JAPAN-APSARA Safeguarding Angkor

Bayon is one of the structures of the Angkor monuments that is at great risk of collapse, and its Northern Library was especially on the verge of total destruction. In September 1999, the work of partial dismantling and reassembling the Northern Library was completed. The knowledge and techniques obtained in the process of this work are being employed in establishing “The Master Plan for the Conservation and Restoration of the Bayon Complex”.

Preserving not only the Appearance, but also the Original Construction Method to the Furthest extent as possible

Restoration method applied up to now has been to enclose the compound soil layer with the reinforced-concrete wall and install sandstone on the outer side as a veneer. This was the best possible method considering the lack of material stones and manpower at that time. The assignment of JSA was not only to respect the traditional construction method to the fullest extent possible, but also to apply a method that would complement for the structural weakness of the original method.

Applying the Stabilizing Process of the Compound Soil Layer Using the Solidification Mechanism of “TATAKI (traditional Japanese method for making a Compacted Sand Layer)”

After careful investigation of reinforcement plans and experimentation, a decision was made to apply the method of adding a very small quantity of slake lime to the sand of which particle size distribution had been adjusted almost uniformly to that of the sand used originally. By applying this method, sandstone and laterite blocks fulfill both ornamental and structural functions of the construction material used in the past.

Support by Modern Technology

While respecting traditional construction methods on the one hand, modern technology is also applied. Stainless steel bolts are infixed in broken sandstone members and are secured with epoxy adhesives mixed with sandstone powder. The joint parts are preserved with polymer cement mortar mixed with sandstone powder, sand, and mineral pigment. Furthermore, modern construction equipment such as mobile cranes and trucks with mini-cranes are utilized at the restoration sites, thus securing safe working environment.

Procuring New Materials

In order to use original construction methods, it is necessary to procure the same materials. We cannot proceed a sufficient structural endurance for restoration without the same quality of sandstone and laterite as the original for the supplement of lost parts, with the precious stones which we know the original place that were found among the scattered stones, even though you blend the sand for the inner building to and condition that is very similar to the ancient times. After searching for stones with the cooperation of the Ministry of Mine and Energy of Cambodia for two years, JSA finally succeeded in obtaining sandstone that was in color and hardness close to the kind used in Bayon, and also in quarrying new laterite blocks. The markedly deteriorated laterite blocks in the foundation mass were exchanged with new material. This fact happened to open a new prospect for the restoration of the Angkor monuments, because beforehand there was hardship from the reason that the quarry was near the base of Khmer Rouge, and land mines and bad road.

Partial Dismantling or Dismantling Entirely

The roof and walls had been deformed considerable due to uneven settlements it was obvious that dismantling and reconstruction was required. Disintegration of the east and west corners were beyond repair, however, as the central part of the foundation mass sank comparatively evenly over a wide range but, it was possible to restore with this part remaining as it was. After the long discussion, JSA respected its originality to the greatest, and also to develop the restoration method for “The Master Plan for the Conservation and Restoration of the Bayon Complex”, we adopted the method which is to leave the central part of the foundation as it is and dismantle only the corner edges of the building.