建筑材料计算试题hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
1、工地入库的强度等级42.5矿渣水泥,取样测得水泥标准试件的抗折、抗压破hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
坏荷载如下表所示。计算其3d及28d强度。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
龄期 抗压破坏荷载(kN) 抗折破坏荷载(kN) hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
3d 26 27 25 24 21 26 1.51 1.52 1.78 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
28d 70 71 71 73 69 75 2.82 2.85 2.75 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(1)抗压强度:RC=P/A,A=40×40=1600mm2,3d抗压强度单值分别为:16.2,16.9,15.6,15.0,13.1,16.2MPa,平均抗压强度为15.5MPa,单值13.1MPa超平均值10%,取其它5个平均值为16.0MPa。28d抗压强度单值分别为43.8、44.4、44.4、45.6、43.1、46.9MPa,平均抗压强度为44.7MPa。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(2)抗折强度:Rf=3PfL/(2bh2),3d抗折强度单值分别为:3.54,3.56,4.17,MPa,平均抗折强度为3.76MPa,单值4.17MPa超平均值10%,3天抗折强度 3.56MPa。28d抗折强度单值分别为6.61、6.68、6.45MPa,28天抗折强度为6.58MPa。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
2、已知某混凝土的水灰比为0.5,用水量为180kg,砂率为33%,混凝土拌和料成型后测其表观密度为2400kg/m3,试求该混凝土配合比。若采用强度等级为32.5的普通水泥,试估计该混凝土28天强度。(rc=1.13,αa=0.46,αb=0.07)hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(1)求水泥用量ChÇGsO3õdbbs.3c3t.comWÑÀǹÇ
C=W/W/C=180/0.5=360kg/㎡hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
求砂S和碎石GhÇGsO3õdbbs.3c3t.comWÑÀǹÇ
S+G=Po—C—WhÇGsO3õdbbs.3c3t.comWÑÀǹÇ
Sp=S/S+GhÇGsO3õdbbs.3c3t.comWÑÀǹÇ
解之得:砂S=614kg 碎石G=1246kg 水W=180kg 水泥C=360kghÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(2)28天抗压强度:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
fw=аafa(C/W-аb)=0.46×1.13×32.5×(2—0.07)=32.6MPahÇGsO3õdbbs.3c3t.comWÑÀǹÇ
3、试设计钢筋混凝土T型梁用C30级混凝土初步配合比(假定重量法)。水泥P.042.5级,强度富余系数1.13;中砂细度模数2.70;5—31.5碎石连续级配,hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
要求坍落度30—50mm。(单位用水量为185kg/m3,砂率35%)hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
假定混凝土表观湿密度为2400kg/m3,配制强度fcu,o=30+1.645×5=38.2MPa,hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
水泥强度为fce=42.5×1.13=48.02MPahÇGsO3õdbbs.3c3t.comWÑÀǹÇ
水灰比=0.46×48.02/(38.2+0.07×0.46×48.02)=0.56hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
水泥用量=330 kg/m3hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
砂用量=660 kg/m3,石子用量=1225kg/m3 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
4、今有砂样一份,筛分结果如下表,试计算其细度模数。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
筛孔尺寸(mm) 9.5 4.75 2.36 1.18 0.6 0.3 0.15 <0.15 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
筛余量(g) 0 20 58 95 129 146 43 9 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
筛孔尺寸(mm) 9.5 4.75 2.36 1.18 0.6 0.3 0.15 <0.15 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
筛余量(g) 0 20 58 95 129 146 43 9 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
分计筛余(%) 0 4.0 11.6 19.0 25.8 29.2 8.6 1.8 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
累计筛余(%) 0 4.0 15.6 34.6 60.4 89.6 98.2 100 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
细度模数=[(15.6+34.6+60.4+89.6+98.2)-5×4]/(100-4.0)=2.90hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
5、某混凝土工程共制取检查试件11组,试验结果如下表,请计算其标准差和变异系数。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
水泥混凝土立方抗压强度(MPa)hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
42.2 45.3 38.5 44.0 48.2 47.5hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
43.3 44.0 44.7 43.4 46.3hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:混凝土抗压强度平均值R=44.3MPahÇGsO3õdbbs.3c3t.comWÑÀǹÇ
标准差 =2.66 MPa hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
变异系数Cv=S/R=6%hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
7.已知某水泥砼试配强度为38.2MPa,经设计并初步拟定了三个水灰比并以此制取三组试件。标养28天强度如下表,试作图确定应采用的水灰比。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
组别 水灰比 强度MPa hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
1 0.49 45.3 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
2 0.54 39.5 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
3 0.59 34.2 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
绘制水灰比与28天抗压强度曲线,见下图hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
根据曲线查得混凝土抗压强度为38.2MPa时,水灰比为0.55.hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
8、已知混凝土的强度等级为C30,经设计水灰比w/c=0.54,单位用水量mwo=180kg/m3,砂率βs=32%,试验测得碎石的表观密度ρ′G =2.70 g/cm3,砂的表观密度ρ′s=2.60 g/cm3,水泥密度ρ′c=3.00 g/cm3,试确定单位水泥、砂、碎石的用量?经试拌坍落度偏大,试分析原因,并提出改善措施?hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:(1)Mco=333 kg/m3,Mso=590 kg/m3,Mgo=1301 kg/m3hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(2)措施:保持w/c不变,减少水泥浆量。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
9、已知混凝土的设计强度等级为C30,强度标准差σ=5.0MPa。经设计得到基准配合比为mca:mwa:msa:mga=360:194:613:1251。进行强度检验制备三组试件,试验结果如表2,混凝土实测湿表观密度为2452kg/m3,试分析计算混凝土的试验室配合比为多大?hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
