Extending Dekking's construction of an infinite binary word avoiding abelian 4-powers

We construct an infinite binary word with critical exponent 3 that avoids abelian 4-powers. Our method gives an algorithm to determine if certain types of morphic sequences avoid additive powers. We also show that there are $\Omega(1.172^n)$ binary words of length $n$ that avoid abelian 4-powers, which improves on previous estimates.