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回复: c20c30c40混凝土配合比设计计算步骤
C40混凝土配合比设计Ðé,H.¼½<bbs.3c3t.comÔ83í7$ Ðé,H.¼½<bbs.3c3t.comÔ83í7$ C40混凝土用于某公路K**+***桥钢筋混凝土施工,要求施工时现场坍落度为30~50mm,碎石的最大粒经为30mm。Ðé,H.¼½<bbs.3c3t.comÔ83í7$材料选择Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 水泥:采用牡丹江产P.O42.5普通硅酸盐水泥。Ðé,H.¼½<bbs.3c3t.comÔ83í7$砂:产地岔林河,细度模数2.62属于中砂,颗粒级配属 Ⅱ区。Ðé,H.¼½<bbs.3c3t.comÔ83í7$碎石:产地冷山,规格分别为16~31.5cm、4.75~16cm,压碎值、含泥量等指标也均符合规范求。Ðé,H.¼½<bbs.3c3t.comÔ83í7$粗集料配合比设计Ðé,H.¼½<bbs.3c3t.comÔ83í7$根据筛分结果粗集料的掺配比例为: 4.75~16cm cm碎石为35%Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 16~31.5cm cm碎石为65%。Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 按照上述比例掺配两种集料,经几次筛分试验,其结果均满足4.75~31.5cm碎石连续级配.Ðé,H.¼½<bbs.3c3t.comÔ83í7$配合比设计Ðé,H.¼½<bbs.3c3t.comÔ83í7$1、计算初步配合比Ðé,H.¼½<bbs.3c3t.comÔ83í7$1)确定混凝土配制强度(fcu,o)。Ðé,H.¼½<bbs.3c3t.comÔ83í7$混凝土设计强度fcu,k=40MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$ 标准差σ=5.0 MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$则混凝土配制强度:Ðé,H.¼½<bbs.3c3t.comÔ83í7$fcu,o= fcu,k+1.645×σ=48.2 MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$2)计算水灰比(W/C)Ðé,H.¼½<bbs.3c3t.comÔ83í7$(1)按强度要求计算水灰比Ðé,H.¼½<bbs.3c3t.comÔ83í7$①计算水泥实际强度Ðé,H.¼½<bbs.3c3t.comÔ83í7$采用42.5普通硅酸盐水泥fce,k=42.5Mpa,富余系数γc=1.13Ðé,H.¼½<bbs.3c3t.comÔ83í7$则水泥实际强度为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$ fce=fce,k×γc =48.0MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ ②计算水灰比Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 碎石 A=0.48Ðé,H.¼½<bbs.3c3t.comÔ83í7$ B=0.52Ðé,H.¼½<bbs.3c3t.comÔ83í7$W/C=A×fce/(fcu,o+A ×B ×f ce)=0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$(2)按耐久性校核水灰比Ðé,H.¼½<bbs.3c3t.comÔ83í7$根据桥梁施工规范要求:严寒地区受严重冰冻,水流侵蚀最大水灰比不得大于0.65。按照强度计算的水灰比符合耐久性要求,故采用0.45。Ðé,H.¼½<bbs.3c3t.comÔ83í7$(3)确定单位用水量Ðé,H.¼½<bbs.3c3t.comÔ83í7$根据要求,混凝土拌和物的坍落度为30~50mm,碎石的最大粒径为30mm。Ðé,H.¼½<bbs.3c3t.comÔ83í7$确定混凝土的单位用水量为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$mwo=185kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$(4)计算单位水泥用量(mco)Ðé,H.¼½<bbs.3c3t.comÔ83í7$①按强度计算单位用灰量Ðé,H.¼½<bbs.3c3t.comÔ83í7$已知混凝土单位用水量为Ðé,H.¼½<bbs.3c3t.comÔ83í7$ mwo=185kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 水灰比W/C=0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$则计算单位混凝土用灰量:Ðé,H.¼½<bbs.3c3t.comÔ83í7$mco=mwo×c/w=411kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$②按耐久性校核单位用灰量Ðé,H.¼½<bbs.3c3t.comÔ83í7$根据桥梁施工技术规范要求:严寒地区受严重冰冻,水流侵蚀作用且有钢筋,混凝土最小水泥用量为300 kg/m3 。按强度计算的单位用灰符合耐久性要求,故采用mco=411kg/m3。Ðé,H.¼½<bbs.3c3t.comÔ83í7$(5) 确定砂率(SP)Ðé,H.¼½<bbs.3c3t.comÔ83í7$根据碎石的最大粒径为30mm,且水灰比为0.45 Ðé,H.¼½<bbs.3c3t.comÔ83í7$选定混凝土砂率为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$SP=33%Ðé,H.¼½<bbs.3c3t.comÔ83í7$(6)计算粗,细集料单位用量(mgo , mso)Ðé,H.¼½<bbs.3c3t.comÔ83í7$假定混凝土毛体积密度为2400 kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$185+411+ mgo+ mso=2400 ¨¨¨¨¨①Ðé,H.¼½<bbs.3c3t.comÔ83í7$mso×100/(mso+mgo) =33%¨¨¨¨¨②Ðé,H.¼½<bbs.3c3t.comÔ83í7$解式①、②得:Ðé,H.¼½<bbs.3c3t.comÔ83í7$ mso=595 kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$ mgo=1209kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$则混凝土初步配合比为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$ mco: mso: mgo=1:1.45:2.94Ðé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ W/C=0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$2、试拌调整,提出基准配合比Ðé,H.