摘要
将机制砂自密实混凝土视为粗骨料加砂浆的固液两相悬浮体系,设计了4组基础砂浆来制备机制砂自密实混凝土,每组在1.5~2.9 mm范围内设置8种砂浆膜厚,研究了基础砂浆流变特性、强度及膜厚对机制砂自密实混凝土工作性能和力学性能的影响,建立了基于基础砂浆性能及膜厚的机制砂自密实混凝土性能预测公式.结果表明:为保证机制砂自密实混凝土的工作性能和力学性能,其优化砂浆膜厚范围为1.9~2.3 mm,对应的基础砂浆最大初始屈服剪切应力范围为51.9~65.2 Pa;预测公式拟合相关系数均达0.90以上,相关性显著.
自密实混凝土(SCC)是指无需人工振捣即可依靠自重完成模板填充的高流动性、高稳定性混凝土.因其具有施工速度快、人工依赖性小、工程质量高、噪音小等优势,并可适用于作业面狭窄和钢筋密集区域,故在现代建筑工程中得到了广泛应
自密实混凝土可以被认为是由粗骨料和砂浆构成的固液两相体
本文基于两相悬浮体系和膜厚理论,设计了不同基础砂浆流变特性、强度和砂浆膜厚的机制砂自密实混凝土,并对其工作性能(坍落扩展度、间隙通过性指标、离析率及T500)和力学性能(抗压强度及抗折强度)进行了测试,研究了基础砂浆流变特性、强度和砂浆膜厚对机制砂自密实混凝土工作性能与力学性能的影响规律,建立了基于基础砂浆流变特性、强度和砂浆膜厚的机制砂自密实混凝土性能预测公式,以期为机制砂自密实混凝土的设计和应用提供参考.
水泥(C)采用2种:一种为重庆小南海水泥厂生产的P·O 42.5R普通硅酸盐水泥,其表观密度为3 020 kg/
Sieve size/mm | Sieve residue(by mass)/% | Accumulative sieve residue(by mass)/% |
---|---|---|
19 | 0 | 0 |
16 | 5.4 | 5.4 |
9.5 | 61.2 | 66.6 |
4.75 | 30.9 | 97.5 |
2.36 | 2.5 | 100.0 |
分别采用编号为Ⅰ、Ⅱ、Ⅲ、Ⅳ的机制砂基础砂浆制备强度等级为C30、C40、C50、C80的机制砂自密实混凝土,其中Ⅰ、Ⅱ、Ⅲ组砂浆采用P·O 42.5R水泥,Ⅳ组砂浆采用P·O 52.5水泥.基础砂浆配合比如
Mortar | Water‑binder ratio | Sand volume fraction | w(FA)/% | w(SF)/% | w(WR)/% |
---|---|---|---|---|---|
Ⅰ | 0.40 | 0.44 | 30 | 0 | 1.2 |
Ⅱ | 0.32 | 0.44 | 30 | 0 | 1.5 |
Ⅲ | 0.26 | 0.44 | 30 | 0 | 2.0 |
Ⅳ | 0.22 | 0.42 | 30 | 2 | 3.0 |
Mortar | Initial yield shear stress/Pa | Plastic viscosity/(Pa·s) | Compressive strength(28 d)/MPa | Flexural strength(28 d)/MPa |
---|---|---|---|---|
Ⅰ | 51.35 | 3.98 | 43.68 | 8.88 |
Ⅱ | 46.31 | 7.57 | 58.61 | 10.16 |
Ⅲ | 21.94 | 20.89 | 65.52 | 11.89 |
Ⅳ | 40.19 | 22.87 | 84.16 | 13.01 |
机制砂自密实混凝土配合比见
Concrete | Tm/mm | Mix proportion/(kg∙ | ||||||
---|---|---|---|---|---|---|---|---|
CA | CS | C | FA | SF | W | WR | ||
C30 | 1.5 | 977 | 774 | 329 | 141 | 0 | 184 | 5 |
1.7 | 937 | 791 | 337 | 144 | 0 | 189 | 5 | |
1.9 | 899 | 807 | 344 | 147 | 0 | 192 | 5 | |
2.1 | 865 | 822 | 350 | 150 | 0 | 196 | 6 | |
2.3 | 833 | 836 | 356 | 153 | 0 | 199 | 6 | |
2.5 | 803 | 849 | 361 | 155 | 0 | 202 | 6 | |
2.7 | 775 | 861 | 366 | 157 | 0 | 205 | 6 | |
2.9 | 749 | 872 | 371 | 159 | 0 | 208 | 6 | |
C40 | 1.5 | 977 | 774 | 367 | 157 | 0 | 165 | 8 |
1.7 | 937 | 791 | 375 | 161 | 0 | 169 | 8 | |
1.9 | 899 | 807 | 383 | 164 | 0 | 172 | 8 | |
2.1 | 865 | 822 | 390 | 167 | 0 | 175 | 8 | |
2.3 | 833 | 836 | 396 | 170 | 0 | 178 | 9 | |
2.5 | 803 | 849 | 402 | 172 | 0 | 181 | 9 | |
2.7 | 775 | 861 | 408 | 175 | 0 | 184 | 9 | |
2.9 | 749 | 872 | 413 | 177 | 0 | 186 | 9 | |
C50 | 1.5 | 977 | 774 | 397 | 170 | 0 | 149 | 11 |
1.7 | 937 | 791 | 406 | 174 | 0 | 153 | 12 | |
1.9 | 899 | 807 | 414 | 177 | 0 | 156 | 12 | |
2.1 | 865 | 822 | 422 | 181 | 0 | 159 | 12 | |
2.3 | 833 | 836 | 429 | 184 | 0 | 161 | 12 | |
2.5 | 803 | 849 | 435 | 186 | 0 | 164 | 12 | |
2.7 | 775 | 861 | 441 | 189 | 0 | 166 | 13 | |
2.9 | 749 | 872 | 447 | 192 | 0 | 168 | 13 | |
C80 | 1.5 | 977 | 739 | 429 | 189 | 13 | 138 | 19 |
1.7 | 937 | 755 | 438 | 193 | 13 | 141 | 19 | |
1.9 | 899 | 771 | 447 | 197 | 13 | 144 | 20 | |
2.1 | 865 | 785 | 456 | 201 | 13 | 146 | 20 | |
2.3 | 833 | 798 | 463 | 204 | 14 | 149 | 20 | |
2.5 | 803 | 810 | 470 | 207 | 14 | 151 | 21 | |
2.7 | 775 | 821 | 477 | 210 | 14 | 153 | 21 | |
2.9 | 749 | 832 | 483 | 213 | 14 | 155 | 21 |

