42907 Design for Durability
The Complete Study & Assessment Guide · Spring 202642907 Overview
- Spring session postgraduate civil engineering at UTS
- Six credit points
- Two hour lecture and workshop weekly
- One hour tutorial and design review
- Two quizzes and two design reports
42907 Design for Durability is a University of Technology Sydney subject taught by the School of Civil and Environmental Engineering, worth 6 credit points and delivered across a 12 week Spring session through a weekly two hour lecture and workshop, a one hour tutorial and design review session, and drop in sessions.
- Assessed by design Seventy of the hundred marks sit in a two part durability design project on one girder bridge, and there is no final examination.
- One procedure, four members The footings, columns, headstock beams and deck slab all get the same seven moves, and the marking runs down them in order.
- Name the governing load first A cover figure with no stated governing environmental load in front of it cannot be marked, and every later mark depends on that one sentence.
- The mix decides, the cover follows Required cover is set by the diffusion coefficient of the concrete you chose, so the binder and the water to binder ratio are the real design variables.
How 42907 is assessed
| Component | Weight | Format |
|---|---|---|
| Assessment task 1: Quiz 1 | 15% | Individual quiz on the durability design life concept, chloride induced and carbonation induced corrosion, corrosion of concrete, and the use of cement and supplementary cementitious materials to improve durability |
| Assessment task 2: Service Life Design Report, being Part 1 of the Major Design Project | 40% | Individual report of 3000 words maximum. Identify the environmental loads on each part of a girder bridge, carry out the service life design of each structural member to derive the concrete cover and quality for the required design life, and compare the findings with the relevant Standards with commentary on the discrepancies |
| Assessment task 3: Quiz 2 | 15% | Individual quiz on alkali silica reaction and its prevention, structural design for durability, electrochemical processes including cathodic protection, and the use of standards and compliance criteria to deliver a stated design life |
| Assessment task 4: Control of early age cracking, being Part 2 of the Major Design Project | 30% | Design of the reinforced concrete top slab of the bridge deck to reduce the risk of restrained shrinkage induced cracking, calculating the time to concrete cracking and the minimum required curing duration with the early age cracking calculator |
The four weights come from the subject's own assessment overview for this offering and sum to 100. The official subject record publishes no assessment detail at all, so every weight, task name and date here is taken from the subject site and the lecture materials rather than from the handbook. Three things need confirming before each deadline. The subject's pages give different answers for when three of the four tasks are due, and the assignment page is the one the submission portal enforces. The two quizzes are described on the lecture slides as timed windows of twenty four hours, with stated coverage that differs between sources. And the second part of the design project is called individual on one page and a group submission on another. No pass condition attached to any individual task appears in the materials available.
Assessment structure
Current 42907 dates
| Date | Item | Control |
|---|---|---|
| Week 5 or Week 6 | Quiz 1 | The assessment page says Week 5 and the schedule table marks it in the Week 6 row; the lecture slides give a dated twenty four hour window in early September |
| Wednesday 23 September 2026, 11:30 pm | Service life design report due | From the assignment page, which also opens the submission window on 1 September. Other subject pages give Week 7, Week 8 and 11 September |
| Week 9 or Week 10 | Quiz 2 | The assessment page says Week 9 and the schedule table marks it in the Week 10 row; the lecture slides give a dated window at the end of September |
| Early November 2026 | Early age cracking report due | The schedule table gives 6 November; the assessment page says Week 12 and the lecture slides say early November with the exact date to be advised |
Dates are as published in the subject's own assessment overview, schedule and assignment pages for this offering, which do not fully agree with one another. Confirm exact deadlines and submission settings in the live LMS.
What 42907 covers
Design for Durability asks one question in four settings: how thick and how good does the concrete cover have to be for this member to survive its design life. The guide opens on the material itself, the cement paste and the pore network that carries every aggressive species inward, then separates durability from design life and service life and sets out the exposure classification that turns a location into a pair of numbers.
The four deterioration processes follow in the subject's own order: chloride induced corrosion and its service life model, carbonation induced corrosion, sulfate attack in aggressive ground, and alkali silica reaction. Cements and supplementary binders sit between them, because the binder choice moves several of those processes in opposite directions.
The last part turns to cracking, shrinkage and the restrained early age cracking of a deck slab, and the final chapter assembles the whole procedure as the design report runs it.
