Grout Formulations Research Articles

Comparing the short-term leaching behaviour of cements containing supplementary cementitious materials in different leachants for low-level waste encapsulation

Pulverized fly ash (PFA) is commonly used as a supplementary cementitious material (SCM) in cement and is permitted for use in cements and grouts used for the encapsulation of low-level nuclear waste. However, with a global decrease in availability of PFA predicted in the near future, alternative SCMs are required. In nuclear encapsulation, a key parameter for a new SCM is that it does not change the leaching behaviour of the grout. We present promising initial leaching data from two SCMs: metakaolin and waste paper fly ash. These were tested for 24 h in two leachants, deionized water and an artificial groundwater, tracking the pH and leachability of a range of elements as the samples equilibrated with the leachants. The study suggests that for many elements, both metakaolin and waste paper fly ash show a very similar leaching behaviour to PFA grout formulations despite differences in the pH equilibration. In general, the tests suggest that the composition of the elute is dominated by leaching from the cementitious phases, and not the SCM. This suggests that further longer-term leaching studies are required as part of testing for SCM suitability for nuclear grouts in order to understand the connections between leaching and grout microstructure.

Analysis of the Rheological Properties of Natural Hydraulic Lime-Based Suspensions for Sustainable Construction and Heritage Conservation.

Natural hydraulic lime (NHL)-based binders play a crucial role in preserving cultural heritage structures, ensuring integrity and longevity. Beyond traditional uses, these binders exhibit potential for integration into both non-structural and structural components, being compatible with innovative manufacturing processes such as digital fabrication. Meticulously designed grouts, with applicability in their fresh and hardened states, are essential for heritage stability. This study explores the relationships between mineral additions, chemical admixtures, and lime for grout formulations, aiming to advance our understanding and inform the optimization of materials for heritage restoration. Key questions include the influence of natural volcanic pozzolan (NVP) and metakaolin (MK) on rheology and the impact of varying ratios of superplasticizer on NHL-based grout's rheological behavior. This systematic evaluation of rheological parameters aims to innovate mix designs, expanding NHL-based binders' applicability in construction and science. Our hypotheses suggest that well-designed lime grout formulations, incorporating NVP and MK, can enhance rheological properties, addressing challenges in sustainable construction and heritage conservation. This research provides valuable insights for optimizing lime-based materials, fostering advancements in heritage restoration, and promoting wider NHL-based binder adoption in diverse construction applications.

Design and implementation of resistive grout for cross-borehole electrical imaging

Electrically resistive grout mixtures were evaluated for cross-borehole electrical resistivity tomography (ERT) applications, which are increasingly used for environmental investigations. Grout is typically used to fill the annular space between the electrodes and the surrounding formation and therefore plays a critical role in electrically connecting the electrodes to the surrounding formation. The ideal grout for cross-borehole ERT applications has a resistivity that is higher than the surrounding formation so that the injected current is channeled within the formation instead of along the wellbore. Bentonite and Portland cement are typically used as materials to fill the annulus in wellbore installations; however, the resistivity of these materials is too low for high-quality ERT imaging. In this study, we tested grout mixtures that combine Portland cement with additives to develop resistive grout options to optimize ERT imaging while maintaining acceptable construction properties. Additives were chosen based on known chemical reactions, verified using powdered X-ray diffraction on select samples, whereby pore water and dissolved ions would be reduced, resulting in an increased resistivity. Additives include pozzolans such a Class F fly ash and Hess pumice. Other additives include slag, aluminum sulfate, and gypsum. Grouts were tested in three groups by additive, with one grout from each group with the highest resistivity selected for an X-ray diffraction analysis and other physical characteristic testing (strength, viscosity, and set time). The resistivity of pozzolan grouts can be predicted using the calcium to silicate and aluminate ratio with resistivities ranging from 76 to 680 Ω-m in 90 days. Grouts using sulfate minerals increase in resistivity more quickly than grouts only using pozzolan additives and have a resistivity range from 970 to 1820 Ohm-m in 90 days. Grouts containing pumice had reduced strength and increased viscosity, but grout containing fly ash and slag maintained similar physical properties to neat Portland cement. This study provides quantitative results that can be used to aid in selection of grout formulations that have a high likelihood of success in terms of construction and ERT image quality.

