Recursive language is closed under concatenation .
Concatenation: If L1 and If L2 are two recursive languages, their concatenation L1.L2 will also be recursive. For Example:
L1= {a^nb^nc^n|n>=0}
L2= {d^me^mf^m|m>=0}
L3= L1.L2
= {a^nb^nc^nd^m e^mf^m|m>=0 and n>=0}