Exhibit 3.20(b)

CERTIFICATE OF MERGER

Providing for the Merger of

SAN DIEGO PRECAST CONCRETE, INC.

(a California corporation)

with and into

CONCRETE XII ACQUISITION, INC.

(a Delaware corporation)

Pursuant to Section 252 of Delaware the General Corporation Law (“DGCL”), Concrete XII Acquisition, Inc., a Delaware corporation, does hereby certify the following for the purposes of merging the corporations listed:

FIRST: The names and states of incorporation of the constituent corporations are as follows:

Name of Corporation:	State:
San Diego Precast Concrete, Inc. (“Old San Diego”)	California
Concrete XII Acquisition, Inc.	Delaware

SECOND: An Acquisition Agreement and Plan of Reorganization, dated as of September 15, 1999 (the “Merger Agreement”), has been approved, adopted, certified, executed and acknowledged by each of the constituent corporations in accordance with the requirements of Section 252 of the DGCL.

THIRD: The surviving corporation shall be Concrete XII Acquisition, Inc., which surviving corporation shall be governed by the laws of the State of Delaware.

FOURTH: The Certificate of Incorporation of Concrete XII Acquisition, Inc. shall be the Certificate of Incorporation of the surviving corporation, except that the Certificate of Incorporation of Concrete XII Acquisition, Inc. shall be amended as follows:

“FIRST: The name of the Corporation is San Diego Precast Concrete, Inc.”

FIFTH: The executed Merger Agreement is on file at the principal place of business of the surviving corporation, which is located at 1300 Post Oak Boulevard, Suite 1220, Houston, Texas 77056.

SIXTH: A copy of the Merger Agreement will be furnished by the surviving corporation, on request and without cost, to any shareholder of either constituent corporation.

SEVENTH: The authorized capital stock of Old San Diego consists of 10,000 shares of Common Stock, no par value per share.

IN WITNESS WHEREOF, Concrete XII Acquisition, Inc. has caused this Certificate of Merger to be executed this 15^th day of September, 1999.

CONCRETE XII ACQUISITION, INC.
By:	/s/    DONALD WAYNE
	Donald Wayne, President

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