Research & Projects

The duration of the project is 3 years and is currently in progress. Project No.: EEQ/2023/000130. 

At present, in the codes and standard practices, any standard method for thermally induced concrete properties for UHPC/HPC/HSC at elevated temperatures has not been established. Based on the literature background and available experimental expertise, it is trying to develop an innovative solution for the mitigation of the existing problems. 

Objectives

• Test method for characterizing concrete properties at elevated temperature.

• Guidelines and testing methods for transient creep strain measurement and mitigation of UHPC at elevated temperatures for structural application.

• Fire resistance rating and performance enhancement of UHPC RC columns at elevated temperatures.

• Performance-based fire resistance design method for evaluating fire resistance rating of UHPC RC columns at standard fire loads.

Results

It is expected on the base of scientific experimental results that the use of PP fibres in concrete can minimize the pore pressure build-up and the ST fibres increase the tensile strength of concrete during exposure to fire. Therefore, the combined fibres in the hybrid form may be resulting a positive impact on transient creep strain mitigation of UHPC/HPC/HSC to improve the fire resistance rating of RC members at catastrophic fire events. Hence, to check the significance of this fact, there is a need to be studied experimentally and to identify a scientific solution. Seen the research gap, this project proposal is trying to solve the existing problems which are still unknown and don't have any scientific solution. 

The duration of the Project was 2 years starting in the financial year 2019 and ended 2021. Project No.: MLP-072002. 

Concrete structures are prone to damage during accidental fires, which can result in significant economic loss and loss of human life. Therefore, it is essential to have fire-resistant measures in place to maintain the structural stability and integrity of reinforced concrete (RC) members during a fire. One of the major issues during a catastrophic fire exposure is the fire-induced explosive spalling of concrete, which occurs within the first few minutes, regardless of whether the concrete sample is water-cured or air-cured. The spalling of concrete is dependent on the inherent moisture content in the concrete, which creates an internal vaporized pressure of up to 3-4 MPa at elevated temperatures. This phenomenon continues until the RC member is completely dry. However, the problem of spalling is more prevalent in High Strength Concrete (HSC) with a low water/cement (w/c < 0.34) ratio, which uses supplementary cementitious material (SCM) additives such as limestone powder, fly ash, silica fume, granulated blast furnace slag, or glass or quartzite filler to enhance the durability and mechanical properties of the concrete mix. The fine particles of SCM and its chemical composition react with the cement binder and available water content, resulting in reduced porosity and increased durability of the concrete. Therefore, the basic water content in HSC is not easily evaporated during fire exposure, creating higher inherent vapour pressure. To avoid the spalling of concrete and maintain structural integrity during a fire, it is crucial to find appropriate solutions to address this specific problem.

Objectives

• Technology for spalling mitigation in high-strength concrete.

• Realistic and economical design for achieving the required fire resistance rating.

• Skill development for technical services.

Results

In  the present research work, it can draw the main relevant conclusions on spalling mitigation of HPC at elevated temperatures are as follows:

• High moisture content in HPC introduced several burst bumps, cracks formation, and spalling of concrete at elevated temperatures.

• The use of SCMs in concrete can significantly influence the compressive strength and introduce severe spalling damage to the HPC samples at elevated temperatures.

• No concrete pieces fell off or severe spalling for cylindrical samples up to 4 hours of exposure to the transient heating of temperature 1000ºC after using the quantity of PP fibre 1.86 kg/m3 and ST fibres 37.30 kg/m3 to 49.74 kg/m3 in HPC.

• In time-dependent behaviour evaluation after the provision of PP fibres and ST fibres for spalling mitigation, major micro-meso level crack formation throughout the section of the concrete cylinder can be observed.

Technology developed 

Banti A. Gedam, Spalling mitigation technology for HSC/HPC at elevated temperature, (Developed Under Project No. MPL072002). 

https://www.youtube.com/watch?v=vbnFdrzT67E&ab_channel=CSIR-CBRI%28BhavanTarang%29

The duration of the Project was 2 years starting in the financial year 2018 and ended 2020. It was Task 4 under Vertical 6, which focused on designing and developing fire safety measures for critical installations. Project No.: HCP-0017. 

RC beam is a critical load-bearing structural member in buildings and is predominately designed for flexural resistance. However, such members come in contact with catastrophic fire in any accidental events, which result maybe lead to being weaker the designed flexural carrying capacity. In such conditions, the associated stability of the RC beam is the most important to maintain structural integrity and for vital safety measures. This is the last option that helps fire safety and evacuation systems when the safety protection measures fail. Therefore, an appropriate simple design provision of fire resistance analysis with performance-based criteria for RC beams in any fire scenario before failure is one of the major requirements.

Now, modern and advanced technology of concrete, i.e., HSC, HPC and self-compacting concrete (SCC) is introducing a challenge for fire resistance design at standard and non-standard fire exposure conditions. Hence, the scientific community is regularly working to find practical solutions and trying to develop numerical and computational techniques focusing on a performance-based solution to evaluate the behavior of structural members in fire-exposed conditions. In this study, one attempt has been made by keeping in view of effective parameters for fire resistance of RC beams at different fire scenarios and proposing a simple fire resistance analysis model.

Objectives

• Design aid for RC beams at elevated temperatures.

• Rehabilitation (strengthening and repairing) technique of the fire-damaged RC beams.

• Databank generation of fire-damaged RC beams. 

Results

In this research study, several helpful observations have been found on the effect of fire scenarios, nominal cover, and type of aggregate. Based on the results of this study, the main relevant conclusions can be described as follows.   

• The existing codes and standards, i.e., NBC, IS 456 and IS 1642 are evaluating fire-resistance rating for RC beams using a prescriptive and empirical approach. Also, these codes and standards do not consider any thermally induced material properties, heat transfer field variations, fire exposure scenarios, and type of aggregate.

• The NBC, IS 456 and IS 1642 do not propose any design method and fire resistance guidelines to evaluate the fire-resistance rating of RC beams.

• For heat transfer analysis within the RC beam, the thermal-induced properties of materials, i.e., conductivity, specific heat, and density play a significant role. The developed heat transfer model predicts more accurate results and conservative side at any particular conditions while existing empirical/semi-empirical equations do not obtain suitable to predict temperature within RC beam.

• The fire resistance analysis model has predicted the flexural behavior of RC beams using thermally induced material properties, which introduces more accurate and conservative results with the experimentally measured database.

• In fire-resistance evaluation, high-intensity fire load either standard or designed at short-duration exposure conditions has exhibited severe deformations of the flexural carrying capacity for RC beams. Also, the nominal cover thickness enhancement and type of calcareous aggregate improve the flexural carrying capacity of RC beams in different fire scenarios.

• The failure criteria for RC beams have significantly influenced the fire-resistance rating. The conventional reinforced steel rebar temperature failure criterion in fire scenarios has not reflected any reasonable results of fire-resistance rating. However, the criterion of flexural carrying capacity reduces 30 percent of the designed RC beam and has introduced reliable information for fire resistance assessment.