Comparison as-as

1. COMPARISONS WITH AS...... AS
One of the most common comparisons used is as......as.
The paired expression as…as expresses that two parts of comparison are equal or the
same in some way. The first as is an adverb. The second as is a preposition that
"heads" the prepositional phrase which takes a noun or a clause as its complement.
Typically, the clause is reduced to the subject or the auxiliary form of the verb.
EXAMPLES:
The apple is as light as the orange.
An apple grows as slowly as an orange.
An apple falls to the ground as quickly as an orange.
 To compare two things that are equal, we use the pattern:
as + adjective indicating quantity + (noun) + as
The quantity adjective you use depends if the noun in the comparison is countable or
uncountable.
COUNTABLENOUNS
Use as many and as few with countable nouns. Note that the noun may be omitted
when it is understood from the context, as in the last example below.
EXAMPLES
They have as many children as we do.
as + adjective indicating quantity + (noun) + as
We have as many customers as they do.
Tom has as few books as Jane.
There are as few houses in his village as in mine.
You know as many people as I do.
I have visited the States as many times as he has.

2. I have three brothers. That's as many as you have. ("Brothers" is understood)
UNCOUNTABLENOUNS
Use as much or as little with uncountable nouns. Note that the noun may be omitted
when it is understood from the context, as in the last example below.
EXAMPLES
John eats as much food as Peter.
Jim has as little patience as Sam.
You've heard as much news as I have.
He's had as much success as his brother has.
They've got as little water as we have.
I'm not hungry. I've had as much as I want. ("Food" is understood”).
In negative form just we must to use not before as........as.
 For the negative form just we must to use not before the comparison but also
we can use quiet and nearly because both are used with the negative but the
difference is the following:
EXAMPLES:
Tina Sam Ted Amy
AGE: 21 21 20 5
Ted is not quiet as old is Tina.
Not quiet as.....as = is used when there is a small difference
Amy is 5.She is not nearly as old as Tina.
Not nearly as.....as = is used when there is a big difference.
Just as…….as= this means exactly
Sam is just as old as Tina.

3. http://www.grammar-quizzes.com/sameas.html
http://www.edufind.com/english-grammar/adjectives-comparing-equal-quantities/
http://esl.fis.edu/grammar/rules/comp.html