三组试件抗压强度试验结果记录表 表2hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
水灰比 0.49 0.54 0.59 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
28d抗压强度fcu(MPa) 45.3 39.5 34.2 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(1)绘制fcu—c/w的关系曲线,hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(2)配制强度fcu,o=38.2MPa,由曲线查得,w/c=0.55hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(3)按强度校核配合比Mwb=194kg/m3,Mcb=353 kg/m3,Msb=613 kg/m3,Mgb=1251 kg/m3,hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(4)计算湿表观密度为2411 kg/m3,修正系数为1.017,hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
实验室配合比为水泥:水:砂:石子=359:197:623:1272。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
10、某工地新进一批 HB335人字纹钢筋,随机抽取一根钢筋,截取一试件做拉力试验,以后又抽取一试件,两试件的试验结果如下表所示:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
指标 试件1 试件2 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
试件长度(mm) 260 260 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
试件重量(g) 408.2 408.1 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
屈服载荷(kN) 70.3 73.3 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
极限载荷(KN) 101.0 108.0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
原标距长(mm) 80 80 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
拉断后标距长(mm) 93.6 92.0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
试判断这批钢筋验收能否通过?hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
指标 试件1 试件2 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
截面积(mm2) 201.3 201.2 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
屈服载荷(kN) 70.3 73.3 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
屈服强度(MPa) 350 365 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
极限载荷(kN) 101.0 108.0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
破坏强度(MPa) 500 535 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
原标距长(mm) 80 80 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
拉断后标距长(mm) 93.6 92.0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
伸长率(%) 17 15 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
通过计算其力学指标与标准比较不能通过验收(伸长率应≥16%)。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
11、某高速公路沥青混凝土路面配合比设计需要使用碎石、石屑、砂、矿粉四种集料,筛析结果如表1,采用图解法设计结果为 碎石:石屑:砂:矿粉=36%:31%:25%:8%。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(1)计算合成级配,结果精确至1%;hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(2)若需调整,分析提出调整思路(调整计算省略)。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
矿质混合料级配计算表 表1hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
材料名称 筛孔尺寸 di (mm) hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
通过率 Pi (%) hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
原始集料级配 碎石 100% 100 96 14 0 0 0 0 0 0 0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
石屑 100% 100 100 100 84 30 10 0 0 0 0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
砂 100% 100 100 100 100 92 80 62 30 15 0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
矿粉 100% 100 100 100 100 100 100 100 100 100 88 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
集料在hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
混合料中hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
用量 碎 石 36 % hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
石 屑 31% hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
砂 25% hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
矿粉 8 % hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
合成级配 (%) hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
级配范围(%) 100 95~100 70~88 48~68 36~53 24~41 18~30 12~22 8~16 4~8 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
答案:hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(1)计算合成级配hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
材料名称 筛孔尺寸 di (mm) hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
通过率 Pi (%) hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
集料在hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
混合料中hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
用量 碎 石 36 % 36 35 5 0 0 0 0 0 0 0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
石 屑 31% 31 31 31 26 9 3 0 0 0 0 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
砂 25% 25 25 25 25 23 20 16 8 4 2 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
矿粉 8 % 8 8 8 8 8 8 8 8 8 7 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
合成级配 (%) 100 99 69 59 40 31 24 16 12 9 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
级配范围(%) 100 95~100 70~88 48~68 36~53 24~41 18~30 12~22 8~16 4~8 hÇGsO3õdbbs.3c3t.comWÑÀǹÇ
(2)调整思路:适量增加碎石用量,减少矿粉用量。hÇGsO3õdbbs.3c3t.comWÑÀǹÇ