Effect of quartz sand replacement by agate rejects in triaxial porcelain

The ceramics industry, given the high volume of materials processed, stands as one of the largest consumers of natural raw materials but has also the capacity and potential to make significant contributions to solving environmental problems associated with other industries rejects. This work investigates the effects of quartz sand replacement by agate rejects (scrap) in a traditional triaxial porcelain composition. The study was carried out using the design of experiments (DoE) method. Characterization results were used to calculate statistically significant and valid regression equations, relating dried and fired body properties with clay, feldspar and agate scrap contents in the unfired mixture. The regression models were then discussed against X-ray diffraction and scanning electron microscopy results and used simultaneously to delimit the combinations of those three raw materials most adequate to produce a porcelainized stoneware floor tile with specified properties. Thus, an alternative use of an otherwise waste material is proposed, which can be translated into economic benefits and an important and welcome relief on environmental and waste disposal concerns.     

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.     

CaO增强复合胶凝材料的性能

使用重金属污泥制备免烧砖。使用CaO钙源优化配置复合胶凝材料的组分,并调控胶凝浆体中的水化产物和未水化相。先基于免烧砖原料的配合比计算复合胶凝体系的钙硅比(Ca/Si)并控制其值为0.8~1.2,设计添加CaO的免烧砖实验方案。使用核磁共振(NMR)、透射电镜-能谱等手段和PCAS分析软件,研究了CaO使高硅复合胶凝材料性能提高的机理。结果表明：随着高硅胶凝体系Ca/Si比在0.8~1.2范围内的提高,免烧砖的力学性能先提高后降低,Ca/Si比的最佳值为1.0,CaO也有一个最佳调控值。随着Ca/Si比的提高7 d试样的吸水率先降低后提高,28 d试样的吸水率线性降低。随着Ca/Si比的提高,试样中平面孔径大于200 μm的孔隙率递减,分形维数先减小后增大;对于孔径小于200 μm的孔结构,随着Ca/Si比的提高孔径为200~200 μm的孔减少,孔径小于200 nm的孔增多,孔的体积呈减小的趋势。复合胶凝体系能抑制污泥免烧砖70%以上的重金属浸出量。     

Preparation of novel ceramics with high CaO content from steel slag

Steel slag, an industrial waste discharged from steelmaking process, cannot be extensively used in traditional aluminosilicate based ceramics manufacturing for its high content of calcium oxide. In order to efficiently utilize such solid waste, a method of preparing ceramics with high CaO content was put forward. In this paper, steel slag in combination with quartz, talcum, clay and feldspar was converted to a novel ceramic by traditional ceramic process. The sintering mechanism, microstructure and performances were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) techniques, combined experimenting of linear shrinkage, water absorption and flexural strength. The results revealed that all crystal phases in the novel ceramic were pyroxene group minerals, including diopsite ferrian, augite and diopsite. Almost all raw materials including quartz joined the reaction and transformed into pyroxene or glass phase in the sintering process, and different kinds of clays and feldspars had no impact on the final crystal phases. Flexural strength of the ceramic containing 40 wt.% steel slag in raw materials can reach 143 MPa at sintering temperature of 1210 °C and its corresponding water absorption, weight loss, linear shrinkage were 0.02%, 8.8%, 6.0% respectively. Pyroxene group minerals in ceramics would contribute to the excellent physical and mechanical properties.     

