The passage is adapted from an article about ancient engineering.
Paragraph 1
Modern concrete, while structurally formidable, is notorious for its vulnerability to environmental degradation, often requiring extensive maintenance within a few decades. In contrast, structures built with Roman concrete, such as the Pantheon and ancient harbor barriers, have survived for millennia despite being subjected to seismic activity and corrosive saltwater. For years, material scientists struggled to explain the exceptional durability of this ancient substance, attributing it vaguely to volcanic ash or proprietary mixing techniques that had been lost to history.
Paragraph 2
Recent chemical analyses of Roman concrete samples have resolved this mystery, revealing that the key lies in a process called "hot mixing." Researchers discovered tiny, millimeter-scale white mineral chunks, known as "lime clasts," throughout the ancient mortar. Previously dismissed as mere evidence of poor mixing or low-quality raw materials, these clasts are actually active self-healing agents. When cracks form in the concrete, rainwater seeping into the fractures dissolves the calcium-rich clasts, recrystallizing the minerals into the cracks and sealing them before significant structural failure can occur.
Which of the following best describes the relationship between Paragraph 2 and Paragraph 1?
- AParagraph 2 refutes a common misconception about modern concrete that was established in Paragraph 1.
- Paragraph 2 explains the chemical mechanism responsible for a durable material introduced in Paragraph 1.Answer
- CParagraph 2 provides a chronological history of the scientific research that led to the hypothesis proposed in Paragraph 1.
- DParagraph 2 outlines a series of practical solutions to the structural failures detailed in Paragraph 1.