Ancient Roman marine structures, such as breakwaters and piers, have endured for over years despite constant exposure to seawater. Modern research reveals that this durability is due to the chemical composition of the concrete used. The Romans mixed volcanic ash, known as pozzolana, with quicklime and seawater. This combination initiated a chemical reaction, yielding a rare silicate mineral called aluminum-tobermorite (). When seawater subsequently percolates through the concrete, it reacts with the remaining volcanic components, causing new crystals to form. Rather than eroding the material, this continuous exposure to seawater causes the crystals to grow and interlock within the pores of the concrete, thereby reinforcing the structural integrity of the barrier over time.
Based on the text, what is true of the aluminum-tobermorite crystals in Roman marine concrete?
- AThey were mined from volcanic deposits by Roman builders before being added to the concrete mixture.
- They grow and interlock inside the concrete's pores as seawater passes through the material.Answer
- CThey dissolve immediately upon contact with seawater, allowing volcanic ash to expand.
- DThey are responsible for the initial solidification of quicklime prior to its exposure to seawater.