¼½<bbs.3c3t.comÔ83í7$1)计算试拌材料用量Ðé,H.¼½<bbs.3c3t.comÔ83í7$按计算初步配合比试拌15L混凝土拌和物,各种材料用量:Ðé,H.¼½<bbs.3c3t.comÔ83í7$水泥:411×0.015=6.165kgÐé,H.¼½<bbs.3c3t.comÔ83í7$水:185×0.015=2.775kgÐé,H.¼½<bbs.3c3t.comÔ83í7$砂:595×0.015=8.925kgÐé,H.¼½<bbs.3c3t.comÔ83í7$碎石: 1209×0.015=18.135kgÐé,H.¼½<bbs.3c3t.comÔ83í7$2)调整工作性,提出基准配合比Ðé,H.¼½<bbs.3c3t.comÔ83í7$按照计算材料用量拌制混凝土拌和物,测定其坍落度为40mm,而且拌和物的粘和性和饱水Ðé,H.¼½<bbs.3c3t.comÔ83í7$性良好,满足施工和易性要求,因此提出基准配合比为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$mco: mso: mgo=1:1.45:2.94 Ðé,H.¼½<bbs.3c3t.comÔ83í7$W/C=0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$3、检验强度Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 1)、采用水灰比分别为0.43,0.45,0.47 拌制三组混凝土拌和物,拌制时用水量不变,水泥用量分别为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 430 kg/m3 Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 411 kg/m3 Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 394 kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 2 8天后抗压强度分别见下表:Ðé,H.¼½<bbs.3c3t.comÔ83í7$水灰比:0.43Ðé,H.¼½<bbs.3c3t.comÔ83í7$试件编号 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 1Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | 2 | 3 | 4 | 5 | 6 | 抗压强度 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 51.5Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 52.0Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 52.1Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 53.5Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 52.6Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 51.8Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | 平均值 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 52.3MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 水灰比:0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$试件编号 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 1Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | 2 | 3 | 4 | 5 | 6 | 抗压强度 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 49.2Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 49.5Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 47.9Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 48.5Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 48.3Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 47.2Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | 平均值 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 48.4MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 水灰比:0.47Ðé,H.¼½<bbs.3c3t.comÔ83í7$试件编号 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 1Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | 2 | 3 | 4 | 5 | 6 | 抗压强度 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 45.3Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 43.2Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 45.5Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 44.7Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 43.8Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 44.2Ðé,H.