Cement Waste Research Articles

Sustainability assessment of half-sandwich panels based on alkali-activated ceramic/slag wastes cement versus conventional building solutions

This study assessed the sustainability of two partition walls and intended to contribute to the Circular Economy in the construction sector. A life cycle approach and a multi-criteria decision support method were applied to know the environmental, functional, and economic performances of the production process of half-sandwich panels based on alkali-activated ceramic/slag waste cement, choosing as system boundary the method “cradle to gate”. The proposed building solutions differ from each other in the type of insulating material used, either extruded polystyrene foam (APXPS) or expanded cork agglomerate board (APICB). Besides, a comparative analysis of the developed building solutions versus three reference constructive solutions: i) a conventional heavyweight partition wall, ii) a lightweight gypsum wall panel, and iii) a conceptual lightweight sandwich membrane building solution was performed. Results showed that the two proposed half-sandwich wall panels (APXPS and APICB) resulted in the most sustainable alternatives, of which the APXPS obtained the best overall results since it combined the best environmental, functional, and economic behavior. Besides, the environmental contribution analysis determined that the greatest environmental burden to the Global Warming Potential (GWP), in the case of the APXPS was associated with the XPS (57%), being the alkali activator (23%) placed as the second major contributor. When the ICB was used as the insulation layer, the energy used (nearly 38%) and the sodium silicate (about 17%) were the larger contributors to CO2 emissions. It is worth mentioning that the use of ICB represented a negative contribution (of about −34%) to the GWP category.

Recent Advances in Alternative Cementitious Materials for Nuclear Waste Immobilization: A Review

Since the emergence of the problem of nuclear waste conditioning, cementation has become an important and developing part of the waste management system, owing to its simplicity and versatility. The continued development of the cementation technique is driven by the improvement and expansion of cementitious materials that are suitable and efficient for nuclear waste solidification. Advances in cement theory and technology have significantly impacted improvements in nuclear waste cementation technology, the quality of fresh and hardened waste forms, waste loading rates, and the reliability and sustainability of the nuclear industry. Modern mineral matrices for nuclear waste immobilization are a broad class of materials with diverse chemical–mineralogical compositions, high encapsulation capacities, and technological and engineering performance. These matrices include not only traditional Portland cement, but also non-Portland clinker inorganic binders. This review focuses on recent trends and achievements in the development of calcium aluminate, calcium sulfoaluminate, phosphate, magnesium silicate, and alkali-activated cements as cementitious matrices for nuclear waste stabilization/solidification.

Experimental study on delamination and strength characteristics of cemented waste rock backfill

To analyze the relation of segregation and strength of cemented waste rock backfill (CWRB), the aggregate distribution, uniaxial compressive strength (UCS), and failure law of the CWRB with different mass concentrations and accelerator contents were investigated by scanning the backfill section and acoustic emission test under uniaxial compression conditions. The test results show that: (1) The higher the mass concentration and accelerator content, the more uniform the aggregate distribution of the specimens; (2) The higher the mass concentration and accelerator content, the better the skeleton structure of the specimens, and the UCS of the specimens was significantly increased from 3.53 MPa to 21.59 MPa; (3) The higher the mass concentration and accelerator content, the material properties of the specimens changed from plastic to elastic, and the integrity of the specimens was better after destruction (4) The relationship between the uniformity coefficient and UCS was constructed by defining the aggregate uniformity coefficient according to the degree of specimen delamination, and the strength increased exponentially with the increase of the aggregate uniformity coefficient.

Assessment of hydrogen production from waste heat using hybrid systems of Rankine cycle with proton exchange membrane/solid oxide electrolyzer

