3501-concrete-lab-2006

3501-concrete-lab-2006 - CGN3501 Civil Engineering Material...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
CGN3501 Civil Engineering Material Lab Preparation and Evaluation of a Concrete Mixture Laboratory Exercise #2 Preparation and Evaluation of a Concrete Mixture Introduction: When making Portland cement concrete, there are two sets of criteria that must be considered: i) Short-term requirements while the concrete is still in the plastic state ( fresh concrete), generally lumped together under the term workability . ii) Long-term requirements of the hardened concrete such as strength, durability and volume stability. The most important parameters for both sets of requirements are the total water content of the mix and the water/cement (W/C) ratio. The workability of the concrete is primarily a function of the total water content, increasing as the water content increases. If, as is commonly (though incorrectly) done, the water content is increased to improve workability without a proportional increase in the cement content, the W/C ratio will also increase, resulting in a decrease in both strength and durability. The ultimate strength of properly cured concrete is almost entirely a function of the W/C ratio since it is the W/C ratio that determines the porosity of the concrete. Purpose: This laboratory exercise will be broken into two separate components. The first part involves concrete mixing and subsequent evaluation of the fresh concrete properties. The second part will examine hardened concrete properties. The purpose of this laboratory exercise is to introduce the student to proper concrete mixing procedures, the evaluation of fresh concrete properties and the determination of hardened concrete properties. An emphasis will be placed on the W/C ratio and its effect on concrete strength. University of Florida – Department of Civil and Coastal Engineering 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CGN3501 Civil Engineering Material Lab Preparation and Evaluation of a Concrete Mixture Part A : Fresh Concrete Properties Concrete Mixing 1) Lay out twelve (12) 4" x 8" cylinders molds 2) Weigh out the following quantities of materials for the mix: Cement : 54 lb Water : 21 lb (W/C 0.40) Fine Aggregate : 62 lb Coarse Aggregate : 73 lb 3) Rinse the mixer with water. Drain excessive water from the mixer after rinsing. Place all of the coarse aggregate and cement in the mixer and run for 30 seconds. Stop the mixer and add the fine aggregate. Run the mixer for another 30 seconds. Stop the mixer and add the water. Turn the mixer on and allow it to run for 3 minutes, followed by a 3 minute rest period. Turn the mixer back on for a final 2 minute mixing period. 4) After mixing is complete, shut the mixer off. Measure the slump, unit weight and air content of the fresh concrete as per the instructions provided hereafter. Record the results. Cast 9 - 4" x 8" cylindrical specimens by placing the concrete in 2 equal layers. Consolidate each layer either by rodding them 25 times or using the vibrating table. (After casting the second layer, the top surface of each specimen should be
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/26/2011 for the course CGN 3501 taught by Professor Mang during the Fall '10 term at University of Florida.

Page1 / 9

3501-concrete-lab-2006 - CGN3501 Civil Engineering Material...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online