Group 3 Exp1 Lab Report PDF

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LBYCVC1 – Construction Materials and Testing LaboratoryGroup No. Group Members3 Du, Jerome Martin S. Go, Vincent Joshua L. Ong, Carl Gavin O. Sia, Garret Wilkenson C. Uy Ching, Mikee Janine T. Experiment No. 1 (Total Evaporable Moisture Content of Aggregate by Drying)1 Introduction1 BackgroundAggreg...

Description

LBYCVC1 – Construction Materials and Testing Laboratory Group No.

3

1. 2. 3. 4. 5.

Group Members Du, Jerome Martin S. Go, Vincent Joshua L. Ong, Carl Gavin O. Sia, Garret Wilkenson C. Uy Ching, Mikee Janine T.

Experiment No. 1 (Total Evaporable Moisture Content of Aggregate by Drying) 1

Introduction 1.1

Background

Aggregates procured for use in concreting jobs often contain moisture. Because water plays a fundamental role in the properties of concrete that include but are not limited to workability, strength development, air entrainment, permeability, and shrinkage, it is thus necessary to determine the moisture content of aggregates so mixture proportions can be carefully adjusted based on actual aggregate moisture content to produce concrete of appropriate characteristics (ASTM International, 1997; Neville, 2004). In actual practice, mixture proportions for a specific mixture design are based on the total water introduced into the concrete mixture. This total water content comes from not only water added in the process of batching but also from free water within or on aggregates. While aggregates can be found in either oven dry, air dry, saturated surface dry, or wet moisture conditions, aggregates are usually obtained in either air dry or wet conditions. Between the two common moisture conditions, wet or damp aggregates are expected to add water to a concrete mixture and increase the watercement ratio, whereas air dry aggregates are expected to absorb cement paste from the mixture. Because of the effects of such on the properties of concrete, the moisture content of aggregates should thus be determined as said (Neville, 2004). A relatively simple method for determining the moisture content of aggregates is described in ASTM C 566 as the standard test method for the determination of total evaporable moisture content of aggregates by drying. The moisture content measured by this method includes moisture in the aggregate pores and surface moisture, whereas water chemically combined with aggregate minerals are not included in the moisture content determined by this method as such water is not evaporable (ASTM International, 1997). 1.2

Objectives

At the end of the experiment, students were expected to determine the evaporable moisture content of a coarse aggregate sample and of a fine aggregate sample by oven-drying based on ASTM C 566. 2

Experimental Procedure

The procedures for the determination of the evaporable moisture content of the coarse aggregate sample and of the fine aggregate sample were conducted as follows: 1. Approximately 6 kg of unrefined coarse materials were fed onto the mechanical splitter to

obtain 3 kg of coarse aggregates for use in this test. Meanwhile, 500 g of fine aggregates were prepared for use in this test. 2. The masses of two labelled containers were measured using the balance up to 0.1 g.

3. The prepared samples of coarse and fine aggregates were separately transferred to the two containers, and the masses of the containers filled with aggregates were measured up to 0.1 g. 4. The containers filled with aggregates were placed in the oven, and the aggregates were allowed to oven-dry at 110 °C for at least 24 hours. 5. The masses of the containers filled with oven-dried aggregates were measured up to 0.1 g. 6. The masses of the coarse and fine aggregates, the masses of the oven-dried coarse and fine aggregates, and the evaporable moisture content of the coarse and fine aggregates were finally computed. 3

Experimental Results 3.1

Coarse Aggregates

Table 1 below shows the raw and calculated data obtained in the determination of the evaporable moisture content of the coarse aggregate sample used in this experiment. Based on the images, the coarse aggregates appeared rough and angular. As can be seen, moreover, only one trial was conducted for which the evaporable moisture content of the coarse aggregate equaled 1.45%. Corresponding calculations involved are shown below the said table. Table 1. Data set for the determination of the moisture content of the coarse aggregates sample Test No. 1 2 3 1. Sample Code Coarse-1 2. Mass of Container (g) 383.2 3. Mass of Sample + Container (g) 3787.3 4. Mass of Sample (g) 3404.1 5. Mass of Oven-Dried Sample + Container (g) 3738.7 6. Mass of Oven-Dried Sample (g) 3355.5 7. Evaporable Moisture Content, p 1.45% 8. Average Moisture Content 1.45% Computation: 4. Mass of Sample

