Production and properties of foamed reservoir sludge inorganic polymers

The feasibility of using reservoir sludge as a raw material in the production of foamed inorganic polymers with different densities is investigated in this work. Reservoir sludge is first crushed, ground down and then calcined at the temperature of 850 °C for 6 h to become calcined reservoir sludge (CRS) powders. A mixture of 30% blast furnace slag and 70% CRS powders is alkali-activated by mixing with different alkaline activating solutions of water, sodium hydroxide and sodium silicate. The viscosities and compressive strengths of the resulting inorganic binders are measured and compared with each other. Furthermore, the inorganic binder paste that has the maximum compressive strength and best workability is mixed with various amounts of preformed air bubbles to produce foamed reservoir sludge inorganic polymer (FRSIP) specimens with different densities. The effects of density on the water absorption, pore size distribution, compressive strength, bending strength and transmission loss of the FRSIP specimens are evaluated.     

Preparation and Properties of Slag Wool Board using Modified Polyvinyl Alcohol as Binder

Slag wool boards were produced by using slag wool as the main raw material and adding modified polyvinyl alcohol (PVA) as the binder. The microstructure, thermal conductivity, compression strength, hydrophobicity, and other properties of the slag wool board were analyzed by using scanning electron microscopy, thermal conductivity tester, electronic universal testing machine, and other equipments. Also, the influence of different types and amount of binder on the properties of the slag wool board was studied. The results show that the addition of silica sol can improve the high temperature resistance of the slag wool board, and the addition of borax can improve the hydrophobic rate and compression strength of the slag wool board. Also, the concentration of PVA has obvious influence on the usage of silica sol and borax. In this study, we found that the optimal ratio of the binder should be 3 wt% addition of PVA, 20 wt% addition of silica sol, and 0.2 wt% of borax (relative to the amount of PVA), under the condition of satisfying the performance index of slag wool board and the convenience to spray the adhesive.     

Alkali-activated metakaolin-slag blends—performance and structure in dependence of their composition

Blast furnace slag and metakaolin were blended together and the combination activated by sodium hydroxide solution. The boundary mixtures were set by the activation of the pure slag and pure metakaolin powders. The type and quantity of the reaction products in the alkaline activated blended binders was determined. It is discussed whether both raw materials react separately and are unaffected by each other or if there is a chemical interaction. The discussion bases on extensive investigations with ²⁹Si and ²⁷Al nuclear magnetic resonance spectroscopy compared with X-ray diffraction and thermal analysis (DTA/TG). Additionally, the strength performance will be presented and related to structure, composition and the amount of the reaction products.     

Influence of curing regimes on compressive strength of ultra high performance concrete

The present paper is aimed to identify an efficient curing regime for ultra high performance concrete (UHPC), to achieve a target compressive strength more than 150 MPa, using indigenous materials. The thermal regime plays a vital role due to the limited fineness of ingredients and low water/binder ratio. By activation of the reaction kinetics, the effectiveness of the binder is enhanced which leads to improvements in mechanical as well as durability properties. The curing cycle employed are ambient air curing, water curing and hot air curing. The specimens were exposed to thermal regime at (90°C/150°C/200°C) for duration of 24, 48 or 72 hours at the age of 3rd and 7th day followed with air curing or water curing till 28 days. The results showed a marked difference in compressive strength ranging from 217 to 142 MPa with change in curing regimes. The samples when thermally cured at the age of 3rd and 7th day produced an average ultimate strength of 217–152 MPa and 196–150 MPa, respectively.     

Production and characterization of lightweight vermiculite/geopolymer-based panels

The production and the properties of lightweight composite panels, with expanded vermiculite as lightweight aggregate and geopolymer as binder, were investigated. Different compositions of the geopolymer binders (metakaolin or alumina-based) and two sizes of expanded vermiculite were tested. The produced composites were subjected to microstructural analyses, as well as to thermal and mechanical tests. Densities ranged between 700 and 900 kg/m³, while the average strength and thermal conductivity were about 2 MPa and 0.2 W/mK, respectively. Results show that lightweight composites can be produced with satisfactory density and mechanical and thermal properties compared with other materials used in building sector, such as plasterboard or cellular concrete.     

