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Relation between permeability and water/cement ratio for mature cement pastes hydrated 93% (Neville 1981).
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This publication provides an overview of the durability of injection grouts. It is intended
for use during planning and construction at the ONKALO underground research facility.
The review has been done with respect to the application conditions, materials and
service life requirements expressed by Posiva Oy. The publication describes all types of...
Context in source publication
Citations
... In summary, the above works have significantly contributed to improving and implementing MCSF64 low-pH grouts in HLRW. However, certain issues, including prolonged setting time, poor early shear strength, and dimensional instability, have been identified with this specific grout mix, resulting in reduced effectiveness and workability during practical grouting [11,22,23]. Therefore, the objective of this paper is to develop a slurry for microfracture grouting based on MCSF64 by incorporating NSP, aluminum sulfate (AS), and united expansion agent (UEA) to enhance the shear strength, setting time, compressive strength, and hydration process of the slurry, while maintaining desirable flowability. ...
The most accepted approach to sealing in high-level radioactive waste repositories (HLRWs) is to develop a low-pH grouting material with a pH of the pore solution of less than 11. Currently, the most widely used binary low-pH grouting material is MCSF64, which comprises 60% microfine cement (MC) and 40% silica fume (SF). In this study, a high-performance MCSF64-based grouting material was developed by incorporating naphthalene superplasticizer (NSP), aluminum sulfate (AS), and united expansion agent (UEA) to enhance the slurry’s shear strength, compressive strength, and hydration process. Orthogonal experiments were conducted to measure the flow time, yield stress, plastic viscosity, initial setting time, shear strength, and compressive strength of the MCSF64-based slurry, and the optimal mix proportion was determined using the Taguchi–Grey relational analysis method. The pH variation of the pore solution, shrinkage/expansion, and hydration products of the optimal hardened slurry were evaluated using simplified ex-situ leaching (S-ESL), a length comparometer, and scanning electron microscopy (SEM), respectively. The results demonstrate that the Bingham model effectively predicted the rheological properties of the MCSF64-based slurry. The optimum ratio for the MCSF64-based slurry was water/binder (W/B) ratio of 1.4, and the contents of NSP, AS and UEA by mass of binder were 1.9%, 3.6% and 4.8%, respectively. The optimal mix exhibited a pH value below 11 after curing for 120 days. The addition of AS and UEA facilitated hydration, shortened the initial setting time, improved early shear strength, and enhanced the expansion ability of the optimal mix under water curing conditions.
... Addition lime or gypsum to clay in addition to their accessibility and low costs, improves their performance due to positive effects on soil properties (Ogundipe 2013;Naghizade Asl et al. 2017. Although cement base composites can produce mulches with more resistance compared to clay and lime (Zare Arnani et al. 2013), they are eroded through abrasion, blow-out by wind born particles and many other environmental factors (Holt 2008). It is therefore necessary to prepare a durable cement based mixture as mulch by adding suitable cheap materials as partial replacement of cement to control affordably wind erosion and movement the sand dunes. ...
... The reason is probably due to the adverse effect of environmental factors (wind, temperature, etc.) on the stability of the cement ? sand mixture which resulted in the decrease in shear strength (Holt 2008). The shear strength of the studied treatments increased after 60 days in comparison to 7 days by 7.5%, 11.4%, 11.3%, 20.6% and 2.3% at micro silica rates of 0.5, 2.5, 5, 7.5 and 12.5% respectively (Fig. 6). ...
... Also in the given treatments contain two layers of the studied Micro silica rates (%) 7 days 60 days Fig. 12 Interaction effects of micro silica rates and time on soil losses mulch, the maximum value of soil loss was found at 0% of micro silica (1.0 kgm -2 h -1 ) and minimum values were found at 2.5%, 5% and 7.5% micro silica and 12.5% of micro silica (0 kgm -2 h -1 ), respectively. The interaction effects of micro silica rates and time (Fig. 12) revealed that there was a significant increase in soil losses for 60 days at micro silica rate of 0% (7%) compared to 7 days which can be due to erosive factors including abrasion, temperature and other environmental physical and chemical factors (Holt 2008), but it decreased significantly for 60 days by application 0.5% of micro silica (7.2%). There was no significant difference between 7 and 60 days of mulching on soil losses at 2.5, 5, 7.5 and 12.5% of micro silica, because no soil erosion was occurred at these rates. ...