Non‐loadbearing partitions of unfired clay masonry – Fire behaviour tests

Unfired clay masonry is the most frequently used construction type for residential buildings worldwide, but the long tradition of building with unfired clay masonry in Germany came to an end with the onset of industrialization. The research project EGsL ”Unfired clay masonry: design and construction principles for a widespread use in residential building taking into account climatic conditions in temperate zones with Germany as example location“ is devoted to the preparation of basic principles based on the current state of knowledge about unfired clay as a building material in order to filter out design and construction principles for residential buildings of modern unfired clay masonry. It is assumed that unfired clay has a much better performance capability than is currently expected from the material. The greatest suspicion about the structural safety of unfired clay buildings is based on the water susceptibility of unfired clay, since unfired clay loses its strength under the action of water. In order to improve confidence in the structural stability of residential buildings of unfired clay masonry, a display at the trade fair BAU 2017 showed the basis for an example application of important constructional joints of a theoretical building of unfired clay masonry. As a follow‐up to this, the EGsL research project now intends to demonstrate the fire protection behaviour of unfired clay internal walls in order to ensure the structural stability of unfired clay buildings. The article reports on a first fire test on non‐loadbearing clay masonry walls and describes an example application of non‐loadbearing clay walls in the new Zinzendorf Gymnasium in Herrnhut.     

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.     

用竹炭和硅藻土为原料制备含炭建筑材料

采用竹炭、硅藻土和粘土为原料,通过干压成型-高温烧成法制备出一种用于内墙装饰的含炭建筑材料,分析了竹炭/硅藻土质量比及烧成温度对含炭建筑材料的物化性能、物相组成及显微结构的影响规律。研究结果表明,竹炭、硅藻土和粘土三种原料复合可以制备较高气孔率、较高强度的含炭建筑材料,其物相主要为石英相与莫来石相,呈现规则孔道结构;在竹炭/硅藻土质量比为15/60,烧成温度为1150℃时,含炭建筑材料具有较好的综合性能,其破坏强度可达459.7N,吸水率10.55%,显气孔率18.4%,达到国标GB/T 4100-2006附录L中对BⅢ类陶质砖的性能要求,而且该材料的比表面积达到34.86m2/g,远红外辐射率达到0.904,具备远红外及吸附等功能,有望成为一种新型的室内功能装饰材料。     

云母和页岩对铁尾矿基多孔保温材料微观性能的影响

为了高附加值地利用铁尾矿,实验以铁尾矿、页岩和云母为基材并添加适量的长石和发泡剂,通过烧结的方法制备铁尾矿基多孔保温材料。采用TGA法分析云母和页岩掺量对粉料低共熔温度和烧成温度的影响,利用XRD、SEM研究云母和页岩比例的变化对铁尾矿基多孔保温材料矿物组成和形貌的影响。结果表明云母-页岩二元体系中云母含量的增加会降低试样的低共熔温度和烧成温度;页岩含量的增加能促使更多的石英参与反应生成斜长石,试样中斜长石的含量略有增加,石英则有所降低;试样内部含有大量分布均匀的气孔,最大孔的孔径约为2mm,在大气孔之间和内部存在许多小气孔。     

自制粉煤灰陶粒填料处理城市污水

利用粉煤灰、黏土、脱水污泥和碳酸钙等原料制备粉煤灰陶粒。通过正交试验确定原料的最优配比,并对自制陶粒进行了性能表征,进一步利用自制曝气生物滤池装置,通过改变运行参数,测试了自制陶粒用作曝气生物滤池填料处理城市污水的效果。结果表明:自制陶粒填料各项性能都符合相关标准;化学需氧量(COD)、总氮(TN)去除率随着水力停留时间(HRT)的增加而增加,当HRT为4h时,总磷(TP)去除率达到最大;低温不利于TN、TP的去除,温度对COD去除率影响不大;当进水中的TN含量为30mg/L时,TN去除率最大。TP去除率随着进水中的TP含量的增加而增加,进水浓度对COD去除率影响不大。     

球磨工艺对低品位石英砂细化效果的影响

以节约粘土资源及开发新型建筑材料为目的,利用长江沿岸低品位石英砂开发研制保温隔热砖。研究了球磨工艺对低品位石英砂细化效果的影响,为制备高性能保温隔热砖奠定了原料基础。结果表明,随着球磨时间的延长,石英砂粉体平均粒径逐渐减小,粒度分布逐渐变窄;随着球磨转速的增加,石英砂粉体平均粒径逐渐减小,粒度分布逐渐变窄;随着球磨装料量的增多,石英砂平均粒径逐渐变大,粒度分布逐渐变宽。综合整个工艺和性能考虑,确定石英砂球磨工艺为球磨时间60min、球磨转速300r/min、球磨机装料量200g/L。     

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.     

