摘要
考虑贝壳含量、龄期等因素,对不同加载应变率下的海水海砂再生混凝土(SSRAC)试件开展了单轴受压应力-应变曲线试验.结果表明:600 d时,与普通混凝土(NAC)相比,SSRAC峰值应力和峰值应变分别提高了10.4%、23.2%,弹性模量降低了29.1%;当掺入贝壳颗粒后,SSRAC应变率敏感性增加;结合试验以及文献数据,基于GB50010模型,考虑不同应变率下特征参数的动态增大系数,提出了适用于中低应变率(1
海水海砂混凝土(SSC)的研究缓解了河砂资源短缺问
在准静态受压下,SSC与普通混凝土(NAC)的应力-应变曲线相似,而SSC峰值应力和弹性模量更
本文在文献[
水泥采用42.5强度等级普通硅酸盐水泥;骨料采用河砂、海砂、天然粗骨料(NCA)及再生粗骨料(RCA),其材料性能见
Aggregate | Apparent density/(kg· | Fineness modulus | w(C | w(shell)/% | w(SO3)/% | Water content(by mass)/% | Water absorption(by mass)/% | Crush index |
---|---|---|---|---|---|---|---|---|
River sand | 2 610 | 2.1 | 0.001 | 1.100 | 0.109 | |||
Sea sand | 2 660 | 2.7 | 0.057 | 2.310 | 0.123 | |||
NCA | 2 660 | 1.0 | 5.1 | |||||
RCA | 2 553 | 3.5 | 6.9 | 14.3 |
Reference | Concrete | Fresh water | Sea water | Cement | River sand | Sea sand | Shell | NCA | RCA | Water reducer |
---|---|---|---|---|---|---|---|---|---|---|
This paper | NAC | 150.00 | 0 | 319.00 | 829.00 | 0 | 0 | 1 099.00 | 0 | 4.79 |
This paper | RAC | 187.37 | 0 | 319.00 | 829.00 | 0 | 0 | 0 | 1 099.00 | 4.79 |
This paper | SSRAC | 0 | 187.37 | 319.00 | 0 | 829.00 | 0 | 0 | 1 099.00 | 4.79 |
This paper | H‑SSRAC | 0 | 187.37 | 319.00 | 0 | 663.20 | 165.80 | 0 | 1 099.00 | 4.79 |
Ref.[15‑16] | SSRAC | 0 | 180.00 | 319.00 | 0 | 829.00 | 0 | 0 | 1 099.00 | 0 |
Ref.[15‑16] | H‑SSRAC | 0 | 180.00 | 319.00 | 0 | 663.20 | 165.80 | 0 | 1 099.00 | 0 |
Ref.[ | SSRAC | 0 | 210.74 | 329.82 | 0 | 727.00 | 0 | 0 | 1 137.00 | 0 |
应力-应变曲线特征参数包括峰值应力、峰值应变、极限应变及弹性模量[
Specimen | Strain rate/ | Peak stress | Elastic modulus | Peak strain | Ultimate strain | ||||
---|---|---|---|---|---|---|---|---|---|
/MPa | COV | Ec/GPa | COV | ×1 | COV | ×1 | COV | ||
SSRAC‑1‑120 d |
1 | 42.86 | 0.087 | 27.54 | 0.265 | 2.732 | 0.152 | 3.417 | 0.079 |
SSRAC‑2‑120 d |
1 | 42.55 | 0.238 | 23.46 | 0.464 | 2.796 | 0.111 | 3.458 | 0.171 |
SSRAC‑3‑120 d |
1 | 37.36 | 0.169 | 19.18 | 0.189 | 2.478 | 0.092 | 3.382 | 0.063 |
SSRAC‑4‑120 d |
1 | 34.72 | 0.211 | 18.83 | 0.304 | 2.534 | 0.058 | 3.353 | 0.115 |
SSRAC‑5‑120 d |
1 | 34.84 | 0.145 | 14.88 | 0.277 | 2.933 | 0.134 | 4.153 | 0.083 |
NAC‑5‑600 d |
1 | 33.44 | 0.068 | 28.20 | 0.231 | 2.433 | 0.186 | 3.500 | 0.149 |
SSRAC‑5‑600 d |
1 | 36.91 | 0.078 | 19.99 | 0.145 | 2.998 | 0.093 | 4.077 | 0.121 |
H‑SSRAC‑1‑120 d |
1 | 45.88 | 0.031 | 28.41 | 0.177 | 2.642 | 0.027 | 3.071 | 0.023 |
H‑SSRAC‑2‑120 d |
1 | 43.15 | 0.122 | 24.16 | 0.535 | 2.712 | 0.070 | 3.419 | 0.093 |
H‑SSRAC‑3‑120 d |
1 | 38.31 | 0.117 | 16.84 | 0.195 | 2.480 | 0.096 | 3.139 | 0.036 |
H‑SSRAC‑4‑120 d |
1 | 36.51 | 0.030 | 17.25 | 0.304 | 2.583 | 0.100 | 3.190 | 0.068 |
H‑SSRAC‑5‑120 d |
1 | 33.87 | 0.089 | 12.99 | 0.095 | 3.181 | 0.048 | 3.974 | 0.049 |
由
总结本文及文献[

图1 不同混凝土特征参数之间的比值
Fig.1 Ratios of characteristic parameters between different concretes
由
不同应变率下的曲线特征参数采用动态增大系数(D)来描述,D指以准静态下特征参数作为基准值时各应变率下特征参数与该基准值的比值.对本文以及文献[

图2 不同混凝土特征参数的动态增大系数
Fig.2 Dynamic increase factor of characteristic points of different concretes
在准静态(1

