Radiological significance of building bricks in Pakistan

Baked clay bricks samples were collected from both urban and rural areas of the North West Frontier Province of Pakistan and natural radioactivity due to 40K, 226Ra and 232Th has been measured in these samples. The specific absorbed dose rates due to natural radioactivity emanating from the walls, floors and ceilings of the typical model rooms made of these building bricks have been calculated applying the mesh size adaptive volume integral methodology. The occupancy factor, representing the weighted average of all the population in the country, was taken to be 0.3 in this study. The values of estimated annual effective dose rates for whole body were found to be 0.38 and 0.35 mSv.y(-1) for the two types of model rooms. These values are smaller than those predicted by UNSCEAR for normal background areas. Thus the building bricks analysed in this study do not pose any significant health problem to the population.     

Radiological significance of beach sand used for climatotherapy from Safaga, Egypt

As a part of national survey to evaluate natural radioactivity in the environment, concentration levels of radioactivity were analysed for sand samples from Safaga, Egypt, which is an ideal area for climatotherapy of psoriasis. Gamma dose rates of three beaches in Safaga were measured. The values ranged from 195.1 to 210.7 nGy h(-1). The activity concentrations (Bq kg(-1)) of radionuclides 238U series, 232Th series and 40K in three different sand profiles (0-5, 5-10, 10-15, 15-25 and 25 - 40 cm) were measured using gamma-ray spectrometry. The annual effective doses were 259 microSv y(-1) for Minveila, 255 microSv y(-1) for Ganet Safaga and 239 microSv y(-1) for Masab El-Ghazel beaches. The dose rates, radium equivalent activities and external hazard indices were evaluated and compared with the international data. These results may contribute to the determination of absorbed dose rate reference levels in Red Sea Coast at Safaga city.     

Radiological characterisation of Artvin and Ardahan provinces of Turkey

Indoor radon concentration measurements were carried out and corresponding annual effective doses due to exposure to indoor radon were determined in Artvin and Ardahan provinces located in the eastern part of Turkey. The measurements were performed for four seasons in order to determine the seasonal fluctuations mostly observed in indoor environments. Indoor radon concentration values were observed to range from 21 to 321 Bq m?3 for the Artvin province and from 53 to 736 Bq m?3 for the Ardahan province. It was observed that minimum indoor radon concentration values were obtained in summer, while the highest ones were observed in winter. Indoor radon concentration values of the current study were compared with those of other provinces in Turkey. As elevated indoor radon concentrations are mostly correlated with high 23?U activity concentrations in soil, a total of 57 and 33 soil samples were collected from the Artvin and Ardahan provinces, respectively, to determine 23?U activity concentration as well as the concentration of 232Th and ??K--naturally occurring radionuclides. It was also observed that soil samples collected from the study areas contained 13?Cs as an artificial radionuclide.     

Natural radioactivity levels of granites used in Turkey

Thirty granite samples commonly used in Turkey were surveyed for natural radioactivity. Concentrations of natural radionuclides in all samples were determined by gamma-ray spectroscopy with hyper-pure germanium detector. The activity concentrations measured for (226)Ra and (232)Th ranged from 0.7±0.1 to 186±1 Bq kg(-1), and from 0.5±0.1 to 249±2 Bq kg(-1), respectively. The activity concentrations obtained for (40)K varied from minimum detectable activity (0.4 Bq kg(-1)) to 1935±11 Bq kg(-1). The radium equivalent activity (Ra(eq)), the absorbed dose rate (D), the external hazard index (H(ex)) and the annual effective dose equivalent were also calculated and compared with the international recommended values. Granite samples were also analysed mineralogically. It was observed that the presence of large amount orthoclase and radiogenic accessory minerals are the sources of high activity concentration levels.     

