Effective Thermal Management in Precast Concrete

Effective Thermal Management in Precast Concrete for Major Infrastructure Projects

The Victoria Park-Canning Level Crossing Removal (LXR) Project is part of the Metronet infrastructure initiative. The project is Perth’s first major elevated rail designed to improve public transport safety, create new and versatile public spaces for the community, and reduce traffic congestion.

When complete, the Victoria Park-Canning Level Crossing Removal Project will feature five new, modern elevated stations, further enhancing connectivity and reducing travel disruptions across Perth. This milestone marks a significant step toward a more efficient and accessible public transport network for the city.

Thermal Management Challenges

BCRC tackled one of the biggest challenges in the precast concrete industry: managing heat during curing. With over 790 precast elements, including piers, Roofs, L-beams, and headstocks, manufactured for the project, implementing effective thermal management strategies was essential to maintaining structural integrity and meeting the tight schedule.

In precast concrete projects, heat of hydration, which is released during cement curing, can lead to thermal cracking and Delayed Ettringite Formation (DEF) if left unchecked. This project encountered added complexity due to the varied geometries and thicknesses of the elements, posing specific challenges:

1. High Binder Content Mixes:

These mixes were essential to achieve the rapid strength gains required but also significantly increased the internal heat, complicating temperature control.

2. Complex Geometries:

The varying thicknesses across different sections of the precast elements led to uneven heat distribution, making it difficult to ensure uniform cooling.

3. Accelerated Curing Requirements:

The project’s ambitious timeline necessitated fast curing, which amplified thermal control issues.

4. Maturity Considerations:

Different parts of each element cured at different rates, demanding close monitoring to avoid defects and inconsistencies.

Developing an Effective Thermal Control Plan

To overcome these challenges, the project team devised a comprehensive thermal control plan incorporating several key strategies:

• FEM-Based Thermal Modelling:

This advanced modelling provided detailed insights into heat flow patterns, identifying hotspots and enabling targeted cooling interventions.

• Cooling Pipe System:

Embedded cooling pipes were strategically placed to dissipate heat in critical areas. Adjusting the pipes’ size, spacing, and flow rates allowed for consistent cooling across the elements.

• Optimized Steam Curing:

The team carefully adjusted the steam curing process to align with the natural heat of hydration, promoting uniform maturation.

• Real-Time Monitoring and Validation: Thermocouples embedded in the elements facilitated continuous temperature monitoring. This real-time data allowed for dynamic adjustments to the cooling system, ensuring effective thermal management.

Results and Key Takeaways

The thermal management strategies implemented on this project resulted in several notable outcomes:

• Minimal Cracking: Almost no significant thermal cracking was observed in the precast elements, demonstrating the effectiveness of the cooling and monitoring systems.

• Accelerated Construction: The ability to strip formwork in hours rather than weeks greatly streamlined the construction process.

• Specification Compliance: Temperature differentials were kept below the project’s stringent limits (70°C peak temperature and 20°C differential), confirming the project’s success in thermal management.

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Key Takeaways for Future Projects

This case study offers important insights into the significance of effective thermal management in complex precast concrete projects:

1. FEM Modelling is Essential: Multi-dimensional thermal analysis allows for accurate predictions of peak temperatures and temperature gradients, particularly in complex structures.

2. Cooling Systems Are Crucial: A well-designed cooling system is indispensable for managing internal heat and preventing thermal cracking.

3. Continuous Temperature Monitoring: Real-time data enables immediate adjustments, ensuring consistent thermal control throughout the curing process.

4. Early Expert Engagement: Engaging thermal management experts early in the design phase can help pre-empt potential issues and streamline project execution.

This project underscores the critical role of robust thermal management in successfully executing large-scale infrastructure initiatives.

September 28, 2024October 1, 2024

Life-Cycle Cost Analysis and Sustainability in Construction

PIANC conference life cycle construction cost

Adopting sustainable practices for new structures is not just an environmental responsibility but a strategic approach to ensure their long-term viability and resilience. BCRC have made the point at many conferences that full probabilistic analysis (FPA) is currently the only approach to modelling durability as no other method calculates the likelihood of failure (i.e. corrosion initiation). While achieving a reliability of 1.3 at the end of the design life is deemed acceptable for most serviceability limit states it may not give the most economic cost over the deign life because it does not take into account the cost of minor repairs that are expected. If designed and constructed appropriately major repairs should not occur.

