Cement Waste Research Articles

Study the Effect of Cement Waste on Some Mechanical Properties of Acrylonitrile-Butadiene Rubber

The basic idea of this paper is to prepare and study the composite rubber material for the manufacturing of an important part in the grain transportation systems in silos of general company for grain trade namely rablat, where it was the experience of this rablat manufactured in the new silo of Hilla/Babylon province for a period of eight months in winches and vector chain was fully proven. In this paper, manufacturing rablat of rubber material; and other supported by brass bosh from Acrylonitrile-butadiene rubber (NBR) reinforced by two materials; first, cement waste from the southern general company, for cement emerging as a result of incidental to the process of calcination and grinding stone in depositing the oven and that has been added by 0–40 pphr with 1 μm grain size, and second silica extracted from the husks of rice which was added with a fixed amount 20 pphr and 10 μm grain size. Mechanical tests were done before and after the addition of cement powder residue and rice husks to rubber by Tansometer to measure the tensile strength, where the growth rate of crack was measured by fatigue device and hardness measured by Wallace bead load hardness. The results show that the rubber material developed and manufactured in this research are consistent with the mechanical properties of the original model with improved tensile strength and hardness with decreased fatigue. Keywords: Acrylonitrile-butadiene rubber, mechanical properties, cement waste, rice husk Cite this ArticleAl-Mosawi Ali I, Al-Maamori Mohammed H, Shaymaa Abbas Abdulsada. Study the Effect of Cement Waste on Some Mechanical Properties of Acrylonitrile-Butadiene Rubber. Journal of Catalyst and Catalysis. 2016; 3(1): 11–14p.

Design and application of environmentally effective concrete with usage of chrysotile-cement waste

Construction is resource-demanding industry, characterized by a large volume of waste. Particularly chrysotile cement waste obtained both in production and in dismantling over age chrysotile-cement products: corrugated asbestos boards and flat sheets, chrysotile-cement tubes. We propose to use dry chrysotile-cement waste as recycled aggregate for concrete. Based on developed compositions and identified properties of heavy concrete with chrysotile-cement waste introduce this technology to the production of foundation wall blocks. The studies confirmed the possibility of using chrysotile-cement aggregate and fine screening of crushing as a secondary coarse and fine aggregates for concrete with proper quality without increasing the cost of the product. Environmental safety of the obtained products was ensured. The direction for implementation of the research project was proposed.

武汉市城区生活垃圾收集处理现状调查

作为特大城市和第四届“全国文明城市”，武汉市如何更有效快速地实现生活垃圾资源化、无害化、减量化已成为城市发展中亟待解决的问题。本文从武汉市城区生活垃圾产量、环卫情况、垃圾处理处置现状、垃圾处理现有项目等方面入笔，综述了武汉市生活垃圾的收运处理情况，整理了目前已建和在建的垃圾焚烧、垃圾卫生填埋、垃圾水泥窑协同处理项目。分析发现，武汉市生活垃圾年增长率为14.7%，在“五焚烧，两填埋，一综合”的垃圾处理布局下，垃圾焚烧率高达95%，垃圾无害化处理率达到100%。基于武汉市发展的特色与趋势，浅析其中存在的问题，并提出相应的解决对策。 As a megacity, Wuhan, has been named the fourth “national civilized city”. How to effectively and quickly achieve the goal of domestic waste recycling, hazard-free use and quantity reduction has become the urgent problem to be solved in the future of Wuhan. Based on the domestic waste output, the sanitation situation, the situation of garbage disposal and garbage disposal projects, this paper summarizes the status of domestic waste collector and garbage treatment in the urban zone of Wuhan. Constructed or under construction projects, such as waste incineration, hygienic sanitary landfill, waste cement kiln disposal in coordination are compiled. It has been found by analysis that annual growth rate of urban domestic waste in Wuhan is about 14.7%. The structure of waste treatment is “five incinerations, two landfills, a comprehensive treatment”, by which, the rate of incineration has reached up to 95%, and the hazard-free treatment rate of waste has reached 100%. Besides, this paper analyzes the existing problems and puts forward some corresponding solutions by taking the characteristics and trends of the development of Wuhan into consideration.

