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The following report is a critique analysis of four different journal reports which were chosen through databases from the universities library services. The chosen reports are in relation to a selected topic of the author's course. The report also compares the analysed journal reports and explains specific correlations between each. This further shows how each journal report provides significant information which corresponds with one another but also provides additional data which is unique on its own.
1. Effect of Surface Macrotexture on Skid Resistance Measurements by the British Pendulum Test.
The report itself is based on a common laboratory and field test called the ‘British Pendulum Test'. The test itself calculates a low friction result value for a specimen of road material. The abstract states that the calculated result value is largely administrated by the surface texture of the test specimen. (Liu, Fwa and Choo, 2004, p.361)
The aim of the report is to test two geometric parameters of using the British Pendulum Test to see if they have any effect on the calculated result. One is the size of the sub-contact areas between the pendulum's test pad and the test specimen. The other is the extent of gaps between the sub-contact areas.
The test methods where split into two different parts.
Part 1 Two different types of specimens were tested which have different aggregates of granite and steel slag. The test specimens were prepared in accordance with an ASTM standard test method (E303). High strength cement was used to fabricate the each test specimen whereby, a total of eighteen test specimens were fabricated, nine for the granite aggregate and nine for the steel slag aggregate. Once the test specimens were created they were tested using the ‘British Pendulum Test' before and after a polishing treatment.
Part 2 consisted of fabricating test specimens using ‘Portland Cement Mortar'. The specimens were poured into formwork moulds which were made out of Styrofoam. Four different types of specimens were made with three replicas for each type. The specimens were then tested for three different parameters using the ‘British Pendulum Test'; the total sliding contact area, the size of the individual sub-contact areas and the gap width between sub-contact areas.
The results of the two tests carried out show that the test machine itself was affected by the macro-texture of the test specimens. This was due as skid resistance (BPN) decreased as when the gap in aggregates in the test specimen increased, it also increased when test specimen sub-contact areas were increased in Part 2 of the test.
The results conclude that the ‘British Pendulum Test' may not produce a true value for skid resistance as different aggregates and difference in aggregate gap dimensions affect the test machine in different ways. It may cause the person carrying out the test to achieve a high approximation of skid resistance from that of a realistic road surface material with wider gaps in aggregate. The person carrying out the test must take caution and ensure that the testing material such as aggregate gap dimension is similar to that of the ASTM standard specified.
This test method may have found flaws in the ‘British Pendulum Test'. However, it is felt that a more accurate test must be carried out to clarify the results found from this report. For example in part 1 of the test Liu, Fwa and Choo (2004, p.305) state that “during specimen fabrication, some deviations of the gaps occurred in the final specimens fabricated, this did not affect the analysis, as the actual gaps were measured and analyzed in the test results”. This statement gives the reader a sense that this test must be re-checked and further tests to be carried out to support the conclusions of this test.
2. Development of correlation equations between different measurements of skid resistance in pavements.
Background: Skid resistance is a measure of friction through the use of different device methods. These methods can be carried out with the use of static and high performance devices. (Bustos et al, 2006, p.177) However in order to calculate friction itself texture must also be taken into account. The measurement of friction is highly important to any driver who is using the roads and Bustos et al (2006) states that “Skid resistance and pavement texture are functional properties that provide safety conditions to drivers.” Road agencies usually carry out a number of tests to obtain a skid resistance measurement. However these tests cannot be directly compared as different equipment applies a different physical principle to the test material being tested. They are usually compared through the use of harmonisation equations. This report shows that problems have been found in correlating certain measurements, such as limitations with texture and an absence of a specific world benchmark. The aim and objective of this report is to develop an alternative method of correlating both skid resistance and texture measurement for different test machines.
The method of achieving this aim is proposed in conjunction with the PIARC (World Road Association) harmonisation procedure. It consists of developing one equation to correlate measurements from different devices. The model itself incorporates a reference curve graph whereby, skid resistance against speed can be applied to. Through the use of data simulation, results were obtained from the model. These results show that through the use of the PIARC model, a correlation of skid resistance and texture can be obtained and observed by applying it to the relevant equation and reference graph. The conclusions have been found that the use of the PIARC model reduces data requirements whilst providing a reference graph whereby measurements from two different devices can be observed.
From this report the reader can clearly see the problems stated by the author of previous measurement analysis of skid resistance and texture measurement. However more evidence could be shown to support that previous methods do not work as well as this new proposed method. Some parts of the report, such as the results section are unclear as to where values have been obtained from. However, the proposed methodology section is explained in simpler terms and easier for the reader to follow. The emphasis of the report and how it can benefit agencies within the industry has shown interest where the reader will want to know further detail as to whether this proposed method has been put in practice.