BCRC recently undertook a Life-Cycle Cost Analysis (LCCA) for a major jetty construction to compare the potential cost of different covers, mix designs and reinforcement types. In this case the construction costs were given by the contractor and the unit cost of a repair were assessed by BCRC based on accessibility. Operational and public costs can be the most significant part of a repair and hence these costs should be developed in conjunction with the client. On this project they were not major inputs. The client should also provide finance rates.

A critical aspect of the analysis is how frequently repairs will be required. In this case BCRC proposed assuming repairs would be undertaken when the probability of failure (PoF) for corrosion initiation increased by 1%. This was consistent with maintaining visual appearance more than structural concerns. As PoF is related to reliability the FPA provides the repair interval as shown in the reliability with time graph (standard FPA output) below. It compares the use of different reinforcement types for the same mix and cover. This was a small part of the much larger number of options considered.

The graph shows that stainless steel has such a high reliability that even at 100 years, no repairs were envisaged. The number of repair cycles increased to four for galvanised steel, and to around 12 for carbon steel. In this case repairs for carbon steel became so frequent that they were not tolerable, but by improving concrete performance and cover carbon steel was the lowest whole of life cost. On other projects where operational or public costs are high stainless steel may become the lowest cost.

Clearly FPA provides whether the reliability at the end of the design life is adequate but also, for any design approach, what the repair cycle and number of repairs for each cycle might be. BCRC’s Frank Papworth will be presenting this and other sustainability aspects for infrastructure at PIANC2024 in Sydney on 28 August.

September 6, 2024November 6, 2024

Cooling Pipe Systems for Concrete in Infrastructure Projects

Innovative Cooling Pipe Systems for Concrete in Major Infrastructure Projects

BCRC, a leader in construction technology, has pioneered advanced cooling pipe systems to tackle the complex challenges of managing concrete’s heat of hydration and mitigating thermal cracking in key transport infrastructure projects.

Cooling Pipe Systems: An Efficient, Cost-Effective Solution

In Australia’s challenging climate, controlling concrete placement temperatures is a persistent challenge for the construction industry. However, BCRC’s post-cooling techniques offer an efficient and cost-effective solution. By embedding cooling pipes within the concrete structure, circulating water absorbs the heat generated during hydration, effectively regulating temperatures and preventing thermal damage.

Innovation Meets NSW Government B80 Specifications

The cooling system, designed by BCRC’s Technical Director, Dr. Inam Khan, was successfully implemented in the Newell Highway Upgrade – New Dubbo Bridge project. Collaborating with Abergeldie Complex Infrastructure, BCRC developed customized cooling systems for critical bridge elements. These systems met Transport for NSW’s rigorous B80 specifications, achieving a peak temperature cap of 70°C and a temperature differential limit of 20°C. This cooling approach met thermal requirements and significantly reduced formwork removal times, accelerating the construction timeline.

A Major Infrastructure Project for the Region

The $263.2 million New Dubbo Bridge is making substantial progress, with a third of its concrete deck—designed to support future traffic—already in place. Jointly funded by the Australian Government, which has contributed $210.6 million, and the NSW Government, which has provided $52.6 million, this project is a vital investment in the region’s infrastructure.

BCRC’s Commitment to Concrete Durability in Harsh Environments

BCRC’s cooling systems underscore the potential for sustainable, effective solutions in modern infrastructure, setting new concrete durability and efficiency standards in Australia’s harsh environments. BCRC’s material engineers ensure that performance and workmanship requirements are rigorously defined for concrete durability. Yet, these standards can only be met if quality control in materials handling, batching, transportation, placement, compaction, finishing, and curing are strictly followed.

With expertise across the entire concrete lifecycle, BCRC offers comprehensive management to achieve fit-for-purpose, high-quality concrete that meets demanding structural needs in challenging climates.