A techno-economic assessment of hydrogen production from waste heat using a proton exchange membrane (PEM) electrolyzer and solid oxide electrolyzer cell (SOEC) integrated separately with the Rankine cycle via two different hybrid systems is investigated. The two systems run via three available cement waste heats of temperatures 360 °C, 432 °C, and 780 °C with the same energy input. The waste heat is used to run the Rankine cycle for the power production required for the PEM electrolyzer system, while in the case of SOEC, a portion of waste heat energy is used to supply the electrolyzer with the necessary steam. Firstly, the best parameters; Rankine working fluid for the two systems and inlet water flow rate and bleeding ratio for the SOEC system are selected. Then, the performance of the two systems (Rankine efficiency, total system efficiency, hydrogen production rate, and economic and CO2 reduction) is investigated and compared. The results reveal that the two systems' performance is higher in the case of steam Rankine than organic, while a bleeding ratio of 1% is the best condition for the SOEC system. Rankine output power, total system efficiency, and hydrogen production rate rose with increasing waste heat temperature having the same energy. SOEC system produces higher hydrogen production and efficiency than the PEM system for all input waste heat conditions. SOEC can produce 36.9 kg/h of hydrogen with a total system efficiency of 23.8% at 780 °C compared with 27.4 kg/h and 14.45%, respectively, for the PEM system. The minimum hydrogen production cost of SOEC and PEM systems is 0.88 $/kg and 1.55 $/kg, respectively. The introduced systems reduce CO2 emissions annually by about 3077 tons.

Derivation of operating conditions for the Jordan cement solidification process and evaluation of disposability of the cement waste form produced in the process

The purpose of this study is to develop a process control program for the cement solidification process of the Jordan Research and Training Reactor (JRTR). The optimal operating conditions of the cement solidification process were found to be a concentrate/cement ratio of 0.65 (water/cement ratio of 0.45) and a salt content of 20 wt%. The compressive strength of the cement solidified material was 17.8–23.8 MPa, which is much higher than the 3.44 MPa specified in the waste acceptance criteria (WAC) for a disposal facility in South Korea, as developed by the Korea radioactive waste agency. In addition, through evaluation of the leaching stability for Cs, Sr, and Co, the leaching index of the samples was confirmed to be >10, 10.8, and 8.05 for Co, Sr, and Cs, respectively; all of these values exceed the WAC leaching index standard of 6.

Experimental investigation of concrete with cementitious waste material such as GGBS & fly ash over conventional concrete

In the present world, the most vital and largely used construction material is concrete. Concrete plays an essential role in construction field. Concrete consist of materials such as binding material (Cement), Fine aggregate (Sand), Coarse aggregate (Gravel), admixture and water. Cement is the most widely used binding material in the construction industry. But utilization of cement as a binding material evolves CO2 gas in the atmosphere which creates lots of environmental problems such as global warming, greenhouse effect, etc. Due to which researchers and scientists look upon different alternative measures to sort the problems related to CO2 emission. Various types of waste coming from industries having cementitious properties such as Fly-ash, Ground granulated blast furnace slag (GGBS), silica fumes, metakaolin, etc. In our research, this by-product have been utilized for manufacturing of concrete as a partial replacement of binding material i.e. cement. In this work, we have prepared different proportions of samples in which binding material can be replaced with Fly-ash and GGBS. The specimen were tested in fresh and hardened state with conventional concrete. This paper concluded that the Fly ash and GGBS are partially replaced with cement in the concrete can give better workability and also exhibits better compressive strength, tensile strength and flexural strength when compared with conventional concrete. This paper also gives better alternatives of by-product to make our environment sustainable, eco-friendly and cost effective.

Mechanical Properties of Self-compacting Concrete Containing Fine Aggregates from Cement Kiln Dust and Hardened Cement Waste

Abstract The aim of this research is to assess the mechanical performance of self-compacting concrete containing different percentages of fine aggregates, produced from the wastes generated by the cement plant industry and construction sites. Eight mixes, incorporating cement kiln dust (CKD) and hardened cement waste with partial fine aggregate replacement of 5%, 10%, 15%, and 20%, were produced and compared with a control mix made with 100% of crushed sand. The workability properties (e.g., flowability, passing ability, and resistance to segregation) and mechanical properties (e.g., compressive, flexural, and splitting tensile strengths) of all mixes were evaluated. The results showed that concretes containing recycled fine aggregates proved to have the best mechanical properties, compared to one made with crushed calcareous sand. However, self-compacting concrete with high mechanical strength could be produced with up to 15% wt. CKD replacement and with 10% wt. hardened cement waste replacement.

