普通混凝土配合比设计说明英.doc

Mix Design of C15/20 1 Environment and Equipment for Test1.1 The laboratory, the temperature in the standard curing room and the humidity shall meet the requirements of the testing regulations.1.2 The specifications, range, accuracy of the test equipment shall adhere to the requirements of the testing regulations with passing the check to be qualified by the Institute of Measurement and Testing of TBS.2 Design Basis2.1 Design Regulations for the Mix Ratio of the Ordinary Concrete: JGJ 55-20232.2 Standard Specification for Highway Bridge Construction: JTJ 041-20233 Materials Selection3.1 Cement: Simba42.5R type of cement will be used with the cement test results table below:PARMETERUNIT OF MEASURESPECIFICATIONSTZS727-2023EN 197-1:2023)SIMBAAVERAGE VALUESCompressive strength mortar test(days)MpaNot less than 1016Compressive strength mortar test(28 days)MpaBetween 42.5and62.546Lnitial setting timeMinutedNot less than 60100Cement mortar expansionMmNot less than 101Sulphuric anhydride%SO3Not less than 3.52.5Chloride content%CINot less than 0.10.023.2 Fine Aggregate: Medium sand in the Nyakabindi River will be used with the test results table below:DescriptionOriginSieve AnalysisFineness ModulusYellow SandNyakabindi River Sand District II2.9GRADING FOR SandTOTAL MASS BEFORE WASHING4716(g)Sieve(mm)M.retained(g)% retainedCumulative retained %Cumulative passing%10.0NILLNILL01006.350.10.199.94.751703.63.796.32.3699821.124.875.21.1880717.141.958.10.681617.359.240.80.42568014.473.626.40.349010.484.016.00.1550510.7945.30.0751553.3982PAN9021000FM2.93.3Coarse Aggregate: 20mm of quarry stones on Nyakabindi Hill will be used with the test results table below: DescriptionTFV(for F=400kN)Flakiness index（%）ACVParticle GradeGravel21523.320.620mmTOTAL MASS BEFORE WASHING5170(g)SIEVE(mm)M.retained(g)% retained% passing28.00NILLNILL10020.0063812.387.714.00276053.434.310.00156030.2416.32043.90.25.00000.22.00000.21.18000.20.6000.20.425000.20.3000.20.15000.20.075000.2pan3+50.203.4 Water: the stored water in dams will be used with the test results table below:ParameterUnits ResultsK53+200RHS4800m2K61+100LHS14400 m2K35+780RHS4800 m2pH7.218.448.04TurbidityNTU14345819Total Suspended Solids(TSS)Mg/L8644011Conductivity(EC)uS/cm176.7227985Total Dissolved Soilds(TDS)mg/L97.18124.5854Choridemg/L17.478.7432.99Sulphate(SO42-)mg/L15017Silicate(SiO3)mg/L8.7110.4746.64 Calculation of Design Strength4.1 Design Contents: the design strength is C15/20 for the ordinary concrete of the Box Culverts and other simmilar uses concrete .The design slump is 25-60mm.4.2 Calculation Steps of the Mix Ratio: Calculated as follows:Test with strength:fcu, 0 fcu, k 1.645 standard deviation of concrete strength - 5.0 fcu, o 15 +1.645 5 =23.2Mpain which: the fcu ,0 - Mix Strength of Concrete (MPa) the fcu, k - Standard Value of Compressive Strength of the Concrete Cube (MPa) the - Standard Deviation of Concrete Strength (MPa)The Strength Standard Deviation of Concrete shall be calculated and determined in accordance with the comparable statistical of the same type concrete and shall meet the requirements below: During the calculation, the number of intensity samples shall not be less than 25 groups. When the concrete strength grade is C20 or C25 level and the calculated strength standard deviation value is less than 2.5MPa, the standard deviation used for calculation of the mix strength shall be taken with no less than 2.5MPa; when the concrete strength grade is equal to or greater than C30 level and the calculated strength standard deviation value is less than 3.0MPa, the standard deviation used for calculation of the mix strength shall be taken with no less than 2.5MPa.5 The Basic Parameters in Concrete Mix Ratio Design 5.1 The determination of water for the plastic concrete Determination of water per cubic meter of concrete shall meet the following requirements: When the water-cement ratio is in the 0.4 - 0.8 range, the water used can be selected from the table below in accordance with the species, size, and consistency of concrete mixture as requested in construction of the coarse aggregate.Water for the Plastic Concrete (Kg/m3)Consistency of MixtureMax Particles of Gravel（mm）Max Particles of Aggregate (mm)ItemIndex102031.540162031.540Slump (mm)10-3019017016015020018517516535-5020018017016021019518517555-7021019018017022020519518575-90215195185175230215205195Note 1: the water in the above table is taken as per average value when using the medium sand; when using the fine sand, the water can be increased with 5-10Kg for per cubic meter of concrete; and the water can be reduced with 5-10Kg when using coarse sand. 2: the water shall be adjusted accordingly when mixed with various additives or admixtures.If the water-cement ratio is less than 0.4, or the concrete using a special molding process is used, the water shall be determined by experiments.According to Design Regulations for the Mix Ratio of the Ordinary Concrete (JGJ 55-2023), the water can be reduced with 5 10kg when using the course sand. The medium sand is selected (coarse, FI=2.9) in our laboratory; and so the mWo =190kg/m3.5.2 Determination of Sand Ratio per cubic meter of concreteIf the slump is 10-60 mm, the sand ratio can be selected from the table below in accordance with the species and size of the coarse aggregate. Concrete Sand Ratio (%)Water-cementratio（W/C）Max Particles of Gravel（mm）Max Particles of Aggregate (mm)1020401620400.426-3225-3124-3030-3529-3427-320.530-3529-3428-3333-3832-3730-350.633-3832-3731-3636-4135-4033-380.736-4135-4034-3939-4438-4336-41Note 1: values in this table are selected when using the medium sand; when using the fine or course sand, the sand ratio can be increased or reduced accordingly.2: the sand ratio shall be increased appropriately when just using a single grain of course aggregate to mix the concrete. 