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Difficulty: MediumInferences from the Text

Recent geochemical analyses of ancient Roman maritime concrete structures have altered historical assumptions regarding the degradation of hydraulic mortars exposed to seawater. While modern Portland-cement concretes rely on an inert aggregate bound by calcium-silicate-hydrate (C-S-H) phases that gradually deteriorate through magnesium and sulfate ion intrusion, Roman mortars incorporated reactive volcanic pozzolana and relict lime clasts. Over centuries of marine exposure, the dissolution of these relict lime clasts fosters an alkaline microenvironment that promotes the post-curing precipitation of aluminum tobermorite and phillipsite crystals within interfacial voids. Because these secondary interlocking crystalline frameworks expand into micro-fractures rather than disrupting the matrix, the material exhibits an autogenous, seawater-activated resilience unseen in contemporary cementitious composites. However, this mineralogical growth requires prolonged contact with open seawater and permeable voids; dense structural formulations or those isolated from continuous fluid exchange do not exhibit comparable post-curing mineral precipitation.

Based on the passage, which of the following statements can be logically inferred regarding the behavior and composition of ancient Roman maritime mortar? (Select all that apply.)

  1. The mechanical resilience of ancient Roman marine concrete increases as a consequence of chemical interactions that would typically degrade standard modern concrete.Answer
  2. B
    The inclusion of volcanic pozzolana ensures that Roman concrete structures will develop secondary crystalline matrices even when installed in completely arid terrestrial environments.
  3. A Roman mortar mixture manufactured without sufficient internal permeability would be less likely to develop post-curing aluminum tobermorite crystals than a more porous marine mixture.Answer
  4. D
    Modern civil engineers have universally abandoned Portland cement in marine applications in favor of replicating ancient pozzolanic formulas.
  5. E
    The dissolution of relict lime clasts in Roman mortar causes immediate structural failure unless aluminum tobermorite crystals precipitate instantly upon contact with water.

Answer

The statements indicating that Roman marine concrete gains resilience from chemical interactions that degrade modern concrete, and that a less permeable Roman mortar formulation is less likely to develop post-curing crystalline growth, are both logically supported by the passage.
The passage establishes that marine contact degrades Portland cement but activates a beneficial crystalline network in Roman mortar, directly supporting the statement regarding contrasting chemical responses. Furthermore, because the passage explicitly states that this mineralogical growth requires permeable voids and is absent in dense formulations, it directly entails that a mixture lacking sufficient permeability would be less likely to develop these secondary crystals.

Step-by-Step Solution

1
Analyze the relationship between environmental exposure and material response in modern versus Roman concrete.
The text shows that marine exposure causes ion intrusion that degrades modern concrete, whereas in Roman mortar, seawater exposure triggers the dissolution of lime clasts and subsequent precipitation of interlocking crystals that enhance resilience.
Establishes textual support for the inference regarding contrasting mechanical responses to seawater interaction.
2
Evaluate the stated physical prerequisites for post-curing mineral precipitation in Roman mortar.
The final sentence specifies that crystalline growth requires 'permeable voids' and that 'dense structural formulations' do not exhibit comparable precipitation.
Confirms the inference that lower internal permeability impedes the development of aluminum tobermorite crystals.
3
Assess the remaining statements against passage scope and logical bounds.
Claims regarding arid environments, contemporary engineering adoption, and instant failure introduce unsupported assumptions and contradictions to explicit text conditions.
Eliminates distractors that rely on outside knowledge or unsupported logical leaps.

Key Concept

Textual Inference and Necessary Deductions in Reading Comprehension
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Inferences from the Text

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