## 4 Discussion
The study of the mineralogical composition of stone before beginning the construction process is a well-known and reliable method to reveal the likely trends of stone weathering over the lifetime of stone covering. Unfortunately, this analysis has not been mandatory in Israel in the relevant period. Therefore, it was completely disregarded during the construction of the Panorama Sea Walls. The physical and mechanical properties of kurkar sandstone have been sufficiently altered and worsened even after a concise service life of the Panorama Sea Walls (see Table 2):  
* Water absorption and Hirshwald's coefficient have been substantially increased;
* Water evaporation and mechanical strength have been considerably decreased. Generally, the high water absorption of natural stone together with its prolonged moisture evaporation (i.e., lousy breathability), and the unstable mineralogical composition are the well-known warning signs of probably rapid decay of external stone cladding in the course of exposure to severe hazardous environmental conditions, as explained in Figure 14. This situation was in the case with the Panorama Sea Wall, i.e., increasing the water absorption and worsening the evaporation characteristics of kurkar sandstone in the course of its service life have been a source, an accelerator, and an outcome (a loop process) of physical weathering, chemical alteration decay degradation of wall siding. Furthermore, this process also led to the low strength characteristics of stones (see Table 2). Impact of Construction Technology on Durability of Kurkar Sandstones in the Historic Sea Walls Versus the Panorama Sea Walls in Acre  
The tests of water absorption and mechanical strength of new stones are mandatory in Israel. The total water absorption of stones used in Israeli buildings' external cladding should be less than 2% (weight %) [8]. However, the project planners decided at the design phase that kurkar stones in the Panorama Sea Walls need not meet this standard specification requirement. This decision was adopted due to the time-honored successful experience with kurkar masonry in Acre's historic seawalls. Unfortunately, this approach was completely wrong because of the different aging behavior of thick dimensional stones in the landmark sea walls compared to the thin stone cladding in the modern Panorama Sea Walls. The critical fact is that the historic seawalls in Acre were constructed more than 200 years ago. The historic masonry construction was based on adhering the blocks of dimensional kurkar ashlar stones using air lime mortar. This kurkar stonework was very popular in offshore construction in Israel till the 1950s, and since the 1960s, the dimensional stones have not been used at all in Israeli construction. Generally, because of the replacement of dimensional building stone in masonry with concrete blocks. These thick dimensional stones in the historical sea walls look today less deteriorated than kurkar stone plates used as the modern Panorama Sea Walls' cladding. (The deterioration and structural problems of stonework in the historic sea walls were described and thoroughly analyzed in the conservation project [40]). A primary reason for this discrepancy in weathering  
Figure 14: Diagram presenting the Interaction between the changes in the different stone properties. behavior of kurkar sandstones exposed to the same external environmental conditions are the different construction technologies:  
* The ashlar kurkar blocks, ca. 0.3-0.6 m long, thick, and wide by size, were used in the Historic Walls' stonework in Acre. In these Walls, the bed joints were made of air lime mortar, [41], see Figure 15. Air lime mortar covered ca. 15% of each kurkar block's total surface, and the rest of the body has been left breathable and useful for the evaporation of moisture from the historic sea walls. The modern Panorama Sea Walls are constituted of the reinforced concrete wall cast against the porous sandstone veneer. This stone veneer has been made of kurkar plates ca.