We present two multiscale reaction-diffusion (RD) systems modeling sulfate attack in concrete structures (here: sewer pipes). The systems are posed on two different spatially separated scales. The only difference between them is the choice of the micro-macro transmission condition. We explore numerically the way in which the macroscopic Biot number BiM connects the two reaction-diffusion scenarios. We indicate connections between the solution of the "regularized" system (with moderate size of BiM) and the solution to the "matched" system (with blowing up size of BiM), where Henry’s law plays the role of the micro-macro transmission condition