Presence of aromatic-rich organic matter and its characterization in grout materials: Implications for radionuclide immobilization

Grout materials are commonly used to immobilize low-level radioactive waste. Organic moieties can be unintentionally present in common ingredients used to make these grout waste forms, which may result in the formation of organo-radionuclide species. These species can positively or negatively affect the immobilization efficiency. However, the presence of organic carbon compounds is rarely considered in models or characterized chemically. Here, we quantify the organic pool of grout formulations with and without slag, as well as the individual dry ingredients used to make the grout samples (ordinary Portland cement (OPC), slag and fly ash), including total organic carbon (TOC) and black carbon, followed by aromaticity evaluation and molecular characterization via Electro Spray Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FTICRMS). All dry grout ingredients contained significant amounts of organic carbon, ranging from 550 mg/kg to 6250 mg/kg for the TOC pool, with an averaged abundance of 2933 ± 2537 mg/kg, of which 60 ± 29% was composed of black carbon. The significant abundance of a black carbon pool implies the presence of the aromatic-like compounds, which was further identified by both phosphate buffer-assisted aromaticity evaluation (e.g., >1000 mg-C/kg as aromatic-like carbon in the OPC) and dichloromethane (DCM) extraction with ESI-FTICRMS analysis. Besides aromatic-like compounds, other organic moieties were also detected in the OPC, such as carboxyl-containing aliphatic molecules. While the organic compound only consists of minor fractions of the grout materials investigated, our observations of the presence of various radionuclide-binding organic moieties suggests the potential formation of organo-radionuclides, such as radioiodine, which might be present at lower molar concentrations than TOC. Evaluating the role of organic carbon complexation in controlling the disposed radionuclides, especially for those radionuclides with strong association with organic carbon, has important implications for the long-term immobilization of radioactive waste in grout systems.

Leaching and transport of technetium from reducing cementitious waste forms in field lysimeters

Field lysimeters tests examined leaching of technetium-99 (99Tc) from two types of cementitious waste forms and found that the presence of blast furnace slag reduced the overall leaching of 99Tc from the waste form. The two cementitious waste forms were a slag-grout 45%/45%/10% mixture of fly ash, blast furnace slag, and cement, respectively, referred to as slag-grout or a 55%/45% mixture of cement and fly ash, respectively, referred to here simply as cement. Duplicate sources of each composition were buried in four lysimeters for approximately 10 months to evaluate leaching characteristics under natural meteorological conditions in South Carolina, USA. Effluent samples were collected four times during the experiment, and the distribution of 99Tc in the sediment was determined by destructively segmenting the lysimeters at the end of the experiment.The transport of Tc within the lysimeter was simulated by assuming advection, dispersion, and sorption in partially saturated porous media, and by using a shrinking-core type approximation for the release of Tc from the source. The shrinking-core model predicted that the oxidation front created by the oxygenated infiltrating groundwater moved into the cementitious source at a rate of 14 μm/day. As this front moved through the source, Tc(IV) was oxidized to the highly mobile Tc(VII) (as TcO4−) species, which then was transported through the sediment primarily via advection due to a small partitioning coefficient (Csolid/Caq; Kd = 0.14 mL/g). The simulations predicted a cycle of accumulation of Tc in sediment at the source between rainfall events, followed by downward advection due to infiltration during rainfall events. The anomalous upward movement of Tc peak was predicted to be due to upward flux caused by evaporation after the experiment was terminated by capping the lysimeter. These experiments demonstrate that Tc leaching from cementitious waste forms under simulated vadose zone oxidizing conditions can be reasonably approximated by the shrinking core model, and the migration of Tc through the sediment is profoundly influenced by the presence of slag in the grout formulation and hydraulic conditions due to the low sorption affinity of TcO4−.