Fiber Efficiency on the Flow Behaviors and Compressibility-Permeability of Fiber-Reinforced Cemented Waste Slurry

Fiber Efficiency on the Flow Behaviors and Compressibility-Permeability of Fiber-Reinforced Cemented Waste Slurry

Evaluation of Construction and Demolition Waste Management in Kuwait

This research aimed to evaluate Kuwait’s current construction and demolition waste (C&D waste) situation by focusing on C&D waste generation and management issues. This work also investigated the causes and factors affecting C&D waste to understand the actual waste management activities and proposed strategies to minimize the waste generated at the local level. This study estimated C&D waste generation rates based on data collected from five construction projects and two demolition projects in Kuwait. In addition, a questionnaire survey was conducted to evaluate the causes of C&D waste generation. The results showed that the average C&D waste quantities generated by construction activities were 49.5 kg/m2 for public/commercial building projects and 35 kg/m2 for residential projects. At the same time, public/commercial construction, residential construction, and demolition works generated 1.480 ton/m2, 0.0495 ton/m2, and 0.035 ton/m2, respectively. The average composition of C&D waste from the construction sector was 35.4% concrete waste, followed by 19.2% tiles/blocks, and 14.2% metals, with the remainder being other materials. Meanwhile, the demolition waste was composed of 70% concrete and cement waste and 20% metals. The results showed that 54% of the projects disposed of their C&D waste directly in the landfills. The leading causes of C&D waste generation were reworks due to changes in specifications, poor material quality, improper material handling, and improper site management. Strategic C&D waste management practices are necessary for sustainable natural resource management and conservation of the environment.

Stability of SrCO3 within composite Portland-slag cement blends

The stability and reactivity of SrCO3 within a blended Portland-slag cement at both 20 °C and 60 °C (to simulate an indicative waste form for disposal) was determined via XRD, TG-MS, SEM-EDX and thermodynamic modelling. Sr14CO3 is a potential long-term sink for trapping radioactive 14C, produced through the nuclear fuel cycle, therefore understanding its stability in potential cementitious waste forms is of interest and importance. Incorporation of 30 wt% SrCO3 in blended Portland-slag cement caused minor reactions to occur, resulting in increased formation of carbonated AFm phases, along with stabilisation of ettringite at 20 °C, precluded at 60 °C due to the reduced stability to ettringite at this temperature. Thermodynamic modelling predicted only minor SrCO3 reactivity up to 360 days, with carbonate remaining stable over this timeframe, validated by our experimental results. Thus, thermodynamic simulations predict that SrCO3 is an effective immobilisation matrix for 14C, within a blended Portland-slag cement waste form, suitable for long-term geological disposal.

Preparation and hydration of industrial solid waste—cement blends: A review

Preparation and hydration of industrial solid waste—cement blends: A review

Industrial graphene oxide-fly ash hybrid for high-performance cemented waste rock backfill

Cemented waste rock backfills (CWRB) play an essential role in mining safety engineering, waste reduction and harm resource recycling. However, the mechanical and permeability-related properties of the CWRB are limited by cement consumption and cost. This study adopted the industrial graphene oxide-fly ash (IGO-FA) hybrid to produce high-performance, cost-saving, and environment-friendly mine backfill materials. The IGO-FA hybrid exhibited the optimal reinforcing efficiency under a 0.5 water-to-cement ratio, where the CWRBs’ mechanical properties and impermeability were enhanced by 5.1%-16.9% and 32.7%-38.9%, respectively, with only 0.007 wt% IGO dosage. Compared with the traditional backfill materials, cement consumption can be reduced by up to 20 wt%. This work not only enhanced the understanding of GO in reinforcing cementitious composites but could also provide an affordable alternative to GO-related composites.