Briques silico-calcaires autoclavées: influence de l’addition de laitier de haut fourneau sur la formation des phases

The mechanical properties of sand-lime bricks produced by autoclaving under different conditions and incorporation of granulated slag have been investigated previously. In this study, the relationship is established between the structure, the phases formed and the strength. Based lime and granulated slag a new binder is developed. This is cured at saturated vapour pressures of 1.0 and 1.8 MPa. The results showed a decrease in compressive strength due to the substitution. The microstructure analysis showed that reaction products consist mainly of 11 Å tobermorite and xonotlite. Also, when increasing the autoclave temperature, it results in an increase in xonotlite relative to tobermorite. The X-ray diffractions of these phases are very low, hardly visible; they are masked by the presence of quartz. Their intensities increase with the presence of slag. The slag seems more reactive with lime than quartz. Observations with the scanning electron microscope allow better to appreciate these phases. By its composition to amorphous structure, the granulated slag does not release new distinct phases of hydrates.     

镍渣/偏高岭土基地聚合物的制备与表征

以工业固体废弃物镍渣和偏高岭土为原料,以水玻璃为激发剂,在相同稠度下制备镍渣/偏高岭土基地聚合物。研究了镍渣种类和掺量对地聚合物力学性能和体积变化的影响,测定了地聚合物的碱溶出情况,并利用XRD、SEM-EDS对地聚合物的矿物组成和微观形貌进行分析。结果表明:随着水淬镍渣掺量的增大,地聚合物的抗压强度先增大后降低,在镍渣掺量为50%、液固比为0.45时,地聚合物的抗压强度最大,28d达到58.8 MPa;而随着风冷镍渣掺量的增大,地聚合物的强度逐渐降低。此外,水淬镍渣/偏高岭土基地聚合物的体积变化主要表现为膨胀,而风冷镍渣/偏高岭土基地聚合物表现为收缩。     

Heat effects on cements produced with GBSF and SS additives

In this study, cement additives are developed by substituting granulated blast furnace slag and steel slag (SS) with the mixture of clinker–plaster. Mortar specimens of cement are prepared with these additives. Measurable properties of the series of cement additives such as the fineness moduli, Blaine values and specific gravities are computed before the casting. The Vicat setting times of specimens are determined according to the terms stated in TS EN 196-3 and the changes in their expansion levels are also detected. Furthermore, the cements produced and the mortar specimens casted are undergone thermal processes at the temperatures of 20, 100, 200, 300, 400, 500, 600, 700 and 800 °C, and mechanical and physical experiments are carried out for each series after the thermal processes. In all the series, sudden losses in strength are observed during the thermal process beyond 600 °C. Consequently, M3a series specimens that are produced with 80% clinker and gypsum in 12% blast furnace slag and 8% SS yield the best results in terms of compressive strength, elasticity modulus and decomposition.     

Natural carbonation of aged alkali-activated slag concretes

Alkali-activated slag concretes stored for 7 years under atmospheric conditions are assessed, and the structural characteristics of naturally carbonated regions are determined. Concretes formulated with a 400 kg/m³ and water/binder (w/b) ratio between 0.42 and 0.48 present similar natural carbonation depths, although these concretes report different permeabilities after 28 days of curing. The inclusion of increased contents of binder leads to a substantial reduction of the CO₂ penetration in these concretes, so that negligible carbonation depth values (2 mm) are identified in concretes formulated with 500 kg/m³ of binder. Calcite, vaterite, and natron are identified as the main carbonation products formed in these concretes. These observations differ from the trends which would be expected in comparable ordinary Portland cement-based concretes, which is attributable to the physical (permeability) and chemical properties of alkali-activated slag concretes promoting high long-term stability and acceptably slow carbonation progress under natural atmospheric conditions.     

