Facility Maintenance Division of Kukje Chemical & Construction Co., Ltd.
Towards a higher sky and fulfill dreams with deeper passion.

Facility Maintenance Division of Kukje Chemical & Construction Co., Ltd.

FRM Method

Fire Resistance Mortar

MLM(Ministry of Land, Transport and Maritime Affairs) New Technology No. 647 (Fire resistant method for concrete structures, casting the fire resistant mortar with the dedicated spray equipment and applying fire resistant coating
Patent no. 10-1016156 (Fire resistant method for concrete structures, using the fire resistant mortar)

1. Overview of FRM Method

Heat load is removed from existing spherical concrete to form concavo-convex and secure adhesive force. Then, dusts and foreign matters are eliminated from the substrate by water jet cleaning, and the fire resistant mortar is sprayed with dedicated equipment. Then, the material is finished with fire resistant coating agent to block external deterioration elements, improve aesthetic features and form new fire resistant protective layer so as to improve durability of existing structures and prevent recurrence of deterioration. In that way, sudden heat can be prevented during the fire to ensure safety of existing structures.

2. Need for FRM Method

Large-scale fire in structures, such as Daegu Subway Jungangro Station fire(2003), fire in the section of Onsu Station on Seoul Metropolitan Railway(2005), and fire on the elevated bridge at Jungdong IC in Bucheon, causes damage to the structures, bringing social infrastructures, such as transportation networks, to a standstill for a prolonged time, as well as casualties, due to degradation of structural strength. The International Tunnelling. Association, European countries, Japan, etc., have established and operated the fire resistant design standards for underground facilities to minimize damage to structures, prevent casualties, and ensure undisrupted operation of transportation networks in case of large-scale fire. In Korea, the fire resistant design standard is yet to be established, and as a result, overseas fire resistance-related laws have been used as references.

Limitation of Existing Fire Resistant Materials

Existing fire resistant materials provide lower fire resistant performance, causing cracks, peeling, exfoliation, and sudden heat, which increases the risk of large-scale disasters such as collapse of structures.

Cases of domestic fire incidents

Cases of overseas fire incidents

Name of Tunnel Mont Blanc Railroad tunnel linking England and France under the Strait of Dover Gotthard Tunnel Gotthard Tunnel
Location France England, France Austria Austria
Year 1999 1996 2001 1997
Extension 11.6Km 49.4Km 16.9Km 16.9Km
Highest Temperature 1000℃ / 53 hours 1100℃ / 9 hours 27 hours 30 minutes
Damage in structures The lining ceiling was destroyed due to the explosive fracture as large as up to 70cm at the ceiling part in the 900m section. The concrete linings were peeled off in the 9.0km section. Within the range of 300m to 500m, segments with a thickness of 40cm were severely destroyed, making the bedrocks exposed. Collapse due to explosive fracture of concrete at the ceiling part in the 250m section Damage was caused to the ceiling part in the 50m section due to explosive fracture measuring 100m2 in size

3. Principle of FRM Method

Development of fire resistant mortar and fire resistant coating agent

Ensuring the safety of structures from fire

Spray equipment for fire resistant mortar

· Prevention of fiber entanglement and nozzle clogging
· Improved dynamic performance and durability, ensuring the workability

Spray equipment for fire resistant mortar

Components and features of equipment

Development of fire resistant method

· Maintain the quality at a constant level and decrease the rebound rate to ensure safety
· Increase eco-friendliness by using industrial by-product slag micropowder and silica fume
· Improve the maintainability by increasing the durability

Design stage Installation stage Maintenance stage
Ensuring the safety of structure by conducting the fire experiment based on the ISO and RABT fire resistant curve Ensuring the quality based on the installation guideline for each process[fire resistant mortar, fire resistant coating agent] Ensuring the durability based on water absorption coefficient test, etc.
Dead load reflected in the design to accommodate to the increase in self-weight Ensuring the safety based on the quality and site management Ensuring the resistance to fire based on the fire resistant test results conforming to the standards and preparation of maintenance guide

Improvement of safety of underground structures, bolstered by advancement of fire resistant technology

Applicability to the sites Distributability Structural safety
Development of fire resistant mortar and double mixing device Meeting the fire resistant performance and quality standards Fire resistance test results meeting the standards
Development of fire resistant method Ensuring the reliability and consistency with public interest Preparation of installation guide and achievement of high durability

Achievement of required fire resistant performance (RABT-fire curve test)

Fire resistant test was conducted for 170 minutes by applying the fire resistant mortar to the surface of concrete block test piece(1,850 X 1,250 X 300mm) under the heating condition according to the RABT-fire curve(Train). The temperature on the concrete surface of test piece and internal temperature were measured. In the test, the concrete with the standard strength of 27MPa was used. The fire resistant mortar was applied to a thickness of 30mm.

· Test location: Korea Institute of Civil Engineering and Building Technology
· Application of fire resistant mortar: FRM30, FRC [applied to a thickness of 30mm]
· Thermocouple(K-type) position: surface of testpiece, 37.5mm [between the surface of testpiece and rebar], 75mm [position of rebar]
· Fire curve: RABT-fire curve applied; heating for 170 minutes; and maximum temperature of 1,200℃

Drawing of testpiece structure

시험체 구조 도면

Results of RABT(Train) fire curve test

No explosive fracture occurred. The RABT(Train) fire curve test showed that the maximum temperature on the interface was 228℃, which conforms to the European fire resistance standard(concrete interface temperature of 380℃ or less) and Japan’s fire resistance standard(concrete interface temperature of 350℃ or less), thus proving excellent fire resistant performance. After completion of the test, no exfoliation of fire resistant mortar occurred. So, the material is considered to help prevent degradation of fire resistant performance of existing structures and promote structural stability.

· Test of RABT(Train) fire curve test by the Korea Institute of Civil Engineering and Building Technology - Testing personnel: Lee Bong-jae, Technical Officer: Kim Hong-yeul

4. Details of FRM method

5. Applications of FRM method

Sequence of works

Physical properties of fire resistant mortar

Fire resistant mortar(for repair)

Sequence of works

Properties of fire resistant mortar

6. Case of applications

7. Certificate of Patent