Mulching is fastest strategy to control sand dune movement in arid and semiarid areas. In the present study the effect of micro silica- cement mixture was evaluated as mulch. For this purpose, an experiment was carried out as a factorial arrangement and a completely randomized design with 3 replicates. Three studied factors included 6 micro silica rates (0 as control, 0.5, 2.5, 5, 7.5 and 12.5 percent), 2 rates of mulch thickness (one and two mm layers) and 2 time series (7 and 60 days). Prepared mulches based on different mixtures of micro silica + sand (400 g) and cement were sprayed on sand trays. Then 4 parameters including shear strength, penetration resistance, threshold friction velocity and soil losses at a wind speed of 15 ms−1 were measured on the studied treatments. Results obtained from the analysis of variances revealed that the effect of micro silica rates, thickness of mulch and time on the studied properties were significant. Mean comparisons also showed that shear strength, penetration resistance and threshold friction velocity increased and soil losses of treatments significantly decreased when the micro silica rates increased. The addition of micro silica to sand- cement mixture increased shear strength and penetration resistance by 76% and 82.5% respectively and decreased soil losses by 100%. The erodibility and mechanical properties of the treatments improved by increasing the thickness of the mulch. Moreover, in all studied treatments more improvements occurred in the mentioned properties of mulches during time. The application 7.5% of micro silica after 60 days was the optimal mulch to improve the soil erodibility and to increase the mechanical resistance against wind erosion.
... Addition lime or gypsum to clay in addition to their accessibility and low costs, improves their performance due to positive effects on soil properties (Ogundipe 2013;Naghizade Asl et al. 2017. Although cement base composites can produce mulches with more resistance compared to clay and lime (Zare Arnani et al. 2013), they are eroded through abrasion, blow-out by wind born particles and many other environmental factors (Holt 2008). It is therefore necessary to prepare a durable cement based mixture as mulch by adding suitable cheap materials as partial replacement of cement to control affordably wind erosion and movement the sand dunes. ...
... The reason is probably due to the adverse effect of environmental factors (wind, temperature, etc.) on the stability of the cement ? sand mixture which resulted in the decrease in shear strength (Holt 2008). The shear strength of the studied treatments increased after 60 days in comparison to 7 days by 7.5%, 11.4%, 11.3%, 20.6% and 2.3% at micro silica rates of 0.5, 2.5, 5, 7.5 and 12.5% respectively (Fig. 6). ...
... Also in the given treatments contain two layers of the studied Micro silica rates (%) 7 days 60 days Fig. 12 Interaction effects of micro silica rates and time on soil losses mulch, the maximum value of soil loss was found at 0% of micro silica (1.0 kgm -2 h -1 ) and minimum values were found at 2.5%, 5% and 7.5% micro silica and 12.5% of micro silica (0 kgm -2 h -1 ), respectively. The interaction effects of micro silica rates and time (Fig. 12) revealed that there was a significant increase in soil losses for 60 days at micro silica rate of 0% (7%) compared to 7 days which can be due to erosive factors including abrasion, temperature and other environmental physical and chemical factors (Holt 2008), but it decreased significantly for 60 days by application 0.5% of micro silica (7.2%). There was no significant difference between 7 and 60 days of mulching on soil losses at 2.5, 5, 7.5 and 12.5% of micro silica, because no soil erosion was occurred at these rates. ...
Mulching is fastest strategy to control sand dune movement in arid and semiarid areas. In the present study the effect of micro silica-cement mixture was evaluated as mulch. For this purpose, an experiment was carried out as a factorial arrangement and a completely randomized design with 3 replicates. Three studied factors included 6 micro silica rates (0 as control, 0.5, 2.5, 5, 7.5 and 12.5 percent), 2 rates of mulch thickness (one and two mm layers) and 2 time series (7 and 60 days). Prepared mulches based on different mixtures of micro silica ? sand (400 g) and cement were sprayed on sand trays. Then 4 parameters including shear strength, penetration resistance, threshold friction velocity and soil losses at a wind speed of 15 ms-1 were measured on the studied treatments. Results obtained from the analysis of variances revealed that the effect of micro silica rates, thickness of mulch and time on the studied properties were significant. Mean comparisons also showed that shear strength, penetration resistance and threshold friction velocity increased and soil losses of treatments significantly decreased when the micro silica rates increased. The addition of micro silica to sand-cement mixture increased shear strength and penetration resistance by 76% and 82.5% respectively and decreased soil losses by 100%. The erodibility and mechanical properties of the treatments improved by increasing the thickness of the mulch. Moreover, in all studied treatments more improvements occurred in the mentioned properties of mulches during time. The application 7.5% of micro silica after 60 days was the optimal mulch to improve the soil erodibility and to increase the mechanical resistance against wind erosion.