3. Laboratory Performance of Crumb Rubber Concrete Block Pavement
Concrete Block Paving (CBP) are normally manufactured off site and are then laid on site on a compacted layer of sand. They are produced on a mass scale and can consist of a wide variety. Different dimensions can be created for different types of blocks including different strength tolerances. However, due to common failures in CBP a new method to improve on these defects has been developed. This is the mixing of crumb rubber into the manufacturing design of CBP. (Ling et al, 2007, p.364) In this report four different types of paving blocks were manufactured with different content of crumb rubber, 0%, 10%, 20% and 30%. These test specimens were then put under a series of different test methods. The tests methods consisted of “load repetition, pull-out, skid resistance, and falling weight test.” (Ling et al, 2007, p.364). One of the tests, the load repetition test, consisted of a specifically built test machine by the authors in order to obtain results. It was called the HALI (Highway Accelerated Loading Instrument).
The results of this series of tests on each of the four developed types of CBP with crumb rubber consisted of a substandard grade for most of the tests such as skid resistance, deformation and rutting. However the test specimens with a higher content of crumb rubber did show a high improvement in toughness. (Ling et al, 2007, p.373).
From these test methods applied to the test specimens the results prove that CBP mixed with crumb rubber can be used in areas of pedestrian walkways, cycle tracks or playgrounds where an area of high tensile concrete is not required. (Ling et al, 2007, p.373).
The report itself gives the reader an insight into different forms of test methods available to use when acquiring certain property values of test specimens. The report itself was clear and concise. The photographs along with diagrams were drawn of high standard which made it easy for the reader to visual how each test method was carried out and the results that they produced, i.e. the three-dimensional view produced using the SURFER computer program. However it was noted that some errors were made when carrying out the tests which could be improved upon in future tests such as the alignment with the HALI load repetition test.
4. Pedestrians on Slippery Surfaces during winter - Methods to describe the Problems and Practical Tests of Anti-Skid Devices.
Every year thousands of people are injured from falls and slippages during the winter season. This is either down to bad weather conditions or lack of maintenance of our roads and footpaths. According to Gard and Lundborg (1999, p.455), in “an analysis of 297 persons aged over 60 treated for injuries in the traffic environment over a one year period showed that the main categories of injury were falls (52%)” . This shows how common accidents are in relation to slippages and pavement surfaces during. The aim of this report was to describe methods developed to analyse problems with the way in which people walk on slippery surfaces and also to analyse 25 anti-skid devices from the Swedish market.
The method used to achieve the first aim was to observe human subjects walking and balance ability with the use of an anti-slip device. This was carried out by two experienced physiotherapists who rated each individual on a structured developed rating scale. This test method was also supported by video evidence. The method used to achieve the second aim consisted of five different individuals whereby each of the 25 anti-slip devices where tested across five different test areas. The results were then taken due to the individuals perceptions of the device. Three of the devices were found to be very useful and could be improved if further research is carried out to develop a European benchmark standard.
The reader found the report interesting as the introduction was very factual based and supported evidence for a need for research such as the study which was carried out in this report. However the reader believes that a more controlled method of testing should be carried out in future testing similar to this study. For example, the author clearly states that “No specific safety precautions were taken during this experiment” Gard and Lundborg (2000, p.460). This is an error in the method of testing from the view of the reader as it is felt that more safety precautions could have been taken especially when dealing with human subjects over the age of 55.
The journal papers chosen for this report are of high significance and relates to the author's research study area of ‘Skid resistance in pedestrian areas'. The analysis of this area will be highly important to the safety of pedestrians who use walkways and pavement areas.
The first journal paper chosen for this report analyses a significant test method and apparatus which is used widely today for the measurement of skid resistance. It significance to the author's related research area is that the test method may be used in the analyses of skid resistance in pedestrian areas. The report itself concludes that the ‘British Pendulum Test' may have probable errors within its technique which must be noted and taken into account when using the test method.
