Design thermal values for unfired clay bricks

This paper reports on a laboratory and theoretical method for determining the design values for thermal conductivity and thermal resistance of unfired clay masonry bricks from both experimental and theoretical design point of view. The paper describes the methodology of obtaining these values using the measured lower and upper lambda limits. In order to determine the basic design thermal value and the design thermal resistance, a Laser-comp FOX 200 thermal conductivity meter equipped with WinTherm32an software package was employed for the laboratory data collection and analysis. Lime or Portland cement (PC)-activated Ground Granulated Blastfurnace Slag (GGBS) binder was used to stabilise Lower Oxford Clay (LOC) for unfired masonry brick specimen production. The major influence of the design values on the thermal conductivity and thermal resistance are illustrated in this study, using two different types of unfired clay bricks (LG and PG) at 2% moisture content prior to test. This paper covers conductivity test for each unfired clay bricks within the temperature range 2.5–17.5 °C. The measured thermal properties of the unfired clay bricks were compared to the design thermal properties of fired bricks. The results were used to predict the design thermal values of unfired clay masonry bricks at varied density and moisture contents prior to testing. A comparison of the measured thermal values for the unfired bricks to the design thermal values of fired clay bricks can also be seen. The results demonstrate that the unfired clay bricks were able to comply with the design thermal requirements for clay masonry units, suggesting that the unfired clay bricks can be used for low-medium cost housing and energy efficient masonry structures.     

Pore structure and frost durability of clay bricks

The interrelationships among pore structure, saturation coefficient and moisture saturation behaviour of burnt clay brick specimens made from two different raw materials and fired to different temperatures are discussed. From these relationships an evaluation method for the forst resistance of clay bricks based on the continuous and the total porosity obtained from mercury intrusion porosimetry is presented.     

Microstructural Characterization of Fired Clay Bricks in the Chontalpa Region, Tabasco, Mexico

In the Mexican state of Tabasco, clay-like materials are of particular interest in the handcraft and construction industries. Combining both and due to the abundance of clay on this region, fired clay bricks are commonly used in construction. These are done in an artesian way without proper quality control. We present a chemical content analysis study for three particular areas in the Chontalpa region in Tabasco, where the mud used to produce the fired clay bricks is obtained. It is found that the mineralogical composition and firing temperature influence the brick porosity promoting textural and physical changes.     

胺类固化剂-插层剂体系对粘土在环氧树脂中剥离的影响

在对胺类固化剂-插层剂体系分析的基础上,选定叔胺类固化剂(BDMA)-Bronsted酸类插层剂(CH3(CH2)11NH3Cl)体系,制得了环氧树脂/粘土纳米复合材料,复合材料的XRD分析表明粘土在环氧树脂中已经剥离.结合有关研究成果,得出以下结论:在其他条件合适的情况下,只要插层剂为Bronsted酸类或者固化剂为叔胺类,就能得到剥离型的环氧树脂/粘土纳米复合材料.     

Kiln-fired clay bricks synergizing nickel–chromium plating sludge and fly ash: mechanical characteristics and cradle-to-gate life cycle assessment

Clean Technologies and Environmental Policy - Life cycle assessment (LCA) of novel fired clay bricks with synergistic co-valorization of nickel-chrome plating sludge (NCPS) and fly ash (FA) is...     

Investigation of kinetics of Cr(VI)-fired brick clay interaction

Fired brick clay is an excellent sorbent for the removal of heavy metal ions from waste water, owing to the availability of pores and interlayer spacing. Consequently, heat treatment of brick clay significantly affects the extent of interaction between the brick clay sorbent and adsorbates. The interaction between Cr(VI), available as Cr(2)O(7)(2-), and brick clay particles fired at temperatures between 200 °C and 600 °C follows pseudo second order kinetics, and the method of initial rates leads to the estimation of the average rate of the interaction process. Kinetics modeling suggests that the mass transfer of the interaction be mainly controlled by time-dependent intraparticle diffusion, as well as immobilization of Cr(VI) species within interlayer structure of the brick clay matrix and interparticle diffusion, both of which are time-independent.     

