First quarter 2013 revenues in the light building products segment increased $3.4 million, or 5%, to $76.7 million. Quarterly gross margin increased by 180 basis points to 26.3% and operating income improved by over 300% to $3.1 million. Adjusted EBITDA improved to $11.9 million from $11.3 million in 2012.
We experienced revenue growth from our product groups that have primary exposure to new residential construction, particularly our stone group. In addition, our concrete block group experienced revenue growth in the quarter based on increased retail and brick sales, which also serve the residential markets. Repair and remodel end market revenue was relatively flat in the quarter, and to achieve our 2013 forecast, we are not anticipating substantial improvements. We anticipate increased raw material costs over the next several quarters, particularly in cement and polypropylene. In order to address these cost pressures, we have raised prices in some of our markets and are improving efficiencies in manufacturing.
On December 31, 2012, we completed the acquisition of the assets of Kleer. Kleer manufacturers high quality and eco-friendly cellular PVC products, including trim boards, millwork, sheet stock, paneling, and moulding, as well as recently introduced decking and railing products. For fiscal 2013, we anticipate nine months of revenue contribution from the acquisition of approximately $30 million. The associated increase in Adjusted EBITDA related to the acquisition is included in our new range of $110 to $125 million. In addition to the cost synergies associated with the integration of Kleer into our siding group, we are excited about the opportunity to increase segment revenue through the introduction of Kleer's products into our existing distribution system. Kleer is an excellent bolt-on acquisition that provides us the opportunity to obtain leadership in an adjacent niche end market.
Heavy Construction Materials SegmentHeadwaters Resources is the largest domestic manager and marketer of coal combustion products (CCPs), including fly ash. Utilization of these materials improves performance of concrete and concrete construction products while creating significant environmental benefits.