Application of vadose zone approach for prediction of radionuclide transfer from near-surface disposal facility

About 100 000 m3 of solid conditioned Low and Intermediate Level Waste, generated during operation and decommissioning of the Ignalina nuclear power plant, are to be disposed of in a near-surface repository.In this study a computer code FEFLOW 5.0 was applied for simulating the transport of the most mobile radionuclides (3H, 14C, 59Ni and 94Nb) within moisture through an unsaturated vault of the near-surface repository in Stabatiškė Site. HYDRUS-1D analysis was used to assess the radionuclide transport in the repository and to estimate initial activity concentrations of radionuclides transported from the cemented waste. Radionuclide release from the vaults in the unsaturated conditions after closure of the repository and consequent contaminant plume transport has been assessed taking into account site-specific natural and engineering conditions and based on a normal evolution scenario.The highest value of 14C activity concentration (about 3.3·108 Bq/m3) in the moisture of soils below engineering barriers is predicted after about 7300 years after repository closure. The predicted maximum activity concentrations of the others modeled mobile radionuclide 3H (after 100 years after repository closure), 94Nb (after 300 000 years) and 59Ni (after 173 000 years) at the groundwater table are 1.1·105, 3.7·104 and 2.4·106 Bq/m3, respectively.

OPTIMIZATION AND VALIDATION OF A CHEMICAL PROCESS FOR URANIUM, MERCURY AND CESIUM LEACHING FROM CEMENTED RADIOACTIVE WASTES

Canadian Nuclear Laboratories (CNL) is developing a treatment and long-term management strategy for a legacy cemented radioactive waste that contains uranium, mercury, and fission products. Extracting the uranium would be advantageous for decreasing the waste classification and reducing the cost of long-term management. The chemical leachability of 3 key elements (U, Hg, and Cs) from a surrogate cemented waste (SCW) was studied with several lixiviants. The results showed that the most promising approach to leach and recover U, Hg, and Cs is the direct leaching of the SCW with H2SO4 in strong saline media. Operating parameters such as particle size, temperature, pulp density, leaching time, acid and salt concentrations, number of leaching/washing steps, etc. were optimized to improve key elements solubilization. Sulfuric leaching in saline media of a SCW (U5) containing 1182 ppm of U, 1598 ppm of Hg, and 7.9 ppm of Cs in the optimized conditions allows key elements solubilisation of 98.5 ± 0.4%, 96.6 ± 0.1%, and 93.8 ± 1.1% of U, Hg, and Cs, respectively. This solubilization process was then applied in triplicate to 7 other SCWs prepared with different cements, liquid ratios, and at different aging times and temperatures. Concentrated sulfuric acid is added to the slurry until the pH is about 2, which causes the complete degradation of cement and the formation of CaSO4. Sulfuric acid is particularly useful because it produces a leachate that is amenable to conventional ion exchange technology for the separation and recovery of uranium.

Mathematical Modeling of Heavy Metals Removal from Bio-film Coated Cylindrical Cement Base Waste Forms

Abstract A mathematical description is presented for the leaching behavior of cobalt and chromium from their solidified/stabilized forms under the attack from biofilms commonly developed by acid forming bacteria such as Thiobacillus thiooxidans or Thiobacillus ferooxidans. The proposed model predicts the metals diffusion and subsequent removal from cylindrical cement waste forms using a Michaelis-Menten-type kinetics, as a special case of the widely accepted Langmuir-Hinshelwood mechanism at the surface of the encapsulating cylinder. The resulting nonlinear model is solved by applying boundary perturbation to reduce the nonlinear problem to an infinite series of linear problems that are solvable by Laplace transform methods. Model predictions compares well with published experimental data and confirms that a Michaelis-Menten-type kinetics is most probably the dominant mechanism for the leaching of heavy metals from cement based waste forms.

Uranium, Cesium, and Mercury Leaching and Recovery from Cemented Radioactive Wastes in Sulfuric Acid and Iodide Media

The Canadian Nuclear Laboratories (CNL) is developing a long-term management strategy for its existing inventory of solid radioactive cemented wastes, which contain uranium, mercury, fission products, and a number of minor elements. The composition of the cemented radioactive waste poses significant impediments to the extraction and recovery of uranium using conventional technology. The goal of this research was to develop an innovative method for uranium, mercury and cesium recovery from surrogate radioactive cemented waste (SRCW). Leaching using sulfuric acid and saline media significantly improves the solubilization of the key elements from the SRCW. Increasing the NaCl concentration from 0.5 to 4 M increases the mercury solubilization from 82% to 96%. The sodium chloride forms a soluble mercury complex when mercury is present as HgO or metallic mercury but not with HgS that is found in 60 °C cured SRCW. Several leaching experiments were done using a sulfuric acid solution with KI to leach SRCW cured at 60 °C and/or aged for 30 months. Solubilization yields are above 97% for Cs and 98% for U and Hg. Leaching using sulfuric acid and KI improves the solubilization of Hg by oxidation of Hg0, as well as HgS, and form a mercury tetraiodide complex. Hg and Cs were selectively removed from the leachate prior to uranium recovery. It was found that U recovery from sulfuric leachate in iodide media using the resin Lewatit TP260 is very efficient. Considering these results, a process including effluent recirculation was applied. Improvements of solubilization due to the recycling of chemical reagents were observed during effluent recirculation.