Fabrication and effective thermal conductivity of multi-walled carbon nanotubes reinforced Cu matrix composites for heat sink applications

A novel particles-compositing method was used for the first time to disperse different contents of multi-walled carbon nanotubes (CNTs) in micron sized copper powders, which were subsequently consolidated into CNT/Cu composites by spark plasma sintering (SPS). Microstructural observations showed that the homogeneous distribution of CNTs and dense composites could be obtained for 0–10 vol.% CNT contents. The CNT clusters were appeared in the powder mixture with 15 vol.% CNTs, which resulted in an insufficient densification of the composites. The effective thermal conductivity of the composites was analyzed both theoretically and experimentally. The addition of CNTs showed no enhancement in overall thermal conductivity of the composites due to the interface thermal resistance associated with the low phase contrast of CNT to copper and the random tube orientation. Besides, the composite containing 15 vol.% CNTs led to a rather low thermal conductivity due possiblely to the combined effect of unfavorable factors induced by the presence of CNT clusters, i.e. large porosity, lower effective conductivity of CNT clusters themselves and reduction of SPS cleaning effect. The CNT/Cu composites may be a promising thermal management material for heat sink applications.     

Development of macroporous calcium phosphate scaffold processed via microwave rapid drying

Porous hydroxyapatite (HA) scaffold has great potential in bone tissue engineering applications. A new method to fabricate macroporous calcium phosphate (CP) scaffold via microwave irradiation, followed by conventional sintering to form HA scaffold was developed. Incorporation of trisodium citrate dihydrate and citric acid in the CP mixture gave macroporous scaffolds upon microwave rapid drying. In this work, a mixture of β-tricalcium phosphate (β-TCP), calcium carbonate (CaCO₃), trisodium citrate dihydrate, citric acid and double distilled de-ionised water (DDI) was exposed to microwave radiation to form a macroporous structure. Based on gross eye examinations, addition of trisodium citrate at 30 and 40 wt.% in the CP mixture (β-TCP and CaCO₃) without citric acid indicates increasing order of pore volume where the highest porosity yield was observed at 40 wt.% of trisodium citrate addition and the pore size was detected at several millimeters. Therefore, optimization of pore size was performed by adding 3–7 wt.% of citric acid in the CP mixture which was separately mixed with 30 and 40 wt.% of trisodium citrate for comparison purposes. Fabricated scaffolds were calcined at 600 °C and washed with DDI water to remove the sodium hydroxycarbonate and sintered at 1250 °C to form HA phase as confirmed in the X-ray diffraction (XRD) results. Based on Archimedes method, HA scaffolds prepared from 40 wt.% of trisodium citrate with 3–7 wt.% of citric acid added CP mixture have an open and interconnected porous structure ranging from 51 to 53 vol.% and observation using Scanning electron microscope (SEM) showed the pore size distribution between 100 and 500 μm. The cytotoxicity tests revealed that the porous HA scaffolds have no cytotoxic potential on MG63 osteoblast-like cells which might allow for their use as biomaterials.     

Rheological studies of nickel oxide and quartz/hematite mixture systems

This study aimed to investigate the rheology of two-mineral mixture systems as a function of pH and solid concentration. Single minerals (nickel oxide, quartz and hematite) and two-mineral systems (nickel oxide–quartz and nickel oxide–hematite) were studied. Rheology tests were conducted to investigate the effect of pH and solid concentration on shear yield stress of suspensions while zeta potential measurements of suspensions were used to explain the rheology results. Rheology results indicated that single mineral experiments showed that 5 and 10 vol.% of quartz and hematite had no shear yield stress whereas the one of nickel oxide was positive value. Shear yield stress of nickel oxide–quartz mixture and nickel oxide–hematite mixtures increased as increasing pH and solid concentration, and the value was higher than the one obtained with only nickel oxide. These results obtained with two-mineral mixture systems were explained by electrokinetic properties of the minerals, i.e. zeta potential of the minerals.     

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.     

