摘要
碱矿渣再生混凝土是以碱激发胶凝材料替代水泥、再生骨料取代天然石子制备而成的新型混凝土,能有效降低波特兰水泥用量,提高废弃混凝土利用率,但尚未见对其力学性能的相关研究。为研究碱矿渣再生混凝土的基本力学性能,以钢纤维取代率和再生骨料取代率为主要试验参数,进行抗压试验、劈裂抗拉试验和抗折试验。研究结果表明:随着再生粗骨料取代率的增加,碱矿渣再生混凝土的抗压强度fcu、劈裂抗拉强度ft和抗折强度fw均降低,再生粗骨料取代率为100%时的降低幅度分别为30%、10%、15%;碱矿渣再生混凝土抗压强度和劈裂抗拉强度随钢纤维体积取代率增加先提高后降低,钢纤维体积取代率为0.6%时,抗压强度和抗折强度达到最大值;碱矿渣再生混凝土抗折强度随钢纤维体积取代率增加而增加。
水泥生产消耗大量的化石燃料,排放大量的二氧化碳,据统计,水泥生产碳排放量约占全球碳排放总量的7%,因此,寻找可替代水泥的建筑材料具有极大的工程应用价
与普通混凝土相比,AASC具有凝结速度快、早期强度高、热稳定强、耐火性能
AAS-RAC具有AASC和RAC优势的同时,也存在脆性较大和强度较低的问题。笔者通过掺入钢纤维来改善AAS-RAC的力学性能,制备了8组共72个不同配比的AAS-RAC试件,研究再生骨料取代率和钢纤维体积取代率对AAS-RAC立方体抗压强度fcu、劈裂抗拉强度ft和抗折强度fw的影响。
粒化高炉矿渣的比表面积和比重分别为440
CaO | SiO2 | Al2O3 | MgO | Fe2O3 | 其他 |
---|---|---|---|---|---|
41 | 34 | 13 | 7 | 1 | 4 |

图1 粒度分布图
Fig. 1 Particle size distribution diagram
碱激发剂由液态硅酸钠、固体氢氧化钠组成,激发剂中SiO2和Na2O的摩尔比为1.7,碱激发剂中含水量为56%。固体NaOH的纯度为96%。试验选取钢纤维以用来改善碱矿渣再生骨料混凝土的力学性能。钢纤维由苏州史尉康金属制品有限公司提供,纤维的详细力学性能如
密度/(kg/ | 长度/mm | 直径/μm | 抗拉强度/MPa | 弹性模量/GPa |
---|---|---|---|---|
7 800 | 12 | 210 | 2 969 | 200.0 |
制作8种不同配比的碱矿渣再生混凝土试件。试件设计考虑了钢纤维体积取代率(0、0.3%、0.6%、0.9 %)和再生骨料取代率(0、25%、50%、75%、100%)的影响。具体试件设计及配合比如
试件 | Vsf/% | VRAC/% | MNA/(kg/ | Msf/(kg/ | MRCA/(kg/ | 矿渣/(kg/ | Na2SiO3/(kg/ | NaOH/(kg/ | 水/(kg/ | 砂/(kg/ |
---|---|---|---|---|---|---|---|---|---|---|
N/0/0 | 0 | 0 | 1 334 | 0 | 0 | 625 | 164 | 27.8 | 152 | 833 |
N/0/25 | 0 | 25 | 990 | 0 | 330 | 625 | 164 | 27.8 | 152 | 833 |
N/0/50 | 0 | 50 | 660 | 0 | 660 | 625 | 164 | 27.8 | 152 | 833 |
N/0/75 | 0 | 75 | 330 | 0 | 990 | 625 | 164 | 27.8 | 152 | 833 |
N/0/100 | 0 | 100 | 0 | 0 | 1 320 | 625 | 164 | 27.8 | 152 | 833 |
S/0.3/100 | 0.3 | 100 | 0 | 23.4 | 1 320 | 625 | 164 | 27.8 | 152 | 833 |
S/0.6/100 | 0.6 | 100 | 0 | 46.8 | 1 320 | 625 | 164 | 27.8 | 152 | 833 |
S/0.9/100 | 0.9 | 100 | 0 | 70.2 | 1 320 | 625 | 164 | 27.8 | 152 | 833 |
注: Vsf为混凝土钢纤维体积分数;VRAC为再生骨料体积分数(VRAC/(VRAC+VNA));MNA为每立方米混凝土的天然粗骨料质量;Msf为每立方米混凝土的钢纤维质量;MRAC为每立方米混凝土再生骨料质量。
AAS-RAC试件制备时,首先将再生骨料与部分水混合,进行预湿处理;其次将液态Na2SiO3、固态NaOH和水按比例均匀混合;再次将预湿后再生骨料、矿粉、砂置于搅拌机中均匀搅拌60 s;随后加入碱性激发剂,并均匀搅拌60 s;最后将混合物置于试模内,放在振动台上振动30 s。为防止试件中的水分蒸发影响试件性能,将试件用塑料薄膜完全密封,放于温度(20±2)℃、相对湿度(90±2)%的养护室,直至试验开始。
再生骨料取代率对AAS-RAC立方体抗压强度的影响如