Concrete basics and transport properties
porosity and permeable voids · water to cement ratio · capillary absorption · diffusion · why transport governs durability02Durability, design life and service life
three definitions · 50 and 100 year targets · the standards family · prescriptive, first principles and performance based routes03Environmental loads and exposure classification
seven classifications · climatic zones · the marine bands by dimension · minimum strength, curing and cover by class04Chloride transport and corrosion initiation
the passive film · depassivation and pitting · initiation against propagation · three diffusion coefficients · binding and the threshold05Service life design for chloride ingress
the error function solution · load against resistance · the ageing correction · threshold conversion · the performance based route06Carbonation induced corrosion of reinforcement
the pH ladder · the root of time front · curing and supplementary binders · initiation plus propagation · the humidity scissor07Cements and supplementary cementitious materials
the four clinker phases · sulfate resisting cement · the pozzolanic reaction · six mechanisms, two running the other way08Sulfate attack, DEF and aggressive soils
ettringite and expansion · early against delayed formation · the aggressive soil tables · prevention and the curing temperature ceiling09Alkali silica reaction and its prevention
the three conditions · gel formation · map cracking · two test methods and their limits · alkali limits and binder levels10Concrete cracking and shrinkage
two crack families · bleeding and permeability · elastic, creep and shrinkage · the three shrinkage components · crack width against crack count11Restrained shrinkage and early age cracking
restraint into tension · the race against strength · time to cracking and curing duration · thermal controls · closing the durability loop12The service life design report: method and marks
four members, seven steps · the marking sequence · the propagation policy · the word budget · the four conclusion promptsIt is a postgraduate subject on the durability design of concrete structures, targeting a design life of 50 years for buildings and 100 years for infrastructure as the Australian Standards require.
The teaching runs from durability and the design life concept, through environmental loads and exposure classification, the corrosion of steel in concrete by chloride ingress and by carbonation, the corrosion of concrete by sulfate attack and alkali silica reaction, and the role of concreting materials, to design from a standard and design from first principles, specifications and quality control, and the control of restrained shrinkage induced early age cracking.
It is a calculation subject as well as a materials subject: the chloride model is an error function solution of Fick's second law and the carbonation model is a root of time front law, and both are run from published performance data to produce a concrete cover in millimetres.
The assessment is built around a single bridge design project rather than an examination, so the marks go to designing each structural member for its own micro environment and then defending that design against the prescriptive requirements of the Standard.
Designing the minimum cover for a permanently submerged member over one hundred years
- +1Fix the durability load from the exposure, not from the mix. A permanently submerged surface does not take the tabulated tidal surface concentration; it takes the value derived from sea water chemistry, which is 0.20 per cent by mass of concrete.
- +1Age the diffusion coefficient across the one year to ten year window and no further: 1.04 times ten to the power minus 0.60 gives 0.2612 times ten to the minus twelve square metres per second. The design takes no credit for ageing beyond ten years.
- +1Convert the design life and compute the spread term. One hundred years is 3.1536 times ten to the ninth seconds, so twice the square root of the coefficient times the time is 0.0574 metres, that is 57.4 millimetres.
- +1Invert the error function solution at the threshold. One minus the error function of the argument equals 0.065 divided by 0.20, which is 0.325, so the error function is 0.675 and the argument is 0.696. The required cover is 0.696 times 57.4, which is 40 millimetres.
- +1Compare with the Standard. A permanently submerged surface is exposure class B2, for which the bridge design standard requires 50 millimetres of cover at 55 MPa and above. The prescriptive value therefore exceeds the first principles result by 10 millimetres and governs the design.
Key terms
- Design life
- The period for which a structure or member is intended to remain fit for its purpose, with minor maintenance. The Australian concrete structures standard targets 50 years and the bridge design standard 100 years, and the design project runs at a hundred.
- Exposure classification
- A code assigned to a concrete surface from its environment, which then fixes a minimum characteristic strength, a minimum curing period and a required cover. Six graded rungs run from A1 up to C2, and a seventh code covers an environment the table never names.
- Apparent diffusion coefficient
- The coefficient used to model chloride ingress in concrete, absorbing the porosity, the interactions between ions in the pore water, the binding capacity of the matrix and the ageing of all three. No reliable model predicts it from mix design, so it is measured or taken from published data.
- Chloride threshold
- The total chloride content at the steel at which the passive film fails and corrosion can begin. This subject designs to 0.4 per cent of cement mass, which converts to about 0.065 per cent of concrete mass at a binder content of 400 kilograms per cubic metre.
- Carbonation coefficient
- The single parameter of the carbonation front law, in millimetres per root year. A value of 2.5 puts the front at 2.5 millimetres after one year and 25 millimetres after a hundred.
- Initiation period
- The time before the steel depassivates, during which nothing is corroding and the cover is doing its work. In the severe marine classes this subject requires the initiation period alone to reach the design life.
- Propagation period
- The time after depassivation during which the steel actively corrodes. A carbonation design may count it up to the point where the cover cracks, and it is calculated as the corrosion depth for cracking divided by the corrosion rate.
- Supplementary cementitious material
- An industrial by product used as part of the binder, chiefly fly ash, ground granulated blast furnace slag or silica fume. It reduces chloride ingress, sulfate expansion and alkali silica expansion, and increases carbonation depth.