The second journal paper chosen for this report is related to the author's research area as it analysis and discusses different test methods which are used today by road agencies to obtain quantitative and qualitative data for skid resistance. The second report concurs with the first report when analysing these specific test methods as one of the test methods analysed is the ‘British Pendulum test'. The report also specifically relates to the first report analysis as to why there are margins for errors with the test method, if it is not carried out carefully. The report states that the “British Pendulum Number (BPN) tends to be affected by the micro and macro texture, resulting into a non-linear equation” (Bustos et al, 2006, p.118). The report describes how there is a difference in correlations between different test methods and further explains how a new proposed method can harmonise all the measurements obtained from more than one device. This explained method describes how an overall equation can be created from different coefficients which not only incorporate the value of skid resistance itself but also the texture measurements of the test material in question. A reference curve is also been developed along with this method which allows the user to clearly compare more than one devices measurement results with another. This can have incredible benefits for test methods such as the ‘British Pendulum test' as previous methods of correlating more than one device measurements has limits. For example Bustos et al (2006, p.118) explains that a previous equation used to correlate a SCRIM (Sideways Co-efficient Routine Investigation Machine) and the ‘British Pendulum test' is limited as “it is applicable for medium texture surfaces, but not for low texture surfaces”.
The report further describes a limitation with another testing device called the Grip Tester, which may also be used in the research area of the author's choice. This limitation is when the devices results are correlated with results from a SCRIM test. The limitation is that the devices do not consider macro-texture effect with different test specimens. Therefore they can only be tested on the texture in which they were calibrated. This also is a similar problem found with that of the ‘British Pendulum test' in the first report.
The third report was chosen by the author as this relates to the research area through test methods used and through the performance of concrete block pavement (CBP) mixed with crumb rubber. Concrete block pavement (CBP) has often been used for many different pedestrian areas in projects.
Similar to the first report, devices are used in a series of test methods to examine the performance of crumb rubber mixed with concrete block pavement. This interests the author as the report shows methods in which the performance of material surfaces may be improved through the enhancement of aggregates during manufacturing. Different sections of the report such as the load cycle testing, skid-resistance testing and the falling weight test were of high interest to the author.
The skid-resistance test corresponds with the two previous reports as the ‘British Pendulum test' device was used. This test was used in conjunction with the four different types of CBP which were manufactured with different content of crumb rubber. This was interesting to see if the additional content of crumb rubber would improve the skid resistance. However, similarly noted in the two previous reports the texture affects the performance of the method test, the ‘British Pendulum test'. This can be seen in this report as both micro and macro-texture was affected in the fabrication of the CBP test specimens which further affected the results obtained from the skid resistance test and also other tests carried out. Ling et al (2009, p.362), explains how the texture was affected when a higher percentage of crumb rubber was added within the mixture of manufacture. He showed that with the higher content of rubber cracks and de-lamination were appearing throughout the layers of the blocks. This further affected the testing of skid resistance when a lower skid resistance value (BPN) was obtained. This was down to the fact that due to the difference in macro-texture from the different manufactured types of block, rubber content polish occurred. This links in with the first report whereby, Liu, Fwa and Choo (2004) found that the difference in macro-texture does affect the results obtained from ‘British Pendulum test'. This may have shown a disadvantage to the adding of rubber content to CBP, however advantages were found in the falling weight test where the higher the rubber content the more toughness the CBP blocks were. This is highly interesting to the author's research area as pedestrians do apply an impact to pavement surfaces when walking. The report concluded in stating that CBP mixed with crumb rubber content could be used in pedestrian areas, such as walkways or playgrounds.
From a different perspective the fourth report was chosen by the author to obtain a wider aspect as to how slippages on pedestrian areas can be minimised. This report does not have any direct corresponding comparison to the other three reports, however the method of testing used in this report has potential to be used in conjunction with other test procedures used in the other three reports and can be of use to the author's research area. For example, in this report the authors used two different methods of testing. One was to examine human subject's actions of walking on slippery surfaces and the other was to examine different devices which can be of use to the subject individuals to prevent slippage. Parts of the procedure were noted such as the use of different test areas, such as the subject could test the anti-slip device on different surfaces, the use of two experienced physical therapists which observed and recorded the subject in a professional manner, the use of different anti slip devices and the use of recording the subjects perception of each device. This may be of potential use to the author during testing of the author's research area and can potentially be combined with the different testing procedures used in the other three reports.
To conclude, the author has found clear linkages between three of the reports and potential linkages in the fourth report which were analysed for the author's research area. The author has found significant information on how testing methods must be carried out carefully in order to obtain a relative result which can be correlated with other testing methods. One of the reports has shown potential for the application for different testing procedures to be carried out with corresponding test methods which may be of benefit to the author's research. The author has also gained knowledge of how the examination of different parameters can be are carried out in order to correlate the result of skid-resistant testing against different methods. However, further research is required on different testing devices which may be used for the author's research.