THE COOLING RATE OF HOT MIX ASPHALT PAVEMENT DUE TO VARIOUS RAINING CONDITION

Transcription

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 7, July 2018, pp , Article ID: IJCIET_09_07_199 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed THE COOLING RATE OF HOT MIX ASPHALT PAVEMENT DUE TO VARIOUS RAINING CONDITION W. Hashim Faculty of Civil Engineering, UiTM Shah Alam, Shah Alam, Malaysia A.K. Arshad, E. Shaffie Institute for Infrastructure Engineering & Sustainability Management, UiTM Shah Alam, Shah Alam, Malaysia N.I.F. Md Noh Department of Civil Engineering, Faculty of Technology Engineering & Built Environment, UCSI University, Taman Connaught, Kuala Lumpur ABSTRACT Construction of pavement during raining condition creates many problems to the pavement surface and even to the pavement structure itself. The Malaysian Public Work Department Specification section 4 (Clause ) clearly specifies that no pavement works shall be conducted during raining, without any justification to the temperature drop. The hot mix asphalt (HMA) is a hot medium where the rain itself is the cold medium which able to make cool of anything it encounters. Combining these two elements will cause the HMA temperature decrease rapidly and the mixture hardened in short time before the compaction process is done sufficiently. Tests were conducted to compare the temperature and the cooling time of HMA with and without water dropping (through raining simulation). Since the raining intensity can be determined by the size of the raindrops, the difference in the shower size hole is good enough to create different intensity of rain to predict the HMA cooling rate when make contact with water. The cooling rate of the HMA during raining condition decreases rapidly by nearly 99% compared to no rain condition giving the Time Available for Compaction (TAC) less than 60 seconds. This research would propose some knowledge on the rates of cooling when the HMA makes contact with water for future reference and a template for future study of pavement cooling rates during raining condition to ensure the sustainability of pavement lifespan. Key words: Hot Mix Asphalt (HMA), Raining Condition, Cooling Rate, Total Available Time for Compaction (TAC). Cite this Article: W. Hashim, A.K. Arshad, E. Shaffie, N.I.F. Md Noh, The Cooling Rate of Hot Mix Asphalt Pavement Due to Various Raining Condition. International Journal of Civil Engineering and Technology, 9(7), 2018, pp editor@iaeme.com

2 The Cooling Rate of Hot Mix Asphalt Pavement Due to Various Raining Condition 1. INTRODUCTION Malaysia is a tropical country of two main seasons throughout the year which are the raining and dry season. Rain has been really synonym with Malaysian weather. Even in dry season we still get large amount of rain water pouring to this land. Therefore, pavement works has to take the raining issue into consideration for sustainability. Pavement works include the Hot Mix Asphalt (HMA) being brought by lorry to the road site and compacted in-situ. Typical HMA brought to site from the plant is around 160 o C to 180 o C of temperature [1]. Compaction of the pavement in Malaysia are frequently done during raining time to accommodate schedule and many parties seem to agree that compaction of that particular time are considerable as the pavement get easily cold. However, if the mix temperature is below 80 o C, the pavement is no longer suitable for compaction. The problems encounter in pavement construction during raining is the pavement usually will deteriorate shortly as the water tends to cool the mix rapidly and compaction process cannot take place perfectly. Water is the universal agent of cooling where it transfers the heat from high temperature area of mix to the lower temperature area (surrounding). Most of the mix arrive at site has to wait for its laying process which yet slowly cooling it. With the aid of water from raining, cooling process gets faster and reduces the Time Available for Compaction (TAC) Problem Statement and Objective The HMA laid on a road surface is around 160 o C to 180 o C of temperature. The temperature will reduce naturally through the physic law as well as by the environmental effect such as wind speed and rain. Rain brings water into the pavement and becomes the cooling agent. Typical compaction process of the HMA shall take place between 160 o C to 80 o C to achieve its durability and strength. Once the temperature of the mix drops below 80 o C, compaction is no longer advisable. There is no clause in JKR specification in compliance to the placement of HMA in raining condition or any test done to verify the effect of raining towards compaction process and TAC. Placement of the HMA in raining condition is theoretically preferred as the pavement becomes stiff quickly and instantly can be used by road users. However, the rapid cooling of the HMA during raining condition will not ensure the compaction process is done in a well manner and the TAC is sufficient for compaction to take place to achieve its durability. The pavement which are not compacted correctly will likely face problem of cracking (alligator cracking) and is the major cause of other road defects. Hence, the study was conducted with objective to evaluate the effect of raining condition on the cooling rate of the HMA and to determine the TAC Scope of Study The study was mainly conducted in a laboratory area where the environmental effect such as wind speed is relatively low and no sunshine to affect the temperature drop. The temperature drop was presumed to be mainly affected by the water from raining simulation. Marshall Mix Design was applied to obtain the optimum binder content (OBC) for the sample preparation in the temperature test. The study focused on comparing the HMA cooling rate with the effect of rain and no rain condition using the temperature detector editor@iaeme.com