软粘土流变微结构突变模型与试验研究

软粘土的力学特性是粘土颗粒在荷载下的微观力学行为的宏观表现,对于软粘土微观方面的研究是了解其宏观性质的基础.该文通过唯象理论的方法建立的软粘土微结构突变模型与本构关系,能够描述软粘土流变固结的力学特性.通过一维流变固结试验对理论进行了验证,试验曲线可以用软粘土的微观特性加以解释.利用最小二乘法对模型中的参数进行了拟合,拟合曲线与试验值的符合程度较好,拟合参数的变化特点同样能体现出软粘土微观结构的力学特性.     

Titelbild: Mauerwerk 2/2018

The decision to build ones' own house is a decision for life. Ziegel fired clay masonry has been a proven building material for thousands of years, is long‐lived, healthy for living space, maintains value, is low‐maintenance and saves energy. Various architectural styles can be built with modern clay masonry units, such as the Bauhaus style in this example. Photo: Lebensraum Ziegel / Unipor     

Preparation of polystyrene–clay nanocomposite by solution intercalation technique

Polymer–clay nanocomposites of commercial polystyrene (PS) and clay laponite were prepared via solution intercalation technique. Laponite was modified suitably with the well known cationic surfactant cetyltrimethyl ammonium bromide by ion-exchange reaction to render laponite miscible with hydrophobic PS. X-ray diffraction analysis in combination with scanning electron microscopy gives an idea of structural and morphological information of PS–laponite nanocomposite for different varying organo-laponite contents. Intercalation of PS chain occurs into the interlayer spacings of laponite for low organo-laponite concentration in the PS–O-laponite mixture. However, aggregation and agglomeration occur at higher clay concentration. The molecular bond vibrational profile of laponite as well as PS–laponite nanocomposite have been explored by Fourier transform infrared spectroscopy. Thermogravimetric analysis along with differential scanning calorimetry results reveal the enhancement of both thermal stability and glass transition temperature of PS due to the incorporation of clay platelets.     

Organophosphorus and DGEBA resins containing clay nanocomposites: flame retardant,thermal, and mechanical properties

Flame-retardant nanocomposites were prepared from diglycidylphenylphosphate (DGPP) and modified montmorillonite (MMT) clay blended with DGEBA in different ratio. T _g of all formulations increased with increasing clay content in the respective series while decreasing with increasing DGPP content. The TGA, LOI, and UL-94 data of all nanocomposites indicated that the materials were thermally stable with high flame retardancy resulting from synergetic effect of phosphorus and inorganic clay. The XRD analysis of the nanocomposites with 1 and 2% of clay indicated the intercalation of clay while rest of the samples displayed exfoliation at high clay content. As compared to neat epoxy system, a maximum increase of 59.3, 45.5, and 93% of tensile, flexural, and impact strengths were observed for the prepared nanocomposites. The SEM analysis of the failure surfaces of all DGPP containing samples showed rough with ridge patterns and river markings on the fracture surface that serves in improving the mechanical properties.     

Selectivity sequences and sorption capacities of phosphatic clay and humus rich soil towards the heavy metals present in zinc mine tailing

Sorption efficacy of phosphatic clay and humus rich soil alone and on combination were tested towards heavy metals present in zinc mine tailing (Zawar Zinc Mine), Udaipur (India). Characterization of the zinc mine tailing sample indicated the presence of Pb, Cu, Zn and Mn in the concentration of 637, 186, 720 and 577microg(-1), respectively. For sorption efficacy, the zinc mine tailing soil were properly amended with phosphatic clay and humus rich soil separately and in combination and leachability study was performed by batch experiment at different pH range from 3 to 9. The data showed that the percent leachability of heavy metal in non-amended soil was 75-90%. After amendment with phosphatic clay percent leachability of heavy metals became 35-45%. Further, the addition of humus soil to phosphatic clay decreased the percent leachability up to 5-15% at all tested pH. Column leachability experiment was performed to evaluate the rate of leachability. The shape of cumulative curves of Pb, Cu, Zn and Mn showed an increase in its concavity in following order: PbCu>Zn>Mn. Further, Langmuir isotherms applied for the sorption studies indicated that phosphatic clay in the presence of humus soil had high affinity for Pb followed by Cu, Zn and Mn, with sorption capacities (b) 139.94, 97.02, 83.32 and 67.58microgg(-1), respectively.     