Radioactivity measurement of primordial radionuclides in and dose evaluation from marble and glazed tiles used as covering building materials in Turkey

Measurements of the natural radioactivity arising from primordial radionuclides ((226)Ra, (232)Th and (40)K) in marble and glazed tile samples used covering building materials in Turkey were carried out by gamma-ray spectrometer with a high purity germanium detector. The mean activity concentrations of the (226)Ra, (232)Th and (40)K in marble and glazed tile samples were found as 8.2, 5.5 and 58.1 Bq kg(-1) and 81.2, 65.4 and 450.1 Bq kg(-1), respectively. The radiation doses received by occupants of buildings in which the sample marble and glazed tiles might be used are estimated using measured activity concentrations of constituent primordial radionuclides and dose conversion factors evaluated by the European Commission from models of tile use. Results obtained are presented for each radionuclide, analysed and compared with relevant national and international legislation, guidance and report, and with the results obtained from other studies. Results show that the use of such decorative building materials in the construction of domestic homes or workplaces in Turkey is unlikely to lead to any significant radiation exposure to the occupants.     

Gamma activity and radiation dose in concrete building blocks used for construction of dwellings in Jos, Nigeria

Radioactivity concentrations of concrete building block samples made and used in Jos, Nigeria, were determined using a gamma ray spectrometry method. The mean values of the radioactivity concentrations were calculated as 66, 126 and 589 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The radium equivalent activities ranged between 131 and 712 Bq kg(-1), with six of the samples exceeding the UNSCEAR reported maximum permissible level of 370 Bq kg(-1). The mean radium equivalent activity (292 Bq kg(-1)) is higher than the values available in the literature for some countries by factors ranging between 2 and 5, a situation that can be traced to the practice of sourcing sand aggregates from mining sites. The indoor annual effective dose for a dwelling of dimension 3.6 x 3.6 x 3.0 m(3) was calculated as 0.81 mSv.     

Standardised building in housing construction and economical construction methods

Building prices and construction costs for housing construction in Germany are growing dynamically. The main cost drivers are still legal, normative and other regulations that are generally drawn up at federal level. However, the trend in building prices also shows that intense building activity is also affecting prices. This trend is also complex: the trend in the groups of trades concerned with carcass work can be categorised between the rate of inflation and increased building prices. The price trend in the whole of technical completion, on the other hand, is disproportionate, and it is these completion trades (heating, ventilation, sanitation and electrical) that are actually driving construction costs. Building materials for primary construction of our residential buildings are also developing at different rates. Masonry falls within the sphere of the general growth rate of prices, while reinforced concrete and wood are much higher. This overall trend shows the finiteness of supposedly simple solutions for accelerating the rate of construction in housing construction. Serial building can only offer a niche solution. Far more intelligent is the use of standardised construction, i.e. repetition of ideal ground plans, development types and standardised buildings that can be adapted to the conditions at each site. Furthermore, it is clear that the use of masonry construction in a multi‐floor residential building is still the most economical type of building to construct in Germany.     

减缩剂的作用及其机理

通过对减缩剂作用和机理的研究表明,减缩剂能较大幅度的降低干燥收缩和相对较小的提高塑性收缩抗裂能力,但在一定程度上降低了砂浆的力学性能.从塑性抗拉强度、表面水份蒸发率和孔结构三个角度对减缩剂的作用机理进行了试验分析,结果表明:减缩剂的加入能较显著的降低水溶液的表面张力,同时也降低了砂浆表面的塑性抗拉强度,增大了表面水份蒸发率,它对塑性收缩抗裂的效果取决于对塑性抗拉强度和毛细管收缩应力影响的权重;表面张力试验表明,减缩剂减小干缩的机理主要在于降低了孔溶液的表面张力;从对孔结构的分析表明,减缩剂掺入后增大了孔隙率,并增加了孔径＞0.1μm的孔的含量,从而降低了掺减缩剂的砂浆力学性能.     

Massive versus lightweight construction in residential building

Masonry as the primary form of construction is currently the most economic option for the building of multi‐storey apartment blocks in Germany in order to provide affordable housing. It can however also be stated that there is definitely further rationalisation potential in masonry construction, in contrast to lightweight construction. In comparison to masonry construction, lightweight building methods show no apparent economic advantages, the ecological balance is objectively equivalent and the fire protection and sound insulation properties have to be provided technically and constructively at high cost in order to comply with the same requirements. Under consideration of a realistic and objective assessment, there is therefore no reason to promote the use of lightweight building methods, such as timber‐frame, from their current status as niche products, especially for residential building.     