3 W. Hashim, A.K. Arshad, E. Shaffie, N.I.F. Md Noh The material used were aggregates and asphalt binder of 80/100 penetration grade, the most commonly used binder in Malaysian pavements. While the mix grade tested is ACW 14, the typical grade used in pavement construction. Raining condition was simulated by preparing different shower of different hole sizes to indicate the size and intensity of the rain drops. Three sizes of hole were prepared to indicate the intensity of rain which were 2mm (light rain), 3mm (medium rain) and 5mm (heavy rain) for the testing. 2. BACKGROUND 2.1. General Introduction of Pavement Temperature Relation with Water Rain waters carry a cold temperature along and are the universal heat conductor. As the water continues to pour on to the pavement, it also carries the heat inside the pavement itself. Figure 1 shows the HMA temperature drop in accordance with the cooling time [2]. Figure 1 Definition of main analysis element 2.2. Placement of Hot Mix Asphalt During Rain Malaysia receives up to mm for the total monthly rainfall during peak raining season, a huge amount to be faced by pavement contractors frequently. In pavement construction, when the lorry carrying HMA arrives at site, the work has to be done even if it is raining as to avoid wastage of cost by returning the HMA to the plant. The connection between temperature and HMA is important as the appropriate temperature of asphaltic concrete will allow proper compaction process resulting to a good, strong and durable pavement. Improper HMA temperature drop increase the chance of HMA to become weak due to the rapid cooling [3]. There are cases reported of a site where the pavement construction was taken place during raining and after a month, the surface area of the pavement starting to lose down. This condition may indicates that the expose surface area where the precipitation comes to contact with having quicker rate of cooling, were not stick to each other better. A laboratory study was performed which showed an increase in air void content and a decrease in stability with lower compaction temperatures [4]. The study indicated that the majority of compaction should be accomplished before the temperature reaches 225 o F and editor@iaeme.com

4 The Cooling Rate of Hot Mix Asphalt Pavement Due to Various Raining Condition while the mix is still in a plastic state. Therefore, to achieve a uniform pavement, closer control of the temperatures in the field should occur [5] Factors of Cooling by Aggregate The aggregate composition itself has some disadvantages on water abortion. Physically aggregates are granular in shape that they are often to have pores inside it which absorb water very efficiently. Water will continue to cool the aggregate quickly if the aggregate continue to vaporize the water itself. If water continues to flow around the aggregate, the effectiveness of aggregates to keep its temperature will decrease as the water flow will cause the heat to be carried away Compaction of Aggregate Compaction of aggregate is crucial in pavement construction. The mix need to be compacted within an appropriate temperature for its durability and strength to be achieved. Normally, it will take place straight away when the mix has been laid as the temperature has already dropped during the transportation process. The TAC is important to determine the sufficient time to compact the mix before it reaches 80 o C when the mix is not suitable anymore to be compacted [6]. Temperature plays important rules in the quality of the pavement and it is measured when compaction work is done. Temperature indicates how efficient the asphalt binder works and how dense the pavement will be as well as telling the condition of the air void of the pavement itself. 3. METHODOLOGY 3.1. General View The experiment was conducted in a laboratory instead of at field as to control the mix from other environmental effect such as wind and sunlight. Raining condition was simulated using different shower of different holes sizes to resemble the water intensity affecting the cooling rate. HMA was prepared through Marshall Mix Design [7] to obtain the general Marshall Properties and OBC of the mix in compliance with JKR specification. ACW 14 was opted for the experiment. The OBC is essential for the sample preparation to test the temperature drop affected by the raining condition. Related specific gravity of the mix was also determined [8]. Then, the testing sample of a rectangular shape was prepared using a specified mold and tested through the rain simulation process. The mix was compacted manually using steel roller to achieve the specified air void. Temperature was taken at the interval of 60 seconds until it reached 80 o C. The whole methodology is best simplified as the chart shown in Figure editor@iaeme.com