- Delayed ettringite formation
- An expansive reaction occurring at late ages in concrete that is already rigid, cracking and spalling it. High curing temperature is its principal trigger, which is why the bridge standard caps concrete temperature during curing.
42907 FAQ
Is 42907 a hard subject?
It is demanding in a particular way rather than uniformly difficult. There is no final examination and very little to memorise for its own sake, but seventy of the hundred marks sit in a two part design project that requires you to carry the same procedure through four structural members without dropping a step.
The calculations themselves are short, an error function evaluation for chloride and a square root law for carbonation, and the difficulty is in choosing the right inputs: the surface concentration depends on the exposure band rather than on the mix, the threshold appears on two different mass bases, and several binder effects run in opposite directions for different deterioration processes.
Students who work the tutorial calculations weekly, and who write down the reasoning beside every number, find the report largely writes itself; students who leave the modelling until the deadline usually discover that a wrong classification in week two invalidated everything built on it.
Can AI help me with 42907?
Yes, as a step by step study aid rather than as a source of engineering facts.
Sia is an AI tutor built for exactly this kind of work: rehearsing a chloride profile calculation until the unit conversions stop being a problem, checking whether you have applied the ageing correction once or twice, quizzing you on which exposure band a described surface falls into, or talking through why a permanently submerged member is classified milder than a tidal one.
What it should not do is supply the numbers your report cites. Every exposure class, cover, strength and coefficient in a durability report has to trace to a Standard clause, a published data table or the project brief, and the subject's own academic integrity guidance applies to how you use any tool. Use it to understand the method, then read the values yourself.
Is this subject examined at the end of the session?
No. The subject is assessed entirely within the session by four tasks: two individual quizzes worth 15 per cent each, and the two parts of a major design project worth 40 and 30 per cent. That changes how you should work, because there is no end of session revision block to fall back on and the forty per cent report depends on lecture material from the first half of the subject.
Falling behind in the first five weeks is expensive in a way it would not be in an examined subject.
What does the design project actually ask for?
A hundred year durability plan for one girder bridge. Four reinforced concrete members are designed, the footings, the columns, the headstock beams and the deck top slab, each in its own micro environment.
For each one you identify the environmental loads and say which governs, specify the concrete including its binder composition, minimum binder content, maximum water to binder ratio and characteristic strength, design the cover from first principles for the governing ingress process, and compare that result with the prescriptive requirement of the bridge design standard.
The second part of the project returns to the deck slab and asks for the time to cracking and the minimum curing duration under restrained shrinkage.
Why does the guide sometimes give two different answers to the same question?
Because the subject's own materials do, and picking one silently would be the worse error. The assessment page, the schedule table and the lecture slides give different dates for three of the four tasks and disagree about whether the second design report is an individual or a group submission.
Two lectures give different minimum strengths for the most severe bridge exposure class, and a corrosion rate table disagrees with the summary printed beside it. Where this happens the guide shows every reading with its attribution and tells you where to confirm, which is also what a professional durability report is expected to do with conflicting source data.
Are the practice questions in this guide official assessment questions?
No. Every worked example and practice item in this guide was written for it, using the standard methods and the published data the subject teaches from. None of them reproduces a quiz question, a tutorial stem or the project brief.
Where a question resembles a real one it is because the method is the same, not because the question was copied, and none of them carries an invented mark value, since the subject publishes no per question mark scheme.
How to prepare for the assessments
Treat 42907 as a design procedure you rehearse rather than a syllabus you revise. The single most useful thing you can build is a working sheet with one row per structural member and one column per decision: micro environment, governing load, exposure class, binder, binder content, water to binder ratio, characteristic strength, curing, first principles cover, prescriptive cover, signed difference and final cover.
Fill it as the semester goes, because every lecture supplies one more column. Drill the two calculations until they are automatic in both directions, the error function solution for chloride and the root of time law for carbonation, paying particular attention to the unit conversions, since both run in metres and seconds and report in millimetres and years.
Learn the exposure tables by using them rather than by memorising them, and always write the sentence that justifies a classification beside the class itself. Watch the three direction pairs this subject reverses relative to intuition: permanently submerged is milder than tidal, blended binders help against chloride and hurt against carbonation, and a permeable soil in groundwater is the harsher soil condition.
Finally, confirm every date and submission mode on the subject site rather than from any study aid, because the subject's own pages do not agree with each other on several of them.
Your AI Engineering tutor for 42907
Stuck on a hard 42907 question? Sia is AskSia’s AI Engineering tutor — ask any 42907 Design for Durability question and get a clear, step-by-step explanation grounded in how the course is actually taught and assessed. Read this whole study guide free, then take your hardest questions to Sia.
