Cabot Corp., Boston, has signed an agreement with the China National Bluestar Group to build a plant to manufacture fumed silica in Tianjin, China. It will be the second fumed silica plant the two companies have built in China. The first was completed in 2004.

Cabot Corp. signed the agreement through its Cabot (China) Ltd. subsidiary. The newly formed joint venture, Cabot Bluestar Chemical (Tianjin) Co. Ltd., will invest roughly $40 million to build the silica facility, which is expected to open in early 2010.

Fumed silica is used in such applications as coatings, adhesives, cements, sealants, cosmetics, pharmaceuticals, inks and abrasives.

Cabot is a global specialty chemicals and materials company whose products include carbon black, fumed silica, inkjet colorants, capacitor materials, and cesium formate drilling fluids.