Aggregate Experiment
I. Introduction
Aggregates contribute to 60-80% of a concrete mix, with water and cement being the other major constituents. Therefore considerable testing and consideration should be placed on aggregate type and size to ensure an adequate concrete mix.
Two tests have been performed to establish the properties of the aggregates: 1. Compacted bulk density test 2. Sieve analysis
II Testing For Compacted Bulk Density
Objectives
* To determine the specific bulk densities of a range of course, fine and mixed aggregates. * To determine the void content of the samples. * From this we can determine the optimum fine to coarse aggregate mix, given the bulk density and minimum void content.
Equipment
* Electronic Balance * Metal Cylinder (AS Compliant) * Metal Scoop * Tamping Steel Rod
Test Procedure 1. Determine the weight and volume of the cylinder (for lab experiment written on side). 2. For the mixed aggregates ensure they are well mixed. Now fill the cylinder with the aggregate to 1/3 the height of the cylinder using the scoop. 3. Compact the aggregate with the tamping rod giving 25 strokes without touching the bottom of the cylinder then stomp the cylinder on the ground 3 times. 4. Repeat steps 2 and 3 another two times so that the cylinder is full and has now being compacted 3 times. 5. Remove the surface aggregate to the level of the cylinder rim by rolling the tamping rod over the rim of the cylinder, working from the centre out. 6. Weigh the final compacted mass of the cylinder comprising the compacted aggregate.
II.I Results – Data & Calculations
Two formulas where used to calculate the data in the following table. Db = (w2 – w1) / Vb
Where Db = Bulk Density (kg/m3) w2 = Cylinder + Aggregate Weight (kg) w1 = Cylinder Wt. (kg) Vb = Aggregate bulk volume (m3) Void Content = 1 - (Db/ Dp) x 100%
Where Dp = Particle Density (kg/m3) = 2600 kg/m3
Please note that
Aggregates contribute to 60-80% of a concrete mix, with water and cement being the other major constituents. Therefore considerable testing and consideration should be placed on aggregate type and size to ensure an adequate concrete mix.
Two tests have been performed to establish the properties of the aggregates: 1. Compacted bulk density test 2. Sieve analysis
II Testing For Compacted Bulk Density
Objectives
* To determine the specific bulk densities of a range of course, fine and mixed aggregates. * To determine the void content of the samples. * From this we can determine the optimum fine to coarse aggregate mix, given the bulk density and minimum void content.
Equipment
* Electronic Balance * Metal Cylinder (AS Compliant) * Metal Scoop * Tamping Steel Rod
Test Procedure 1. Determine the weight and volume of the cylinder (for lab experiment written on side). 2. For the mixed aggregates ensure they are well mixed. Now fill the cylinder with the aggregate to 1/3 the height of the cylinder using the scoop. 3. Compact the aggregate with the tamping rod giving 25 strokes without touching the bottom of the cylinder then stomp the cylinder on the ground 3 times. 4. Repeat steps 2 and 3 another two times so that the cylinder is full and has now being compacted 3 times. 5. Remove the surface aggregate to the level of the cylinder rim by rolling the tamping rod over the rim of the cylinder, working from the centre out. 6. Weigh the final compacted mass of the cylinder comprising the compacted aggregate.
II.I Results – Data & Calculations
Two formulas where used to calculate the data in the following table. Db = (w2 – w1) / Vb
Where Db = Bulk Density (kg/m3) w2 = Cylinder + Aggregate Weight (kg) w1 = Cylinder Wt. (kg) Vb = Aggregate bulk volume (m3) Void Content = 1 - (Db/ Dp) x 100%
Where Dp = Particle Density (kg/m3) = 2600 kg/m3
Please note that
References: NRMCA, 2007, Aggregate grading, viewed 5 April 2010, <http://concreteproducts.com/mag/concrete_aggregate_grading/> PCA, 2008, Cement & Concrete basics: Aggregate, 5 April 2010, <http://www.cement.org/basics/concretebasics_aggregate.asp> Obla, K. & Kim, H, 2008, On aggregate grading, 5 April 2010, <http://www.nrmca.org/research_engineering/Documents/ConcreteInternationalarticleagggrading.pdf>