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Papers by Scott Jones

In recent years, there has been great interest in reducing the cement content of concrete, due t... more In recent years, there has been great interest in reducing the cement content of concrete, due to the high energy and carbon dioxide footprints of cement production. There are numerous (waste) materials that can be substituted for cement in the concrete mixture proportions, including fly ash, slag, silica fume, metakaolin, waste glass, etc. However, a more abundant material substitute would be limestone powder, created from the same limestone that is currently heavily employed in cement production as the primary source of calcium oxide. This technical note presents an approach to replacing not only cement powder, but effectively cement paste consisting of the cement and water, with appropriately sized limestone powder(s). Such an approach effectively extends the conventional utilization of centimeter-sized coarse aggregates (rocks) and millimeter-sized fine aggregates (sand) that occupy between 65 % and 75 % of the volume of a concrete structure to include micro-aggregates ranging between about 1 µm and 100 µm in size. Here, to demonstrate the feasibility of this approach, demonstration mixtures of pastes, mortars, and concretes are each formulated with limestone powder replacement for a significant portion of their cement paste component, achieving cement reductions of up to 28 % in concrete, for example. For these mixture modifications, the water-to-cement mass ratio (w/c) is maintained at or above 0.4 to provide sufficient water to react with all of the cement, so that none of this most costly component of cement-based materials goes to waste. Meanwhile, the water-to-solids ratio (w/s) is reduced to a value in the range of 0.22 to 0.40 in order to maximize the limestone powder replacement level, while still providing sufficient flow and rheology, by using reasonable dosages of high range water reducing admixtures. The fresh, early age, and long term performance properties of these high volume limestone powder (HVLP) mixtures are contrasted with a w/c=0.4 ordinary portland cement (OPC) paste or mortar, or a w/c=0.5 OPC concrete reference, respectively. In general, the properties and performance of these more sustainable mixtures are similar or even superior to those of the corresponding reference mixture, suggesting that these new paradigm HVLP concretes could be readily substituted for existing conventional OPC mixtures. The reduced shrinkage (autogenous and drying) of the mortars with limestone powder replacement, due to their reduced paste content, is highlighted because of its likelihood to reduce concrete cracking. However, beyond measurements of electrical resistivity, this study has not specifically focused on durability issues and additional research on this topic is recommended as these new mixtures are reduced to (field) practice.

Cement and Concrete Composites, 2015

The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosi... more The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosion and eventually compromises a structure’s integrity. To extend its service life and improve safety, it is crucial to develop sound repair strategies for our nation’s infrastructure. In this paper, results are presented for numerical simulations to study the effectiveness of fillers for repair of cracks in concrete, so as to delay the onset of corrosion in reinforcing steel. Concretes without cracks and with either a 50 µm or 500 µm wide crack located directly above the steel reinforcement are simulated, with the addition of silica fume, a corrosion inhibitor, or epoxy-coated reinforcement being considered as additional scenarios. The effectiveness of the crack filler depends not only on its inherent diffusivity with respect to chloride ions, but also on its ability to penetrate and fill the damaged zone or interface between the open crack region and the bulk concrete. Additional simulations indicate that using continuum models instead of models that include details of the rebar placement can lead to underestimating the chloride concentration and overestimating the service life. Experiments are needed to study the ingress of chlorides in damaged (interfacial) regions adjacent to the crack or at the reinforcement surface, as the local transport properties of these regions can significantly influence service life predictions.

Concrete International, Sep 2014

The prediction of concrete service life is of paramount importance for upgrading our nation’s bui... more The prediction of concrete service life is of paramount importance for upgrading our nation’s built infrastructure. Although computer models for predicting the service life of reinforced concrete exposed to chlorides (e.g., road salts) have been developed and enhanced during the past 15 years, there are many real-world considerations that complicate accurate and representative modeling of field structures. However, recent advances in both concrete-specific models and general-purpose modeling platforms are permitting detailed investigations of the influences of many of these real-world parameters of interest. This paper reviews these real- world considerations and provides some examples of how they are being addressed via advanced modeling capabilities.

Chloride ions, resulting from the application of de-icing salts, travel through the concrete matr... more Chloride ions, resulting from the application of de-icing salts, travel through the concrete matrix by diffusion in a connected pore network. Cracks in concrete facilitate chloride movement by allowing ions to bypass the concrete matrix and travel directly to reinforcing bars, reducing the protective capacity of the alkaline environment and the time to corrosion initiation. In this study, five concrete mixtures, two of which are high volume fly ash (HVFA) mixtures are investigated. Their diffusivity is assessed via electrical resistivity measurements and their chloride binding capacity is measured by submerging ground mortar specimens in a solution of NaCl. Neutron tomography of epoxy and methacrylate-filled cracks provides insights into the ability of concrete crack fillers to seal cracks. These results are incorporated into a service life model where the chloride ion concentration in a reinforced concrete slab is computed given a chloride ion exposure condition. The output of the ...

