Transcription of Concrete Mix Design Calculations
1 1/22/20141 Concrete Mix Design CalculationsCalculationsConcrete Mix Design Wet Cast (Slump) Dry Cast (no Slump) Dry Cast (no Slump)Combination of Art and , Cement, & Aggregate As the water to cement ratio increases, the strength of a Concrete mix mix decreases. As the surface area of the aggregate increases the more water will be needed to maintain a given slump. Coarser Surface Texture Particle Shape Particle Size Distribution As the air content increases, the strength of the Concrete It s a calculation: w/c ~ lbs.
2 Of water / lbs. of cement w/cm~ lbs. of water / lbs. of cementitious Water / Cementitious RatioOften when w/c is discussed its really w/cmthat is intended as the reference=Water cement cement ratioWater needs to be drinkable or meet ASTM expressed as decimal45 lbs of water100 lbs of cement1/22/201435 Specific Gravity The relative density of a material compared to water The ratio of a material s weight to the weight of an equalTerminology The ratio of a material s weight to the weight of an equal volume of water Bulk specific gravity (SSD).
3 Used to determine the solid volume (absolute volume) of a material going into Concrete It is determined by submerging the material in water for ygg24 hours in order to fill any permeable voids6 Specific GravityWater: Water: Specific Specific Gravity = = : Stone: Specific Specific Gravity = = Volume, but Times More MassSame Volume, but Times More MassCement for SSD Bulk Specific GravityCoarse Aggregate Using Basket Suspended in water:Coarse Aggregate Using Basket Suspended in water:B / (B B / (B -- C) = SSD Bulk Specific GravityC) = SSD Bulk Specific Gravitywhere:where:B = weight of SSD sample in airB = weight of SSD sample in airC = weight of SSD sample in waterC = weight of SSD sample in waterField Calculation of SSD Bulk Specific Gravity:Field Calculation of SSD Bulk Specific Gravity.
4 Weight of Aggregate @ SSDW eight of Aggregate @ SSDW eight of Aggregate @ SSDW eight of Aggregate @ SSDW eight of equal volume of water displacedWeight of equal volume of water displaced== Specific GravitySpecific Gravity1245 grams of SSD aggregate1245 grams of SSD aggregate== grams of water grams of water Mix Design It s always about volume! What is absolute volume?1/22/201459 Relationship of Materials to Volume specific gravity of Type I Cement = is Absolute Volume? specific gravity of water = 1 gallon of water weights pounds water weights pounds / cubic footPounds of X Absolute Volume10 Basic Concrete Mix DesignMaterialsPounds of Cementious667 Miller / Concrete Mix DesignMaterialsPounds of Volume667 X Cementious667 Miller X X / Concrete Mix DesignMaterialsPounds of Cementious667 Miller X X / X 271/22/20147 Water / Cement Ratio = W/CMaterialsPounds of VolumeWater / Cementious667 Miller
5 667 Weight (mass) / (unit weight)MaterialsPounds of VolumeDesign(unit weight) Cementious667 Miller / @ air, unit weight (density) = Design with Cement & Fly Ash133 lbs. fly ash667 Total lbs. Cm= 20% ashIt s about volume!Note: lower water demand due to fly ash- for same slumpMix Design with Cement & Fly AshProportion the mix toyield 27 but how much sand, stone .. what ratio?Sand / Aggregate ratio is by volumeIt s about volume!1/22/20149 Mix Design with Cement & Fly AshVolume without aggregate = - =18 28 ft3requiredIt s about volume!
6 FtrequiredSand to Aggregate RatioVolume of SandVolume of Total Aggregate=Rules of thumb ?Manufactured Concrete Pipe60-80% Packerhead Mix45-65%Dry Cast1/22/201410 Calculating sand & stone to yield 27ft3 of Concrete Assume this Concrete needs to haveSand / Aggregate ratio of 0 42 Assume this Concrete needs to have Sand / Aggregate ratio of Volume of Sand042 Total Volume of Aggregate= of SandVolume of Sand = ft3= poundsof sandPounds of Material=Absolute X Absolute VolumePounds of Material (sand)
7 X ft3 Evert Sand = = 1270 lbs1/22/201411 Calculating poundsof stonePounds of MaterialSG X624= Absolute X of Material (stone) X - = ft3 Total Aggregate VolumeSand VolumeMiller Stone = = 1720 lbsSSD Mix Design1/22/20141223 Aggregate MoistureAggregate MoistureBone DryorOven DryAir DrySaturatedandSurface DryAbsorbed moisture(absorption)SSD (ideal)Add WaterMoistFree moisture(moisture content)Subtract WaterMoisture AdjustmentsMoisture Management is Critical (How much free water)Total aggregate moisture = aggregate absorption + free water(TM = absorption + free water) = + free water, (% free water = ) X 1720 = 26pounds of free water on the = + free water, (% free water = )
8 X 1270 = 59 pounds of free water on the Sand1/22/20141325 Water AdjustmentIf 26 + 59 pounds of water rides in on the aggregates you must take that amount of water out of the waterWater on aggregates Batch water295-85210 Moisture AdjustmentTotal moisture= Free moisture + Aggregate absorptionSSD & batch totalswill be the same1/22/2014142728 Where can I get this? Portland Cement Association (PCA)5420 Old Orchard RoadSkokie, IL 60077-1083847 9666700 PH847 966-6700 PH847 966-8389 FXInfo @