Subaperture processing for ultrasonic imaging

Ultrasonic subaperture processing using aperture synthesis and beam space interpolation is presented. The number of beam lines scanning the image plane for a given transmit-receive subaperture combination is chosen according to the spatial sampling criteria for that combination. On each beam line, echo signals over the entire array are collected through electronic multiplexing of array channels, where the transmit subaperture at the transducer center is fired K successive times, with K equal to the number of nonoverlapping receive subapertures. For every receive subaperture, the number of beam lines is increased through digital interpolation using a linear filter with spatial frequency band associated with the subaperture. Interpolated beam lines from all receive subapertures are then added to obtain a high resolution sector image. The efficiency of subaperture processing for different system configurations is tested on experimental rf data acquired from two different phantoms using a 3.5 MHz, 128-element transducer array. The proposed subaperture processing reduces the number of firings for data acquisition, and thus allows real-time imaging with very low susceptibility to motion artifacts.     

Wooden furniture wastes as pore formers in fired clay bricks: mechanical properties and environmental emissions

Clean Technologies and Environmental Policy - In the present work, wooden furniture wastes were used as pore-forming agents for the manufacture of fired clay bricks. The main objectives of this...     

Predicting porosity content in triaxial porcelain bodies as a function of raw materials contents

This work describes the relationships observed between the porosity of fired ceramic test pieces and the raw materials contents in the unfired mixture. The investigation was carried out using the mixture experiments design approach coupled with response surface methodology, which enables the calculation of statistically significant models for the properties from a limited number of experimental results. Ten formulations of a clay mixture, potash feldspar and quartz sand were processed in the laboratory under fixed conditions, similar to those used on wall and floor tile industrial practice, and characterized. Closed porosity (CP) was estimated from the analysis of back-scattered SEM photomicrographs, open porosity (OP) was calculated as the product of bulk density and water absorption, and total porosity (TP) was calculated from OP and CP values. Characterization results were used to calculate statistically significant and valid regression equations, relating those properties with the raw material contents in the unfired mixture. For the particular raw materials and processing conditions used, the models clearly show how quartz contributes to increasing OP and the crucial role played by feldspar when CP and TP are to be minimized (circa 3 vol.%), and how the clay content can counteract that effect and lead to maximum closed porosity (∼14 vol.%).     

Red clay-based porous ceramic with pores created by yeast-based foaming technique

Red clay-based porous ceramic has been fabricated by using a biological foaming technique through reaction of yeast with starch in aqueous ceramic suspension. The starch plays a dual role as a growth substrate for gas bubble generation and a binder for ceramic particles. Starch-loaded ceramic slurries (55 wt% ceramic solid) were prepared, consisting of red clay, quartz, feldspar, and starch. Three types of starches were used, namely, cassava starch, corn starch, and rice flour. The rheological characterization of starch-loaded ceramic slurries showed shear thinning behavior. This resulted into a high foaming factor depending on the types of starches loaded and increased addition of yeast. Total fired porosities obtained were between 17 and 70%. These correspond to open porosities between 15% and 50%, and close porosities range from 6% to 35%. Microstructural investigation of the fired porous compacts showed irregular pore morphologies equipped with interconnecting channels that represent the open porosity.     

Thermal treatment of toxic metals of industrial hazardous wastes with fly ash and clay

Waste generated from galvanizing and metal finishing processes is considered to be a hazardous due to the presence of toxic metals like Pb, Cu, Cr, Zn, etc. Thermal treatment of such types of wastes in the presence of clay and fly ash can immobilizes their toxic metals to a maximum level. After treatment solidified mass can be utilized in construction or disposed off through land fillings without susceptibility of re-mobilization of toxic metals. In the present investigation locally available clay and fly ash of particular thermal power plant were used as additives for thermal treatment of both of the wastes in their different proportions at 850, 900 and 950 degrees C. Observed results indicated that heating temperature to be a key factor in the immobilization of toxic metals of the waste. It was noticed that the leachability of metals of the waste reduces to a negligible level after heating at 950 degrees C. Thermally treated solidified specimen of 10% waste and remaining clay have shown comparatively a higher compressive strength than clay fired bricks used in building construction. Though, thermally heated specimens made of galvanizing waste have shown much better strength than specimen made of metal finishing waste. The lechability of toxic metals like Cr, Cu, Pb and Zn became far below from their regulatory threshold after heating at 950 degrees C. Addition of fly ash did not show any improvement either in engineering property or in leachability of metals from the solidified mass. X-ray diffraction (XRD) analysis of the solidified product confirmed the presence of mixed phases of oxides of metals.     