图1 两相悬浮体系及膜厚理论示意图
Fig.1 Sketch map of two‑phase suspension system and mortar film thickness theory
(1) |
式中:Ve、Vv、Vc分别为富余砂浆、空隙砂浆、粗骨料的体积分数,%;e为空隙比,即粗骨料自然堆积空隙体积与粗骨料实体体积(包括闭口孔隙)的比值,%;ρcpd、ρcad分别为粗骨料的堆积密度和表观密度,kg/
根据GB/T 17671—2021《水泥胶砂强度检验方法(ISO法)》,测试基础砂浆抗压强度和抗折强度,抗压试件尺寸为40 mm×40 mm×40 mm,抗折试件尺寸为40 mm×40 mm×160 mm.根据GB/T 50081—2019《混凝土物理力学性能试验方法标准》,测试机制砂自密实混凝土抗压、抗折强度,抗压试件尺寸为100 mm×100 mm×100 mm,抗折试件尺寸为100 mm×100 mm×400 mm.
采用Anton Paar MCR‑102型旋转流变仪对基础砂浆的流变特性进行测试,选取8 mm球形转子,剪切速率设定为1~100
(2) |
式中:τ为剪切应力,Pa;τ0为初始屈服剪切应力,Pa;η为塑性黏度,Pa·s;γ为剪切速率,

图2 不同砂浆制备的自密实混凝土的填充性随砂浆膜厚的变化规律
Fig.2 Plot of Tm vs. filling ability of SCC prepared by different mortars
如
上述结果表明:混凝土的流动性由砂浆膜厚和砂浆流变特性共同决定,砂浆膜厚影响粗骨料之间的润滑层厚度,而流变特性则影响着砂浆层的润滑效果.砂浆初始屈服剪切应力对于混凝土坍落扩展度的影响更为显著,而砂浆塑性黏度则与流动速率关系更为密切.自密实混凝土要求坍落扩展度不小于550 mm、T500不大于15 s,因此砂浆膜厚不宜小于1.9 mm.
间隙通过性指标反映了自密实混凝土遇到钢筋阻碍时的坍落扩展度损失,其数值越大则间隙通过性越差.不同砂浆制备的自密实混凝土的间隙通过性指标随砂浆膜厚的变化规律如

图3 不同砂浆制备的自密实混凝土的间隙通过性指标随砂浆膜厚的变化规律
Fig.3 Plot of Tm vs. passing ability of SCC prepared by different mortars
不同砂浆制备的自密实混凝土的离析率随砂浆膜厚的变化规律如