Paper pulp waste— a new source of raw material for the synthesis of a porous ceramic composite

A synthetic porous ceramic composite material consisting of the mullite, cordierite and cristobalite phases is produced from a mixture of paper pulp waste and clay by reaction sintering at 1400°C. Physicomechanical properties such as bulk density, porosity, cold crushing strength and cold modulus of rupture have been studied. The presence of mullite, cordierite, cristobalite and quartz as major phases and montellecite, tatanite, forsterite and anorthite as minor phases have been confirmed by X-ray diffraction pattern. SEM studies revealed the presence of well developed needle shaped mullite and quartz crystals. The paper also discusses the possible uses of this type of porous composite material.     

Evolution of ultrasonic velocity and dynamic elastic moduli with shear strain in granular layers

Ultrasonic wave transmission has been used to investigate processes that influence frictional strength, strain localization, fabric development, porosity evolution, and friction constitutive properties in granular materials under a wide range of conditions. We present results from a novel technique using ultrasonic wave propagation to observe the evolution of elastic properties during shear in laboratory experiments conducted at stresses applicable to tectonic faults in Earth’s crust. Elastic properties were measured continuously during loading, compaction, and subsequent shear using piezoelectric transducers fixed within shear forcing blocks in the double-direct-shear configuration. We report high-fidelity measurements of elastic wave properties for normal stresses up to 20 MPa and shear strains up to 500 % in layers of granular quartz, smectite clay, and a quartz-clay mixture. Layers were 0.1–1 cm thick and had nominal contact area of $5 \mathrm{cm} \!\times \! 5 \mathrm{cm}$ . We investigate relationships among frictional strength, granular layer thickness, and ultrasonic wave velocity and amplitude as a function of shear strain and normal stress. For layers of granular quartz, P-wave velocity and amplitude decrease by 20–70 % after a shear strain of 0.5. We find that P-wave velocity increases upon application of shear load for layers of pure clay and for the quartz-clay mixture. The P-wave amplitude of pure clay and quart-clay mixtures first decreases by $\sim $ 50 and 30 %, respectively, and then increases with additional shear strain. Changes in P-wave speed and wave amplitude result from changes in grain contact stiffness, crack density and disruption of granular force chains. Our data indicate that sample dilation and shear localization influence acoustic velocity and amplitude during granular shear.     

X射线K值法在水泥物相中的应用

美国F.H.Chung提出的K值法近几年来在建材是到了推广和应用。基于K值法，我们采用计算机软件来计算峰的面积，从而 准确性，用化学纯原料制成水泥熟料中的四个主要矿物即C3S，C2S，C3A和C4AF；然后再用K值法对水泥熟料中的四个主要矿物进行定量分析研究，同时研究不同定量峰、参比物对结果的影响。实验研究结果表明，利用X射线K值法可以测定水泥熟料中的物相含量。     

A novel method for producing open-cell Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> ceramic foams with controlled cell structure

A novel method was introduced to prepare open-cell Al₂O₃–ZrO₂ ceramic foams with controlled cell structure. This method used epispastic polystyrene (EPS) spheres to array ordered templates and centrifugal slip casting in the interstitial spaces of the EPS template to obtain cell struts with high packing density. Aqueous Al₂O₃–ZrO₂ slurries with up to 50 vol.% solid contents were prepared and centrifuged at acceleration of 2,860g. The effect of the solid contents of slurries on segregation phenomena of different particles and green compact uniformity were investigated. In multiphase system, the settling velocities of Al₂O₃ and ZrO₂ particles were calculated. Theory analysis and calculated results both indicated segregation phenomenon was hindered for slurries with 50 vol.% solid content. The cell struts of sintered products had high green density (61.5%TD), sintered density (99.1%TD) and homogeneous microstructures after sintered at 1,550 °C for 2 h. The cell size and porosity of Al₂O₃–ZrO₂ ceramic foams can be adjusted by changing the size of EPS spheres and the load applied on them during packing, respectively. When the porosity increased from 75.3% to 83.1%, the compressive strength decreases from 3.82 to 2.07 MPa.     

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.