Evolution of bonding behavior of GFRP reinforcement⁃seawater⁃sea sand concrete under seawater conditions

doi:10.19491/j.issn.1001-9278.2022.12.014

Abstract

Abstract:

To investigate the bonding behavior of GFRP bars and seawater⁃sea sand concrete under seawater environment， totally 54 GFRP bars⁃seawater⁃sea sand concrete center pullout specimens were designed and tested. A temperature acceleration experiment was conducted to study the changes of bond strength of the specimens after corrosion in the clear water and seawater environments， and the rising section of the bond slip curve of specimens was analyzed. The results indicated that the increase of temperature accelerated the degradation of bond strength of GFRP reinforcement⁃seawater⁃sea sand concrete specimens. The bond strength decreased by about 15% at 60 ºC compared to that at 10 ºC. The effect of the seawater condition on the bond strength of the specimens is slightly more significant than that of the clear water condition. The rising section of the bond slip curve of the specimens was analyzed using the BPE， CMR， and Malvar models， and the results indicated that the Malvar model was suitable for the rising section of the bond slip of GFRP reinforcement⁃seawater⁃sea sand concrete under the seawater condition. According to the TSF life prediction， the bond strength of the GFRP reinforcement⁃seawater⁃sea sand concrete specimens presented a retention rate of 65.58 % after 100 years of use under the 20 ºC seawater condition.

Key words: glass?fiber?reinforcement polymer bar, seawater sea?sand concrete, seawater conditions, bond?slip curve, bond strength prediction

CLC Number:

TQ 327.1

JIN Qingping, ZHOU Dian, HU Yanlei. Evolution of bonding behavior of GFRP reinforcement⁃seawater⁃sea sand concrete under seawater conditions[J]. China Plastics, 2022, 36(12): 92-99.

Figures/Tables 17

盐份

NaCl

MgCl₂

Na₂SO₄

CaCl₂

KCl

质量浓度

/g•L^-1

Tab.1. Artificial seawater composition

Fig.1. Schematic diagram of a pull⁃out specimen （dimension units： mm）

腐蚀环境	腐蚀温度/℃	腐蚀周期/d	F_max/kN	s_max/mm	τ_max/MPa
清水	10	3.65	130.05	30.65	20.70
		18.00	128.65	31.65	20.49
		36.5	126.60	29.73	20.16
	40	3.65	128.95	29.35	20.53
		18.00	121.75	31.18	19.39
		36.5	115.55	31.56	18.40
	60	3.65	126.40	33.13	20.13
		18.00	119.65	30.44	19.05
		36.5	108.15	29.53	17.22
海水	10	3.65	129.75	28.76	20.66
		18.00	127.95	31.47	20.37
		36.5	126.75	29.45	20.18
	40	3.65	125.45	27.16	19.98
		18.00	123.35	26.72	19.64
		36.5	112.65	28.84	17.94
	60	3.65	123.80	26.90	19.71
		18.00	116.75	28.17	18.59
		36.5	106.35	28.67	16.93

Tab.2. Bond test results of all the GFRP⁃seawater sea sand concrete specimens

Fig.2. Schematic diagram of the force on the specimen

破坏条件	破坏模式
f₁>τ_u &f₂<f_t	拔出破坏
f₁<τ_u &f₂>f_t	劈裂破坏
F>F_u	GFRP筋拉断破坏

Tab.3. Failure modes and conditions of all the specimens

Fig.3. Specimen failure form

Fig.4. Retention rate of bond strength of specimens at different temperature

Fig.5. Retention rate of bond strength of specimens at different conditions

Fig. 6. Degradation mechanism of GFRP bar⁃seawater⁃sea sand concrete bond performance

黏结滑移本构模型	黏结滑移模型表达式
BPE	$τ τ 1 = s s 1 α s ≤ s 1; τ = τ 1 s 1 ≤ s ≤ s 2; τ = τ 1 - τ 1 - τ 2 s 2 - s 3 s 2 - s s 2 ≤ s ≤ s 3; τ = τ 3 s > s 3$
mBPE	$τ τ 1 = s s 1 α s ≤ s 1; τ τ 1 = 1 - p s s 1 - 1 s 1 ≤ s ≤ s 3; τ = τ 3 s > s 3$
Malvar	$τ τ m = F (s / s m) + (G - 1) (s / s m) 2 1 + (F - 2) (s / s m) + G (s / s m) 2; τ f t = A + B 1 - e - C σ f t; s m = D + E σ$
CMR	$τ = τ m a x 1 - e - s s r β$

黏结滑移本构模型	黏结滑移模型表达式
BPE	$τ τ 1 = s s 1 α s ≤ s 1; τ = τ 1 s 1 ≤ s ≤ s 2; τ = τ 1 - τ 1 - τ 2 s 2 - s 3 s 2 - s s 2 ≤ s ≤ s 3; τ = τ 3 s > s 3$
mBPE	$τ τ 1 = s s 1 α s ≤ s 1; τ τ 1 = 1 - p s s 1 - 1 s 1 ≤ s ≤ s 3; τ = τ 3 s > s 3$
Malvar	$τ τ m = F (s / s m) + (G - 1) (s / s m) 2 1 + (F - 2) (s / s m) + G (s / s m) 2; τ f t = A + B 1 - e - C σ f t; s m = D + E σ$
CMR	$τ = τ m a x 1 - e - s s r β$

Tab.4. Common bond⁃slip constitutive model

Fig.7. 36.5 d fitting curve of clear water

Fig.8. 36.5 d fitting curve of seawater

Fig.9. Mean value of correlation coefficient

相关系数（R²）	总数	均值	标准差	方差	变异系数
BPE	18	0.983 9	0.011 9	1.417 8×10^-4	0.012 1
CMR	18	0.978 2	0.009 6	9.139 2×10^-5	0.009 8
Malvar	18	0.994 6	0.003 1	9.813 6×10^-6	0.003 2

Tab.5. Dispersion analysis of the correlation coefficient of the fitted curve

Fig.10. Bond strength retention ⁃ corrosion cycle double logarithmic fitting curves

环境温度/℃	清水环境		海水环境
环境温度/℃	40	60	40	60
达到80 %强度保留率所需时间/d	371	88	404	64
TSF（参考温度40 ℃）	1	4.216	1	6.312 5

Tab.6. Predicted service time of GFRP reinforcement⁃seawater marine sand concrete under different temperatures in clear water and seawater environment

Fig.11. Prediction of bond strength of GFRP reinforcement⁃seawater marine sand concrete under clear water and seawater environment

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