Creep Behavior of Reinforced and Unreinforced Recycled Lump/Aggregate Concrete

doi:10.12141/j.issn.1000-565X.220046

Abstract

Abstract:

Compressive creep tests on thirty-seven recycled lump/aggregate concrete (RLAC) specimens were carried out to reveal the creep behavior of RLAC by taking the replacement ratio of demolished concrete lumps (DCLs), replacement ratio of recycled coarse aggregates (RCAs), replacement ratio of recycled sand rooted from alluvial-proluvial (A-P) soil, stress level and reinforcement ratio as parameters. The results show that the specific creep of reinforced/unreinforced RLAC is greater than that of reinforced/unreinforced recycled aggregate concrete (RAC). The increase rate of RLAC is 10.1% when unreinforced and the increase rate is 13.4% and 11.5% when the reinforcement ratio is 1.16% and 1.57%, respectively As the replacement ratio of RCAs in new concrete increased from 30% to 50%, the specific creep of reinforced/unreinforced RLAC increased by 7.4% and 11.4% respectively; when the fine aggregate (i.e., river sand) of new concrete is completely replaced by the recycled sand from A-P soil, the creep behavior of reinforced/unreinforced RLAC shows almost no change, but both of the shrinkage deformation decreased. As the reinforcement ratio increases from 1.16% to 1.57%, the specific creep of RLAC and RAC decrease by 5.0% and 6.6%, respectively. Reinforcement reduces the shrinkage deformation of RAC and RLAC, and the reduction grows with the increase of reinforcement ratio. As the replacement ratio of RCAs in new concrete increased from 30% to 50%, the elastic modulus of RLAC have little change and it is also almost free from the impact of replacing the fine aggregate (i.e., river sand) of new concrete with the recycled sand from A-P soil; and when the stress level is less than 0.4, the specific creep of RLAC is nearly deemed as irrelevant to the stress level.

Key words: demolished concrete lump, recycled coarse aggregate, recycled sand rooted from alluvial-proluvial soil, recycled lump/aggregate concrete, creep behavior

CLC Number:

TU528

WU Bo, CHEN Zhaonan, WANG Hui. Creep Behavior of Reinforced and Unreinforced Recycled Lump/Aggregate Concrete[J]. Journal of South China University of Technology(Natural Science Edition), 2022, 50(7): 35-42.

Figures/Tables 11

Table 1

Parameters of unreinforced specimens"

试件编号	D×H /（mm×mm）	f_cu，new/MPa	f_cu，old/MPa	$η D C L$ /%	f_{cy，250，CC}/MPa	$η R A$ /%	$η A P S$ /%	N_c/kN	N_L/kN	$n$	试件数量
L0A50S100N40	250×750	47.5		0	36.0	50	100	1 766	707	0.4	2
L100A0S0N40	150×300		35.4	100	36.0			500	200	0.4	2
L25A50S100N40	250×750	47.5	35.4	25	31.0	50	100	1 522	608	0.4	2
L25A50S100N30	250×750	47.5	35.4	25	31.0	50	100	1 522	456	0.3	2
L25A30S100N40	250×750	48.7	35.4	25	31.6	30	100	1 552	620	0.4	2
L25A50S0N40	250×750	46.9	35.4	25	30.7	50	0	1 508	603	0.4	2
L0A50S100N0	250×750	47.5		0	36.0	50	100		0	0.0	1
L100A0S0N0	150×300		35.4	100	36.0				0	0.0	1
L25A50S100N0	250×750	47.5	35.4	25	31.0	50	100		0	0.0	1
L25A30S100N0	250×750	48.7	35.4	25	31.6	30	100		0	0.0	1
L25A50S0N0	250×750	46.9	35.4	25	30.7	50	0		0	0.0	1

Table 1

Table 2

Parameters of reinforced specimens"

试件编号	D×H /（mm×mm）	$η D C L$ /%	$η R A$ /%	$η A P S$ /%	N_u/kN	N_L/kN	n	n_c	Ρ /%	试件数量
L0A50S100N40R1	250×750	0	50	100	2 048	819	0.4	0.44	1.16	2
L0A50S100N40R2	250×750	0	50	100	2 077	831	0.4	0.43	1.57	2
L25A50S100N40R1	250×750	25	50	100	1 806	722	0.4	0.44	1.16	2
L25A50S100N40R2	250×750	25	50	100	1 836	734	0.4	0.44	1.57	2
L25A50S100N30R2	250×750	25	50	100	1 836	551	0.3	0.33	1.57	2
L25A30S100N40R2	250×750	25	30	100	1 865	746	0.4	0.44	1.57	2
L25A50S0N40R2	250×750	25	50	0	1 821	728	0.4	0.44	1.57	2
L0A50S100N0R1	250×750	0	50	100	2 048	0	0.0	0.00	1.16	1
L0A50S100N0R2	250×750	0	50	100	2 077	0	0.0	0.00	1.57	1
L25A50S100N0R1	250×750	25	50	100	1 806	0	0.0	0.00	1.16	1
L25A50S100N0R2	250×750	25	50	100	1 836	0	0.0	0.00	1.57	1
L25A30S100N0R2	250×750	25	30	100	1 865	0	0.0	0.00	1.57	1
L25A50S0N0R2	250×750	25	50	0	1 821	0	0.0	0.00	1.57	1

Table 2

Table 3

Table 4

Fig.1

Fig.2

Fig.3

Table 5

Fig.4

Fig.5

Fig.6

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新混凝土	水灰比	水的用量/ （kg·m^-3）	水泥用量/ （kg·m^-3）	粗骨料用量/（kg·m^-3）		细骨料用量/（kg·m^-3）		减水剂用量 /（kg·m^-3）
新混凝土	水灰比	水的用量/ （kg·m^-3）	水泥用量/ （kg·m^-3）	再生	天然	河砂	再生砂	减水剂用量 /（kg·m^-3）
A50S100	0.5	215	430	570.4	570.4		614.3	0.301
A30S100	0.5	215	430	342.2	798.6		614.3	0.301
A50S0	0.5	215	430	570.4	570.4	614.3		0.301

钢筋直径/mm	屈服强度/MPa	极限强度/MPa
12	534	643
14	440	621
8	487	676

[1]	WU Bo, DING Jinpeng. Compressive and Chloride Resistance Properties of Recycled Aggregate Concrete Mixed with Hole Slag [J]. Journal of South China University of Technology(Natural Science Edition), 2023, 51(9): 120-128.
[2]	WU Bo, HUANG Tingting. Carbonation Properties and Pore Characteristics of Different Interfaces in Recycled Lump/Aggregate Concrete [J]. Journal of South China University of Technology(Natural Science Edition), 2023, 51(7): 52-60.
[3]	WU Bo YE Wenjie. Experimental Investigation into Axially Compressive Behavior of Circular Concrete-Filled Steel Tubular Columns with Built-in High-Strength Steel Tube [J]. Journal of South China University of Technology (Natural Science Edition), 2020, 48(4): 1-8.
[4]	WU Bo CHEN Yufei. Experimental Study on Punching Performance of Compound Concrete Slabs [J]. Journal of South China University of Technology (Natural Science Edition), 2019, 47(8): 1-8.
[5]	YANG You-fu HUANG Xiang-yu. Compressive Behavior of Rectangular Recycled Aggregate Concrete-Filled Steel-Tubular Stub Columns [J]. Journal of South China University of Technology (Natural Science Edition), 2017, 45(12): 121-127.