Concrete Lab Report
For this lab, the Portland Type 1 cement was pulverized before the sand and course aggregate were added. Once the solid materials were uniformly mixed and piled into the shape of a volcano, the water was slowly added to achieve a uniform mixing of the materials, see Figure 1. Uniform mixing of concrete is essential to achieve the maximum strength of the hardened concrete.
Figure 1. Mixture of solid before water was added.
Water reducer was applied to selected mixtures for testing. The water reducer was added through initial mixture with water from where standard mixing procedure was followed. Water reducer contains a catalyst which creates a more complete hydration of Portland cement. The benefits of water reducer include creating a more workable, stronger, and durable mix.
Macrosynthetic Fibers were added to a few mixtures for comparisons between standard mixtures to be made. The fibers were combined with coarse aggregate in the mixing process. The advantages of fibers are a reduction of in-place cost and expansion-contraction, increased durability, and increased stress distribution.
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The weight of the measure was recorded prior to placing three equal layers of concrete. Each layer was rodded with 25 strokes followed by the sides of the measure tapped 10 to 15 times with a mallet. ASTM C 138 requires this procedure, which simulates the vibration done in the field to remove air voids. The weight of the filled measure was recorded.
Air Content Test
Following ASTM C 231, the percent of air voids in the concrete was measured. A similar procedure as the unit weight test was completed filling a wetted, cylindrical mold with three layers. Each with layer had 25 strokes of the tamping rod and 10 to 15 taps on the mold from a mallet. The lid device was the placed on top of the smooth concrete surface and locked into place. An open valve was filled with water until the air voids had been filled. After locking the valves shut, the device was pumped until it reached the calibration point. The pressure was released and the dial gage value recorded.