图2 再生骨料取代率对AAS-RAC立方体抗压强度的影响
Fig. 2 Influence of recycled aggregate content substitution rate on compressive strength of AAS-RAC
试验研究表明,钢纤维的掺入可有效增加AAS-RAC立方体抗压强度。为研究钢纤维体积取代率对AAS-RAC立方体抗压强度的影响,将不同钢纤维体积取代率试件立方体抗压强度列于

图3 钢纤维体积取代率对AAS-RAC立方体抗压强度的影响
Fig. 3 Influence of steel fiber volume substitution rate on compressive strength of AAS-RAC
再生骨料取代率对AAS-RAC劈裂抗拉强度的影响如

图4 再生骨料取代率对AAS-RAC劈裂抗拉强度的影响
Fig. 4 Influence of recycled aggregate content substitution rate on splitting tensile strength of AAS-RAC
钢纤维体积取代率对AAS-RAC劈裂抗拉强度的影响如

图5 钢纤维体积取代率对AAS-RAC劈裂抗拉强度的影响
Fig. 5 Influence of steel fiber volume substitution rate on splitting tensile strength of AAS-RAC
再生骨料取代率对AAS-RAC抗折强度的影响如

图6 再生骨料取代率对AAS-RAC抗折强度的影响
Fig. 6 Influence of recycled aggregate content substitution rate on flexural strength of AAS-RAC
钢纤维体积取代率对AAS-RAC抗折强度的影响如

图7 钢纤维体积取代率对AAS-RAC抗折强度的影响
Fig. 7 Influence of steel fiber volume substitution rate on flexural strength of AAS-RAC
再生骨料取代率对AAS-RAC基本力学性能的影响如

图8 再生骨料取代率对AAS-RAC力学性能的影响
Fig. 8 Influence of recycled aggregate content substitution rate on mechanical properties of AAS-RAC
钢纤维体积取代率对AAS-RAC基本力学性能的影响如