Drying-induced changes in the structure of alkali-activated pastes

Drying of cement paste, mortar, or concrete specimens is usually required as a pre-conditioning step prior to the determination of permeability-related properties according to standard testing methods. The reaction process, and consequently the structure, of an alkali-activated slag or slag/fly ash blend geopolymer binder differs from that of Portland cement, and therefore there is little understanding of the effects of conventional drying methods (as applied to Portland cements) on the structure of the geopolymer binders. Here, oven drying (60 °C), acetone treatment, and desiccator/vacuum drying are applied to sodium silicate-activated slag and slag/fly ash geopolymer pastes after 40 days of curing. Structural characterization via X-ray diffraction, infrared spectroscopy, thermogravimetry, and nitrogen sorption shows that the acetone treatment best preserves the microstructure of the samples, while oven drying modifies the structure of the binding gels, especially in alkali-activated slag paste where it notably changes the pore structure of the binder. This suggests that the pre-conditioned drying of alkali activation-based materials strongly affects their microstructural properties, providing potentially misleading permeability and durability parameters for these materials when pre-conditioned specimens are used during standardized testing.     

橡胶粒子对微发泡聚丙烯复合材料发泡行为与力学性能的影响

利用型腔体积可控注塑发泡装置制备微发泡聚丙烯(PP)/粉末橡胶复合材料,通过橡胶粒子的分散性以及复合材料的结晶行为,研究不同橡胶粒子对聚丙烯复合材料发泡行为和力学性能的影响。结果表明:橡胶粒子的加入使微发泡聚丙烯材料的泡孔分布细密而均匀,微发泡聚丙烯/马来酸酐接枝聚丙烯/粉末丁腈胶(PP/PP-MAH/NBR)复合材料的发泡质量较理想,其泡孔密度和尺寸分别为7.64×106个/cm3,29.78μm;综合泡孔结构和力学性能,微发泡聚丙烯/聚丙烯接枝马来酸酐/粉末羧端基丁腈胶(PP/PP-MAH/CNBR)复合材料的力学性能最优,与纯PP比较其冲击强度提升了2.2倍,拉伸强度仅仅降低了26%,是理想的微发泡复合材料。     

Ceramic foams from preceramic polymers

The direct foaming of preceramic polymer mixtures, followed by high temperature pyrolysis in an inert atmosphere, can be employed to fabricate ceramic foams with impressive strength, stiffness, thermomechanical and thermochemical durability, and electromagnetic properties. Flexural strength and stiffness were superior to those of foams produced using conventional replication process technologies. Excellent strength retention and thermal fatigue resistance was exhibited during long term static and cyclic thermal exposure to 1200 °C in air. Further improvements can be realized through judicious selection of the preceramic polymers and pre-pyrolysis process modifications. Fabrication of foams with graded porosity and multifunctionality, via the incorporation of electrically-, thermally-, and magnetically-active fillers was demonstrated. This direct foaming technology offers substantial opportunity for the near-net shape fabrication of lightweight, inorganic foam structures with tailored thermal, elastic, mechanical, electrical and magnetic characteristics for high temperature applications. Electronic Publication     

Use of Ti in hard metal alloys – Part II: mechanical properties

WC‐Co hard metal is a material of high hardness, high compressive strength and wear resistance while maintaining good toughness and thermal stability. Samples of nanosized WC powders with 10 wt% Co, WC‐10 wt% Ti, WC‐9 wt% Ti‐1 wt% Co were cold pressed at 200 MPa and sintered at 1500°C during 1 hour under vacuum of 10^–2 mbar. The characterization of the sintered materials was performed by the measurements of densification, HV30 hardness, fracture toughness and compression strength. The results showed that it is possible to process a hard metal through a Powder Metallurgical conventional route from nanoscaled WC grains, using Ti (or a Ti‐Co mixture) as a binder phase, with good mechanical properties.     

