Biodeterioration of Concrete Sewer Pipes: State of the Art and Research Needs
Bibliographic record
Abstract
Biodeterioration of concrete sewers is a common problem that results in concrete disintegration and significant damage. Two stages are normally identifiable in the process: an initiation stage, during which the concrete pore water pH is reduced from an initial value of over 12 to a value of about 9 by ingress of hydrogen sulfide gas and carbon dioxide (carbonation) and subsequent reaction with the hydrated cement paste; and a second stage, active biodeterioration, during which microorganisms excrete sulfuric acid that attacks the hydrated cement paste (HCP). Various national codes and standards provide some guidance to mitigate this problem. Sulfur-oxidizing microorganisms growing on the sewer walls have been isolated as the main culprit, but other phenomena come into play before biodeterioration occurs. Steady-state biodeterioration rates of 3 mm/year have been proposed in the literature. A detailed literature review was conducted to evaluate the various aspects of concrete biodeterioration and determine further research needs. This state-of-the-art report summarizes the deterioration mechanisms involved in biodeterioration of concrete sewers and the work necessary to complete the modeling of this phenomenon. A conceptual model of the processes is presented.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.003 | 0.004 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.005 | 0.008 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.004 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".