# Why does slaked lime water lose alkalinity over time?

When I throw 3 handfuls of white lime $\ce{Ca(OH)_2}$ into 60 gallons of tap water, the initial pH value is 11.4, but unknowingly it changes to pH 7.

What is the chemistry behind it?

How long does it take to completely change to neutral pH at open space?

I put lime in the water to pasteurize straw for mushrooms, and I need to know how long and how to make neutral pH faster so that I can pour the neutral water in the soil, so it won't ruin the soil.