Radiological aspects of the usability of red mud as building material additive

Several researchers have examined and achieved favourable results in connection with the building industry's use of red mud extracted in large quantities from the processing of bauxite. These days more and more precedence is being given to limiting the radiological dose to the population. In this study carried out in Hungary, the use of red mud, bauxite, and clay additives recommended for the production of special cements, were examined from a radiological aspect.

²²⁶Ra and ²³²Th activity concentrations measured in Hungarian bauxite, red mud and clay samples were significantly similar with the levels for such raw materials mentioned in international literature.

Taking radiation protection aspects into consideration, none of these products can be directly used for building construction. Taking Hungarian and international values into consideration, a small amount of red mud, not exceeding 15% could be used for brick production, for example as a colouring material. However, beyond this amount the standards for building materials would not be met.

For the production of cements an even stricter limit needs to be determined when both bauxite and red mud are used.     

Failure analysis of 10 year used wooden building

In this paper the factors influencing the service life of one specific building have been studied using as an example a cottage rebuilt into a private house. The building is situated on the northern coast of Estonia, 35 km west of Tallinn. The cottage was taken into active use in 1990. The end of the service life was 2000. Therefore the service life of this building was only 10 years. The main reason for the end of the service life was damage done by dry rot (Serpula lacrymans). Dry rot spread so far that it could not be stopped and could not economically be treated. The analysis of influences on the service life is made in accordance with the standard ISO-15686 factors (ISO 15686-1:2000 and ISO 15686-2:2001): quality of components, design level, work execution level, indoor environment, outdoor environment, in-use conditions, maintenance level.     

Design of clay/cement mixtures for extruded building products

In this work, ternary mixes of sand, cement and kaolin are studied in order to design extruded building products with reduced environmental impact. Firstly, the amount of water required to reach the extrusion rheological criterion and the immersed mechanical strength are studied. Results lead to a compressive strength prediction tool (derived from Feret model) which provides the compressive strength of a given ternary mix. Then, the dimensional and immersion stabilities of ternary mixes are studied. It shows that for mixes containing more kaolin volume than cement volume, mechanical strength is largely influenced by the saturation state. Finally, collected data show that cement stabilized clay blocks and high content cement substitution concrete can be designed with clay/cement mixes.     

Radioactivity in building materials used in and around Dhaka city

The activity levels of (226)Ra, (232)Th and (40)K were determined using gamma-ray spectroscopy in different commercial brands of cement, sand and hollow concrete bricks, which were collected from the building material suppliers of Dhaka City. The activity concentrations in the samples were found to be somewhat higher than in other countries. An effort has been made to assess the radiation hazard associated with these materials by determining the gamma activity concentration index I. It was found that the value of I for all the samples was 相似文献   

Carbonation durability of blended cement pastes used for waste encapsulation

Blended cement pastes are currently used for encapsulation of low level and intermediate level nuclear waste in the UK. However, there is still little information on the long-term durability of those mixes to some chemical attacks. Accelerated testing may predict the long-term durability or at least help the selection of more durable formulations. In this work, blended blastfurnace slag (BFS)/Portland cement (OPC) pastes containing 60, 75 and 90% BFS and pulverised fuel ash (PFA)/OPC pastes with 40, 55 and 75% PFA were cured at 20 and 60°C for 90 days then submitted to natural and accelerated carbonation (5% CO₂). The effects of the curing temperature as well as the OPC replacement level on the carbonation ratio are presented. Results showed a good correlation between natural and accelerated carbonation for the pastes studied. Carbonation was found to be governed by the amount of calcium hydroxide available in the mixes before the process started.     

