What is the primary thing with which Ralph is concerned in chapter 6?
Ralph is primarily concerned with his role as leader, and keeping order on the island. In part, this means emphasizing the importance of the fire, and attempting to rein in the wild desires of the other boys. Jack and Ralph are placed at odds in this chapter, as Jack encourages the boys to hunt & essentially live savagely, while Ralph wants to consider each problem logically. Ralph is growing increasingly grownup and urges responsibility, but he still lacks the authority to actually enforce what he believes. On the other hand, Jack is growing increasingly more popular as he encourages the other boys to follow his childish actions. For him, it is fun to play soldier, hunt, and break the rules. It's not fun to keep the fire burning. In dangerously increasing increments, Jack is undermining the frail system of the island and introducing anarchy to the boys. He knows well the motivating and intimidating power of fear, and he uses it to his advantage. Although Ralph has good intentions, he cannot fight this turn away from civilization.
Also, in this chapter, most boys are terrified of the beast they imagine to be on the island. Ralph attempts to deal with this in an organized manner, but panic soon breaks out. He wins control once more, & he & Jack explore the one uncharted area of the island. Their opposing perceptions of it reveal their differing personalities. Ralph sees it as an obstacle to overcome so they can return to the business of maintaining the fire. Jack sees its military value. Ralph still clings to his position of responsibility and insists they must eliminate the place as the beast’s lair before they can continue. The boys that enter the island see its fort potential as well and playfully roll the rocks over the edge. Ralph, growing increasingly adult, has no time for this childish behavior. He must maintain the unpopular mantle of responsibility. Jack seizes upon this in order to strengthen his position, and it is he who leads the boys back off the island.
He is primarily concerned with keeping the fire going.
While Jack is becoming more obsessed with hunting and obtaining power, Ralph realizes that none of that matters as much as the hope of someday leaving the island.
So most of the characters become more afraid of the beast, Ralph becomes even more aware of the fact that the best way to deal with the beast is to get away from it... by being rescued from the use of the signal fire.