The Transformation and Leachability of Fly Ash/Cement Waste Forms Subjected to the Simultaneous Effect of Heat and Chemistry

The utilization of cement waste forms with high content of fly ash is a potential method in large-volume immobilization of low- and intermedium-level radioactive waste at near-surface. However, the migration behavior of radionuclides in fly ash/cement waste forms under geological environment is still unclear. This study researched the transformation of products, pore structure as well as the leachability of Ca2+, Na+, and simulated radioactive nuclides (Sr2+ and Cs+) in fly ash/cement waste forms under simultaneous effect through X-ray diffractometer (XRD), mercury intrusion porosimetry (MIP), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, the relationship between the decalcification and the leaching of Sr2+ and Cs+ was established by the fitting curves of apparent diffusion coefficient. The results indicated that the products of fly ash/cement waste forms were kept stable under simultaneous effect and the pore structure has excellent resistance to temperature. The increasing salt concentrations of leachant and temperature promoted the leaching of radionuclides while the protection layer formed at 60–80°C inhibited this phenomenon. The relationship of apparent diffusion coefficient between Sr2+ and Ca2+ was quadratic nonlinear, while the relationship between Cs+ and Ca2+ showed a linear relationship. Compared to cement waste forms, fly ash/cement waste forms were more stable. In addition, the long-term retention ability of fly ash/cement waste forms to Cs+ was more outstanding than Sr2+.

Utilization of CO2-Cured Waste Cement Powder to Enhance the Properties and Microstructure of Cement Mortar and Paste

Utilization of waste concrete has been become an urgent requirement for sustainable development due to the huge amounts of construction waste. The most promising strategy is to treat construction wastes by CO2 curing. This study investigates the properties and microstructure of cement mortar with CO2-cured waste cement powder (CWCP). The results showed the CWCP showed a rapid pH value decline from 12.9 to 10.2 within 12 h, the value was maintained at 8.4, and showed no obvious change after carbonation after 72 h. The CO2 uptake of CWCP increased rapidly in the first 2 h and reached 26.4% at 168 h. The C-S-H, Ca(OH)2, and traces of ettringite in waste cement powder (WCP) were transformed to calcium carbonate and silica gel after carbonation treatment. The flowability of cement mortar decreased with addition of WCP and CWCP content. The compressive strength of cement mortar with WCP decreased with replacement of cement beyond 10%, and incorporation of below 20% CWCP increased the compressive strength of mortar. In addition, the replacement of cement with 10%–20% CWCP or 10% WCP showed a lower water absorption compared with control cement mortar. The presence of calcium carbonate in the CWCP resulted in the formation of monocarbonate, which stabilized the ettringite and led to a denser microstructure compared with control cement paste.

Cement Immobilization of Hazardous and Radioactive Electric Arc Furnace Dust

This paper reveals an appropriate ingredient to operating the hazardous and radioactive electric arc furnace dust (EAFD) from the steel production factory using the cement immobilization technique. The cement specimens were prepared by mixing tap water with the binders (i.e., ordinary Portland cement: OPC, and the EAFD) at the different EAFD replacement of 0%, 15%, 25%, 35%, 40%, 45%, and 50% by weight. The water-to-binders ratio was fi xed at 0.40. The compressive strength test on the fabricated samples was performed at two different curing times of 14 and 28 days. It was found that the highest compressive strength of the samples can be obtained when the EAFD loading was 25%. However, the compressive strength criteria for the cement waste form, the use of the ingredient with the higher EAFD loading (35% EAFD with 28-day curing time) for the immobilization is favorable while meets the criteria. The phase composition and microstructure morphology of all samples were analyzed by X-ray diffraction (XRD), X-ray fl uorescence (XRF) and scanning electron microscopy (SEM-EDS).

Potential applicability of tailings as fine aggregate for concrete paving slabs

Statistics of recent years shows an annual increase in the volume of technogenic waste (in particular "tailings") of mining and metallurgical enterprises of Kazakhstan by about 1.5 billion tons, which at the current time is already about 4.7 billion that entails certain environmental and economic consequences. This article proposes the potential use of the tailings of the enterprises as a fine aggregate to partially replace the consumption of cement in the concrete mixture for the manufacture of paving slabs. Carbonate tailings of Kazzinc LLP enterprise were used. To determine the optimum composition of concrete mix with the use of tailings were made control and 4 experimental compositions with the replacement of part of the cement waste in the amount of 5, 10, 15, 20% respectively. Samples of concrete mixtures were tested for compressive strength, flexural tensile strength, abrasion, frost resistance, and resistance to wetting and drying. According to the test results, it was found that as the concentration of tailings increases, the physical-mechanical and operational indicators of the concrete mixture and concrete for the manufacture of paving slabs improve.

