PENGARUH RENDAMAN AIR LAUT PASANG (ROB) TERHADAP KINERJA LATASTON (HRS-WC) BERDASARKAN UJI MARSHALL DAN UJI DURABILITAS MODIFIKASI

Abstract

ABS tRACT THE INFLUENCE OF SEA WATER TIDE (ROB) IMMERSION TO THE PERFORMANCE OF HOT ROLLED SHEET-WEARING COURSE (HRS-WC) BASED ON MARSHALL TEST AND MODIFICATION OF DURABILITY TEST Most of roads in Indonesia, particularly the ones lie on the seashore areas, such as Semarang, are usually immersed by highly acid seawater tide (rob). In recent years, the area of Semarang, which are immersed by rob is getting wide. Some of the flexible pavement roads, which are immersed by the rob, get broken. Considering those, it is essential to conduct a study on the influence of seawater tide (rob) to the performance of hot asphalt mixture — the latest specification of lataston HRS-WC (2001). The findings of preparation and test to the sample material, the amount of both aggregate and asphalt, as well as the gradation of HRS-WC mixture indicate that the sample materials meet the requirement of latest specification. Marshall method was applied at the first term research to find the Optimum Asphalt Content (OAC). The second term research was aimed to get the value of Marshall at standard condition (2 x 75 blows) as well as the value of refusal density (2 x 400 blows) which was aimed to discover VIM, VMA, VFA, density, stability, flow, MQ, and the IRS of standard immersion. The modification of immersion was applied to find the first value of durability index (r,R) and the value of second durability index (S., SA). Four samples of rob water, those were rob water taken from laboratory, from LIK Semarang, from Ronggowarsito street, and from Mpu Tantular street, were used in the immersion test. The samples of water were checked their colour, smell, pH, level of chloride, level of sulphate, total value of alkalinity and the total value of acid. Fist term research found that the OAC value was 7% to 7.5% and the OAC 7.25% was decided as the sample material. The second term research showed that there was a correlation between Marshall value and the immersion time, the result of void analysis met the requirement at standard density level (2x75 blows). At refusal density level (2x400 blows), the VIM values of the four samples of rob water did not meet the requirement at 24 hour of immersion. The value of stability test, flow and MQ, at standard condition and at refusal condition for all immersion time and total acid meet the required standard. IRS value at standard and refusal condition for immersion time and total acid value meet the required standard at 72 hours of immersion. Meanwhile, at the immersion time of 120 hours and 168 hours, the IRS value did not meet the required value, as the asphalt capability to maintain cohesion and adhesion between aggregate was getting weak. Modification of immersion test discovered Durability I Index, where immersion time caused the increasing of index score (r and R) at both standard condition and refusal density condition. This indicates that the HRS-WC losses its power. Modification of immersion also discovered Durability II index, where immersion time leads index score of residual stability (Sa) to decrease at both standard and refusal density condition. This resul indicates that the duration level of the HRS-WC is getting low. This also shows that the longer time FIRS-WI immersed in rob water and the higher the acid level of the rob water resulted in decreasing density level of iI mixture and decreasing the capability of asphalt in maintaining cohesion and adhesion of aggregate. Void analysis shows that optimum asphalt content 7.25% (Median of 7% and 7.5%) has not resulted the b performance of HRS-WC. It is estimated that optimum asphalt content is between 7% and 7.25%. FIRS-WC immersed in neutral water (pH closes to 7) has better performance compared to the one immerse acid rob water or in base rob water. It cannot be concluded specifically that the level of chloride influences' performance of HRS-WC because it was found that total value of acid responsible for the decreasing of 1-WC performance. It was also found that the sulphate degree of rob water caused decreasing of HRS performance. This happened to the samples with sulphate degree of 53 mg/I as the sulphate degree more th mg/I can neutralize the acid of rob water (the findings show that the higher the sulphate degree causes the the total value of acid). In that condition, HRS-WC performance was getting better. It can be concluded that the high level of acid of seawater tide (rob) will reduce duration of HRS-WC pa construction. When this construction is immersed in rob water, it can only maintain asphalt and ag cohesion and adhesion for 72 hours. Key Word : HRS-WC, Refusal Density, Total Value of Acid, Durability Index.