图9 钢纤维体积取代率对AAS-RAC力学性能的影响
Fig. 9 Influence of steel fiber volume substitution rate on mechanical properties of AAS-RAC
研究了碱矿渣再生粗骨料混凝土抗压性能、劈裂抗拉性能和抗折性能,考虑了再生粗骨料取代率和钢纤维体积取代率对其力学性能影响,主要结论如下:
1)AAS-RAC抗压强度fcu、劈裂抗拉强度ft和抗折强度fw均随再生粗骨料取代率增加而降低。这是由于再生粗骨料内部存在原始界面过渡区,表面存在大量微裂缝,这使得再生粗骨料力学性能较弱,进而降低了AAS-RAC力学性能。
2)适量钢纤维会提高AAS-RAC抗压强度fcu和劈裂抗拉强度ft,但过量钢纤维反而会降低AAS-RAC的fcu和ft。这是由于适量钢纤维可桥接于荷载作用下产生的微裂缝两侧,进而抑制了微裂缝发展及延伸,提高了AAS-RAC强度。过量钢纤维易在混凝土材料内部产生团簇效应,进而降低了AAS-RAC强度。
3)与钢纤维对AAS-RAC抗压强度fcu和劈裂抗拉强度ft影响不同,钢纤维体积取代率小于0.9%时,AAS-RAC抗折强度fw随钢纤维体积取代率的增加而提高。这是由于AAS-RAC抗折破坏为试件受拉区混凝土受拉失效破坏,发展较为迅速,而受拉区钢纤维桥接于裂缝两侧,抑制受拉区裂缝开展,同时可替代受拉区开裂混凝土承受部分拉应力,进而提高了AAS-RAC的抗折强度fw。
4)再生粗骨料取代率对AAS-RAC的抗压强度fcu的影响最为显著,而对劈裂抗拉强度ft的影响最弱。钢纤维体积取代率对AAS-RAC抗压强度fcu的影响最为显著,其次为劈裂抗拉强度ft,而对抗折强度fw影响最弱。
参考文献
FLOWER D J M, SANJAYAN J G. Green house gas emissions due to concrete manufacture [J]. The International Journal of Life Cycle Assessment, 2007, 12(5): 282-288. [百度学术]
VISHWAKARMA V, RAMACHANDRAN D. Green Concrete mix using solid waste and nanoparticles as alternatives-A review [J]. Construction and Building Materials, 2018, 162: 96-103. [百度学术]
MALHOTRA V M. Introduction: Sustainable development and concrete technology [J]. Concrete International, 2002, 24(7): 22. [百度学术]
PROVIS J L, VAN DEVENTER J S J. Alkali activated materials [M]. Dordrecht: Springer Netherlands, 2014. [百度学术]
DAS S, SAHA P, JENA S P, et al. Geopolymer concrete: Sustainable green concrete for reduced greenhouse gas emission-A review [J]. Materials Today: Proceedings, 2022, 60: 62-71. [百度学术]
AMER I, SAHA P, JENA S P, et al. A review on alkali-activated slag concrete [J]. Ain Shams Engineering Journal, 2021, 12(2): 1475-1499. [百度学术]
PROVIS J L. Alkali-activated materials [J]. Cement and Concrete Research, 2018, 114: 40-48. [百度学术]
SANDANAYAKE M, GUNASEKARA C, LAW D, et al. Greenhouse gas emissions of different fly ash based geopolymer concretes in building construction [J]. Journal of Cleaner Production, 2018, 204: 399-408. [百度学术]
SILVA R V, DE BRITO J, DHIR R K. Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production [J]. Construction and Building Materials, 2014, 65(1): 201-217. [百度学术]
EGUCHI K, TERANISHI K, NAKAGOMEA, et al. Application of recycled coarse aggregate by mixture to concrete construction [J]. Construction and Building Materials, 2007, 21(7): 1542-1551. [百度学术]
HOSAN A, HAQUE S, SHAIKH F. Compressive behaviour of sodium and potassium activators synthetized fly ash geopolymer at elevated temperatures: A comparative study [J]. Journal of Building Engineering, 2016, 8: 123-130. [百度学术]
MONTICELLI C, NATALI M E, BALBO A, et al. Corrosion behavior of steel in alkali-activated fly ash mortars in the light of their microstructural, mechanical and chemical characterization [J]. Cement and Concrete Research, 2016, 80: 60-68. [百度学术]
BABAEE M. Chloride-induced corrosion of reinforcement in low-calcium fly ash-based geopolymer concrete [J]. Cement and Concrete Research, 2016, 88: 96-107. [百度学术]
FERNANDEZ-JIMENEZ A, GARCÍA-LODEIRO I, PALOMO A. Durability of alkali-activated fly ash cementitious materials [J]. Journal of Materials Science, 2007, 42(9): 3055-3065. [百度学术]
LASKAR S M, TALUKDAR S. Development of ultrafine slag-based geopolymer mortar for use as repairing mortar [J]. Journal of Materials in Civil Engineering, 2017, 29(5): 04016292. [百度学术]