5 W. Hashim, A.K. Arshad, E. Shaffie, N.I.F. Md Noh Aggregate Gradation (ACW 14) Preparation of Marshall Samples (ACW 14) Density-Voids Analysis Marshall Stability and Flow Tests Raining Condition Test Sample Mould Preparation Compaction of Sample Raining Condition Test Result and Discussion Figure 2 Planning Stage 3.2. Raining Condition Test The fundamental idea of this research is to evaluate the cooling rate of HMA cause by rain water effect. Having to test sample on-site during actual raining condition will lead to sample being affected by other environmental element such as wind. Therefore, a raining condition was simulated in the laboratory by using a shower of different holes sizes Sample Mold Preparation Once the OBC is determined, the mold made of wood at specified dimension was prepared to have HMA installed in it. A hole was made at each side of the mold for a thermometer to be inserted to determine the inner temperature of the sample. The mold is practically rectangular in shape as to resemble the actual look of pavement and it is learned that the heat is distributed efficiently around the area of mix through the straight edge instead of the circular one. Circular edge tend to distribute heat in not a uniform way which lead to unstable temperature distribution in the sample thus will likely not giving accurate result. The size of mold is 30.5cm x 30.5cm x 50mm in which 50mm being the thickness. 50mm is the common thickness used in pavement construction in Malaysia and is essential to provide adequate drainage to the pavement itself [9]. Figure 3 shows the dimension of mold and the location for temperature readings which were taken from surface and inner side editor@iaeme.com

6 The Cooling Rate of Hot Mix Asphalt Pavement Due to Various Raining Condition Figure 3 Sample Mold Raining Simulation Raining was simulated by preparing 3 sizes of shower head holes of 2mm, 3mm and 5mm which presents the water drop size. The size and intensity of the water drops are the variable in comparison to the temperature drop. The basic principal on determining the size of water drops is through the size of the shower holes in which rain drops are usually varies from 2 to 5 mm according to its intensity [10]. From this principal, the water drop which is the variable in this test can be changed, the larger the variables in this test, the more accurate the results are. Figure 4 shows the diagram of the shower holes. Figure 4 Shower Head 4. RESULTS AND DISCUSSIONS The results acquired show a major difference between the cooling rate of HMA affecting by no rain and raining condition. Figure 5 and Table 1 show the TAC between the control sample (no rain condition) and testing sample (raining condition). The control samples takes in average of 33 minutes to cool from 160 c to 80 c. While the temperature of the testing sample editor@iaeme.com

7 W. Hashim, A.K. Arshad, E. Shaffie, N.I.F. Md Noh tend to decrease tremendously by the range of 98%-99% to reach the minimum 80 o C temperature for compaction as compared to the control sample. The results indicate that generally HMA paved during raining condition has less than 45seconds of TAC before it reaches the 80 o C temperature which theoretically will not allow a proper and complete compaction process to take place. The bigger size and the higher intensity of rain give the shorter TAC. Figure 5 TAC for different raining condition on HMA Size of Rain Table 1 TAC and cooling rate for different raining condition on HMA Inner (average) (seconds) Time Available for Compaction (TAC) Surface (average) (seconds) Average (second) Reduction (%) Cooling Rate (average in o C/sec) No Rain Controlled mm % 1.9 (Light) 3mm % 4 (Medium) 5mm (Heavy) % 6.2 From the result, it indicates that the water could affect cooling rate of HMA quite seriously. The water tends to immediately remove the heat giving a short and in appropriate time for compaction before the mix reaches the critical 80 o C temperature. Even the lightest rain size can absorb the heat as quick as 45 seconds or by 98% reduction as compared to the no rain condition. The percentage has plunged much higher for medium and heavy rain and which has been forecasted earlier as higher volume of water pouring onto the pavement causing its temperature to drop rapidly and the heat being carried out are in large amount. Temperature of the surface area that made the first contact with the water tend reduce faster than the inner one. By theories, the short time of TAC which is just in seconds will not allow proper compaction process to take place. As due to that, the durability of the pavement is hardly achieved leading to defects in short period. The water used in the lab is simply the tab water in which the rain water temperature is far cooler, causing the pavement to cool quicker. The rain water has more large momentum than the simulated testing shower as the falling height is much higher causing it to penetrate much deeper into the pavement. The rain study gives editor@iaeme.com