Cement and Concrete Composites, 2015

The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosi... more The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosion and eventually compromises a structure's integrity. To extend its service life and improve safety, it is crucial to develop sound repair strategies for our nation's infrastructure. In this paper, results are presented for numerical simulations to study the effectiveness of fillers for repair of cracks in concrete, so as to delay the onset of corrosion in reinforcing steel. Concretes without cracks and with either a 50 lm or 500 lm wide crack located directly above the steel reinforcement are simulated, with the addition of silica fume, a corrosion inhibitor, or epoxy-coated reinforcement being considered as additional scenarios. The effectiveness of the crack filler depends not only on its inherent diffusivity with respect to chloride ions, but also on its ability to penetrate and fill the damaged zone or interface between the open crack region and the bulk concrete. Additional simulations indicate that using continuum models instead of models that include details of the rebar placement can lead to underestimating the chloride concentration and overestimating the service life. Experiments are needed to study the ingress of chlorides in damaged (interfacial) regions adjacent to the crack or at the reinforcement surface, as the local transport properties of these regions can significantly influence service life predictions.

The prediction of concrete service life is of paramount importance for upgrading our nation's bui... more The prediction of concrete service life is of paramount importance for upgrading our nation's built infrastructure. Although computer models for predicting the service life of reinforced concrete exposed to chlorides (e.g., road salts) have been developed and enhanced during the past 15 years, there are many real-world considerations that complicate accurate and representative modeling of field structures. However, recent advances in both concrete-specific models and general-purpose modeling platforms are permitting detailed investigations of the influences of many of these real-world parameters of interest. This paper reviews these realworld considerations and provides some examples of how they are being addressed via advanced modeling capabilities.

Proceedings of the 4th International Conference on the Durability of Concrete Structures, 2014

Electrical measurements are becoming a common method to assess the transport properties of concre... more Electrical measurements are becoming a common method to assess the transport properties of concrete. For a saturated homogenous system, the surface resistance and the uniaxial resistance measurements provide equivalent measures of resistivity once geometry is appropriately taken into account. However, cementitious systems are not always homogenous. This article compares bulk and surface resistance measurements in cementitious materials intentionally composed of layered materials (i.e., layers with different resistivities). For this study, layered systems were composed of paste and mortar layers, representing the heterogeneity that can exist in the surface layers of field applications as a result of differences in moisture content, segregation, ionic ingress, carbonation, finishing operations, or ionic leaching. The objective of this article is to illustrate that these electrical measures can differ in layered systems (with sharp layer boundaries) and to demonstrate the impact of the surface layer properties on the estimation for the underlying material properties, for both cylindrical and prismatic specimens. Accounting for the effects of a surface layer requires a separate correction in addition to the overall specimen geometry corrections.

Construction and Building Materials, 2015

Limestone (calcium carbonate, CaCO3) has long been a critical component of concrete, whether as t... more Limestone (calcium carbonate, CaCO3) has long been a critical component of concrete, whether as the primary raw material for cement production, a fine powder added to the binder component, or a source of fine and/or coarse aggregate. This paper focuses on the latter two of these examples, providing a multi-scale investigation of the influences of both fine limestone powder and conventional limestone aggregates on concrete performance. Fine limestone powder in the form of calcite provides a favorable surface for the nucleation and growth of calcium silicate hydrate gel at early ages, accelerating and amplifying silicate hydration, and a source of carbonate ions to participate in reactions with the aluminate phases present in the cement (and fly ash). Conversely, the aragonite polymorph of CaCO3 exhibits a different crystal (and surface) structure and therefore neither accelerates nor amplifies silicate hydration at a similar particle size/surface area. However, because these two forms of CaCO3 have similar solubilities in water, the aragonite does contribute to an enhancement in the reactivity of the aluminate phases in the investigated systems, chiefly via carboaluminate formation. In 100 % ordinary portland cement (OPC) concretes, 10 % of the OPC by volume can be replaced with an equivalent volume of limestone powder, while maintaining acceptable performance. A comparison between limestone and siliceous aggregates indicates that the former often provide higher measured compressive strengths at equivalent levels of hydration, even when the two aggregate types exhibit similar elastic moduli. This suggests that the interfacial transition zone in the limestone-based concretes exhibits a higher degree of bonding, likely due to the favorable physical (texture) and chemical nature of the limestone surfaces. These observations reinforce the value of utilizing limestone to increase the performance and sustainability of 21st century concrete construction.

