Investors with an interest in Building Products - Concrete and Aggregates stocks have likely encountered both Cemex (CX) and Vulcan Materials (VMC). But which of these two stocks is more attractive to value investors? We'll need to take a closer look to find out.The best way to find great value stocks is to pair a strong Zacks Rank with an impressive grade in the Value category of our Style Scores system. The proven Zacks Rank emphasizes companies with positive estimate revision trends, and our Style Scores highlight stocks with specific traits.Cemex and Vulcan Materials are sporting Zacks Ranks of #2 (Buy) and #4 (Sell), respectively, right now. Investors should feel comfortable knowing that CX likely has seen a stronger improvement to its earnings outlook than VMC has recently. But this is just one factor that value investors are interested in.Value investors also try to analyze a wide range of traditional figures and metrics to help determine whether a company is undervalued at its current share price levels.Our Value category grades stocks based on a number of key metrics, including the tried-and-true P/E ratio, the P/S ratio, earnings yield, and cash flow per share, as well as a variety of other fundamentals that value investors frequently use.CX currently has a forward P/E ratio of 16.17, while VMC has a forward P/E of 32.26. We also note that CX has a PEG ratio of 0.41. This figure is similar to the commonly-used P/E ratio, with the PEG ratio also factoring in a company's expected earnings growth rate. VMC currently has a PEG ratio of 2.78.Another notable valuation metric for CX is its P/B ratio of 1.04. The P/B ratio pits a stock's market value against its book value, which is defined as total assets minus total liabilities. For comparison, VMC has a P/B of 3.51.These metrics, and several others, help CX earn a Value grade of A, while VMC has been given a Value grade of C.CX is currently sporting an improving earnings outlook, which makes it stick out in our Zacks Rank model. And, based on the above valuation metrics, we feel that CX is likely the superior value option right now.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Cemex S.A.B. de C.V. (CX): Free Stock Analysis Report Vulcan Materials Company (VMC): Free Stock Analysis Report To read this article on Zacks.com click here.