... For example, the w/b of 1.42 shown in Table 2 changes to an effective w/b of 1.0. This information can be used to estimate the long-term durability performance, but the k-value is still under discussion [26]. ...
The current solution to the problem of using cementitious material for sealing purposes in a final radioactive waste repository is to develop a low-pH cement grout. In this study, the material properties of a low-pH cement grout based on a recipe used at ONKALO are investigated by considering such factors as pH variation, compressive strength, dynamic modulus, and hydraulic conductivity by using silica fume and micro-cement. From the pH measurements of the hardened cement grout, the required pH (< pH 11) is obtained after 130 days of curing. Although the engineering properties of the low-pH cement grout used in this study are inferior to those of conventional high-pH cement grout, the utilization of silica fume and micro-cement effectively meets the long-term environmental and durability requirements for cement grout in a radioactive waste repository.
This Chapter is related to durability issues. Physical effects are considered first, referring to the consequences of water introduced in masonry by the grouting (freezing and dissolution of soluble phases). Subsequently, chemical effects are considered, such as sulphate reactions, alkali-silica reactions, possible chlorides’ attack and leaching. The chapter ends with a brief presentation of literature results of durability tests, and with a guide for the selection of binders vs durability.
Population increments in big cities have resulted by problems of people such as transportation, health, service and drinkable water necessities etc... In order to meet utility water requirements, underground tunnels are sometimes burrowed for transmitting water from far away resources. One of them was the Ayazağa conduit tunnel in İstanbul excavated by NATM in a rock media from poor to extremely poor formation. After excavating and properly supporting media, a compact grout application is performed before a “consolidation grout phase (CGP)”, that is subject of this paper. In CGP, A set of holes for every 3 m approximately, which filled out by cement injection, were drilled from pipe inside in to the compaction grout shell first and support shell in second till going through 0.5m in formation third. An undergraduate thesis examining this application and process, focused on a portion of current tunnel from the CGP point of view. Nevertheless, rock parameters on the tunnel face were recorded by side geologists. When these data and amount of the injected CGP are analyzed, some remarkable relationship can be seen between formation and amount of CGP injections that may help practitioners to predict injection levels and cost evaluation in the similar formations.
Cement-based grout plays a significant role in the design and performance of nuclear waste repositories: used correctly, it can enhance their safety. However, the high water-to-binder ratios, which are required to meet the desired workability and injection ability at early age, lead to high porosity that may affect the durability of this material and undermine its long-term geochemical performance.In this paper, a new methodology is presented in order to help the process of mix design which best meets the compromise between these two conflicting requirements. It involves the combined use of the computer programs CEMHYD3D for the generation of digital-image-based microstructures and CrunchFlow, for the reactive transport calculations affecting the materials so simulated. This approach is exemplified with two grout types, namely, the so-called Standard mix 5/5, used in the upper parts of the structure, and the “low-pH” P308B, to be injected at higher depths.The results of the digital reconstruction of the mineralogical composition of the hardened paste are entirely logical, as the microstructures display high degrees of hydration, large porosities and low or nil contents of aluminium compounds.Diffusion of solutes in the pore solution was considered to be the dominant transport process. A single scenario was studied for both mix designs and their performances were compared. The reactive transport model adequately reproduces the process of decalcification of the C–S–H and the precipitation of calcite, which is corroborated by empirical observations. It was found that the evolution of the deterioration process is sensitive to the chemical composition of groundwater, its effects being more severe when grout is set under continuous exposure to poorly mineralized groundwater. Results obtained appear to indicate that a correct conceptualization of the problem was accomplished and support the assumption that, in absence of more reliable empirical data, it might constitute a useful tool to estimate the durability of cement-based structures.