Study on Creep Characteristics of Cemented Waste Rock Backfills

Slip instability and tensor instability are two kinds of failure modes of cemented waste rock backfills. In order to simulate the creep characteristics of cemented waste rock backfills, PFC was carried out. The results show that: rocks inside the models will have displacement under load. The expansion is caused by large lateral displacement of the rocks. A non-stationary creep model of cemented waste rock backfills was established based on the results of simulation. This model can be used to describe the whole creep characteristics of cemented waste rock backfills better.

Load Settlement Behaviour of Fly ash Mixed with Waste Sludge and Cement

One of the effective utilization strategies for fly ash and waste sludge is to use it as a fill material to raise low lying areas. Bearing capacity and settlement are the required input for the design of foundations on such fills. To determine the bearing capacity, plate load tests were carried out on the compacted beds of fly ash, fly ash-waste sludge and fly ash-waste sludge–cement. The tests were conducted by keeping 90, 95 and 100 % relative compaction, fresh and fresh submerged conditions, aged (28 days) and aged (28 days) submerged conditions as variables of the tests. The load-settlement curves were plotted for fly ash and mix blends. The minimum load was obtained for fly ash under submerged condition, further the test results show that the fly ash becomes flowable on submergence. On the other hand when the fly ash was mixed with waste sludge and cement, the load carrying capacity was found to improve to a greater extent. Test beds prepared with fly ash–cement-waste sludge under as compacted condition (fresh) show very high load carrying capacity (1600–2180 kN/m2). An analytical method has also been validated for fly ash–cement-waste sludge mix which was developed to estimate the settlement of footing resting on fly ash taking into account the pre-consolidation stresses. The non linearity of load-settlement behavior was appropriately modeled, on the basis of available plate load test data incorporated in the method. The method requires as input, the pre-consolidation stress and Young’s modulus of compacted mix of fly ash-waste sludge–cement. A comparison of load-settlement values observed in plate load tests and predicted values for the mix 47 %FA + 45 %S + 8 %C, using the proposed method shows good agreement. Hence, this relationship may also be useful to the field engineers to check the reported load-settlement values for such types of mixes in the field.

Cork waste in cement based materials

Abstract Cork is a natural material that has always been associated to mankind having huge potential and many uses. The cork industry worldwide consumes more than 280,000 t of cork a year. However, about 20% to 30% of the raw cork received at the processing units is rejected, mainly as cork dust. Finding useful applications for the rejected cork may have important economic and environmental implications. Trying to combine the advanced technology of self-compacting concrete and use of this waste from the cork industry, this study concerns the possibility of using cork powder as a substitute for fines in mixtures of self-compacting concrete. An experimental program was carried out to assess the behavior of this material in the mixture and define properties in terms of strength and durability of self-compacting concrete containing cork powder. It was found that it is possible to use an abundant waste material from the cork industry, cork powder, as fines in Self Compacting Concrete resulting in a good strength level (C 30/37) and suitable durability for common applications.

CO2 Fixation Process with Waste Cement Powder via Regeneration of Alkali and Acid by Electrodialysis: Effect of Operation Conditions

The effect of the operation conditions on the recovery of acid–alkali pairs by electrodialysis was studied to improve the efficiency of the newly developed mineral carbonation process for carbon dioxide fixation. Sodium nitrate (NaOH + HNO3), sodium chloride (NaOH + HCl), and potassium chloride (KOH + HCl) showed almost equal performance in the recovery process for the two fixed membrane configurations. For the same salt, the configuration of anion-exchange membrane bipolar membrane (AEM–BPM) showed higher recovery rate and lower power consumption than the cation-exchange membrane bipolar membrane (CEM–BPM) configuration. Significantly higher recovery rates were observed when potassium acetate was used for the CEM–BPM configuration. A higher recovery rate was observed for a lower initial concentration, but the power consumption was lower for higher initial concentrations. Calcium in waste cement powder can be rapidly leached with acetic acid. The results showed that the process performance would be signif...