图3 试件SSRAC‑5‑120 d和SSRAC‑5‑600 d的归一化应力-应变曲线模型
Fig.3 Normalized stress‑strain curve models for SSRAC‑5‑120 d and SSRAC‑5‑600 d specimens
结合试验和文献数
SSRAC强度按下式计算.
(1) |
式中:fc为轴心抗压强度;fcu为立方体抗压强度;系数k可取0.788
汇总文献[
(2) |
式中:t为龄期;αn为强度调整系数.
不同龄期下SSRAC和RAC的强度调整系数如
Concrete | 7 d | 90 d | 180 d | |||
---|---|---|---|---|---|---|
αn | COV | αn | COV | αn | COV | |
SSRAC | 1.42 | 0.12 | 0.83 | 0.10 | 0.76 | 0.15 |
RAC | 0.86 | 0.24 | 0.93 | 0.11 | 0.78 | 0.14 |
对于NAC,其弹性模量与立方体抗压强度标准值(fcu,k)之间有如下关系
(3) |
式中:p、q为拟合参数.
考虑轴心抗压强度和立方体抗压强度的线性关系,以峰值应力σcp替代fcu,k,代入

图4 峰值应力和弹性模量的拟合曲线
Fig.4 Fitted curve of peak stress versus elastic modulus
NAC的峰值应力和峰值应变之间关系如

图5 峰值应力和峰值应变的拟合曲线
Fig.5 Fitted curve of peak stress versus peak strain
(4) |
式中:m、n为拟合参数.
由
GB50010模型中压力-应变曲线下降段的形状参数αc和峰值应力之间的关系如

图6 峰值应力和形状参数的拟合曲线
Fig.6 Fitted curve of peak stress versus αc
(5) |
式中:u、v为拟合参数.
由
Fitting parameter | NA | SSRAC | RA | ||
---|---|---|---|---|---|
p | 2.200 0 | 0.982 8 | 0.971 8 | 2.634 0 | 0.321 0 |
q | 34.700 0 | 100.191 5 | 42.186 2 | ||
m | 0.172 0 | 0.325 7 | 0.906 2 | 0.184 2 | 0.196 4 |
n | 0.700 0 | 0.034 5 | 1.031 5 | ||
u | 0.157 0 | 0.225 1 | 0.115 8 | 0.151 1 | 0.129 8 |
v | 0.905 0 | 2.081 9 | -0.181 8 |
采用GB50010模型计算各应变率下的形状参数,峰值应力直接采用
Strain rate/ | αc of SSRAC | αc of H‑SSRAC | ||||
---|---|---|---|---|---|---|
Calculated | Fitted | Calculated | Fitted | |||
1 | 3.51 | 5.95 | 0.982 2 | 7.78 | 7.23 | 0.929 3 |
1 | 3.89 | 2.84 | 0.986 8 | 3.27 | 3.72 | 0.983 2 |
1 | 1.81 | 2.45 | 0.990 6 | 3.16 | 2.32 | 0.997 8 |
1 | 2.24 | 2.34 | 0.988 5 | 3.95 | 3.19 | 0.995 0 |
1 | 1.44 | 2.60 | 0.998 8 | 3.55 | 3.02 | 0.991 7 |
将采用2种方式获取的形状参数代入GB50010模型,得出不同应变率下SSRAC和H‑SSRAC的预测应力-应变曲线,如

图7 不同应变率下SSRAC和H‑SSRAC的预测应力-应变曲线
Fig.7 Predicted stress‑strain curves of SSRAC and H‑SSRAC at different strain rates
CEB‑FIP规
(6) |
(7) |
式中:为应变率;为基准应变率,取1
动态增大系数计算参数a见
Dynamic increase factor | SSRAC | H‑SSRAC | ||
---|---|---|---|---|
a | a | |||
0.061 5 | 0.999 0 | 0.083 3 | 0.999 6 | |
0.187 0 | 0.996 6 | 0.207 9 | 0.977 5 | |
-0.020 9 | 0.995 4 | -0.019 0 | 0.984 4 | |
1.282 8 | 1.389 9 |
由

图8 应力-应变曲线模型平均值曲线
Fig.8 Mean value curves modified by stress‑strain model
RAC内部存在新界面过渡区(新砂浆与老砂浆之间)和老界面过渡区(原始天然粗骨料与老砂浆之间),这是导致RAC力学性能劣化的关键因素之

图9 RAC和SSRAC的微观形貌
Fig.9 Microstructure of RAC and SSRAC
基于

图10 各应变率下应力-应变曲线模型平均值曲线
Fig.10 Mean value curves modified by stress‑strain model with different strain rates
李龙
(1)加载应变率为1
(2)随着应变率的增加,SSRAC峰值应力和弹性模量的动态增大系数明显增大,而峰值应变和极限应变的动态增大系数变化规律不明显.与再生混凝土(RAC)相比,SSRAC弹性模量的动态增大系数有较大提升,且随贝壳含量增加,高贝壳含量的海水海砂再生混凝土(H‑SSRAC)特征参数的动态增大系数相对于SSRAC有一定程度的提升.
(3)通过修正,GB50010模型可描述准静态下SSRAC受压应力-应变曲线;其特征参数的动态增大系数与加载应变率线性相关;下降段形状参数在1
(4)海水海砂的加入能够提升RAC的力学性能;在中、低应变率下,影响SSRAC应变率敏感性的主要因素为新砂浆,当贝壳颗粒含量增加时,新砂浆强度降低,因此SSRAC峰值应力和弹性模量的应变率敏感性增加;后续研究需建立贝壳颗粒含量对模型参数的影响.同时,可掺入再生细骨料,进而探究海水海砂对其力学性能及应变率敏感性的影响.
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