¼½<bbs.3c3t.comÔ83í7$ | 平均值 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 44.5MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$ | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 2)、绘制灰水比和强度曲线:Ðé,H.¼½<bbs.3c3t.comÔ83í7$强度(Mpa)Ðé,H.¼½<bbs.3c3t.comÔ83í7$灰水比 ( 略 )Ðé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 由混凝土强度与灰水比关系曲线关系可知,与试配混凝土强度38.2Mpa的灰水比值为2.22即水灰比为0.45。Ðé,H.¼½<bbs.3c3t.comÔ83í7$4、确定试验室配合比Ðé,H.¼½<bbs.3c3t.comÔ83í7$1)强度修正Ðé,H.¼½<bbs.3c3t.comÔ83í7$根据强度、灰水比关系曲线,按强度修正后混凝土各材料用量为:Ðé,H.¼½<bbs.3c3t.comÔ83í7$用水量mwb=185kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$水泥用量 mcb =411kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$砂用量msb =595kg/m3 Ðé,H.¼½<bbs.3c3t.comÔ83í7$碎石用量 mgb =1209kg/m3 Ðé,H.¼½<bbs.3c3t.comÔ83í7$实测混凝土拌和物的毛体积密度为ρh=2470kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$校正系数K=2470/2400=1.03Ðé,H.¼½<bbs.3c3t.comÔ83í7$修正后混凝土各材料用量为Ðé,H.¼½<bbs.3c3t.comÔ83í7$水185×1.03=190kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$水泥411×1.03=423kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$砂595×1.03=612kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$碎石1209×1.03=1244kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$则试验室配合比为mcb sb gb=1:1.45:2.94Ðé,H.¼½<bbs.3c3t.comÔ83í7$W/C=0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 根据试验室配合比拌制12组抗压试件,标准养护28天后抗压强度见下表:Ðé,H.¼½<bbs.3c3t.comÔ83í7$试件编号 | 1 | 2 | 3 | 4 | 5 | 6 | 抗压强度Ðé,H.¼½<bbs.3c3t.comÔ83í7$ (Mpa) | 48.5 | 49.2 | 48.7 | 49.2 | 47.9 | 45.9 | 试件编号 | 7 | 8 | 9 | 10 | 11 | 12 | 抗压强度Ðé,H.¼½<bbs.3c3t.comÔ83í7$ (Mpa) | 48.9 | 48.0 | 51.7 | 52.4 | 49.2 | 48.7 | Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 2)、强度评定Ðé,H.¼½<bbs.3c3t.comÔ83í7$1、计算实测强度的平均值(mfcu)及标准差(sfcu)Ðé,H.¼½<bbs.3c3t.comÔ83í7$标准差sfcu=1.68Ðé,H.¼½<bbs.3c3t.comÔ83í7$平均值mfcu=49.0MpaÐé,H.¼½<bbs.3c3t.comÔ83í7$2、根据试件组数(N=12)判定合格系数Ðé,H.¼½<bbs.3c3t.comÔ83í7$λ1=1.70 Ðé,H.¼½<bbs.3c3t.comÔ83í7$ λ2=0.9Ðé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 3、强度评定Ðé,H.¼½<bbs.3c3t.comÔ83í7$(1)mfcu-λ1sfcu≥0.9fcu.kÐé,H.¼½<bbs.3c3t.comÔ83í7$49.0-1.7×1.68=46.1Mpa>0.9×40=36.0Mpa 合格Ðé,H.¼½<bbs.3c3t.comÔ83í7$(2)fcu.min≥λ2fcu.kÐé,H.¼½<bbs.3c3t.comÔ83í7$45.9Mpa≥0.9×40=36.0Mpa 合格Ðé,H.¼½<bbs.3c3t.comÔ83í7$故该12组混凝土试件块强度评定合格Ðé,H.¼½<bbs.3c3t.comÔ83í7$上述式中:Ðé,H.¼½<bbs.3c3t.comÔ83í7$ sfcu ————混凝土强度标准差Ðé,H.¼½<bbs.3c3t.comÔ83í7$mfcu————混凝土强度平均值Ðé,H.¼½<bbs.3c3t.comÔ83í7$fcu.k————混凝土设计强度值Ðé,H.¼½<bbs.3c3t.comÔ83í7$fcu.min————混凝土强度的最小值Ðé,H.¼½<bbs.3c3t.comÔ83í7$λ1 . λ2————评定合格系数.查表得出Ðé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 5、结论:Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 经过理论推算和试验室结果,确定最终配合比:Ðé,H.¼½<bbs.3c3t.comÔ83í7$mcb sb gb=1:1.45:2.94Ðé,H.¼½<bbs.3c3t.comÔ83í7$W/C=0.45Ðé,H.¼½<bbs.3c3t.comÔ83í7$Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 每立米混凝土各材料用量:Ðé,H.¼½<bbs.3c3t.comÔ83í7$水192kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$ 水泥 423kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$砂612kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$碎石1244kg/m3Ðé,H.¼½<bbs.3c3t.comÔ83í7$
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