Unlike modern Portland cement, which degrades structurally when exposed to saltwater due t… — LSAT

Unlike modern Portland cement, which degrades structurally when exposed to saltwater due to calcium silicate hydrate leaching, ancient Roman marine concrete (opus caementicium) increased in compressive strength over centuries submerged in seawater. Recent microstructural analyses indicate that this resilience stems from a continuous post-curing reaction between seawater and volcanic ash pozzolans, primarily pumice containing the mineral phillipsite. When alkaline seawater percolates through interlocking micropores in the lime-ash mortar, it dissolves residual volcanic glass, triggering the precipitation of interlocking crystalline plates of aluminous tobermorite and phillipsite within existing voids. These authigenic minerals not only arrest propagation of microcracks generated by mechanical wave action but also reinforce the surrounding matrix. However, because this crystallization relies on the dissolution of permeable, unconsolidated ash components, synthetic formulations that fully vitrify the ash prior to mixing fail to exhibit any comparable self-strengthening behavior.

Which of the following is most strongly supported by the passage regarding the structural properties of Roman marine concrete?

A
The infiltration of seawater would cause ancient Roman concrete to deteriorate if the submerged structure were completely shielded from mechanical wave action.
B
Modern Portland cement could achieve long-term resilience comparable to Roman concrete if mixed with high concentrations of industrial silica fume.
The formation of crystalline plates that prevent crack propagation requires that the volcanic ash in the original mixture retain non-vitrified, dissolvable constituents.Cevap
D
Microscopic fractures within the concrete mortar must already be present before any dissolution of residual volcanic glass by seawater can occur.
E
The compressive strength of Roman marine concrete submerged in seawater increases at a constant, uniform rate indefinitely.

Cevap

The formation of crystalline plates that prevent crack propagation requires that the volcanic ash in the original mixture retain non-vitrified, dissolvable constituents.

The correct answer accurately reflects the causal relationship detailed in the final sentence of the passage: the formation of self-reinforcing crystalline plates depends directly on the chemical dissolution of unconsolidated volcanic ash components, which is prevented if the ash is fully vitrified before mixing.

Adım Adım Çözüm

Analyze the question stem and passage structure

Identified that the task requires selecting an inference that is most strongly supported by the chemical and structural mechanisms outlined in the passage.

LSAT inference questions require finding a claim that is directly entailed or strongly corroborated by the explicit text.

Locate textual evidence regarding the formation of authigenic minerals and pre-mixing conditions

The final sentence states that crystallization relies on the dissolution of permeable, unconsolidated ash components and that fully vitrifying the ash prior to mixing eliminates the self-strengthening reaction.

This establishes a necessary condition: the ash must not be fully vitrified and must contain dissolvable material for the crystalline plates to precipitate.

Evaluate answer choices against the textual constraint

The choice stating that retaining non-vitrified, dissolvable constituents is required for crystalline plate formation matches the author's argument without exceeding the scope.

Eliminates unsupported assumptions regarding outside industrial additives, reversed conditional timelines, or unwarranted claims of indefinite linear growth.

Anahtar Kavram

Inferring necessary physical and chemical conditions from explicit causal explanations in a scientific reading passage.

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Cevap

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