ATIŞ C D, GÖRÜR E B, KARAHAN O, et al. Very high strength (120 MPa) class F fly ash geopolymer mortar activated at different NaOH amount, heat curing temperature and heat curing duration [J]. Construction and Building Materials, 2015, 96: 673-678. [百度学术]
PAN Z, SANJAYAN J G. Stress-strain behaviour and abrupt loss of stiffness of geopolymer at elevated temperatures [J]. Cement and Concrete Composites, 2010, 32(9): 657-664. [百度学术]
PALOMO A, BLANCO-VARELA M T, GRANIZO M L, et al. Chemical stability of cementitious materials based on metakaolin [J]. Cement and Concrete Research, 1999, 29(7): 997-1004. [百度学术]
COLLINS F, SANJAYAN J G. Effect of pore size distribution on drying shrinking of alkali-activated slag concrete [J]. Cement and Concrete Research, 2000, 30(9): 1401-1406. [百度学术]
DURAN ATIŞ C, BILIM C, ÇELIK Ö, et al. Influence of activator on the strength and drying shrinkage of alkali-activated slag mortar [J]. Construction and Building Materials, 2009, 23(1): 548-555. [百度学术]
THOMAS J J, ALLEN A J, JENNINGS H M. Density and water content of nanoscale solid C-S-H formed in alkali-activated slag (AAS) paste and implications for chemical shrinkage [J]. Cement and Concrete Research, 2012, 42(2): 377-383. [百度学术]
COLLINS F, SANJAYAN J G. Microcracking and strength development of alkali activated slag concrete [J]. Cement and Concrete Composites, 2001, 23(4/5): 345-352. [百度学术]
RANJBAR N, ZHANG M. Fiber-reinforced geopolymer composites: A review [J]. Cement and Concrete Composites, 2020, 107: 103498. [百度学术]
ALOMAYRI T, SHAIKH F U A, LOW I M. Synthesis and mechanical properties of cotton fabric reinforced geopolymer composites [J]. Composites Part B: Engineering, 2014, 60: 36-42. [百度学术]
ZHOU X Y, ZENG Y S, CHEN P, et al. Mechanical properties of basalt and polypropylene fibre-reinforced alkali-activated slag concrete [J]. Construction and Building Materials, 2021, 269: 121284. [百度学术]
ZHANG Z H, YAO X, ZHU H J, et al. Preparation and mechanical properties of polypropylene fiber reinforced calcined Kaolin-fly ash based geopolymer [J]. Journal of Central South University of Technology, 2009, 16(1): 49-52. [百度学术]
BERNAL S, DE GUTIERREZ R, DELVASTO S, et al. Performance of an alkali-activated slag concrete reinforced with steel fibers [J]. Construction and Building Materials, 2010, 24(2): 208-214. [百度学术]
SOARES D, DE BRITO J, FERREIRA J, et al. Use of coarse recycled aggregates from precast concrete rejects: Mechanical and durability performance [J]. Construction and Building Materials, 2014, 71: 263-272. [百度学术]
肖建庄, 吴磊, 范玉辉. 微波加热再生粗骨料改性试验[J]. 混凝土, 2012(7): 55-57. [百度学术]
XIAO J Z, WU L, FAN Y H. Test on modification of recycled coarse aggregate by microwave heating [J]. Concrete, 2012(7): 55-57. (in Chinese) [百度学术]
KATKHUDA H, SHATARAT N. Improving the mechanical properties of recycled concrete aggregate using chopped basalt fibers and acid treatment [J]. Construction and Building Materials, 2017, 140: 328-335. [百度学术]
混凝土物理力学性能试验方法标准: GB/T 50081—2019 [S]. 北京: 中国建筑工业出版社, 2019. [百度学术]
Standard for test methods of concrete physical and mechanical properties: GB/T 50081—2019 [S]. Beijing: China Architecture & Building Press, 2019. (in Chinese) [百度学术]
NAZARIMOFRAD E, SHAIKH F U A, NILI M. Effects of steel fibre and silica fume on impact behaviour of recycled aggregate concrete [J]. Journal of Sustainable Cement-Based Materials, 2017, 6(1): 54-68. [百度学术]