In recent years, there has been great interest in reducing the cement content of concrete, due t... more In recent years, there has been great interest in reducing the cement content of concrete, due to the high energy and carbon dioxide footprints of cement production. There are numerous (waste) materials that can be substituted for cement in the concrete mixture proportions, including fly ash, slag, silica fume, metakaolin, waste glass, etc. However, a more abundant material substitute would be limestone powder, created from the same limestone that is currently heavily employed in cement production as the primary source of calcium oxide. This technical note presents an approach to replacing not only cement powder, but effectively cement paste consisting of the cement and water, with appropriately sized limestone powder(s). Such an approach effectively extends the conventional utilization of centimeter-sized coarse aggregates (rocks) and millimeter-sized fine aggregates (sand) that occupy between 65 % and 75 % of the volume of a concrete structure to include micro-aggregates ranging between about 1 µm and 100 µm in size. Here, to demonstrate the feasibility of this approach, demonstration mixtures of pastes, mortars, and concretes are each formulated with limestone powder replacement for a significant portion of their cement paste component, achieving cement reductions of up to 28 % in concrete, for example. For these mixture modifications, the water-to-cement mass ratio (w/c) is maintained at or above 0.4 to provide sufficient water to react with all of the cement, so that none of this most costly component of cement-based materials goes to waste. Meanwhile, the water-to-solids ratio (w/s) is reduced to a value in the range of 0.22 to 0.40 in order to maximize the limestone powder replacement level, while still providing sufficient flow and rheology, by using reasonable dosages of high range water reducing admixtures. The fresh, early age, and long term performance properties of these high volume limestone powder (HVLP) mixtures are contrasted with a w/c=0.4 ordinary portland cement (OPC) paste or mortar, or a w/c=0.5 OPC concrete reference, respectively. In general, the properties and performance of these more sustainable mixtures are similar or even superior to those of the corresponding reference mixture, suggesting that these new paradigm HVLP concretes could be readily substituted for existing conventional OPC mixtures. The reduced shrinkage (autogenous and drying) of the mortars with limestone powder replacement, due to their reduced paste content, is highlighted because of its likelihood to reduce concrete cracking. However, beyond measurements of electrical resistivity, this study has not specifically focused on durability issues and additional research on this topic is recommended as these new mixtures are reduced to (field) practice.

Cement and Concrete Composites, 2015

The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosi... more The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosion and eventually compromises a structure’s integrity. To extend its service life and improve safety, it is crucial to develop sound repair strategies for our nation’s infrastructure. In this paper, results are presented for numerical simulations to study the effectiveness of fillers for repair of cracks in concrete, so as to delay the onset of corrosion in reinforcing steel. Concretes without cracks and with either a 50 µm or 500 µm wide crack located directly above the steel reinforcement are simulated, with the addition of silica fume, a corrosion inhibitor, or epoxy-coated reinforcement being considered as additional scenarios. The effectiveness of the crack filler depends not only on its inherent diffusivity with respect to chloride ions, but also on its ability to penetrate and fill the damaged zone or interface between the open crack region and the bulk concrete. Additional simulations indicate that using continuum models instead of models that include details of the rebar placement can lead to underestimating the chloride concentration and overestimating the service life. Experiments are needed to study the ingress of chlorides in damaged (interfacial) regions adjacent to the crack or at the reinforcement surface, as the local transport properties of these regions can significantly influence service life predictions.

Concrete International, Sep 2014

The prediction of concrete service life is of paramount importance for upgrading our nation’s bui... more The prediction of concrete service life is of paramount importance for upgrading our nation’s built infrastructure. Although computer models for predicting the service life of reinforced concrete exposed to chlorides (e.g., road salts) have been developed and enhanced during the past 15 years, there are many real-world considerations that complicate accurate and representative modeling of field structures. However, recent advances in both concrete-specific models and general-purpose modeling platforms are permitting detailed investigations of the influences of many of these real-world parameters of interest. This paper reviews these real- world considerations and provides some examples of how they are being addressed via advanced modeling capabilities.

Chloride ions, resulting from the application of de-icing salts, travel through the concrete matr... more Chloride ions, resulting from the application of de-icing salts, travel through the concrete matrix by diffusion in a connected pore network. Cracks in concrete facilitate chloride movement by allowing ions to bypass the concrete matrix and travel directly to reinforcing bars, reducing the protective capacity of the alkaline environment and the time to corrosion initiation. In this study, five concrete mixtures, two of which are high volume fly ash (HVFA) mixtures are investigated. Their diffusivity is assessed via electrical resistivity measurements and their chloride binding capacity is measured by submerging ground mortar specimens in a solution of NaCl. Neutron tomography of epoxy and methacrylate-filled cracks provides insights into the ability of concrete crack fillers to seal cracks. These results are incorporated into a service life model where the chloride ion concentration in a reinforced concrete slab is computed given a chloride ion exposure condition. The output of the ...