3: for the thin-wall parts, the larger value shall be selected. 4: the sand ratio in the above table refers to the weight ratio of the total sand and aggregate. 5: when the slump is greater than 60mm, the sand ratio of concrete can be determined by the test, but also can be adjusted by 1% of increase with each 20mm slump of increase on the basis of the above table.6: when the slump is less than 10 mm, the sand ratio shall be determined by the testAccording to the menu, here we choose 36% of the sand ratio as our requirment5.3 Calculation of the Water-cement Ratio: 0.46 of the aa, 0.07 of the ab, and the coefficient of cement grade surplus 1.10 shall be taken:W/C=aafce,gc /(fcu,o +aaabc fce,g)=0.4642.51.1/（23.20.460.0742.51.1）=0.87aa、ab - Regression Coefficient fce - The Measured Value of compressive strength of concrete for 28 days When there is no measured value of compressive strength for 28 days, the fce value in the formula may be determined as follows: fce=c*fce,gc - the surplus coefficient of the grade value of cement strength can be determined according to the actual statistical data.fce, g - Grade Value of Concrete Strength (MPa) fce value can be calculated through the strength for 28 days which is calculated The regression coefficients such as aa and ab shall be determined as the following:() The regression coefficients of aa and ab shall be determined through the relationship of the water-cement ratio and the concrete strength which is set up by the experience of cement aggregate used in the construction.() The regression coefficients can be selected from the table below when lacking of the statistical data of the above test.Stone VarietyCoefficientAggregateGravelaa0.460.48ab0.070.335.4 The Amount of Cement Selected for per cubic meter of concrete: mCo=mWo/(W/C)= 185/0.87=212kg/m3mCo - the amount of cement for (Kg) mWo - the water for the per cubic meter of concrete with base mix ratio (Kg) 5.5 The determination of the amount of coarse aggregate and sand The determination of the amount of coarse aggregate and sand shall meet the following requirementsThe following formula shall be used When using the gravimetric method:mCo+mgo+mso+mwo=mcps =mso/mgo+mso*100%mCo - the amount of cement for per cubic meter of concrete mgo - the amount of course aggregate for per cubic meter of concrete mso - the amount of fine aggregate for per cubic meter of concrete mwo - the water for per cubic meter of concrete s - Sand Ratio (%) mcp - the presumed weight of the per cubic meter of concrete mix (kg), its value can be taken as 2350-2450 Kg the amount of fine aggregate mSo =（presumed weight - mWo- mCo）s =（2350-212-185）0.38 = 742kg/m3the amount of fine aggregate mGo = presumed weight - mWo- mCo- mSo =2350-185-212-742=1211kg/m3 The primary mix ratio can be get if calculated by mass method: mCo ：mSo ：mGo ： mWo=212:742:1211:185 = 1:3.5:5.7:0.876 Adjust the workability and propose the base mix ratio 6.1Trial of base mix ratio 0.025m3 of the concrete mixture is mixed by calculation of the primary base mix ratio with a variety of materials as follows: Cement: 212 0.025 = 5.3 kgGravel: 1211 0.025 =30.3kgSand:742 0.025 = 18.55kg Water: 185 0.025 =4.6kgWhen the concrete mixture is mixed even by calculating the amount of the materials, the slump test shall be done.6.2 Adjust of base mix ratioThe base mix ratio shall be adjust by the slump test result. If the test slump is higher than the degsin , normally we add Aggregate and sand with same sand ratio to achieve the design slump . If it is lower than the design ,we add water and cement with the same water-cement Ratio.Record how much of the adding materail, than calculate the alternatived base mix ratioNoWater-cement ratioWater(KG)Cement(KG)Aggregate(KG)Sand(KG)Sand ratio10. 82185225122271837After adjust0.8220.87185212121174238After adjust0.8730.92185201119876639After adjust0.92Note：for the smaller Water-cement ratio one, the sand ratio shall reduce 1%.for the larger Water-cement ratio one, the sand ratio shall increase 1%. Water per m3 dont change.6.3 Make the concrete cubes For the mix design, we need make 3 lots of testing cubes to test 28days strength according to the base mix ratio/alternatived base mix ratio.There are different water-cement ratio of minus and add 0.05 with the base mix ratioNoWater-cement ratioWater(KG)Cement(KG)Aggregate(KG)Sand(KG)Sand ratio10.8220.8730.92After make the cubes ,measure the weight of cube and calculate the bulk density instead of the assumed density.NoAssumed density(KG/m3)Real bulk density(KG/m3)RatioWater(KG)Cement(KG)Aggregate(KG)Sand(KG)1236.4 Test the strength of cubesNoWater-cement ratioWater(KG)Cement(KG)Aggregate(KG)Sand(KG)28day strengh10.8220.8730.927 Finalize the mix desginDraw the relationship Water-cement and 28day strengh.find the correpond water-cement ratio of desgin strength 33.2Mp is the final water-cement ratio. NoWater-cement ratioWater(KG)Cement(KG)Aggregate(KG)Sand(KG)Sand ratio(%)1