郭樟根, 陈晨, 范秉杰, 等. 再生粗细骨料混凝土基本力学性能试验研究[J]. 建筑结构学报, 2016, 37(Sup2): 94-102. [百度学术]
GUO Z G, CHEN C, FAN B J, et al. Experimental research on mechanical behavior of concrete made of coarse and fine recycled aggregates [J]. Journal of Building Structures, 2016, 37(Sup2): 94-102. (in Chinese) [百度学术]
ANIKE E E, SAIDANI M, OLUBANWO A O, et al. Effect of mix design methods on the mechanical properties of steel fibre-reinforced concrete prepared with recycled aggregates from precast waste [J]. Structures, 2020, 27: 664-672. [百度学术]
陈会凡, 管巧艳, 刘洪波. 矿渣再生骨料混凝土力学性能研究[J]. 混凝土, 2012(5): 91-93. [百度学术]
CHEN H F, GUAN Q Y, LIU H B. Study on the mechanical behavior of concrete containing slag and recycled concrete aggregate [J]. Concrete, 2012(5): 91-93. (in Chinese) [百度学术]
张丽娟. 钢纤维再生混凝土配合比设计及其性能计算方法[D]. 郑州: 郑州大学, 2017. [百度学术]
ZHANG L J. Mixture design and performance calculation method of steel fiber reinforced recycled concrete [D]. Zhengzhou: Zhengzhou University, 2017. (in Chinese) [百度学术]
章文姣, 鲍成成, 孔祥清, 等. 混杂纤维掺量对再生混凝土力学性能的影响研究[J]. 科学技术与工程, 2016, 16(13): 106-112, 123. [百度学术]
ZHANG W J, BAO C C, KONG X Q, et al. Experimental study on mechanical properties of hybrid fiber basic of recycled concrete [J]. Science Technology and Engineering, 2016, 16(13): 106-112, 123. (in Chinese) [百度学术]
AFROUGHSABET V, BIOLZI L, OZBAKK-ALOGLU T. Influence of double hooked-end steel fibers and slag on mechanical and durability properties of high performance recycled aggregate concrete [J]. Composite Structures, 2017, 181: 273-284. [百度学术]
张义顺, 金祖权, 李小雷. 混凝土在受压下的破坏机理研究[J]. 焦作工学院学报(自然科学版), 2002, 21(2): 123-126. [百度学术]
ZHANG Y S, JIN Z Q, LI X L. Study on the destruction mechanism of concrete under the pressure [J]. Journal of Jiaozuo Institute of Technology, 2002, 21(2): 123-126. (in Chinese) [百度学术]
程文瀼, 王铁成, 颜德姮, 等. 混凝土结构[M]. 3版. 北京: 中国建筑工业出版社, 2005: 10. [百度学术]
CHENG W R, WANG T C, YAN D H. Concrete structure [M]. Beijing: China Architecture & Building Press, 2005: 10. (in Chinese) [百度学术]
秦红杰. 再生混凝土抗折强度尺寸效应的试验研究及细观数值模拟[D]. 长沙: 湖南大学, 2020. [百度学术]
QIN H J. Experimental study and mesoscopic numerical simulation on the size effect of flexural strength of recycled aggregate concrete [D]. Changsha: Hunan University, 2020. (in Chinese) [百度学术]
霍俊芳, 白笑笑, 姜鹏飞, 等. 钢纤维和聚丙烯纤维再生混凝土力学性能研究[J]. 混凝土, 2019(8): 92-95, 99. [百度学术]
HUO J F, BAI X X, JIANG P F, et al. Research on mechanical properties of steel fiber and polypropylene fiber recycled concrete [J]. Concrete, 2019(8): 92-95, 99. (in Chinese) [百度学术]
张学兵, 匡成钢, 方志, 等. 钢纤维粉煤灰再生混凝土强度正交试验研究[J]. 建筑材料学报, 2014, 17(4): 677-684, 694. [百度学术]
ZHANG X B, KUANG C G, FANG Z, et al. Orthogonal experimental study on strength of steel fiber reinforced fly ash recycled concrete [J]. Journal of Building Materials, 2014, 17(4): 677-684, 694. (in Chinese) [百度学术]
杨粉, 陈爱玖, 王静, 等. 钢纤维再生混凝土劈拉、抗折强度试验研究[J]. 混凝土, 2012(12): 11-14. [百度学术]
YANG F, CHEN A J, WANG J, et al. Experiments of splitting tensile and flexural strength mechanical properties of steel fiber recycled concrete [J]. Concrete, 2012(12): 11-14. (in Chinese) [百度学术]
SHAH S F A, CHEN B, ODERJI S Y, et al. Comparative study on the effect of fiber type and content on the performance of one-part alkali-activated mortar [J]. Construction and Building Materials, 2020, 243: 118221. [百度学术]