图4 不同砂浆制备的自密实混凝土的离析率随砂浆膜厚的变化规律
Fig.4 Plot of Tm vs. segregation rate of SCC prepared by different mortars
机制砂自密实混凝土力学性能如

图5 不同砂浆制备的自密实混凝土的强度随砂浆膜厚的变化规律
Fig.5 Plot of Tm vs. strength of SCC prepared by different mortars
由
基于机制砂自密实混凝土的基础砂浆初始屈服剪切应力、砂浆膜厚以及坍落扩展度,绘制三维散点图,如

图6 机制砂自密实混凝土坍落扩展度拟合曲面
Fig.6 Slump flow fitting curved surface of SCC incorporated with crushed sand
(3) |
式中:ρ为基础砂浆密度,kg/
机制砂自密实混凝土坍落扩展度等高线图如

图7 机制砂自密实混凝土坍落扩展度等高线图
Fig.7 Slump flow contour map of SCC incorporated with crushed sand

图8 满足自密实混凝土要求的砂浆膜厚及初始屈服剪切应力范围
Fig.8 Range of Tm and τ0 that meets the SCC requirement
基于基础砂浆强度、膜厚以及机制砂自密实混凝土的抗压、抗折强度测试结果,绘制三维散点图,如
(4) |
(5) |

图9 机制砂自密实混凝土强度拟合曲面
Fig.9 Strength fitting curved surface of SCC incorporated with crushed sand
机制砂自密实混凝土强度等高线图如

