarges shares.


It is the
      further intent of the Settlor to benefit Venezuelan Corp. by making it
      a beneficiary of the Trust to the extent that the provisions of the Trust
      provide Venezuelan Corp. (i) with the right to direct the voting of the
      Shares as set forth in Section 6.4 (a)(ii) and (ii) with an opportunity
      to (x) ensure that the strategy and policies of Venezuelan Corp. will not
      be substantially modified as a result of a successful tender or exchange
      offer for Lafarges shares and (y) take the action necessary or desirable
      to protect the interests of all equity holders of Venezuelan Corp.


The primary
      purpose of this Article VI is (x) to provide a mechanism for the commencement
      and termination of an Operative Period or a Five-year Period and (y) to
      set forth the powers and duties of the Trustees in connection with and
      during an Operative Period or a


|PADOCS01/2254077.2 | Lafarge
        (Venezuela) HoldingsFirst
      Amendment to Trust Agreement | Conformed
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4

Five-year
    Period. To the extent that there is any conflict between this Article VI
    and any other Article of this Trust Agreement, as amended, the provisions
    of this Article VI shall prevail.

4.Change
          of Situs.
          (a) Pursuant to Section 6.4(g) of the Trust Agreement and in order
          to effectuate the purpose and intent of, and in compliance with, the
          Trust, the Trustees and the Settlor hereby agree and declare that the
          Trust and the Trust Agreement shall from the date hereof be governed,
          construed and regulated by the laws of England.


(b)   The
      Trustees as defined herein shall continue as Trustees of the Trust.


5.Headings.The
      section headings herein are for convenience of reference only, do not constitute
      part of this Amendment, and shall not be deemed to limit or otherwise affect
      any of the provisions hereof.


6.Effective
          Date.
          This Amendment shall be effective only upon execution by the Settlor
          and all Trustees.


7.Counterparts.
        This Amendment may be executed in one or more counterparts, and by the
        different parties hereto in separate counterparts, each of which when
        executed shall be deemed to be an original, but all of which taken together
        shall constitute one and the same instrument.


8.Force
          and Effect.
          Except to the extent amended by this Amendment, the Trust Agreement
          shall remain in full force and effect.


|PADOCS01/2254077.2 | Lafarge
        (Venezuela) HoldingsFirst
      Amendment to Trust Agreement | Conformed
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5

IN WITNESS
      WHEREOF, the undersigned have hereunto set their hands and agree to be
      bound by the terms of this Amendment as of May, 2003.




| | LAFARGE
        ASLAND S.A
| | --------------------------
| |                           
| | By                        
| |                           
| | Name                      
| |                           
| | Title                     



| |                            |  |                               |  | THE
        BANK OF NEW YORK, Trustee
| | -------------------------- |  | ----------------------------- |  | -------------------------------------
| |                            |  |                               |  |                                      
| | /s/ Alfred
        J. Ross |  | /s/
        John H. F.Haskell |  | By                                   
| |                            |  |                               |  |                                      
| | Trustee                    |  | Trustee                       |  | Name                                 
| |                            |  |                               |  |                                      
| |                            |  |                               |  | Title                                
| |                            |  |                               |  |                                      



|PADOCS01/2254077.2 | Lafarge
        (Venezuela) HoldingsFirst
      Amendment to Trust Agreement | Conformed
        Copy
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