8 The Cooling Rate of Hot Mix Asphalt Pavement Due to Various Raining Condition small part in the pavement cooling due to rain or water effect and needs to be an guideline on rain effect to the compaction process where there were more aspect to be consider which can contribute to the fast rate of cooling the HMA. 5. CONCLUSION AND RECOMMENDATION From the test conducted, the results clearly indicate that paving works done in raining condition will increase the cooling rate thus reduce the TAC of HMA in which less time is available for the compaction process to take place. The laboratory testing through raining simulation is a simple justification apart from the actual rainwater pouring onto the pavement. The rainwater that varies from its size which indicates the volume of water carried tends to cool the HMA as quickly as larger the size goes. The temperature of the HMA surface area that made the first contact with the water will reduce rapidly causing this layer to be hardened first. The inner layer will then decrease much faster of its temperature as the water starts to penetrate the void. Reduction of temperature from 160 o C to 80 o C in less than 45 second is theoretically too fast for a compaction process to take place hence would justify that pavement works during raining condition are highly not advisable. Getting optimally hardened by 80 o C, the HMA could still be compacted by the roller from its weighing power but the process will not ensure the durability from the compaction is well achieved leading to quick defects in future. The TAC is critical as it depends on the cooling rate which is easily affected, especially under watery condition as shown by result from the test conducted. Therefore, recommendations are laid out to lead to a better control of TAC under adverse conditions. It is recommended that the compaction process shall not be continued in any circumstances during raining condition. Force compaction on low temperature HMA shall not be a practice at site as this will affect the workability of the pavement in the future. ACKNOWLEDGEMENT Special thanks to the Universiti Teknologi MARA (UiTM) for the funding and financial support. Appreciation also goes to the management Faculty of Civil Engineering, UiTM as well as colleagues and technical staffs for their constant support and encouragement. REFERENCES [1] Wardati H., Mohd. R.H, Nurfarah N.I., Nur I.M.Y., Mohd. E.A. dan Norhidayah A.H. The Cooling Rate of Hot Mix Asphalt Due To Various Raining Condition. Jurnal Teknologi (Sciences & Engineering) 78: 4 (2016) [2] Jendia, S. And Jarada, A. Traffic Opening Time and Time Available For Compaction For Fresh Asphalt Layer Using Slab Specimens Model. The Islamic University Journal (Series of Natural Studies and Engineering) Vol.14, No.1, P.11-35, 2006, ISSN [3] Hans R. Pruppacher and James D. Klett. Microphysics of Clouds and Precipitation. Reidel, Boston pp [4] Parker, Charles F. Temperature in Bituminous Mixtures. Highway Research Board Special Report 54. Washington, D.C pp [5] Steven A. Read (2001). Construction-Related Asphalt Concrete Pavement Temperature Differentials and the Corresponding Density Differentials. Washington State Transportation Center (TRAC) editor@iaeme.com

9 W. Hashim, A.K. Arshad, E. Shaffie, N.I.F. Md Noh [6] Hashim, W., Noor, M. N. M., Shaffie, E., Rahman, Z. A., & Arshad, A. K. (2018, April). Cooling Time of Porous Asphalt Pavement Affecting Compaction Process Due To Various Raining Condition. In IOP Conference Series: Earth and Environmental Science (Vol. 140, No. 1, p ). IOP Publishing. [7] American Society For Testing Material. The Marshall Method for the Design and Control of Bituminous Paving Mixtures. ASTM D 1559 [8] American Association of State Highway And Transportation Officials. Bulk Specific Gravity of Compacted Bituminous Mixtures Using Saturated Surface Dry Sample. AASTHO T166 [9] Jabatan Kerja Raya. Standard Specification For Road Work, Section 4: Flexible Pavement. Kementerian Kerja Raya JKR/SPJ/2008-S4. [10] Freddy L. Roberts, Prithvi S.Kandhal, E. Ray Brown, Dah-Yinn Lee, Thomas W. Kennnedy. Hot Mix Asphalt Materials, Mixtures, Design and Construction. NAPA Research and Education Foundation 2 nd edition editor@iaeme.com