图10 机制砂自密实混凝土强度等高线图
Fig.10 Strength contour map of SCC incorporated with crushed sand
(1)机制砂自密实混凝土的填充性、离析率与基础砂浆膜厚呈正相关,与基础砂浆初始屈服剪切应力呈负相关;间隙通过性指标随基础砂浆初始屈服剪切应力降低而提高.机制砂自密实混凝土强度与基础砂浆强度之间具有显著的正相关性,随砂浆膜厚增加而先增大后减小.建议对机制砂自密实混凝土进行两相悬浮体系设计时,宜控制砂浆膜厚为1.9~2.3 mm,基础砂浆最大初始屈服剪切应力为51.9~65.2 Pa.
(2)机制砂自密实混凝土的坍落扩展度与基础砂浆初始屈服剪切应力及膜厚的关系密切,可以通过拟合公式来进行预测.
(3)机制砂自密实混凝土的抗压、抗折强度与基础砂浆的抗压、抗折强度及膜厚密切相关,可分别通过拟合公式来进行预测.
(4)在两相悬浮体系假定下,基础砂浆流变特性及膜厚从本质上影响着机制砂自密实混凝土的性能.理论上,粗骨料的理化特性产生的吸附效应是有限的,当砂浆膜厚达到一定厚度时,其对砂浆性能影响有限,而对混凝土的影响基本可以忽略;粗骨料的级配影响砂浆总体积,但并不直接影响砂浆性能及膜厚,因此本文预测公式具有普适性.后续相关研究仍将持续,以进一步验证和优化该设计方法.
参考文献
NAIK T R, KUMAR R, RAMME B W, et al. Development of high‑strength, economical self‑consolidating concrete[J]. Construction and Building Materials, 2012, 30:463‑469. [百度学术]
SHI C J, WU Z M, LÜ K X, et al. A review on mixture design methods for self‑compacting concrete[J]. Construction and Building Materials, 2015, 84:387‑398. [百度学术]
DEVI K, AGGARWAL P, SAINI B. Admixtures used in self‑compacting concrete:A review[J]. Iranian Journal of Science and Technology, Transactions of Civil Engineering, 2019, 44(2):377‑403. [百度学术]
CHEN X, GUO Y G, LI B, et al. Coupled effects of the content and methylene blue value(MBV) of microfines on the performance of manufactured sand concrete[J]. Construction and Building Materials, 2020, 240:117953. [百度学术]
HE X B, GAO J, LIU Y X, et al. Gradation optimization of continuous‑graded crushed sand based on mortar performance[J]. Construction and Building Materials, 2022, 358:129423. [百度学术]
HAN Z, ZHANG Y S, ZHANG W H, et al. Study on comprehensive morphological parameters of manufactured sand based on CT scanning and entropy method and its application in rheology of manufactured sand mortar[J]. Construction and Building Materials, 2023, 370:130628. [百度学术]
汤明, 杨松, 郭加付, 等. 考虑石粉对流变性影响的自密实混凝土配合比设计[J]. 建筑材料学报, 2022, 25(2):191‑198. [百度学术]
TANG Min, YANG Song, GUO Jiafu, et al. Mix design of self‑compacting concrete considering the effect of limestone powder on rheology[J]. Journal of Building Materials, 2022, 25(2):191‑198. (in Chinese) [百度学术]
王振, 李化建, 黄法礼, 等. 石灰岩机制砂混凝土抗冻性能研究[J]. 建筑材料学报, 2023, 26(5):516‑523, 537. [百度学术]
WANG Zhen, LI Huajian, HUANG Fali, et al. Frost resistance of limestone manufactured sand concrete[J]. Journal of Building Materials, 2023, 26(5):516‑523, 537. (in Chinese) [百度学术]
KABAGIRE K D, YAHIA A, CHEKIRED M. Toward the prediction of rheological properties of self‑consolidating concrete as diphasic material[J]. Construction and Building Materials, 2019, 195:600‑612. [百度学术]
SAAK A W, JENNINGS H M, SHAH S P. New methodology for designing self‑compacting concrete[J]. ACI Materials Journal, 2001, 98(6):429‑439. [百度学术]
何小兵, 沈武福, 贾秋炳, 等. 砂浆流变特性及其膜厚对自密实混凝土性能的影响[J]. 东南大学学报(自然科学版), 2020, 50(3):463‑470. [百度学术]
HE Xiaobing, SHEN Wufu, JIA Qiubing, et al. Effects of mortar rheological characteristics and film thickness on self‑compacting concrete[J]. Journal of Southeast University(Natural Science Edition), 2020,50(3):463‑470. (in Chinese) [百度学术]
LI J J, CHEN Y H, WAN C J. A mix‑design method for lightweight aggregate self‑compacting concrete based on packing and mortar film thickness theories[J]. Construction and Building Materials, 2017, 157:621‑634. [百度学术]
KWAN A K H, LI L G. Combined effects of water film, paste film and mortar film thicknesses on fresh properties of concrete[J]. Construction and Building Materials, 2014, 50:598‑608. [百度学术]
何小兵, 刘树鑫, 刘亚, 等. 微细钢纤维自密实混凝土二次配合比设计新方法[J]. 建筑材料学报, 2020, 23(1):56‑63. [百度学术]
HE Xiaobing, LIU Shuxin, LIU Ya, et al. A new two‑step mix proportion design of micro‑steel fiber reinforced self‑compacting concrete[J]. Journal of Building Materials, 2020, 23(1):56‑63. (in Chinese) [百度学术]
MURATA J, KUKAWA H. Viscosity equation for fresh concrete[J]. ACI Materials Journal, 1992, 89(3):230‑237. [百度学术]
胡小芳, 苏志学. 改进式坍落度筒法测定新拌混凝土流变性能[J]. 混凝土, 2006(8):64‑69. [百度学术]
HU Xiaofang, SU Zhixue. The method of modified slump cone measuring fluidity of fresh concrete[J]. Concrete, 2006(8):64‑69. (in Chinese) [百度学术]
SEDRAN T, DELARRARD F. Optimization of SCC thanks to packing model[C]//Proceedings of 1st International RILEM Symposium on Self‑compacting Concrete. Paris:RILEM Publication SARL, 1999, 7:321‑332. [百度学术]
NIELSSON I, WALLEVIK O H. Rheological evaluation of some empirical test methods—Preliminary results[C]//Third International RILEM Symposium. Reykjavik:RILEM Publication SARL, 2003, 33:59‑68. [百度学术]
JIAO D W, SHI C J, YUAN Q, et al. Effect of constituents on rheological properties of fresh concrete—A review[J]. Cement and Concrete Composites, 2017, 83:146‑159. [百度学术]
SUA‑IAM G, MAKUL N. Effect of incinerated sugarcane filter cake on the properties of self‑compacting concrete[J]. Construction and Building Materials, 2017, 130:32‑40. [百度学术]
谢越韬, 王易阳, 周虎. 自密实混凝土间隙通过性试验研究[J]. 新型建筑材料, 2017, 44(12):27‑31. [百度学术]
XIE Yuetao, WANG Yiyang, ZHOU Hu. Experimental study on the passing ability of self‑compacting concrete(SCC)[J]. New Building Materials, 2017, 44(12):27‑31. (in Chinese) [百度学术]
EL‑CHABIB H, NEHDI M. Effect of mixture design parameters on segregation of self‑consolidating concrete[J]. ACI Materials Journal, 2006, 103(5):374‑383. [百度学术]
ESMAEILKHANIAN B, KHAYAT K H, YAHIA A, et al. Effects of mix design parameters and rheological properties on dynamic stability of self‑consolidating concrete[J]. Cement and Concrete Composites, 2014, 54:21‑28. [百度学术]