Laboratory and numerical study on innovative grouting materials applicable to borehole heat exchangers (BHE) and borehole thermal energy storage (BTES) systems

In this study, a laboratory-scale prototype of a borehole field has been designed and built to assess various innovative grouting products in a fully controlled environment. Three novel grout formulations are developed and evaluated: enhanced grout, a mixture of enhanced grout and microencapsulated phase change material, and a mixture of enhanced grout and shape stabilized phase change material. The objective is to evaluate the enhancement in their thermal properties (i.e., thermal conductivity and thermal energy storage capacity) compared to those using a commercial reference grout. Besides, three-dimensional numerical modeling is performed to provide a better understanding of the heat transfer and phase transition inside and outside the grout columns and to study the capability of the developed grouts to be used in a borehole heat exchanger or as borehole thermal energy storage system. To the best of the authors' knowledge, there have been just a few numerical studies on using phase change materials inside borehole heat exchangers to assess thermal energy storage applications. The experimental and numerical results showed much higher efficiency of the grout developed with a high thermal conductivity than the reference grout in terms of heat transfer in both the grout column and the surrounding sand. Furthermore, the results indicated the noticeable influence of the microencapsulated phase change material's presence in the grout formulation in terms of heat absorption/storage during the phase transition (from solid to liquid). However, it is concluded that reengineering shape stabilized phase change material should be conducted to make it more appropriate for thermal energy storage applications.

Workability and Mechanical Properties of Superplasticized Microfine Cement Grouts

Superplasticizer (SP) is essential to enhance the groutability of microfine cement (MC) in civil engineering, however, combined effects of cement type, SP type, amount of SP and water-solid ratio (W/S) on engineering performance of MC are not clear currently. In this research, workability and mechanical properties of superplasticized microfine cement grouts (SMCG) with various SPs are evaluated systematically. Three different MCs (CEM I, CEM II/B-M and CEM III/B based on EN 197-1) and four SPs (one naphthalene-based (N), one melamine-based (M) and two polycarboxylate-based (PCE)) were used to study the effect of grout formulation. The properties investigated included rheological behavior (mini-slump, flowability, time-dependent viscosity and initial viscosity), fresh-state property (bleeding, effective W/S and final setting time), mechanical performance (shrinkage, flexural strength (FS), unconfined compressive strength (UCS), and FS/UCS) and microstructure. The new method of static viscosity was adopted and viscoelasticity was evaluated. The ranges of W/S and SP content were 1.0–2.0 and 0–2.5%, respectively. The results show that the dispersion effects of SP on rheological behavior were followed by PCE, M and N in order of the influence degree. The instability, long-setting and oversaturation were easily caused by excessive SP. SP could be helpful for improving FS or bending toughness. Considering workability and mechanical performance of SMCG, the W/S is suggested to be within 1.5, the optimal amounts of N, M and PCE are recommended as 1.5–2.0%, 1.2–1.5% and 0.9–1.2%, respectively.

Feasibility and economic evaluation of grouting materials containing binary and ternary industrial waste

In this study, the feasibility and environmental impact of using zeolite powder (ZP), basalt powder (BP), and unprocessed coarse fly ash (UFA) as grouting materials were evaluated. The rheological properties, workability, and compressive strengths of cementitious systems containing cement, ZP, BP, and UFA were tested, and three-parameter models were used to characterize the relationships between these properties. The resource consumption, electricity consumption, and greenhouse (CO2) and pollution (PM, SO2, and NOx) gas emissions of different grout formulations were evaluated by combining life cycle assessment (LCA) and economic cost assessment. The results showed that the incorporation of ZP, BP, or UFA improved the cohesiveness and bleeding rate of the grout. Some formulas had adverse effects on the rheology and compressive strength. The ternary blends of these mineral admixtures effectively solved this problem. In particular, the blends of BP and UFA not only retained cohesiveness and segregation resistances but also exhibited good rheological properties and compressive strengths.LCA and the economic evaluation indicated that the utilization of ZP and BP reduced the resource and electricity consumption, harmful gas emissions, and economic costs. Among them, BP’s annual production and mining costs were better than those of ZP. The production of UFA had a negative impact on resource consumption and environmental pollution but had the best economic effect among the three waste materials. A blend with 10% BP and 10% UFA was the optimal combination, which could simultaneously meet the requirements of the grouting performance and economic cost.

Facile Synthesis of Graphene from Waste Tire/Silica Hybrid Additives and Optimization Study for the Fabrication of Thermally Enhanced Cement Grouts.

