Analysis of Mechanical Performance of Precast Concrete Floor Slabs Containing Recycled Components

doi:10.12141/j.issn.1000-565X.250287

Abstract

Abstract:

The direct utilization of recycled components derived from meticulously demolished old concrete members in new structural elements holds significant potential for saving materials, reducing energy consumption, and lowering carbon emissions. However, the performance of such new members requires systematic investigation for quantitative understanding. As a preliminary exploration, this paper investigated the flexural performance of precast concrete floor slabs containing recycled components. Flexural experiments were conducted under both sagging and hogging moments. The influences of factors such as the surface treatment methods of recycled components and the strength difference between new and old concrete on the sagging moment flexural performance was examined. Furthermore, the effect of the configuration of locally added connecting reinforcement on the hogging moment fle-xural performance was studied. A calculation methods for the flexural capacity of these slabs was proposed. The results show that: (1) the sagging moment flexural capacity of the recycled-component slabs is significantly higher than that of monolithic cast reference slabs; (2) Different surface treatment methods for the recycled components generally had a limited impact on the sagging moment capacity; (3) the addition of local connecting reinforcement at the ends of the recycled components notably enhanced the hogging moment flexural capacity; for practical enginee-ring, the configuration using directly laid lapped reinforcement is recommended. The results of the proposed me-thods for calculating flexural bearing capacities are generally conservative.

Key words: concrete, recycled component, precast floor slab, flexural performance, bearing capacity

CLC Number:

TU375

LI Yan, WU Bo, ZHENG Shuya, WU Xiang. Analysis of Mechanical Performance of Precast Concrete Floor Slabs Containing Recycled Components[J]. Journal of South China University of Technology(Natural Science Edition), 2025, 53(12): 71-81.

Figures/Tables 22

Fig.1

Table 1

Fig.2

Fig.3

Fig.4

Table 2

Table 3

Compressive strengths of concrete"

混凝土		$f c u$ /MPa	$f c$ /MPa
C30商品混凝土		35.5	23.7
自制C30混凝土	第1批	39.8	26.6
	第2批	42.5	28.2
	第3批	40.2	26.8
自制C40混凝土		55.1	35.5

Table 3

Table 4

Mechanical properties of steel bars"

钢筋规格		$f y$ /MPa	$f u$ /MPa
C8	第1批	442.0	610.0
C8	第2批	440.0	620.1
C20		428.8	583.0

Table 4

Fig.5

Table 5

Fig.6

Fig.7

Fig.8

Table 6

Fig.9

Fig.10

Fig.11

Table 7

Fig.12

Fig.13

Table 8

Comparison between calculated and measured flexural bearing capacities of specimens"

试件编号	实测值/（kN $∙$ m）	计算值1/（kN $∙$ m）	计算值1/实测值	计算值2/（kN $∙$ m）	计算值2/实测值
MS	24.32	15.32	0.63	20.93	0.86
CS	42.36	27.07	0.64	36.55	0.86
TS	43.17	27.07	0.63	36.55	0.85
ES	43.35	27.07	0.62	36.55	0.84
HS	44.03	27.07	0.61	36.55	0.83
HS-300	43.35	27.07	0.62	36.55	0.84
HS-C40	45.02	27.45	0.61	37.26	0.83

Table 8

Table 9

References 15

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试验类型	试件编号	制作方式	再生部件处理方式	植筋配置	再生部件取代率	新/旧混凝土强度等级	新、旧纵筋连接构造
再生部件混凝土预制楼板正弯矩受弯试验	MS				0.00	C30/
	CS		上下表面凿毛+水泥界面剂		0.51	C30/C30
	TS		上下表面凿毛+横向开槽		0.51	C30/C30
	ES		上下表面凿毛+环氧树脂植筋	C10@200	0.51	C30/C30
	HS		上下表面凿毛+高强灌浆料植筋	C10@200	0.51	C30/C30
	HS-300		上下表面凿毛+高强灌浆料植筋	C10@300	0.51	C30/C30
	HS-C40		上下表面凿毛+高强灌浆料植筋	C10@200	0.51	C40/C30
再生部件混凝土预制楼板负弯矩受弯试验	MC	整浇			0.00	C30/
	PC1	预制装配	上下表面凿毛+高强灌浆料植筋	C10@200			无连接
	PC2				0.51	C30/C30	旧纵筋端部与新纵筋采用短钢筋棒焊接连接
	PC3						旧纵筋端部与新纵筋采用弯折钢筋焊接连接
	PC4						旧纵筋端部焊接加长钢筋，加长钢筋不与新纵筋连接
	PC5						旧板板面布设搭接钢筋，搭接钢筋不与新纵筋连接

新混凝土	水泥类别	质量/kg
新混凝土	水泥类别	水泥	水	砂	碎石	减水剂
C30	P.S.A 32.5	79	36	175	142	0.158
C40	P.O 42.5R	79	36	175	142	0.158

试件编号	开裂荷载	极限荷载
MC	15.4	26.9
PC1	15.1	26.2
PC2	14.6	26.2
PC3	15.1	35.4
PC4	15.3	38.0
PC5	15.5	41.3

试件编号	实测值	计算值
MC	23.50	15.27
PC1	23.03	15.27
PC2	23.03	15.27
PC3	29.24	27.60
PC4	30.99	27.04
PC5	33.22	27.82