Efficiency of coating layers used for thermal protection of FRP strengthened beams

Peer review under responsibility of Housing and Building National Research Center.

Figures & data

Table 1 Mix proportions of concrete mix used to cast all beams.

Cement (kg)	Coarse aggregate (kg)	Fine aggregate (kg)	Water (l)
400	1470	735	200

Table 2 Mix proportions of 1 m³ of mortars used as protective layers.

Layer	Perlite (l)	Vermiculite (l)	Clay (l)	Sand (kg)	Cement (kg)	Water (l)	Fiber (g)	Air-entrained admix (l)
PC mortar	–	–	–	1600	500	200	900	4
Perlite mortar	1 m^3	–	–	–	500	330	900	4
Vermiculite mortar	–	1 m^3	–	–	500	415	900	4
Aswan clay	–	–	1 m^3	–	500	500	1800	4

Fig. 1 Dimensions and reinforcement of tested beams.

Fig. 2 RC beams strengthened by FRP.

Table 3 Details of the experimental program.

Protection type	Strengthening	Room temp	Elevated temperature °C for 2 h
		25 °C	100 °C	200 °C	300 °C	400 °C	500 °C	600 °C
Unprotected	No	B1,B2	B5,B6	B7,B8	B9,B10	B11,B12	B13,B14	B15,B16
Unprotected	GFRP	B3,B4						B17,B18
Type 1	GFRP							B19,B20
Type 2	GFRP							B21,B22
Type 3	GFRP							B23,B24
Type 4	GFRP							B25,B26
Type 5	GFRP							B27,B28
Type 6	GFRP							B29,B30
Type 7	GFRP							B31,B32
Type 8	GFRP							B33,B34
Type 9	GFRP							B35,B36

Fig. 3 The electric furnace before and after placing a protected concrete beam.

Fig. 4 Temperature measurement and Data Acquisition System.

Fig. 5 Four-point bending test for beams.

Fig. 6 Failure mode of beams not subjected to elevated temperature. (a) Unstrengthened beam (b) FRP-strengthened beam.

Fig. 7 Failure mode of unprotected RC beams after 2-h exposure to 500 and 600 °C.

Fig. 8 Failure loads of unprotected RC beams after 2-h exposure to high temperature.

Table 4 Failure loads of unprotected RC beams.

Beam	Strengthening	Temperature (°C)	Protection layer	Failure load (kN)	Ratio to control (B1, B2) (%)
B1, B2	–	25	–	30	100
B3, B4	GFRP	25	–	38	126.67
B5, B6	–	100	–	30	100
B7, B8	–	200	–	27.1	90.33
B9, B10	–	300	–	22.8	76.00
B11, B12	–	400	–	18.7	62.33
B13, B14	–	500	–	15.6	52.00
B15, B16	–	600	–	10.3	34.33
B17, B18	GFRP	600	–	10.3	34.33

Fig. 9 Temperature measured under coating types 1–9 when exposed to 600 °C for 2 h.

Fig. 10 FRP-strengthened RC beams protected by type 1 and 4 after exposure to 600 °C. (a) Beam protected by type 1 (Perlite mortar) (b) Beam protected by type 4 (Aswan clay).

Fig. 11 Failure loads for protected FRP-strengthened RC beams exposed to 600 °C.