This work evaluates the effects of newly designed graphene/silica hybrid additives on the properties of cementitious grout. In the hybrid structure, graphene nanoplatelet (GNP) obtained from waste tire was used to improve the thermal conductivity and reduce the cost and environmental impacts by using recyclable sources. Additionally, functionalized silica nanoparticles were utilized to enhance the dispersion and solubility of carbon material and thus the hydrolyzable groups of silane coupling agent were attached to the silica surface. Then, the hybridization of GNP and functionalized silica was conducted to make proper bridges and develop hybrid structures by tailoring carbon/silica ratios. Afterwards, special grout formulations were studied by incorporating these hybrid additives at different loadings. As the amount of hybrid additive incorporated into grout suspension increased from 3 to 5 wt%, water uptake increased from 660 to 725 g resulting in the reduction of thermal conductivity by 20.6%. On the other hand, as the concentration of GNP in hybrid structure increased, water demand was reduced, and thus the enhancement in thermal conductivity was improved by approximately 29% at the same loading ratios of hybrids in the prepared grout mixes. Therefore, these developed hybrid additives showed noticeable potential as a thermal enhancement material in cement-based grouts.

Iodine immobilization by silver-impregnated granular activated carbon in cementitious systems

Silver (Ag)-based technologies are amongst the most common approaches to removing radioiodine from aqueous waste streams. As a result, a large worldwide inventory of radioactive AgI waste presently exits, which must be stabilized for final disposition. In this work, the efficacy of silver-impregnated granular activated carbon (Ag-GAC) to remove iodide (I−), iodate (IO3−) and organo-iodine (org-I) from cementitious leachate was examined. In addition, cementitious materials containing I−, IO3−, or org-I loaded Ag-GAC were characterized by iodine K-edge XANES and EXAFS to provide insight into iodine stability and speciation in these waste forms. The Ag-GAC was very effective at removing I− and org-I, but ineffective at removing IO3− from slag-free grout leachate under oxic conditions. I− or org-I removal was due to the formation of insoluble AgI(s) or Ag-org-I(s) on the Ag-GAC. When I−-loaded Ag-GAC material was cured with slag-free and slag grouts, I− was released from AgI(s) to form a hydrated I− species. Conversely, when org-I loaded Ag-GAC material was cured in the two grout formulations, no change was observed in the iodine speciation, indicating the org-I species remained bound to the Ag. Because little IO3− was bound to the Ag-GAC, it was not detectable in the grout. Thus, grout formulation and I speciation in the waste stream can significantly influence the effectiveness of the long-term disposal of radioiodine associated with Ag-GAC in grout waste forms.

A ‘Sandwich’ Specimen Preparation and Testing Procedure for the Evaluation of Non-Structural Injection Grouts for the Re-Adhesion of Historic Plasters

ABSTRACT Non-structural injection grouting aims to stabilise delaminated plaster by introducing in the void, typically between delaminated plaster layers, a compatible adhesive material with bulking properties (the injection grout). Injection grout formulations are firstly tested in the laboratory to determine their performance characteristics including their physical-mechanical compatibility with the original materials (plaster or other building materials). However, laboratory tests on grouts are often not sufficiently representative of actual cases in which the grout sets between two plaster layers. This problem is particularly significant when water vapour permeability, capillary water absorption and adhesion need to be assessed. A study was conducted on the development of a ‘sandwich’ system (plaster-grout-plaster) to better simulate the real situation. This paper describes a new methodology for such specimen preparation and the adapted procedures for laboratory testing. The results are discussed comparing them with those obtained from standard specimen preparation and testing procedure.

Iodine speciation in cementitious environments

Iodine-129 is a key risk driver in most low-level waste cementitious waste repositories. Objectives of this study were to determine iodine speciation in cementitious materials with slag (Grout+slag) and without slag (Grout–slag) and its impact on iodine immobilization. Irrespective of which iodine species was amended to the aqueous phase, there were no significant differences in uptake-Kd values (∼3 L/kg). However, when the various iodine species were hydrated with the grout, the release-Kd values (6.1–121.8 L/kg) were significantly greater than the uptake-Kd values, and the amended iodine speciation (I− ≪ org-I ≤ IO3−) and grout formulation (Grout–slag < Grout+slag) had a significant impact on release-Kd values. In grout samples amended with I− and IO3−, org-I was formed and comprised a majority of the iodine in the leachate after 28 days of equilibration. The formed org-I originated from organic carbon (C) in the grout material (∼1200 mg/kg C). For the first time, these studies demonstrate that multiple iodine species can co-exist simultaneously in grout porewater, the iodine species initially added to the grout can greatly affect iodine immobilization, and the addition of slag to the grout formulation increased iodine immobilization. These results may have important implications on radioiodine waste disposal.