Production and characterization of geopolymers based on mixed compositions of metakaolin and coal ashes

Mixtures of coal ashes from pulverized coal combustion (PCC) or fluidized bed combustion (FBC) and metakaolin were used to synthetize geopolymers. Upon full characterization of the raw powders (chemical and mineralogical composition), geopolymerization tests were conducted using an alkali aqueous solution of NaOH/Na₂SiO₃ at different dilutions. The produced geopolymers were subjected to SEM analysis, as well as to leaching, thermal and mechanical tests. The final microstructure and the properties of the geopolymers indicate that FBC ash can be conveniently used as a partially reactive filler in combination with the metakaolin powder. The composite material has good thermal performance and compressive strength (∼30 MPa) suitable for the building sector.     

Characterization of rigid polyurethane foams containing microencapsulated Rubitherm<Superscript>®</Superscript> RT27: catalyst effect. Part II

Catalyst Tegoamin 33 has been used for the synthesis of rigid polyurethane (RPU) foams containing microencapsulated Rubitherm^® RT27 and having a high mechanical resistance. These materials could be employed in buildings for thermal insulation and thermal energy storage (TES). The fillers content influence on the foaming process and also the foam properties was evaluated. It was observed that a foam containing up to a 18 wt% of microcapsules can be manufactured, improving the TES capacity while maintaining the mechanical properties of the neat foam. Besides, it was observed that the mechanical resistance of foams synthesized using catalyst Tegoamin 33 are higher than those obtained when catalyst Tegoamin BDE was employed, with the mechanical resistance of the foam containing 21 wt% being higher than those of foams synthesized with catalyst BDE containing only 11 wt% of fillers while maintaining the advantages of an improvement in TES capacity. A general model of reaction curve of n tank-in-series of a same time constant was used to fit the rising curves. This model allowed to predict the final volume of the synthesized foam. Finally, TES capacities and mechanical properties of the synthesized foams were in the range of those reported in literature. Moreover, foam densities satisfied the restriction established by the Spanish regulation for building applications.     

Comportement au gel interne de bétons sous contraintes mécaniques

The literature relative to the freezing of concrete is based on freezing-thawing cycle data obtained from specimens which are not subjected to mechanical stresses. In the present study, the initial tensile stresses of concrete are taken into account. Data were developed on control mortars, containing a smaller amount of cement than standard ones in order to represent the actual content of cement in concrete. Two binders, both with and without an air-entraining agent, were utilized: ordinary Portland cement and metakaolin-blended cement, in which the ordinary Portland ciment/metakaolin ratio was 80/20. Prismatic specimens of mortars (40×40×160 mm³) were subjected, in a novel manner, to freezing-thawing cycles in the presence of variable flexural stress rates: 0 to 85% of the rupture load. In order to separate the freezing effect from the load effect, measurements were conducted both in a cold-heat chamber and in a room where the temperature was maintained at 20°C. The strength evolution was analysed and some microstructural properties were assessed (porosity, hydrates). The results obtained show that this new method of testing allows the acceleration of damage when the rate of flexural stress reaches about 60% of the rupture load. The mortar containing metakaolin performs as well as mortars containing air-entraining agents (ordinary Portland ciment-air-entraining agent; metakaolin-air entraining agent). The microstructural analyses explain the behaviour of the different mortars.     

Fabrication and investigation of influence of CaCO3 as foaming agent on Al-SiCp foam

Closed cell aluminum foams have been used in various disciplines of engineering. Aluminum foams provide high strength with the advantage of low weight. In the current research, CaCO₃ is used as a foaming agent for producing closed-cell aluminum foams. For the fabrication of homogenous foam, optimization of process parameters was done. The effect of SiC as a thickening agent on structural property of foams viz. density and porosity have been inspected. Foams with density 0.40–0.86 g/cm³ were produced. The produced foams were studied under axial compression tests for evaluating mechanical properties. It can be inferred from the results that by adding 3 wt.% CaCO₃, the uniform viscosity of melt was achieved and a homogeneous foam structure is achieved with optimum porosity. Also, 5 wt.% addition of CaCO₃ in melt and stirring speed at 1400 rpm tend to increase porosity and decrease cell wall thickness. The optimum values for thickening agent SiC, foaming agent CaCO₃ at stirring speed 1400 rpm were found out to be 15 wt.%, 3 wt.%. The effect of relative density, the addition of thickening and foaming agent is studied.     

