Candy is alientated in a variety of ways throughout the novella.
From the time readers are introduced to Candy, it is clear that he is separated from the rest of the men for a couple of reasons. First, he is significantly older. Secondly, he is crippled. Both of these features keep him separate from the other men because he is less capable of completing tasks that they can. He is often left out of rounds of horse-shoes and drinking.
In chapter 3, Candy is mocked by Carlson for the smell and age of the dog that Candy has befriended for years. Carlson pressures Candy into letting Carlson put the dog down. All of the other men were on Carlson's side and Candy felt alone and separated again.
In chapter 5, the men go to town to drink and they leave both Lennie and Candy behind. Obviously Lennie is left behind because he probably couldn't control himself in that circumstance. Candy's age keeps him from going with the men.