Electrokinetic nondestructive in-situ technique for rehabilitation of liners damaged by fuels.

Underground Storage Tanks (UGST) are often used to store hydrocarbon products and fuels. Liners under such tanks are normally formed to prevent leaching or/and overflow to groundwater. Similar protection is required in case of waste fuels, which are discharged to disposal sites (e.g. ponds, landfill). Thus, a successful protection depends on the liner formation, which might undergo destruction due to leaching. This paper presents the results of experimental investigation to examine the serviceability of liner against leachate infiltration. In order to simulate the behavior of sand-bentonite liners affected by alternative fuels (ethanol and biofuel), the leaching column tests were applied and the hydraulic conductivity was used as an indicator of the effectiveness of the rehabilitation process. Furthermore, the silicate grout solution and pretreatment with surfactant under the effect of electrokinetic phenomena to pre-wash the biofuel residuals in liner were investigated. Silica grout formulations were developed and adequate curing periods were established for electro-silicatization process. Results showed that hydraulic conductivity was reduced fourfold for the case of using three-step electro-rehabilitation for alternative fuels under pressure of 40 kPa, and reduced threefold in the case of 100 kPa pressure on liner.

Inorganic anions as retarders for deep borehole disposal grouts

Deep borehole disposal (DBD) provides an alternative to comparatively shallow mined repository concepts for many high-level radioactive wastes. Filling the annular space around the waste containers with cement grout will support them during placement and seal against ingress of groundwater. The elevated temperature and pressure (∼120°C and 50 MPa) will cause acceleration of grout thickening and setting, so retardation is required. The DBD Research Group at The University of Sheffield has developed grouts based on class G oil well cement that use organic retarders, but their presence may increase the solubility of any radionuclides released from the waste packages. New DBD grout formulations using sodium phosphate and sodium borate as inorganic retarders are reported in this paper. To place the wet grout, the onset of thickening needs to be delayed for at least 4 h. Sodium borate was found to provide this retardation at 90°C (0·75% addition) and nearly retarded sufficiently at 120°C (1% addition). Sodium phosphate did not provide sufficient retardation at either temperature. Neither compounds influenced the phases formed, but may suppress the crystallisation of calcium silicate hydrates. This work demonstrates that the performance of these inorganic materials in this application is inferior to that of organic retarders.

Research on Water-Free Injection Grouts Using Sieved Soil and Micro-Lime

ABSTRACTFor the in-situ conservation of architectural surfaces, grout injection is a widely used and approved technique, even though it is an irreversible intervention. The research presented in this article explores grouting using sieved soil and micro-lime dispersed in isopropanol for plaster reattachment on earthen support. The grout formulations have been evaluated in several laboratory tests and at mock-up’s that look at the workability of fresh grout and the performance of the cured grout. On-site tests provide additional information about applicability and the performance of the grout with weakened historic earthen substrates. The results indicate that the tested formulations with varying percentages of micro-lime show good flowability on absorbing substrates and tolerable shrinkage. Results both from flexural strength tests and microscopic investigation demonstrate that the water-free soil- lime grouts provide good bonding to both the substrate and delaminated plasters. Higher lime content results in higher mechanical strength, indicating the grouts potential to be developed into suitable conservation materials for both plaster reattachment and crack repair in the conservation of earthen architecture.

Comparison of calorimetric methods for the assessment of slag cement hydration

ABSTRACTThis study aims to contribute to future-proofing the supply of cement powders for the UK’s nuclear waste cementation program, by enabling rapid and reliable assessment of heat evolution from candidate grout formulations. Isothermal conduction calorimetry and semi-adiabatic calorimetry experiments were carried out at room temperature, to monitor the heat of hydration of blended blast furnace slag (BFS)-Portland cement formulations of relevance for wasteform grout applications. By changing the particle size distribution of the BFS, the physical and chemical properties of the cement grout are altered, and this can be monitored and understood through comparison between the two calorimetry methods.