Immobilization mechanism of radioactive borate waste in phosphate-based geopolymer waste forms

The solidification of radioactive borate waste (BW), which contains a high concentration of boron ions using cement waste forms is challenging because soluble borate hinders the cement hydration reaction. Here, BW was immobilized using a phosphate-based geopolymer, and the phase change of BW in the geopolymer was investigated. The geopolymers could solidify BW up to 50 wt% depending on the water content and heat curing conditions. In geopolymers cured at high temperatures (60 and 90 °C), the 7-day compressive strength increased as the BW waste loading increased up to 40 wt%. Heat curing promoted geopolymerization and the precipitation of amorphous boron phosphate, leading to an increase in the compressive strength. The formation of a new amorphous boron phosphate phase was confirmed by performing XRD, MAS NMR, and SEM analyses of the geopolymers and reaction products. These results can improve our understanding of the immobilization mechanism of BW in phosphate-based geopolymers.

Effects of agricultural by-product on mechanical properties of cemented waste soil

Waste soil produced from construction sites currently emerges as a big problem to environment. These soils cannot be reused directly cause of its weakness in strength properties. Hence, this study focuses on improving mechanical properties of waste soil by using cement and corn husk fiber . The environment has also benefited from using corn husk fiber since corn husk is agricultural by-product. In order to evaluate the impact of corn husk fiber and cement on mechanical characteristics of waste soil, a series of laboratory experiments containing tension and compression test is carried out. In addition, scanning electron microscopy (SEM) test is conducted to investigate interaction between fibers and soil-cement matrix. Fiber content from 0 to 1% by dry soil mass and corn husk lengths of 10 and 30 mm are used in this research. The results present that strength properties of cemented soil are enhanced when fiber is added. The most improvements corresponding to compressive strength , splitting tensile strength , and direct tensile strength are 30.6%, 206.1%, and 27.9%, respectively. A strong interaction between fibers and soil-cement matrix observed from SEM results in the improvement of strength properties of cemented soil. Fiber inclusion contributes to the more ductile and durable behavior under loading. Fiber length and fiber content have a remarkable effect on the cemented soil behavior. The increase in fiber length and content leads to the increase in residual stress and the decrease in loss of post-peak stress. • Corn husk is utilized in waste soil reinforcement. • Effect of corn husk fiber on cemented soil is investigated. • The addition of fiber delays failure process of cemented soil. • Fiber inclusion improves failure strength up to 206%. • Presence of fibers at crack contributes to the appearance of residual direct tensile stress.

Evaluation of disposal stability of cement waste forms mixed with concentrated liquid waste for efficient treatment of AUC process waste

Evaluation of disposal stability of cement waste forms mixed with concentrated liquid waste for efficient treatment of AUC process waste

Utilization and life cycle assessment of low activity solid waste as cementitious materials: A case study of titanium slag and granulated blast furnace slag

The dumping of cement production and industrial solid waste can cause severe environmental impact. In order to reduce the environmental impact of cement production and reasonably dispose of solid waste, a new type of cementing material was developed using industrial solid waste as raw materials. It solves the problem that low activity solid waste is difficult to reuse and makes up for the less research, which considered both preparation and environmental evaluation. The orthogonal tests of cement mortar strength as well as life cycle assessment were carried out. The results from variance and range analyses of the orthogonal tests revealed that the fraction of solid waste mainly affected the compressive strength of the solid waste cement mortar, and its specific surface area primarily influenced the flexural strength. After curing for 28 days, the compressive and flexural strength values of the developed cementing material were 40.6 MPa and 8.6 MPa, respectively. The results of life cycle impact assessment indicated that the developed solid waste cement had more environmental advantages than ordinary cement in 18 midpoints environmental impact types, and could diminish environmental impact by 16.1 % on the whole. The solid waste cement has achieved great environmental gains in the human toxicity, natural land transformation, metal depletion, climate change and other environmental impact categories. In addition, the clinker calcination, transportation and material mining were identified as critical processes responsible for the human toxicity, natural land transformation and metal depletion. Through sensitivity and uncertainty analyses, the development of the solid waste cement was proved to be the most effective method to decrease the environmental impact of cement. Finally, the methods of further reducing the environmental impact of cement were proposed.