Calcined Clay Pozzolan as an Admixture to Mitigate the Alkali-Silica Reaction in Concrete

Sarfo-Ansah, James; Atiemo, Eugene; Boakye, Kwabena Appiah; Adjei, Delali; Adjaottor, Albert A.

doi:10.4236/msce.2014.25004

Cited by 15 publications

(26 citation statements)

References 13 publications

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“…This is in line with the findings of other studies [32,36], that CH is the most allergic component for the corrosive media. CH is consumed during pozzolanic reaction, thus reducing CH content durability of hydrated cement is improved [32][33][34][35][36]. It was also found that the "Calcined" clay modified samples showed more resistance to sulfate attack than that of "As is" clay modified samples as shown.…”

Section: "800°c Calcined" Mmt Modified Mortarssupporting

confidence: 93%

“…Excess Mmt above this 25% replacement level is more than the pore filling requirement that causes weakness, which can lead to an increase in sulfate attack, ultimately reducing the compressive strength [50]. This is in line with the findings of other studies [32,36], that CH is the most allergic component for the corrosive media. CH is consumed during pozzolanic reaction, thus reducing CH content durability of hydrated cement is improved [32][33][34][35][36].…”

Section: "800°c Calcined" Mmt Modified Mortarssupporting

confidence: 88%

“…This is due to the fact that use of pozzolona clay in mortars led to the production of additional calcium silicate hydrate (CSH) by consuming the hydrated product calcium hydroxide (CH) in the presence of moisture. CH is the main target for corrosive ions, thus reducing CH amount causes a reduction in expansive ettringite and gypsum, ultimately minimize the sulfate attack and chloride attack [32][33][34][35][36].…”

Section: "800°c Calcined" Mmt Modified Mortarsmentioning

confidence: 99%

“…CH is the most allergic component for the corrosive media. CH is consumed during pozzolanic reaction, thus reducing CH content durability of hydrated cement is improved [32][33][34][35][36]. Due to low heat of hydration pozzolanic incorporated blended cement shows high resistance to thermal cracking.…”

Section: Introductionmentioning

confidence: 99%

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Durability of Mortars Modified with Calcined Montmorillonite Clay

et al. 2019

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This study aims to evaluate the performance of mortars containing locally available Pakistani montmorillonite (Mmt) clay mineral as partial replacement of cement in various curing environments. The local montmorillonite clay in “As is” (20°C) and “heated” (100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C & 1000°C) conditions was incorporated in mortar cubes as partial replacement of cement. Montmorillonite clay of all the temperatures was replaced by 15%, 20%, 25%, 30% and 35% of cement mass in mortar cubes. The Strength Activity Index (SAI) was calculated to determine the optimum activation temperature for the clay. Compressive strengths of the controlled mix and montmorillonite modified mortars were evaluated under the Sodium Sulfate (SS) (5% solution) and mixed (Sodium Sulfate + Sodium Chloride (SCS)) (5% +3.5% solution) curing environments to study its durability performance. Upon thermal treatment montmorillonite clay showed maximum activation at 800°C temperature. Mortar containing (800°C) calcined montmorillonite clay with 25% cement replacement exhibit competent compression results. Moreover, up on exposure to aggressive environments, montmorillonite clay mortars performed better than the control samples. The mortar cubes exposed to Sulfate environment (SS) were more damaged in compression than that exposed to mixed environment (SCS), for all replacement levels and time exposures.

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Section: "800°c Calcined" Mmt Modified Mortarssupporting

confidence: 93%

Section: "800°c Calcined" Mmt Modified Mortarssupporting

confidence: 88%

Section: "800°c Calcined" Mmt Modified Mortarsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Durability of Mortars Modified with Calcined Montmorillonite Clay

et al. 2019

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“…The low porosity in blended cement mortars can be attributed to the fact that pozzolana materials such as calcined clays increase nucleation sites for precipitation of hydration products resulting in pore refinement thus lowering the porosity [26]. CH produced during hydration of OPC-H 2 O consumed in pozzolanic reaction forming secondary CSH and CAH [27].…”

Section: Porositymentioning

confidence: 99%

Chloride Ingress in Chemically Activated Calcined Clay-Based Cement

Marangu

Thiong’o

Wachira

2018

Journal of Chemistry

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Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800 ∘ C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC) at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na 2 SO 4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC), and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients ( app ) were estimated from solutions to Fick's second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of app , compared to OPC, PPC, and nonactivated PCC35.

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Properties of activated blended cement containing high content of calcined clay

Marangu

Karanja

Muthengia

2018

Heliyon

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This paper presents findings of an experimental investigation on sodium sulphate (Na2SO4) activated calcined clay – Portland cement blends in sulphuric acid media. Calcined clays were blended with Ordinary Portland Cement (OPC) at replacement levels of 40% 45% and 50 % by mass of OPC to make blended cement labelled PCC40, PCC45 and PCC50 respectively. Initially, pozzolanicity and setting time tests were conducted. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using 0.5M Na2SO4 solution and their compressive strengths determined on the 2nd, 7th, 28th and 90 th day of curing. The 28th day cured mortar prisms were subjected to porosity test. Moreover, 5 × 5 × 5 cm mortar cubes were also prepared and their weight and strength loss was taken as a measure of their acid resistivity after an immersion time of 7, 14, 28, 56, 84 and 120 days in 3 % of sulphuric acid at 23 ± 1 °C. OPC, commercial Portland Pozzolana Cement (PPC) and PCC40, PCC45 and PCC50 cement were cast using water and similarly investigated for comparison purposes. The results obtained showed that chemically activated cements exhibited higher pozzolanic activity, lower porosity, shorter setting times and higher resistance to acid attack compared to non-activated cements. However, OPC was found to be non-pozzolanic.

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Calcined Clay Pozzolan as an Admixture to Mitigate the Alkali-Silica Reaction in Concrete

Cited by 15 publications

References 13 publications

Durability of Mortars Modified with Calcined Montmorillonite Clay

Durability of Mortars Modified with Calcined Montmorillonite Clay

Chloride Ingress in Chemically Activated Calcined Clay-Based Cement

Properties of activated blended cement containing high content of calcined clay

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