Low-temperature sintered pollucite ceramic from geopolymer precursor using synthetic metakaolin

In this article, pollucite ceramic with high relative density and low coefficient of thermal expansion (CTE) was prepared from Cs-based geopolymer using synthetic metakaolin. Crystallization and sintering behavior of the Cs-based geopolymer together with thermal expansion behavior of the resulted pollucite ceramic were investigated. On heating at 1200 °C for 2 h, the amorphous Cs-based geopolymer completely crystallized into pollucite based on crystal nucleation and growth mechanism. Selected area diffraction analysis and XRD results confirmed the resulted pollucite ceramic at room temperature was pseudo-cubic phase with superlattice structure. Compared with Cs-based geopolymer using natural metakaolin, geopolymer using synthetic metakaolin in this article showed a much lower viscous sintering temperature range, which started at 800 °C, reached a maximum value of ?7.47 × 10^?4/°C at 1121.9 °C, and ended at 1200 °C. Cesium volatilization appeared only when temperature was above 1250 °C. Therefore, densified pollucite ceramic can be prepared from Cs-based geopolymer using synthetic metakaolin without cesium volatilization. Abnormal thermal shrinkage of pollucite ceramic was observed at temperature range from 25.3 to 54.6 °C because of pseudo-cubic to cubic phase transition, and its average CTE was 2.8 × 10^?6/°C from 25 to 1200 °C.     

Fabrication and Sintering Behavior of Zinc-Doped Biphasic Calcium Phosphate Bioceramics

Dense bioceramics with improved mechanical properties have been prepared using sol–gel derived zinc doped biphasic calcium phosphate (BCP) powders. Zinc concentration was varied in the range of 0,1, 2, 4, 5, 10, and 15 mol%. The compaction of the powders followed by sintering provided the dense ceramics. The effects of zinc concentration doped and sintering temperature on phase stability and mechanical characteristics were examined. The presence of Zn changed the phase of dense BCP, leading to improved mechanical properties. Zn free BCP attained the highest density of only 92.6% after 1400°C sintering, equally achieved by 4 mol% Zn-doped BCP at a lower temperature of 1200°C. It is presumed that the steady increase in the compact density up to 4 mol% zinc incorporation was contributed by progressive consolidation in the BCP structure, but the density dropped again from 5 mol% until 15 mol% due to low density β-tricalcium phosphate phase formation. This study showed that Zn doping was effective in producing high strength dense BCP with 3.40 GPa hardness and 1.43 MPa · m^1/2 fracture toughness.     

Mechanical properties of prestressed self-consolidating concrete

Since the mix design of self-consolidating concrete (SCC) differs from that of conventional concrete, mechanical properties of SCC may differ from those of vibrated concrete. An experimental program was performed to evaluate mechanical properties of SCC used for precast, prestressed applications. Sixteen SCC mixtures with a fixed slump flow of 680 ± 20 mm were prepared with different mixture parameters, including binder content and binder type, w/cm, dosage of viscosity-modifying admixture, and sand-to-total aggregate volume ratio. Two high-performance concrete mixtures that represent typically concrete used for precast, prestressed applications were investigated for the control mixtures. They were proportioned with 0.34 and 0.38 w/cm and had slump values of 150 mm. Mechanical properties of SCC were compared to code provisions to estimate compressive strength, elastic modulus, and flexural strength. The modified ACI 209-90 and CEB-FIP MC90 codes are found to provide good estimate for compressive strength prediction. The AASHTO 2007 model can provide good prediction of the elastic modulus and flexural strength of SCC.