October 18, 2021July 17, 2024

BCRC as a Keynote Speaker Partner at Concrete 2021-Virtual Conference

BCRC Keynote Speaker and Partner at Concrete 2021 Conference

BCRC proudly announces its participation as a Keynote Speaker Partner for Oscar R. Antommattei at the CIA event – Concrete 2021 (5-8 September).
Experience an engaging and exciting virtual program including keynote speakers, invited speakers and over 150 technical presentations. The four-day program will bring together global leaders in the concrete industry, covering all aspects of concrete materials, design, construction, repair, and maintenance, to discuss and share information on how innovation and smarter thinking will allow us to deal with disruption.

Don’t miss out and Register now!!!

BCRC as a Keynote Speaker Partner at Concrete 2021-Virtual Conference blog concrete main

Team BCRC is presenting Multiple Papers at CONCRETE 2021 (5-8th September):

Our director Frank Papworth will give a presentation on the importance of using the right model for durability design. He uses the simple graphs below to show that the equations used to predict depths of critical chloride level, and carbonation depth, over time must recognize that the variables in the formula are distributions. Because this is not fully detailed in simple models like Life 365 and CSTR 61 engineers judgement on the suitability of different materials is often flawed. The paper also explores they way forward with full probability analysis (FPA) in the design of structures.

BCRC as a Keynote Speaker Partner at Concrete 2021-Virtual Conference blog concrete graph — Graph: Demonstrating the equations used to predict depths of critical chloride level, and carbonation depth, over time must recognize that the variables in the formula are distributions.

In a separate paper our Herman Jong shows how the FPA has been used to check AS5100.5 Deemed to Satisfy requirements. Frank will also team with Rodney Paul in a session on the work of the fib and CIA Durability Committees.

Quite separate to that our Gulraiz Ijaz presents on innovate sacrificial anode for cathodic protection that meet code criteria while our Robert Munn (Bob) provides an update on a lithium byproduct for use in concrete.

September 30, 2019September 2, 2021

Tasmania Bridges Project

BCRC Consultants Rebecca Newby and Summer Wang undertook a durability assessment of six bridges located throughout Tasmania as part of repair work scheduled for the structures. BCRC completed the following activities:

Visual inspection and drummy survey
Cover survey
Resistivity testing
Carbonation testing
Rebound hammer testing
Analysis and reporting with remediation recommendations

If you have an enquiry or would like to speak to an expert, call us on 02 9131 8018.

Visit our LinkedIn page to view more photos of this project.

Tasmania Bridges Project Pipers Brook bridge 2 bcrc 768x432 1

Tasmania Bridges Project Humphreys Rivulet 3 bcrc 768x576 1

June 30, 2019October 20, 2021

Sydney Harbour Wharf Project

BCRC Engineers Gulraiz and Inam inspecting a Sydney Harbour Wharf for Concrete Durability prior to redevelopment of the Wharf. They are sampling the concrete which will be laboratory tested and the results analysed to assess each element’s residual life based on the reliability required.

Target reliability is emerging as one of the most important factors in durability design. It was first introduced into Australian methodology in CIA’s Z7/01 by BCRC’s Frank Papworth.

They are also using an advanced Ground Penetrating Radar (GPR) that uses stepped frequency antenna and downloads data automatically to the internet. It is revolutionising how reinforcement is visualised in concrete and provides rapid scanning of concrete cover distribution, a vital input into full probabilistic durability design.

We have a wide range of cutting-edge concrete Non-Destructive Test devices, making BCRC Australia’s industry leader in the concrete inspection field. Methods such as, Ultrasonic Pulse Echo (UPE), Impact Echo (IE), Impulse Response (IR), Cross Hole Sonic Logging (CHSL) and Spectral Analysis of Surface Waves (SASW) are some of the advanced methods we utilise for evaluating concrete structures.

In each case, stress waves or electromagnetic waves are introduced into the concrete and reflected waves or structure responses are measured. These methods have seen rapid development and acceptance in many countries in Europe, North America and Singapore. All are now used in Australia through BCRC.

To learn more about Concrete Durability Testing, contact us on 02 9131 8018.