Chemical stabilization of chromate in blast furnace slag mixed cementitious materials

Cement waste form (CWF) technology is among the leading approaches to disposing of metals and liquid low-level nuclear waste in the United States. One such material, saltstone, includes slag, fly ash and Portland cement to enhance the immobilization of contaminants (e.g., Cr, 99Tc) in alkaline liquid wastes. To evaluate the stability of such redox sensitive contaminants in saltstone, the effects of slag as a source of reductant on Cr immobilization was evaluated in aged (<300d) saltstone monoliths. Specifically, we investigated the effects of artificial cement pore waters on the Cr release and the spatially resolved Cr chemical state analysis using synchrotron based microfocused X-ray microprobe analysis. The microprobe analysis indicated the heterogeneous distribution of insoluble Cr(III)-species in saltstone. Although at most of 20% Crtotal was leached at the top few (2–3) millimeter depth, the release of Cr(VI) was small (<5%) at 5–30mm with slight changes, indirectly suggesting that Cr is likely present as insoluble Cr(III) species throughout the depths. The study suggests that this saltstone formulation can effectively retain/immobilize Cr under the oxic field condition after ⩽300d of aging time.

An investigation on the recycling of hydrated cement from concrete demolition waste

Construction and demolition waste (CDW) recycling is generally limited to the use of the coarser fraction as aggregate for new concrete. The recovery of fine aggregates requires a cleaning by removing the hydrated cement waste (HCW). In this paper, the possibility to use HCW extracted from CDW as alternative component for the production of new clinker is explored.A pure HCW sample was prepared and used in partial replacement of natural materials in raw admixtures for new clinker production. At a replacement degree of 30%, a new Portland clinker containing almost 50% of C3S could be produced with a huge spare in the release of CO2 (about 1/3 less). At higher HCW dosage a non-Portland clinker containing almost 80% of C2S has been obtained: its use as supplementary cementing material in blended cements revealed satisfying long term performances.

Immobilization of radioactive waste in cement: Iodine binding by cementitious materials under highly alkaline conditions

This work is directed to assess iodine interactions with hardened cement paste (HCP) under highly alkaline conditions (pH &gt; 12) with/without a reductant. For this purpose, a series of Kd (distribution coefficient) experiments using 127I as a tracer were performed. The Kd values of iodine were in the order of 172–1095 mL g–1 in the batch experiment without a reductant, and in the order of 83–92 mL g–1 in the experiment with a reductant. The percentage of iodine leached out from HCP throughout the experiment suggested its very strong binding with cementitious materials. The obtained results allow supposing that chemical speciation of iodine has influence on the interaction of iodine with HCP under highly alkaline conditions.

시멘트 풀의 직접수성탄산화에서 Chloride 첨가제와 pH의 영향

Recently, carbon capture and storage (CCS) techniques have been globally studied. This study was conducted to use waste cement powder as an efficient raw material of mineral carbonation for sequestration. Direct aqueous carbonation experiment was conducted with injecting pure gas (99.9%) to a reactor containing reacting solution and the pulverized cement paste (W:C

Magnetic iron oxides in the cementation technology of the boron-containing radioactive waste

Two ways of synthesis of non-detachable dispersed particles of magnetic materials useful for the boron-containing waste cementation process regulation were developed. Powder XRD showed that the method of carbothermic recovery of nanoscale iron hydroxide allows obtaining a mixture of iron oxides with content of the magnetic phase up to 70%. Method of low-temperature hydrogen reduction of the raw materials allows obtaining various compositions of a-iron and iron oxides with the possibility to change the size of the final particles in a wide range. The possibility of using composites of magnetic iron oxides and metal oxide compositions instead of ferromagnetic rods with VEP of boron-containing liquid radioactive waste in the fluidized field was studied. It was shown that the use of fine and nano particles of the iron oxides in the pre-treatment of the boron-containing LRW increases the strength of the final compounds and accelerates the cement setting compounds from 13 to 5-9 days.

The use of the chrysotile cement waste as the secondary aggregate for the concrete

The article presents the results of research on the effective concrete with secondary chrysotile cement aggregate. One of the important problems of modern science of construction materials is the use of secondary resources for the production of construction materials, and a considerable part of them are the chrysotile cement waste and scrapped chrysotile cement products. The aim of presented research is the development of effective concrete for the production of foundation wall blocks with the use of crushed chrysotile cement products as a secondary aggregate. The main characteristics of the secondary chrysotile cement aggregate have been determined. The concrete with different compositions and with different content of secondary chrysotile cement rubble has been studied. The dependences of the strength and the specific strength of concrete with a constant W/C ratio and constant binder consumption on the consumption of the secondary aggregate have been obtained. It is stated that the introduction of secondary chrysotile cement aggregate does not significantly effect the water resistance and frost resistance of the concrete. It is shown that the variation of the fractions of secondary aggregates and the binder makes it possible to obtain the effective concrete with a wide range of strength values.

