Los Angeles lab report - Essay Example

The test of reference is done on the fraction size 10/14mm. In order to understand the operation of the Los Angeles test, an experiment was set to determine the resistance to fragmentation. Apparatus The apparatus that would be used in this experiment include: Los Angeles Machine Recycled Concrete Aggregate Scale Tray Sieve Method. A 5kg of Recycled Concrete Aggregate was introduced in the cylinder via a hatch. The thecharge of eleven steel balls, with each ranging between 45mm and 49mm in diameter, while weighing in totallity between 4690g to 4860g was also added.

The hatch lid was bolted in place with the cylinder being rotated about 500 revolutions at a given rate of 31 to 33 RPM (Revolution Per Minute). The machine was operated in a soundproofed cabinet. A built-in counter stopped the machine after 500 revolutions. The hatch was opened, and the contents of the cylinder were emptied into trays set underneath the opening. The balls were removed and the aggregate was sieved using a 1.6mm sieve. For the fraction that was retained on the sieve, was weighed.

The result, the Los Angeles Coefficient, was calculated using . All the data collected was recorded in table 1. Table 1: Data collected. Type of aggregate Recycled Concrete Aggregate Initial mass of sample (g) 5000 Mass retained on the 1.6mm sieve (g) 3790 g Type of aggregate Thames Aggregate Initial mass of sample (g) 5000 Mass retained on the 1.6mm sieve (g) 3943 Calculations The Los Angeles Coefficient, LA, was calculated as follows: Aggregate with a LA value of less than 30 (LA30) is considered strong enough for use in coating and road surface treatments (i.e. surface dressing).

For example, a faulty scale or a faulty Los Angeles machine may automatically affect the readings of the experiment. It is recommended that for experimental errors to be reduced the following steps should be followed. During the experiment one should ensure that at least three readings for a particular step are taken then an average of the reading obtained to minimize the errors of parallax. The experiment needs to be done at least twice to confirm the recorded values and minimize the errors.

The Los Angeles Machine and all the apparatus used for the experiment should always be checked before the start of the experiment to ascertain their efficiency (BS 1377-4, 1990). The experiment could also be done in an area with vacuum conditions in order to minimize the interferences in obtaining the readings demonstrated to air resistance. Whenever the capacitor is by-passed by an emitter, and capacitance of the coupled capacitor is large in regards to the AC frequency signal, the capacitors would be approximated as a circuit that is short (BS EN 1097-2, 1998).

Whenever the input signal or voltage is increased the output voltage and the signal would be further vary around the dc bias point that has been established (Highways Agency , 2009). This effect would continue up to when the limiting condition of the voltage is reached. For the current in the circuit, the limiting condition would be VCC/RC, at the end, considered to be high, and a zero at the end considered to be low of the swing. The voltage of the emitter collector and the supply limit reaches a limit when they have a zero and VCC.

Additionally, the voltage output and the varying current around the point of bias gives out ac power towards the load (Highways Agency, 2009). The delivered ac power is made to go through the load referred to as RC. AC signal, on