as ... as possible，当然是比较结构。第一个 as 是参与比较的程度副词，第二个 as 是比较连词，引导（省略成分的）比较从句。

I will come as soon as possible. 我尽可能早来这里。

【分析】

我们先去掉比较成分，剩下： I will come soon. 我早来这里。

那么，“早来这里” 应该多么早呢？应该跟 “可能的早” 一样早。那就用比较结构：

I will come as soon as possible.  

在 possible 之前省略了 it is，一般是不需要添加的。

I will come as soon as it is possible.

在 it is possible 中，it 指你来这件事，这个情况。it is possible 还可以用 I can 表示：I will come as soon as I can.

举一反三，以此类推：

You must make the houses as strong as possible. 你应该把房屋建得尽可能结实。

I'd like to see you as early as possible. 我想要尽早见你。

I want to clear my debts as quickly as possible. 我想把我的债务尽快还清。

They were warned to speak as little as possible. 他们得到告诫要尽量少说话。