回复:c20c30c40混凝土配合比设计计算步骤
原始资料:d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
1、混凝土设计强度等级为C30(空心板)无强度历史统计资料,桥梁所在地区属寒区。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
2、组成材料:PO42.5等级牡丹江牌水泥,密度PC=3.1×103Kg/m3,富裕系数=1.13,砂为中砂表观密度P'S=2.65×103Kg/m3,碎石最大粒径dmax=40mm,表观密度P'g=2.75×103Kg/m3,水为一般饮用水。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
设计步骤:d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(一)设计初步配合比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
1、确定混凝土配制强度(Ryp=Ry+1.65б=30+1.645×5=38.2MPad³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
2、计算水灰比(w/c)d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(1)按强度要求计算水灰比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Rs=RCRb=1.13×42.5=48MPad³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(2)计算混凝土水灰比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
w/c=ARs/Ryp+ABRs=0.48×48/38.2+0.48×0.52×48=23/50.1=0.46d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(3)按耐久性校核水灰比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
根据混凝土所处环境属于寒区允许最大水灰比为0.55.按强度计算水灰比是0.46。符合耐久性要求,采用计算水灰比0.46。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
3、选定单位用不水量(Mwo)d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
由于碎石最大粒径40mm,选用混凝土用水量:Mwo=175Kg/m3d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
4、计算单位用灰量(Mco)d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(1)按强度计算单位用灰量d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mco= Mwo/ w/c=175/0.46=380 Kg/m3d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(2)按耐久性校核单位用灰量d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
根据混凝土所处环境属寒区配筋混凝土,最小水泥用量不低于300 Kg/m3,按强度计算单位用灰量380 Kg/m3,符合耐久性要求,采用单位用灰量为380 Kg/m3。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
5、选择砂率(βs)d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
胜根据碎石最大粒径40 mm及水灰比w/c=0.46,选定混凝土砂率取βs=32%。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
6、计算砂石用量d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(1)采用质量法d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
已知:单位用灰量Mwo=175 Kg/m3,砂率βs=33%d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mso+Mgo=Pcp-Mco-Mwod³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mso/Mso+Mgo=0.33d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
假设混凝土混合料湿表观密度Pcp=2400 Kg/m3d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mso+Mgo=2400-380-175d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mso/Mso+Mgo=0.33d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
解得砂用量Mso=609 Kg/m3,碎石用量Mgo=1236 Kg/m3d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
按质量法计算初步配合比:d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mco : Mwo : Mso : Mgo =380 : 175 : 609 : 1236d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
即: 1 : 0.46 : 1.6 : 3.25 w/c=0.46d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(二)试拌混凝土,提出基准配合比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
1、按计算初步配合比试拌15L混凝土拌后物,测定其坍落度为2.5cm,满足施工和易性要求,其粘聚性和保水性亦良好。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
2、提出基准配合比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Mca :Msa :Mga=1 :1.6 : 3.25, w/c=0.46d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
(三)检验强度,测定试验室配合比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
1、检验强度d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
采用水灰比分别为(w/c)A=0.41 B=0.46 C=0.51拌制三组混凝土拌和物。砂、碎石用量不变,用水量亦保持不变。三组配合比经拌制成型,在标准条件养护28d后,A组抗压强度为41.5MPa,B组抗压强度为34.0MPa,C组抗压强度为28.5MPa。d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
绘制混凝土配制强度Ryp=38.2MPa的灰水比c/w2.38关系曲线即水灰比w/c=0.42d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
2、确定试验室配合比d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Msb+Mgb=2400-417-175d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
Msb/ Msb+ Mgb=0.33d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
即Msb=596,Mgb=1213d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
修正后配合比Mcb:Msb:Mgb=417:596:1213=1:1.43:2.91d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
水灰比Mwb/Mcb=175/417=0.42d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
计算湿表观密度Pcp=417+175+596+1213=2401 Kg/m3d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
实测湿表观密度P'cp=2400 Kg/m3d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
修正系数б=2400/2401=1d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*
因此试验室配合比为Mcb':Msb':Mgb'=1:1.43:2.91, w/c=0.42d³ê°ÖªËãbbs.3c3t.comA3¿\Õßç*