摘要
以榆神矿区煤矸石为粗骨料,通过288个棱柱体抗折强度试验,分析了煤矸石含碳量、煤矸石取代率及水灰比对煤矸石混凝土抗折强度的影响.结果表明:当不同矿源煤矸石含碳量由0.91%增加至2.09%时,煤矸石混凝土抗折强度降低了21.1%~32.6%;与普通混凝土相比,不同煤矸石取代率下煤矸石混凝土抗折强度降低了20.5%~47.5%;当水灰比由0.25增加至0.45时,煤矸石混凝土抗折强度降低了8.0%~15.3%.综合考虑了煤矸石含碳量和煤矸石取代率的影响,提出了适用于不同矿源煤矸石混凝土抗折强度的预测公式.
近年来,随着中国建筑行业的不断发展,天然骨料的大量开采,致使许多地区石材资源已接近枯竭.煤矸石作为煤炭开采过程中所排放出的岩石,现有存量已超过50亿
国内外学者针对煤矸石混凝土的研究,多以其抗压强度为
综上所述,本文采用榆神矿区煤矸石为粗骨料,并以煤矸石取代率及水灰比为变量,设计了48组煤矸石混凝土.通过288个煤矸石混凝土棱柱体的抗折强度试验,分析了煤矸石混凝土试件的破坏形态,讨论了不同矿源煤矸石含碳量、煤矸石取代率及水灰比对煤矸石混凝土抗折强度的影响,提出了适用于不同矿源煤矸石混凝土抗折强度的预测公式.
试验所用煤矸石(CG)均取自榆神矿区,根据煤矸石矿源不同,将其简称为S矿、Z矿、H矿、N矿及Y矿煤矸石,分别记作S‑CG、Z‑CG、H‑CG、N‑CG、Y‑CG.实测各矿源煤矸石的基本性能如
CG | Carbon content (by mass)/% | Calorific value/(kJ·k | Loss on ignition (by mass)/% | Water absorption ratio (by mass)/% |
---|---|---|---|---|
S‑CG | 2.09 | 1 869.34 | 23.96 | 8.4 |
Z‑CG | 1.31 | 1 458.99 | 10.65 | 5.1 |
H‑CG | 1.33 | 1 557.45 | 10.49 | 5.0 |
N‑CG | 1.28 | 664.75 | 9.76 | 5.7 |
Y‑CG | 0.91 | 424.31 | 6.40 | 5.5 |
采用颚式破碎机将块状S‑CG~Y‑CG煤矸石进行破碎,然后通过筛分,并按一定比例混合,制备成煤矸石粗骨料,分别记作S‑CGCA~Y‑CGCA,制备流程如