Mechanical characteristics of clay structural ceramics containing coal fly ash

In this work, the mechanical characterization of ceramic products processed from red clay with different amounts of added coal fly ash was investigated. Coal fly ash produced by power plants is a waste material that constitutes an alternative source of minerals for the production of traditional building ceramics, as it is a complex mixture of several oxides such as SiO₂, Al₂O₃, CaO, Fe₂O₃, Na₂O, TiO₂, which are usually present in the composition of such ceramics. A powder technology and firing route was followed for the processing of the clay and coal fly ash based ceramics. Different proportions of waste (10, 25 and 50%, by weight) were added to red clay, and then the mixed powders were pressed to form compacts that were fired at a selected temperature in the range 850–1,150°C. The effects of waste content and of heating conditions on the microstructure and mechanical characteristics of the obtained materials were investigated. The density, porosity, water absorption, flexural strength, hardness and fracture toughness of the produced materials were evaluated. A comparison was made between the properties of the produced ceramics with those of traditional ceramic materials used in construction, e.g. floor or wall tiles, and it was observed that the clay based products with coal fly ash additions may be used in similar applications.     

White paste for stoneware tiles for pavement using raw clay material from Burkina Faso

Raw materials from Burkina Faso were used in the production of white pastes for stoneware tiles for pavement. The basic material which is kaolin clay (Loulouka) was added with some natural plastic clay (Korona), feldspar, talc, sand for the formulations of batches for these tiles. Four batches (S1, S2, S3 and S4) consisting of raw basic clay material, plastic clay, feldspar, talc and sand have been prepared for the elaboration of tiles sintered up to 1,150 °C. The changes during the sintering process of tiles were investigated by means of X-ray diffraction and scanning electron microscopy. Mainly mullite, enstastite and glassy phase were formed during the sintering at 1,150 °C. Also the physical properties (water absorption, linear shrinkage) and flexural strength of the tiles were measured. These above properties were improved notably with increasing temperature because of mainly the formation of mullite and glassy phase which reduces the number of pores and their size. The tiles fired at 1,150 °C obtained with batch consisting of 62 % mass of basic material, 20 % mass of feldspar, 10 % mass of sand, 5 % mass of plastic clay and 3 % mass of talc (S4) belong in Europeans Standards-class BIb.     

Thermal Transmittance of Porous Hollow Clay Brick by Guarded Hot Box Method

The thermal property of a porous hollow clay brick was determined by measuring the thermal transmittance of the wall made of porous hollow clay bricks. Prior to the production of porous hollow clay bricks, nonporous and porous tiny clay bricks were prepared to determine the physico-mechanical properties by modifying the amount of wood flour and firing temperature. The bricks were produced by uniaxial pressing and then fired in an electric furnace. Their physico-mechanical properties were measured by water absorption, apparent porosity, bulk density, and compressive strength. The porous tiny clay bricks were produced with three types of wood flour: coarse wood flour (1–0.36 mm), medium-sized wood flour (0.36–0.15 mm), and fine wood flour (< 0.08 mm). The thermal transmittance of porous hollow clay bricks was determined through the guarded hot box method, which measures the wall made of porous hollow clay bricks and nonporous cement bricks. The two walls had a thermal transmittance of 1.42 and 2.72 \(\hbox {W}\cdot \hbox {m}^{-2}\cdot \hbox {K}^{-1}\), respectively. The difference in thermal transmittance was due to the pores created with fine wood flour (< 0.08 mm) as a pore-forming agent.     

Feasibility study of using brick made from municipal solid waste incinerator fly ash slag

This study deals with the effect of MSWI slag on fired clay bricks. Brick samples were heated to temperatures which varied from 800 to 1,000 degrees C for 6h, with a heating rate of 10 degrees C/min. The material properties of the resultant material then determined, including speciation variation, loss on ignition, shrinkage, bulk density, 24-h absorption rate and compressive strength. Toxicity Characteristic Leaching Procedure tests were also conducted. The results indicate that the heavy metal concentrations in the leachates met the current regulatory thresholds. Increasing the amount of MSWI slag resulted in a decrease in the water absorption rate and an increase in the compressive strength of the MSWI-slag bricks. The 24-h absorption rate and compressive strength of the MSWI-slag brick made from samples containing slag sintered at 1,000 degrees C all met the Chinese National Standard (CNS) building requirements for second-class brick. The addition of MSWI slag to the mixture reduced the degree of firing shrinkage. This indicates that MSWI slag is indeed suitable for the partial replacement of clay in bricks.