FORMULAÇÃO DE ARGAMASSA EXPANSIVA PARA LAVRA DE ROCHAS ORNAMENTAIS UTILIZANDO MINÉRIOS NÃO-METÁLICOS DA REGIÃO NORDESTE DO PAÍS

One of the most significant methods of advanced technology for mining, the rock massif is employing expansive mortar for cutting of Rock. Furthermore, the entire expansive mortar commercialized in the Brazilian domestic market are imported, as well as those in industrialized country. Both have components from the external market. The aim of this work is to develop expansive mortar with raw materials that have regional and pressure sufficient to remove the rocks of granite and marble type expansion. For this, expansive grout formulations using calcium oxide, calcium carbonate, carboxymethylcellulose are used - CMC (Portland) cement, and from the chemical analysis by means of thermal analysis, X-ray diffraction and laser granulometry compared the results with a commercial mortar. The results indicated that the formulations showed characteristics similar to the commercial mortar

Break-up testing of waste-form materials

AbstractThe Nuclear Decommissioning Authority (NDA) is developing a safety case for the long-term management of higher activity wastes. This includes safety assessments of transport to and operations at the repository. One of the main faults and hazards to be considered is waste package response to impact accidents.The criteria of impact performance for waste packages are based upon activity release of particulates generated from the break up of the waste form during impact. The NDA approach to impact performance is based upon waste package response from finite element modelling in combination with break-up tests.Previous break up research commissioned by the NDA has concentrated on commercial graphite and glass samples. These extended studies, undertaken by the National Nuclear Laboratory in collaboration with the Department of Aerosol Technology of the Fraunhofer Institute of Toxicology and Experimental Medicine, provide break-up data specific to nuclear facilities and waste materials. These include archived unirrradiated graphite used to construct Magnox reactor cores and reflectors, simulant high level waste glass, selected grout formulations and selected metal-in-grout formulations.

Pretreatment of Tc-Containing Waste and Its Effect on Tc-99 Leaching from Grouts

AbstractA salt solution (doped with Tc-99), that simulates the salt waste stream to be processed at the Saltstone Production Facility, was immobilized in grout waste forms with and without (1) ground granulated blast furnace slag and (2) pretreatment with iron salts. The degree of immobilization of Tc-99 was measured through monolithic and crushed grout leaching tests. Although Fe (+2) was shown to be effective in reducing Tc-99 to the +4 state, the strong reducing nature of the blast furnace slag present in the grout formulation dominated the reduction of Tc-99 in the cured grouts. An effective diffusion coefficient of 4.75 x 10-12 (Leach Index of 11.4) was measured using the ANSI/ANS-16.1 protocol. The leaching results show that, even in the presence of a concentrated salt solution, blast furnace slag can effectively reduce pertechnetate to the immobile +4 oxidation state. The measured diffusivity was introduced into a flow and transport model (PORFLOW) to calculate the release of Tc-99 from a Saltstone Vault as a function of hydraulic conductivity of the matrix.

Laboratory stabilization/solidification of tank sludges: maximizing sludge loading

Highly radioactive, mixed-waste sludges that have been collected in tanks at Oak Ridge over several decades are being combined for treatment and disposal. Stabilization of the sludges in the different tank sets was tested prior to the proposed combination and treatment. This paper is the third one in a series on the laboratory stabilization/solidification of these tank sludges. It discusses efforts to maximize the sludge loading with no strength criterion for the grout formulation. Grout formulations were tested in the laboratory both with surrogates and with actual samples of tank sludge. Hydrogels eliminated free water generation, even at sludge loadings of >90 wt%, albeit strong monoliths did not form at such high loadings. Correlations established the dependence of the chromium and mercury performance in the Toxicity Characteristic Leach Procedure for the surrogates on the slag content of the grout while the lead performance depended on the extract pH. The surrogate sludge loading was limited by the chromate content to about 90 wt%, meeting Universal Treatment Standard limits. However, tests with actual sludges at such high loadings revealed problems with lead and silver stabilization that were not experienced with the surrogate testing.