= Mass of Sample + Container - Mass of Container = 3787.3 g - 383.2 g = 3404.1 g 6. Mass of Oven-Dried Sample = Mass of Oven-Dried Sample + Container - Mass of Container = 3738.7 g - 383.2 g = 3355.5 g 7. 𝑝 =

𝑊−𝐷 𝐷

× 100% =

3404.1 g − 3355.5 g 3355.5 g

× 100% = 1.45%

Based on the results of the single trial conducted, the moisture content of the coarse aggregate sample at 1.45% may indicate that the aggregate is in its air dry moisture condition. While the sample may also be in a saturated surface dry condition given the lack of information on the aggregate utilized, an air dry condition should be more likely based on physical or visual assessment of the coarse aggregate tested. Although the moisture content of the coarse aggregate sample is qualitatively small, when large quantities of aggregates are utilized which is commonly the case among concreting jobs, this basic quantity must still be recognized to ensure the appropriate mixture design is achieved. Given that only one trial was conducted, no means of assessing precision are available. Two or

more trials should have been conducted to obtain means of assessing data precision. In terms of accuracy, meanwhile, since the moisture content of coarse aggregates or gravel are usually within 1% and 2%, the moisture content of the coarse aggregate obtained herein at 1.45% indicates

qualitatively accurate results. No means of assessing absolute accuracy of the moisture content of the actual aggregate sample are but available. In the conduct of this experiment, possible sources of error include personal errors and instrumental errors. Personal errors should primarily be incurred in the mishandling or improper handling of the sample such that portions or parts of the sample may have been lost as the test was conducted. Incomplete drying of the sample may have also occurred despite the 24-hour drying period since mass of the oven-dried sample was only measured once, but this would normally not be a cause of error as a 24-hour drying period is normally sufficient. Instrumental errors, on the other hand, may primarily occur as a result of a lack of calibration of the mass balance utilized. 3.2

Fine Aggregates

Table 2 below shows the raw and calculated data obtained in the determination of the evaporable moisture content of the fine aggregate sample used in this experiment. Based on the video, the fine aggregates appeared rough and angular. As can be seen, moreover, only one trial was conducted for which the evaporable moisture content of the fine aggregate equaled 2.26%. Corresponding calculations involved are shown below the said table.

Table 2. Data set for the determination of the moisture content of the fine aggregates sample Test No. 1 2 3 1. Sample Code Fine-1 2. Mass of Container (g) 201.1 3. Mass of Sample + Container (g) 702.8 4. Mass of Sample (g) 501.7 5. Mass of Oven-Dried Sample + Container (g) 691.7 6. Mass of Oven-Dried Sample (g) 490.6 7. Evaporable Moisture Content, p 2.26% 8. Average Moisture Content 2.26% Computation / Remarks: 4. Weight of Sample = Weight of Sample + Container - Weight of Container = 702.8 g - 201.1 g = 501.7 g 6. Weight of Oven-Dried Sample = Weight of Oven-Dried Sample + Container - Weight of Container = 691.7 g - 201.1 g = 490.6 g 7. 𝑝 =

𝑊−𝐷 𝐷

× 100% =

501.7 𝑔 − 490.6 𝑔 490.6 𝑔

× 100% = 2.26%

Based on the results of the single trial conducted, the moisture content of the fine aggregate sample at 2.26% may indicate that the aggregate is in its air dry moisture condition. Similar to indications by the results of the test on the coarse aggregate sample, while the sample may also be in a saturated surface dry condition given the lack of information on the aggregate utilized, an air dry condition should be more likely based on physical or visual assessment of the fine aggregate tested. Although the moisture content of the fine aggregate sample is also qualitatively small, when large quantities of aggregates are utilized, this basic quantity must still be recognized to ensure the appropriate...