Experiment 1 Answer to Questions (1)

ANSWER TO QUESTIONS Q.1) Is the moisture content of soil expressed as a percentage of the weight or as a percentage of the volume? Ans. In the performed experiment we used the gravimetric water content or the percentage of

the weight in determining the water content or the soil moisture. It is defined as the mass of the water relative to the mass of the dry soil particles. Q.2) What are the six categories of soil types identified in the ASTM classification system? Ans. Sand, silt,clay, gravel,cabbles and boulders are the six categories of soil types that are identified in the ASTM classification system. Q.3) For which soil type is surface forces important? Why?

Ans. The soil type which significantly influences by the surface forces is fine-grained soils. Due to the large surface areas of fine-grained soil their behaviour was greatly affected by surface forces. Also, the clay-water interaction coupled with the large surface areas results in clays having larger water-holding capacity in a large number of smaller pore spaces compared with coarse-grained soils. Q.4) What is adsorbed water? Ans. Adsorbed water influences the way a soil behaves. As a matter of fact, plasticity in soils is attributed to adsorbed water. Also, it is the water which is bound to soil particles as a result of the attraction between the electrical charges of negative surface charges on soils and the positively charged side of water molecules from surrounding water.

Q.5) Can you remove the adsorbed water by oven drying at 105°C? Explain. Ans. The standard temperature using an oven is 105 ±± 5°° C when drying most of soils, with the exception of gypsum. This range of temperature cannot remove the adsorbed water because it requires a definite amount of energy to be removed. Also, the plasticity in soils is attributed to adsorbed water. Q.6)When a soil sample is dried in an oven during the moisture content determination test what standard is used to determine that the sample is completely dry? Ans. Soils which may appear dry have 2 to 5 percent water content. In many soils, such as those which is transported which in the past have been transported and worn by streams and any loads or

other action on the soil will cause no appreciable change, even over long period of time. Also, we can check the color of the soil to check if it is already dry. A dry sample has a lighter color than wet ones. Q.7) Why is it not recommended to leave an ovendried sample in the open air for a long time before measuring its dry weight? Ans.In determining the dry weight of soil, it is not recommended to leave an oven-dried sample in the open air for a long time because the soil sample will acquire some moisture that already exist in the surroundings. Also, the change in temperature due to the high temperature in the oven and the cooler temperature in the surroundings will cause moisture. Thus, the dry weight may be affected and it will result to discrepancies in the data collected. If it takes too long to obtain the weight it is advisable

to put a cover on the container or put the sample dried soil into a desiccator.

Q.8) Excluding oven drying, are there other methods to determine the water content of soils? Ans. Besides oven drying, there are many other procedures used to determine the water content in soil. There are direct methods such as; ● using methyl alcohol ●calcium chloride On the other hand, for indirect methods are; ●tensiometer ●gypsum blocks ● pressure membrane and pressure plate apparatus

●neutron scattering method ● gamma ray absorption method ●feel and appearance method ● soil moisture characteristic curve.

Q.9) Soil must be baked in an oven to drive off the moisture during a moisture content determination test. Is there an approved ASTM method for using a microwave oven for this test?

Ans. Yes. ASTM D4643 also known as Standard Test Method for Determination of Water (Moisture) Content of Soil by Microwave Oven Heating serves as a guide when using microwave oven in determining water content. But it is best suited for minus No. 4 sized

material. Larger size particles can be tested; however, care must be taken because of the increased chance of particle shattering. On the other hand, when needing accurate results this method is not appropriate.

Q.10) What is the major advantage of using the nuclear gage to determine the moisture content of a soil instead of using the laboratory procedure? Ans. The major advantage of using the nuclear gage or nuclear methods is that it is use as a rapid, non-destructive practice compared to the laboratory procedures. The non-destructive nature allows repetitive measurements at a single test location and statistical analysis of results. This

method is usually used for quality control and acceptance testing of compacted soil and soilaggregates mixtures.

Q.11) Is it possible to measure the water content of sands? Ans. Yes, it is possible to measure the water content of sand because it is considered as a soil having large particle sizes with an approximate diameter of 0.002-0.05 mm. In addition, the fact that it is being under the variation of soil structures as granular soil, texture and water content can be determined by the infiltration process factors of soil.

Q.12) Why do we used a fixed temperature range to dry soils? What is the effect on soils of microwave drying? Ans. The significance of using fixed temperature range to dry soil is that it will give a constant weight of the dry sample which is used in determining the water content of the soil. Ans. Microwave drying can be used to dry soil faster compare to the conventional oven drying. But the change in the plasticity and the swelling potential of the soils are in a decreasing manner when preheating in a microwave oven resulting to the changes on the soil structure, decomposition of organic matters which include mineralization and micro flora.

Q.13) What is the function of the container lid and dessicator when determining the water content of soil? Ans. The container lid and dessicator avoid the absorption of moisture in the air to exist due to the sudden change in temperature. If the dry samples can’’t be weighed right away, the container lid must be placed over the sample and placed in the dessicator afterwards.