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                                                                   Exhibit 10.21
                             COST SHARING AGREEMENT


This Cost Sharing Agreement dated of January 2, 1996 has been made by and
between LAFARGE MATERIAUX DE SPECIALITES, a company duly organized and validly
existing under the laws of France and having its principal office at 17 ter,
rue de la Vanne, 92542 Montrouge, FRANCE (hereinafter "LMS") and LAFARGE
CORPORATION, a company duly organized and validly existing under the laws of
the United States of America and having its principal office at 11130 Sunrise
Valley Drive, S.300, 4600, Reston, Virginia, the USA (hereinafter "L. Corp.")


                                    RECITALS


WHEREAS, LMS intends to develop its business in North America and, to this
effect, needs to identify potential development opportunities in the North
American specialty products marketplace;

WHEREAS, L. Corp. is interested by such analysis for its own business, intends
to contribute to its performance and may provide LMS with local assistance for
making such analysis;

WHEREAS, LMS and L. Corp. have agreed to establish and share the costs of a new
unit to be established for researching potential profitable markets for their
respective products in North America;


NOW, THEREFORE, IN CONSIDERATION OF THE FOREGOING AND OTHER GOOD AND VALUABLE
CONSIDERATION, THE RECEIPT AND SUFFICIENCY OF WHICH ARE HEREBY ACKNOWLEDGED,
THE PARTIES HEREBY AGREE AS FOLLOWS:

1.         A new unit of one person shall be established jointly by LMS and L.
           Corp. with the purpose to research, identify and analyze potential
           development opportunities for LMS'and L. Corp.'s products in North
           America. Any additional employee(s) must be agreed to by the
           parties. Such unit will be based at L. Corp.'s headquarters in
           Reston, Virginia.

           The person in charge of said unit shall be an employee of L. Corp.
           beginning at such time as he is legally permitted to work in the
           United States.  He will then use the customary means, in terms space
           and services, as put by L. Corp. at the disposal of any of its own
           staff.
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           This person shall report to Executive Vice President International
           Development, at LMS, France and to the Senior Vice President
           Planning and Marketing at L. Corp. Periods and vehicles of such
           reporting shall be agreed between them at their own convenience.  At
           the date of this Agreement and for the full 1996 year, it is
           expected that such unit will be represented by Mr. Pierre CASTIEN.

2.         LMS and L. Corp. each shall pay 50% of the costs of such unit,
           including overhead costs for use of space and services, salary and
           benefits for the person working in the unit, travel expenses and all
           other costs reasonably related to the purpose of the unit.

           The parties have approved a 1996 budget of USD 300,000 for the unit.
           The LMS' contribution to such budget shall be invoiced by L. Corp.
           to LMS, based upon actual costs incurred, in one installment at the
           beginning of each second half year.

3.         If a specific business opportunity is identified by the unit, LMS
           and L. Corp., or Lafarge Canada Inc. in the event the investment
           opportunity is in Canada, each shall have the right to invest up to
           50% and have an up to 50% ownership interest in any venture to be
           established accordingly (or such other investment amount and
           percentage ownership as the parties may agree upon); provided,
           however, that neither party shall be obligated to participate in any
           such venture and if one party declines to so participate, the other
           party may pursue such venture either alone or with another joint
           venture partner.

4.         Any venture entered into jointly by LMS and L. Corp. shall be
           governed by a definitive agreement and related documents executed by
           the parties.

5.         The term of this Agreement shall be one year form the date hereof.
           The parties may mutually agree to renew this Agreement from year to
           year and shall jointly approve a budget for the unit at the
           beginning of each such renewal year.

6.         This Agreement shall be governed by the laws of the Commonwealth of
           Virginia.


IN WITNESS WHEREOF, the parties have entered into this Agreement as of the date
set forth above.



LAFARGE CORPORATION                          LAFARGE MATERIAUX DE SPECIALITES



By:  /s/ Larry J. Waisanen                   By:  /s/ Olivier Legrain
Title: Senior Vice President                 Title:  General Manager
         and CFO