Cement and Concrete Composites, 2015

The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosi... more The ingress of chlorides in reinforced concrete leads to the onset of steel reinforcement corrosion and eventually compromises a structure's integrity. To extend its service life and improve safety, it is crucial to develop sound repair strategies for our nation's infrastructure. In this paper, results are presented for numerical simulations to study the effectiveness of fillers for repair of cracks in concrete, so as to delay the onset of corrosion in reinforcing steel. Concretes without cracks and with either a 50 lm or 500 lm wide crack located directly above the steel reinforcement are simulated, with the addition of silica fume, a corrosion inhibitor, or epoxy-coated reinforcement being considered as additional scenarios. The effectiveness of the crack filler depends not only on its inherent diffusivity with respect to chloride ions, but also on its ability to penetrate and fill the damaged zone or interface between the open crack region and the bulk concrete. Additional simulations indicate that using continuum models instead of models that include details of the rebar placement can lead to underestimating the chloride concentration and overestimating the service life. Experiments are needed to study the ingress of chlorides in damaged (interfacial) regions adjacent to the crack or at the reinforcement surface, as the local transport properties of these regions can significantly influence service life predictions.

The prediction of concrete service life is of paramount importance for upgrading our nation's bui... more The prediction of concrete service life is of paramount importance for upgrading our nation's built infrastructure. Although computer models for predicting the service life of reinforced concrete exposed to chlorides (e.g., road salts) have been developed and enhanced during the past 15 years, there are many real-world considerations that complicate accurate and representative modeling of field structures. However, recent advances in both concrete-specific models and general-purpose modeling platforms are permitting detailed investigations of the influences of many of these real-world parameters of interest. This paper reviews these realworld considerations and provides some examples of how they are being addressed via advanced modeling capabilities.

Proceedings of the 4th International Conference on the Durability of Concrete Structures, 2014

Electrical measurements are becoming a common method to assess the transport properties of concre... more Electrical measurements are becoming a common method to assess the transport properties of concrete. For a saturated homogenous system, the surface resistance and the uniaxial resistance measurements provide equivalent measures of resistivity once geometry is appropriately taken into account. However, cementitious systems are not always homogenous. This article compares bulk and surface resistance measurements in cementitious materials intentionally composed of layered materials (i.e., layers with different resistivities). For this study, layered systems were composed of paste and mortar layers, representing the heterogeneity that can exist in the surface layers of field applications as a result of differences in moisture content, segregation, ionic ingress, carbonation, finishing operations, or ionic leaching. The objective of this article is to illustrate that these electrical measures can differ in layered systems (with sharp layer boundaries) and to demonstrate the impact of the surface layer properties on the estimation for the underlying material properties, for both cylindrical and prismatic specimens. Accounting for the effects of a surface layer requires a separate correction in addition to the overall specimen geometry corrections.

Construction and Building Materials, 2015

Limestone (calcium carbonate, CaCO3) has long been a critical component of concrete, whether as t... more Limestone (calcium carbonate, CaCO3) has long been a critical component of concrete, whether as the primary raw material for cement production, a fine powder added to the binder component, or a source of fine and/or coarse aggregate. This paper focuses on the latter two of these examples, providing a multi-scale investigation of the influences of both fine limestone powder and conventional limestone aggregates on concrete performance. Fine limestone powder in the form of calcite provides a favorable surface for the nucleation and growth of calcium silicate hydrate gel at early ages, accelerating and amplifying silicate hydration, and a source of carbonate ions to participate in reactions with the aluminate phases present in the cement (and fly ash). Conversely, the aragonite polymorph of CaCO3 exhibits a different crystal (and surface) structure and therefore neither accelerates nor amplifies silicate hydration at a similar particle size/surface area. However, because these two forms of CaCO3 have similar solubilities in water, the aragonite does contribute to an enhancement in the reactivity of the aluminate phases in the investigated systems, chiefly via carboaluminate formation. In 100 % ordinary portland cement (OPC) concretes, 10 % of the OPC by volume can be replaced with an equivalent volume of limestone powder, while maintaining acceptable performance. A comparison between limestone and siliceous aggregates indicates that the former often provide higher measured compressive strengths at equivalent levels of hydration, even when the two aggregate types exhibit similar elastic moduli. This suggests that the interfacial transition zone in the limestone-based concretes exhibits a higher degree of bonding, likely due to the favorable physical (texture) and chemical nature of the limestone surfaces. These observations reinforce the value of utilizing limestone to increase the performance and sustainability of 21st century concrete construction.