图1 煤矸石粗骨料制备流程图
Fig.1 Production process of coal gangue coarse aggregate
实测煤矸石粗骨料筛分结果如
Coarse aggregate | Cumulative sieve residue(by mass)/% | ||||
---|---|---|---|---|---|
2.36 mm | 4.75 mm | 9.50 mm | 19.00 mm | 31.50 mm | |
S‑CGCA | 96 | 95 | 89 | 41 | 2 |
Z‑CGCA | 96 | 94 | 76 | 22 | 0 |
H‑CGCA | 97 | 94 | 84 | 42 | 2 |
N‑CGCA | 96 | 93 | 83 | 35 | 0 |
Y‑CGCA | 96 | 92 | 80 | 29 | 0 |
Coarse aggregate | Particle size/mm | Bulk density/(kg· | Apparent density/(kg· | Crush indicator(by mass)/% | Needle and plate particle content(by mass)/% | Sulfide and sulfate content(by mass)/% | Organic content |
---|---|---|---|---|---|---|---|
S‑CGCA | 5.0-31.5 | 1 060 | 2 020 | 20 | 4 | 0.18 | Qualified |
N‑CGCA | 5.0-31.5 | 1 200 | 2 250 | 18 | 3 | 0.24 | Qualified |
Z‑CGCA | 5.0-31.5 | 1 320 | 2 390 | 13 | 9 | 0.32 | Qualified |
H‑CGCA | 5.0-31.5 | 1 290 | 2 450 | 14 | 4 | 0.19 | Qualified |
Y‑CGCA | 5.0-31.5 | 1 360 | 2 560 | 12 | 4 | 0.90 | Qualified |
NCA | 5.0-31.5 | 1 490 | 2 700 | 10 | 3 |
由
水泥选用P·O 42.5级普通硅酸盐水泥;细骨料采用天然中砂,实测堆积密度为1 430 kg/
采用S矿、H矿、Z矿、N矿及Y矿煤矸石粗骨料制备煤矸石混凝土S‑CGC、H‑CGC、Z‑CGC、N‑CGC、Y‑CGC,试验前对各矿源煤矸石粗骨料通过洒水进行预湿处
Group | mw/mc | r/% | Sand rate(by mass)/% | Mix proportion/(kg· | ||||
---|---|---|---|---|---|---|---|---|
Water | Cement | Sand | CGCA | NCA | ||||
S‑0.25‑100% | 0.25 | 100 | 41 | 160 | 640 | 533 | 767 | 0 |
S‑0.35‑100% | 0.35 | 100 | 41 | 160 | 457 | 608 | 875 | 0 |
S‑0.45‑100% | 0.45 | 100 | 41 | 160 | 356 | 650 | 935 | 0 |
S‑0.25‑70% | 0.25 | 70 | 41 | 160 | 640 | 570 | 574 | 246 |
S‑0.35‑70% | 0.35 | 70 | 41 | 160 | 457 | 645 | 650 | 278 |
S‑0.45‑70% | 0.45 | 70 | 41 | 160 | 356 | 687 | 692 | 296 |
S‑0.25‑40% | 0.25 | 40 | 41 | 160 | 640 | 607 | 349 | 524 |
S‑0.35‑40% | 0.35 | 40 | 41 | 160 | 457 | 682 | 392 | 589 |
S‑0.45‑40% | 0.45 | 40 | 41 | 160 | 356 | 723 | 416 | 625 |
Group | mw/mc | Sand rate(by mass)/% | Mix proportion/(kg· | ||||
---|---|---|---|---|---|---|---|
Water | Cement | Sand | CGCA | NCA | |||
NC‑0.25 | 0.25 | 41 | 160 | 640 | 656 | 0 | 944 |
NC‑0.35 | 0.35 | 41 | 160 | 457 | 731 | 0 | 1 052 |
NC‑0.45 | 0.45 | 41 | 160 | 356 | 773 | 0 | 1 112 |
每组配合比下均制备了6个100 mm×100 mm×400 mm的棱柱体试件与15个100 mm×100 mm×100 mm的立方体试件,分别用于测试煤矸石混凝土试件的抗折强度(ftf)与立方体抗压强度(fcu).试验共计浇筑棱柱体试件288个与立方体试件720个,试验结果见
Group | fcu /MPa | ftf /MPa | Group | fcu /MPa | ftf /MPa | Group | fcu /MPa | ftf /MPa |
---|---|---|---|---|---|---|---|---|
S‑0.25‑100% | 27.3 | 3.1 | S‑0.35‑100% | 23.8 | 2.7 | S‑0.45‑100% | 22.5 | 2.6 |
S‑0.25‑70% | 32.3 | 4.0 | S‑0.35‑70% | 30.5 | 3.4 | S‑0.45‑70% | 26.3 | 3.3 |
S‑0.25‑40% | 40.7 | 5.9 | S‑0.35‑40% | 35.0 | 4.1 | S‑0.45‑40% | 30.6 | 3.9 |
Z‑0.25‑100% | 32.5 | 4.4 | Z‑0.35‑100% | 30.2 | 3.5 | Z‑0.45‑100% | 27.0 | 3.4 |
Z‑0.25‑70% | 38.1 | 4.6 | Z‑0.35‑70% | 34.1 | 4.4 | Z‑0.45‑70% | 31.7 | 4.1 |
Z‑0.25‑40% | 46.7 | 5.1 | Z‑0.35‑40% | 37.7 | 5.0 | Z‑0.45‑40% | 37.0 | 4.9 |
H‑0.25‑100% | 34.4 | 3.7 | H‑0.35‑100% | 29.6 | 4.1 | H‑0.45‑100% | 28.4 | 3.7 |
H‑0.25‑70% | 39.2 | 4.4 | H‑0.35‑70% | 34.9 | 4.0 | H‑0.45‑70% | 32.2 | 3.9 |
H‑0.25‑40% | 48.9 | 6.0 | H‑0.35‑40% | 39.5 | 5.9 | H‑0.45‑40% | 38.4 | 5.8 |
N‑0.25‑100% | 35.6 | 3.8 | N‑0.35‑100% | 29.2 | 3.8 | N‑0.45‑100% | 28.5 | 3.7 |
N‑0.25‑70% | 40.1 | 4.6 | N‑0.35‑70% | 31.1 | 4.2 | N‑0.45‑70% | 32.1 | 4.1 |
N‑0.25‑40% | 44.2 | 4.9 | N‑0.35‑40% | 43.1 | 4.8 | N‑0.45‑40% | 37.2 | 4.6 |
Y‑0.25‑100% | 35.8 | 4.4 | Y‑0.35‑100% | 31.2 | 4.1 | Y‑0.45‑100% | 30.9 | 3.9 |
Y‑0.25‑70% | 41.8 | 4.6 | Y‑0.35‑70% | 36.7 | 5.2 | Y‑0.45‑70% | 34.5 | 5.0 |
Y‑0.25‑40% | 50.3 | 6.3 | Y‑0.35‑40% | 41.2 | 5.8 | Y‑0.45‑40% | 40.2 | 5.6 |
NC‑0.25 | 59.1 | 7.4 | NC‑0.35 | 47.9 | 6.7 | NC‑0.45 | 42.4 | 6.3 |
加载过程中,煤矸石混凝土试件在达到峰值荷载前无明显变形,而在达到峰值荷载后试件被迅速折成两段,整个破坏过程较为突然,属于脆性破坏.不同矿源的煤矸石混凝土抗折强度试验破坏过程均与普通混凝土相似,典型试件裂缝扩展形态如

