Rebound Hammer Test result of old repaired masonry wall using premixed mortar additive in tidal flooding prone area

Abstract

The coastal areas of Java, especially Semarang and Demak, are tidal flooding-prone areas. In fact, tidal flooding decreases the quality of life in coastal areas due to the capacity of seawater in destroying the building, houses, and environment. One innovation is introduced in this paper, which is the premixed mortar additive to repair masonry walls of house in tidal-prone areas. Principally, some measures should be done to address the problems caused by tidal flooding. In this research, masonry walls were improved by applying premixed mortar additive. The results were investigated after its long term performance, for more than one year, by using non destructive Rebound Hammer Test. This research was conducted by experimental activity. There were two masonry walls that had been repaired about a year ago. Some old masonry and concrete bricks of the walls had been substituted by new concrete bricks made of polymer-modified mortar with Moringa oleifera and Gracilaria Sp. and then covered by premixed mortar additive. Those masonry walls were built in Sriwulan village, Sayung and Pucang Gading— as the control site. Non destructive Rebound Hammer Test was applied on the masonry walls aged 12, 13, and 14 months. Each masonry wall was tested by 5 (five) zones (A, B, C, D, and E). Ten shoots were applied on each zone. The findings revealed: 1) In dry area, Pucang Gading site, there is a consistent performance of compressive strength masonry wall aged 12, 13, and 14 months, 2) In tidal flooding-prone area, Sayung site, there is fluctuative performance of compressive strength masonry wall aged 12, 13, and 14 months, 3) Compressive strength of masonry walls aged 14 months in Pucang Gading site is generally fluctuative, particularly at zone A to E (39.4 MPa to 44 MPa), while in Sayung site, compressive strength of zone A to E indicates declining values (44.3 MPa to 40.8 MPa), 4) At age 14 months, the compressive strength of zone B and E in Sayung site is lower than that in Pucang Gading site, due to tidal flooding, and 5) Slight distinction of compressive strength in Pucang Gading and Sayung site may be provided by premixed mortar additive that covers the walls.