Material Science and Applied Chemistry ______________________________________________________________________________________________ 2012 / 25 Application of Building Stone in the Old Kingdom of Ancient Egypt as an Indicator of Changes in Knowledge Agnese Kukela1, Valdis Seglins2, 1-2University of Latvia Abstract. The study investigates the construction stages, introduced. These innovations concerned large-scale materials and binder used in the Step Pyramid of Djoser to application of building stone and binder of far better quality, determine its current state of preservation. This research has and they resulted in construction of previously unthinkable allowed identifying 5 different building stone selection stages, structures. In this sense, the Step Pyramid of Djoser is a marking the development of knowledge on construction materials and their properties. This pyramid is exposed to deterioration unique structure and provides evidence for numerous attempts processes threatening stability of the structure. Unconsidered to implement innovations concerning geological knowledge restoration strategy just aggravates the situation, but this study on building stone available and its properties, binder and its would assist in elaboration of appropriate conservation measures. variations for different purposes, thus marking an extremely important stage in the initial development of the silicate Key words: stone material, stone processing, indicators of chemistry. Furthermore, it also concerns the areas of planning, knowledge, Ancient Egypt development of building constructions, engineering calculations, etc. The experiments and innovations promoted rapid diversification of building material. Such improved I. INTRODUCTION knowledge was successfully applied to developing the world’s The Old Kingdom of Ancient Egypt (ca. 2686-2160 BC) is major stone construction project – the complex of pyramids at notable as a time of rapid changes in the society and also in Giza. the building. The skills and knowledge obtained during the Predynastic period regarding the building of complex and II. GEOLOGICAL STRUCTURE AND ENVIRONMENTAL multi-level underground tombs were decreasing, yet CONDITIONS OF THE TERRITORY familiarity with rocks, their properties and treatment features The Saqqara plateau is situated about 40 km southeast of was rather high; moreover, the tools necessary had already Cairo on the left bank of the river Nile and rises for 17 – 25 m been developed. During this period the adobe material above modern flood terrace of the river. Starting from the production and building abilities improved and starting from Early Dynastic times this plateau was used as a necropolis the 2nd Dynasty individual construction elements (door which served as such for about 3 thousand years. The tombs openings, columns, flour slabs) were produced of stone. At the were built as underground structures, as well as mastabas and beginning of the 3rd Dynasty grand flat-mound tombs pyramids, their combination and as simple Coptic cemeteries. (mastabas) were being built reaching 35 000 cu.m in Nowadays, these are outskirts of the desert with active construction volume. The building stone was rarely used, movement of sand, requiring regular care and maintenance of whereas gypsum and adobe plaster of various compositions the monuments located on the plateau. The climate is very dry; were applied frequently. rainless period may last for several years, whereas sand storms In the architecture of Ancient Egypt mortar mainly fulfilled are very frequent, thus intensifying the deterioration of the two functions. It was used as a binding material between the monuments. stone blocks and as a sliding material to reduce friction of The Saqqara plateau is formed by middle and late Miocene heavy blocks being put in the position [1]. But, since the Mokkatam Formation (separate lower part of Maadi group) as quality of shaping of building blocks and their positioning, layered and rhythmic lime rocks at shallow sea conditions. especially in the body of the structures, was rather low, the The lower part of the rhythm consists of 30 – 50 cm thick mortar, along with a mixture of small pieces of stone was also massive sandy limestone layer, covered by 10 – 15 cm thick used to fill the gaps between the blocks. lime marl. These layers are overlaid by up to 10 cm thick layer The use of gypsum mortar is known from the times of the of marl and argillite. The next rhythm basement layer is sandy 2nd Dynasty. It mainly consisted of burned gypsum and sand, limestone or sandstone with carbonate cement, which is not frequently with chipped limestone. Yet, quality of such plaster always marked clearly and is followed by less sandy and was rather low. Moreover, the quality of novel materials used massive limestone. At the upper section the proportions of as a binder is even lower and it can be easily distinguished layers change and clayey rocks prevail. At the top of rhythm also nowadays. the proportion of the limestone and marl/argillite reaches At the end of the 3rd Dynasty, the time linked with the almost 1:1. The thickness of rhythms is not constant and reign of king Djoser, numerous innovations had been variations are observed from 0.7 – 1.2 m up to 4 – 5 m. 31 Material Science and Applied Chemistry 2012 / 25_________________________________________________________________________________________________ Sometimes local depressions are visible, where the thickness For this reason, several sets of photographic documentation of clayey rock layer reaches several meters. The general of the pyramid’s facades and fragmentary verification of the tendency marks the increase in clayey layers thickness data obtained applying non-destructive methods on site were towards the south, but to the north these rocks have used as a main source of information. considerable amount of gypsum. Aforementioned grey and yellowish grey layers of sandy limestone are the main building materials in this area used in construction of the necropolis, and the upper part of the geological section at some parts is exposed to the stem escarpments of the plateau. The Saqqara plateau is located in the seismically active area, where earthquakes with magnitude of about 4.0 happen yearly. As a result, massive limestone layers are cracked forming a peculiar structure of blocks measuring approximately 0.30 – 0.40 m (Fig. 1). Fig. 2. Schematic representation of stages in building the Step Pyramid [2]. M1, M2, M3 – initial mastaba rebuilding stages; P1, P2 – pyramid rebuilding stages For the needs of the study, the 3D geospatial model of the pyramid was created using MicroStation V8i software [3], allowing supplementation of this model with numerous levels of specific information. One of such layers contains data on typical forms of weathering of the pyramid stone material and its weathering intensity [4]. Detailed identification of weathering forms was carried out on samples areas verified on site with further manual interpretation of high resolution photographic documentation. The state of preservation or Fig. 1. Exposed fragment of geological section of Saqqara plateau damage due to weathering of exposed surface of the stone blocks of each façade of the Step Pyramid was assessed. Larger intact natural limestone blocks are of rare Additionally, the types of binding mortar and its preservation occurrence. Seismic activities affect the monuments located were identified [5]. on the plateau and result in loss of the stability of their The quality of building blocks used in the various phases of structure. construction of the pyramid was also appraised. A number of criteria to evaluate the quality of building blocks were set, III. MATERIALS AND METHODS such as size of the blocks (diversity and variations) and The study was conducted in the Step Pyramid complex that uniformity of the material chosen (selection of stone material encompasses several temples, the pyramid and its complicated of same composition and properties), treatment of surface of underground system of galleries and passages embracing the the blocks (unprocessed, tooled edges, processed edges, area of 15 ha constructed just in 20 years. The pyramid was smoothed surface), pre-processing of the blocks enhancing built in several stages, gradually progressing from initial their quality (removal of the layers of clayey rocks easily square mastaba until forming a four-step pyramid and later a affected by weathering). Potential sites of ancient stone six-step pyramid of rectangular base as it is currently exposed material extraction were studied as well. Such sites are eastern (Fig. 2). This funerary complex has been robbed, rebuilt and and north-eastern escarpments of Saqqara plateau partly reconstructed already starting from antiquity times. Therefore, accessible for visual examination with numerous ancient it is hard to identify the time of particular construction or tombs located there. Such examination enabled the authors to restoration. In the search for cheep building materials, the compare the results obtained with the data of the other studies construction and finishing materials of the pyramid’s complex on quality of the stone material used in the construction of the were stolen; temples and subsidiary buildings were partially pyramids [6,7]. ruined. Therefore, starting from the year 2005 our study was mainly IV. RESULTS AND DISCUSSION focused on the investigation of the Djoser’s pyramid, which The appraisal of the quality of stone production and was rebuilt to a lesser