图2 典型试件裂缝扩展形态
Fig.2 Crack propagation pattern of typical specimen

图3 典型试件折断面形态
Fig.3 Broken section shape of typical specimen
从
各因素对煤矸石混凝土抗折强度的影响如

图4 各因素对煤矸石混凝土抗折强度的影响
Fig.4 Influence of various factors on flexural strength of coal gangue concretes
由
由
从
现有关于混凝土抗折强度的计算公式主要是基于混凝土抗压强度计算得到,如欧洲混凝土委员会(CEB)规范《Model code for concrete structures》给出的普通混凝土抗折强度计算公式为:
(1) |
印度规范IS 456《Indian standard code of practice for plain and reinforced concrete(third revision)》中建议ftf与fcu的换算公式为:
(2) |
晏
(3) |
通过现有式(

图5 煤矸石混凝土抗折强度理论值与试验值
Fig.5 Calculated and test values of flexural strength of coal gangue concretes
由
基于现有计算公式形式(,α为系数),并考虑不同矿源煤矸石含碳量C与煤矸石取代率r的影响,通过回归分析,得到不同矿源煤矸石混凝土抗折强度的建议公式为:
(4) |
通过
(1)不同矿源的煤矸石粗骨料吸水率(5.0%~8.4%)均显著高于天然粗骨料(0.5%),表明煤矸石粗骨料中存在较多孔洞.当煤矸石混凝土受力后,煤矸石粗骨料内部孔洞处存在应力集中现象,从而直接导致煤矸石混凝土试件折断面上存在大量煤矸石粗骨料破坏.
(2)当不同矿源煤矸石的含碳量由0.91%(Y矿)增加至2.09%(S矿)时,煤矸石混凝土抗折强度降低了21.1%~32.6%.煤矸石含碳量是影响煤矸石混凝土抗折强度的主要因素,且煤矸石取代率越高,煤矸石含碳量对抗折强度的影响越显著.
(3)在不同水灰比下,煤矸石取代率始终是影响煤矸石混凝土抗折强度的主要因素,而随着煤矸石取代率的增加,与普通混凝土相比,煤矸石混凝土抗折强度降低了20.5%~47.5%.
(4)对于以粗骨料破坏为主的煤矸石混凝土而言,相较于煤矸石含碳量与煤矸石取代率,水灰比对于抗折强度的影响较小,当水灰比由0.25增加至0.45时,煤矸石混凝土抗折强度降低了8.0%~15.3%.
(5)基于普通混凝土抗折强度计算公式,并考虑煤矸石含碳量与煤矸石取代率的影响,提出了适用于不同矿源煤矸石混凝土抗折强度的预测公式.
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