Credit:
Figure 1. Stereomicroscope photomicrographs showing significant distress/cracking in the plain concrete due to ASR (A&B), while relatively minimal damage in the internally cured concrete (C & D). In the LWA concrete, the microcracks initiated within the reactive particles due to ASR extending into the surrounding paste for a very short distance, while in the companion plain concrete, prevalent ASR gel-filled cracks and microcracks extending from reacted chert particles into the paste and most of these cracks continue in the concrete by passing dominantly around and in a few through aggregate particles.