Experimental burning of used automotive crankcase oil in a dry-process cement kiln

An experimental program was carried out at the St. Lawrence Cement Company Limited, Mississauga, Ontario, in which 330,000 gallons of used lubricating oil was burned as a portion of the total fuel requirement for a dry-process cement kiln. The plant uses a dual four-stage preheater with a by-pass system. The oil was primarily composed of automotive crankcase drainings and contained approximately 0.6% lead, 0.15% bromine, 0.1% zinc and 0.1% phosphorus.Lead, zinc and phosphorus emissions in the kiln exhaust gases were not found to be increased during waste-oil burning. A small reduction in particulate emissions was found during waste-oil burning. A small increase in bromide emissions was found to occur during the waste-oil burn. A material balance was carried out for lead, bromine, zinc and phosphorus which indicated that these elements were retained in the process solids. Lead, zinc, phosphorus and some of the bromine were retained in the cement clinker. Most of the bromine was retained in the collected dust from the precipitator on the by-pass system.     

面向建筑物重建的相机标定方法研究

由于灭点具有很多独特的几何属性且大量地存在于建筑物场景中,因此针对建筑物重建,提出了一种基于灭点的相机标定方法。首先通过构造各种几何约束关系,如灭点与相机矩阵间的关系、世界坐标原点和相机矩阵间的关系,逐步实现相机矩阵的度量重建和欧氏重建,获得相机矩阵的值,然后通过分解相机矩阵得到相机的内外部参数。该方法在标定过程中无须借助任何标定物,求解过程简单,标定速度快。实验结果表明,该方法可以满足虚拟现实中建筑物场景重建的需要。     

Assessing the carbon sequestration potential of magnesium oxychloride cement building materials

Magnesium oxychloride cement (MOC) boards have the potential to offset carbon emissions through carbon mineralization, a process whereby carbon dioxide (CO₂) is converted to carbonate minerals. Boards (0–15 years old) contained MOC phase 5 (21–50 wt%), brucite, primary (e.g., magnesite) and secondary (hydromagnesite and chlorartinite) carbonate minerals. Quantitative mineralogy, electron microscopy and carbon abundance data demonstrate that secondary carbonates form through the reactions of MOC and brucite with CO₂ within interfacial water layers after board manufacturing. Stable carbon isotopic data confirmed the source of sequestered CO₂ as being from the atmosphere. Average carbonation rates were approximately 0.07 kg CO₂/m² board/year or 9.8 kg CO₂/t board/year over 15 years, offsetting ∼20–40% of estimated carbon emissions. In experiments using 10% and 100% CO₂ gas, carbonation was accelerated by approximately 400 and 1600 times in comparison to the passive rate. Integration of carbonation reactions into MOC board production could provide significant carbon offsets.     

关于陶粒混凝土高层泵送施工的探讨

本文通过具体工程实例,研究了陶粒混凝土通过调整配合比,改进保水性、黏结性,适当增加容重,保证施工坍落度,最终实现高层泵送,解决了困扰施工多年的难题。     

Natural radioactivity in granite stones used as building materials in Iran

Due to increasing concern about environmental radiological protection, specific radioactivity concentrations of (226)Ra, (232)Th and (40)K in different types of commonly used granite stone samples collected from the Tehran city of Iran have been determined by means of a high-resolution HPGe gamma-spectroscopy system. The activity concentrations of (232)Th, (226)Ra and (40)K in the selected granite samples ranged from 18 to 178, 6 to 160 and 556 to 1539 Bq kg(-1), respectively. The radium equivalent activities (Ra(eq)) are lower than the limit of 370 Bq kg(-1) set by NEA-OECD [Nuclear Energy Agency. Exposure to radiation from natural radioactivity in building materials. Report by NEA Group of Experts. OECD (1979)], except in two samples. The internal hazard indexes have been found well below the acceptable limit in most of the samples. Five samples of investigated commercial granite stones do not satisfy the safety criterion illustrated by UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation. Exposure from natural sources of radiation. Report to the General Assembly (1993). Applying dose criteria recently recommended by the EC [European Commission Report on Radiological Protection Principles Concerning the Natural Radioactivity of Building Materials. Radiation Protection 112 (1999)] for superficial materials, all investigated samples meet the exemption dose limit of 0.3 mSv y(-1).