Technetium Getters to Improve Cast Stone Performance

ABSTRACTA cementitious waste form known as Cast Stone is the baseline waste form for solidification of aqueous secondary wastes, including Hanford Tank Waste Treatment and Immobilization Plant (WTP) secondary liquid effluents to be treated and solidified at the Hanford Site Effluent Treatment Facility. Cast Stone is also being evaluated as a possible supplemental immobilization technology to provide the necessary low activity waste (LAW) treatment capacity to complete the Hanford tank waste cleanup mission in a timely and cost effective manner. Two radionuclides of particular concern in these waste streams are technetium-99 (99Tc) and iodine-129 (129I). These radioactive tank waste components are predicted to contribute the most risk to groundwater – the most probable pathway for future environmental impacts associated with the cleanup of the Hanford site. A recent environmental assessment of Cast Stone performance, which assumes a diffusion controlled release of contaminants from the waste form, calculates groundwater in excess of the allowable maximum permissible concentrations for both contaminants. There is, therefore, a need and an opportunity to improve the retention of both 99Tc and 129I in Cast Stone. One method to improve the performance of Cast Stone is through the addition of “getters” that selectively sequester Tc and I, therefore reducing their diffusion out of Cast Stone. In this paper, we present results of Tc and I removal from solution with various getters. Batch sorption experiments were conducted with deionized water (DIW) and a highly caustic LAW simulant with a 7.8 M average Na concentration. In general, the data show that the selected getters are effective in DIW but their performance is compromised when experiments are performed with the 7.8 M Na Ave LAW simulant. The diminished performance in the LAW simulant may be due to competition with Cr present in the 7.8 M Na Ave LAW simulant and to a pH effect that may create a negatively charged surface that can repel negatively charged species.

Experimental Study on Acoustic Emission Characteristics of Cemented Waste Rock Backfills with Two Different Structures during Creep Process

The studies on acoustic emission characteristics of cemented waste of rock backfills with two different structures during creep process were carried out by virtue of short-term creep test under different stress levels. The results show that: When two parts of the stone combinations in the test specimens are combined in a minor angle (30°~60°) (type I), under sustained loading without failure, acoustic emission amplitude will increase during steady creep stage with surface crack opening and propagating. When two parts of the stone combinations in the test specimens are combined in a large angle (60°~90°)(type II), under sustained loading without failure, the test specimens show two varied features. On one hand, acoustic emission amplitude will decrease significantly during steady creep stage, with surface crack opening and propagating which will mainly occur during decelerated creep stage. On the other hand, acoustic emission amplitude is rather fluctuating during sustained load stage which leads to separation and drop of parts of the test specimen. One common trait of these two types of test specimens is that, the whole decelerated creep and steady creep stages show relatively stable acoustic emission amplitude before destruction. During accelerated creep stage, acoustic emission amplitudes appear as wave type in type I test specimens with shear fracture and accretion type in type and II test specimens with tensor failure.

Microstructure changes of waste hydrated cement paste induced by accelerated carbonation

From the perspective of effective utilization of resources and environmental preservation, accelerated carbonation of waste cement paste is a promising and environmentally beneficial application. Greenhouse gas CO2 can be captured, waste hydrated cement can be reused, and building materials with excellent performance can be produced. In this study, samples were exposed to high CO2 concentration (99.9wt%, 0.2MPa) for accelerated carbonation. The compacts with water/solid ratio of 0.15 absorbed 19.8wt% CO2 after carbonated for 2h, and the compressive strength was 28.6MPa. The total pore volume decreased from 0.41cm3/g to 0.26cm3/g due to the precipitation of calcium carbonate and silica gel. Rietveld refinement quantitative phase analysis and TG analysis showed calcium carbonate are mainly from Ca(OH)2 and C–S–H, accounting for about 70–80% of the total calcium carbonate. Ca(OH)2 has superiority in the early carbonation period, and the carbonated compacts has a relative higher “compressive strength-to-CO2 uptake” value, corresponding. When the carbonation degree of C–S–H and other carbonation phase exceed Ca(OH)2 in the later stage, the compressive strength has a slower gain tendency.