Water Saturation Coefficient Research Articles

Fibrous Noble Opals: Electron and Atomic-Force Microscopy and Spectrometry Data

The work deals with results of study of hydrothermal noble opals. It has been established that hydrothermal opals are composed of multiple clusters: chaotic packs, fibers and grid layers. An effect of the water saturation coefficient on the opal optical properties was considered.

Limestone on the ‘Don Pedro I’ facade in the Real Alcázar compound, Seville, Spain

Abstract This paper discusses the research conducted prior to restoring the ‘Don Pedro I’ facade on the Real Alcázar or royal palace at Seville, Spain. The different types of stone on the facade were located and characterized, and their state of decay mapped. Although other materials (brick, rendering, ceramics, marble) are present on the facade, its main elements are made from two types of limestone: palomera and tosca , each in a different state of conservation and exhibiting distinct behaviour. Colour parameters, real and bulk densities, compactness, open porosity, water saturation coefficient and total porosity were determined to characterize the two varieties. In addition, ultrasonic techniques were used to map the various levels of decay on the facade, stone by stone, for future interventions. The findings show that owing to its petrographical and petrophysical properties, palomera stone is of a lower quality than tosca stone, and has undergone more intense deterioration.

Salt weathering in dual-porosity building dolostones

The influence of rock fabric on physical weathering due to the salt crystallization of selected brecciated dolostones is discussed. These dual-porosity dolostones are representative of heterogeneous and anisotropic building rocks, and present highly complex and heterogeneous rock fabric features. The pore structure of the matrix and clasts is described in terms of porosity and pore size distribution, whereas the relative strength for each textural component is assessed using the Knoop hardness test. The whole characterisation process was carried out using the same samples as those used in the standard salt durability test (EN-12370), including connected porosity, the water saturation coefficient, fissure density, compressional wave velocity and waveform energy. Results show the most important rock fabric elements to be considered are the matrix and clast properties and the nature of fissures. Firstly, a relatively weak matrix was the focus of major granular disintegration as it presents high porosity, low pore radius and reduced strength. Secondly, narrow micro-fissures appear to be important in the decay process due to the effectiveness of crystallization pressure generated by salt growth. On the contrary, macro-fissures do not contribute greatly to rock decay since they act as sinks to consume the high supersaturations caused by growth of large crystals. Additionally, an analysis of stress generated by crystallization was carried out based on the general situation of a lenticular crystal geometry. Finally, the relationships between whole petrophysical properties and durability were established using a principal component analysis. This analysis has clearly established that the durability of rocks affected by salt crystallization mechanisms diminishes in weaker and anisotropic rocks with high porosity and fissure density.

Stabilized aeration on chutes

1. Relation (8) was established, according to which the coefficient of aeration of a rapid uniform flow (coefficient of stabilized aeration), regardless of the roughess of the bed, is uniquely determined by the measure of the dissipation of specific energy — its gradient (I). 2. Relation (15), being a more accurate realization than (4) of relation (8) for cross sections bounded by a conditional free surface with a local value of the water saturation coefficient βloc=0.01−0.02 (aloc=0.99−0.98), was developed. Relation (15) is recommended for engineering calculations in the entire practical range. 3. The establishment of relation (8) clears up the problem of modeling the phenomenon of stabilized aeration in prismatic channels, reducing it to the condition I=idem, with simultaneous provision of the necessary path length of stabilization. 4. Relation (6) does not correspond to the actual data on aeration of rapid flows.

Development of light-weight insulating clay products from the clay-sawdust-glass system

Employing a simple dry-pressing and sintering process, lightweight clay products with various physical, mechanical and thermal properties have been fabricated from mixtures of maplewood sawdust, clay and soda-lime glass grains prepared from recycled waste glass. Studies showed that thermal conductivity, compressive strength, and cold water absorption of the sintered sawdust-clay products are significantly modified by the addition of sawdust particles to the clay mixes. Studies also showed that portions of the clay particles can be replaced with soda-lime glass grains of similar sizes. These light-weight composite clay products have compressive strength in excess of 31 MN/m 2, thermal conductivity value in the range 0.21–0.39 W/m, °C and water saturation coefficient of about o.72. The fabricated clay products exhibit attractive characteristics as building materials and could contribute to energy conservation because of their high thermal insulation value.

Studies on Water Absorption Property of Artificial Lightweight Aggregates

In recent years many artificial lightweight aggregates have been introduced and marketed widely as structural concrete aggregates. The water absorption property of lightweight aggregates exerts influence on the fundamental properties of fresh and hardened concretes.Since the absorption property of the aggregates shows wide variations, 15 kinds of aggregates, including 11 artificial lightweight aggregates, one expanded slag, 2 pumices and one river gravel, were selected as the specimens for several water absorption tests under various conditions such as in normal water, boiling water, pressurized water and vacuum in order to find the common nature and interrelation among them. The rapid absorption tests such as boiling or pressurized test were not applied to the fine aggregates because of their high absorbability.The main results obtained are as follows : (1) The water saturation coefficient is about 70% by volume for fine artificial lightweight aggregates after one-day immersion in water, but it is generally lower for the coarse aggregates except for the natural aggregates.(2) The water absorption of the heat-treated aggregates is very high and it is proportional to the heat-treatment temperature.(3) From the water absorption after 30 minutes boiling, the long-term absorbability and pumpability of the lightweight aggregates can be estimated rapidly and easily.(4) The absorption in boiling water is proportional to that under pressurized condition for lightweight aggregates. This correlation is particularly notable for the oven-dried aggregates.(5) The absorption from the crosscut section of artificial aggregates is proportional to those under boiling and pressurized conditions as well as to the aggregate particle size of non-pelletized artificial aggregates. Such absorption characteristics enables us to estimate the permeability of these internal structures.