A Tychonoff almost realcompactification

Let $X$ be a Tychonoff topological space. A Tychonoff almost realcompact space $aX$ is constructed that contains $X$ as a dense subspace and has the property that if $f:X \to Y$ is continuous and $Y$ is Tychonoff and almost realcompact, then $f$ can be extended continuously to $aX$. Several characterizations of $aX$ are given, and the relationships between $aX$, the Hewitt realcompactification $vX$, and the minimal $c$-realcompactification $uX$ are investigated. Properties of the projective covers of these spaces, and their relation to $vE(X)(E(X)$ denotes the projective cover of $X$), are discussed.