Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of construction materials company Texas Industries (NYSE: TXI) were spiking today, gaining as much as 10% in intraday trading.

So what: Last week, my fellow Fool Evan Niu noted the expiration of the standstill agreement between Texas Industries and one of its largest shareholders, Nassef Sawiris. The agreement had prevented Sawiris from acquiring more than 20% of the company's outstanding stock and its expiration stoked expectations that he'd start snapping up shares, potentially with an eye toward a takeover.

In the wake of that expiration, it appears that Sawiris is wasting no time making his intentions clear. After the close of trading on Friday, his investment vehicle, NNS Holding, revealed that on Dec. 1 it purchased another 203,901 shares of Texas Industries -- a $6 million commitment.

Now what: It certainly appears that Sawiris has his sights set on Texas Industries. And based on the market action since the expiration of the standstill agreement, investors are betting heavily that Sawiris' pursuit will be profitable for them.

However, it's important to keep in mind that in a situation like this a lot can happen between point A (today) and point B (a Sawiris takeover of Texas Industries). For that reason, Foolish investors that have the stock on their radar will want to be sure that they like the company involved here, not just the speculative prospect of a takeover.

Want to keep up to date on Texas Industries? Add it to your watchlist.