Effect of brief heat-curing on microstructure and mechanical properties in fresh cement based mortars

Ballester, Paloma; Hidalgo, Antonio Vásquez; Mármol, I.; Morales, J.; Sánchez, L.

doi:10.1016/j.cemconres.2009.04.002

Cited by 20 publications

(12 citation statements)

References 16 publications

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“…The increase in porosity under microwave curing is due to the microwave heating applied at early age, similar to the increase in porosity due to conventional heating reported by the other researchers [34,[43][44][45]. For example, Kjellsen et al [45] showed an increase in porosity from 10.93 to 15.11% for plain cement paste cured in water at 20 and 50°C respectively, by using backscattered electron image analysis.…”

Section: The Effect Of Microwave Curing On Porositysupporting

confidence: 79%

“…It is due to the effect of the short period of high temperature exposure at early age on long-term strength development. A similar reduction of compressive strength also occurs due to conventional heat curing [4,[33][34][35]. The effect of curing temperature on early and later age strength also depends on the type of cementitious repair materials [33,36].…”

Section: Effect Of Microwave Curing On Compressive Strengthmentioning

confidence: 82%

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Bond of steel reinforcement with microwave cured concrete repair mortars

2017

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This paper investigates the effect of microwave curing on the bond strength of steel reinforcement in concrete repair. Pull-out tests on plain mild steel reinforcement bars embedded in four repair materials in 100 mm cube specimens were performed to determine the interfacial bond strength. The porosity and pore structure of the matrix at the steel interface, which influence the bond strength, were also determined. Test results show that microwave curing significantly reduces the bond strength of plain steel reinforcement. The reduction relative to normally cured (20°C, 60% RH) specimens is between 21 and 40% with low density repair materials and about 10% for normal density cementitious mortars. The corresponding compressive strength of the matrix also recorded similar reduction and microwave curing resulted in increased porosity at the interface transition zone of the steel reinforcement.A unique relationship exists between bond strength and both compressive strength and porosity of all matrix materials. Microwave curing reduced shrinkage but despite the wide variation in the shrinkage of the repair mortars, its effect on the bond strength was small. The paper provides clear correlations between the three parameters (compressive strength, bond strength and porosity), which are common to both the microwave and conventionally cured mortars. Therefore, bond-compressive strength relationships used in the design of reinforced concrete structures will be also valid for microwave cured elements.

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Section: The Effect Of Microwave Curing On Porositysupporting

confidence: 79%

Section: Effect Of Microwave Curing On Compressive Strengthmentioning

confidence: 82%

Bond of steel reinforcement with microwave cured concrete repair mortars

2017

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“…From this spectroscopic study, we can see multiple peaks of CaCO 3 at around 874 cm -1 and 1425 cm -1 due to the in-plane bending of Carbonate (CO 3 ) [10]. A small peak of Ca(OH) 2 is seen in the anhydrated cement near 3640 cm -1 maybe due to the exposure of cement to atmosphere.…”

Section: Spectroscopymentioning

confidence: 77%

“…Figure 3 depicts the time trace of how C-S-H is formed during the hydration process. During the initial period, there is an exponential rise in the frequency due to the formation of C-S-H (initially from C3S) because of the reaction mechanism of the silicate species with water to produce hydration products and a change in the nature of Si-O vibrations due to increased stiffness in both local and bulk matrix [6,[10][11][12]. Figure 3 depicts that from 1 day to about a week, there is a slow reduction in the wavenumber (frequency), possibly due to the incorporation of water into the C-S-H matrix.…”

Section: Spectroscopymentioning

confidence: 99%

Terahertz spectroscopy of concrete for evaluating the critical hydration level

et al. 2014

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Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.

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“…CH is relatively mobile in the cement paste matrix and can easily be leached out. Dissolution and leaching of CH increases the porosity within the cement system and decrease the pH level which consequently compromise strength and durability of cement based products [17] [18]. The pH level in cement and cement extenders during hydration and pozzolanic reaction is very vital for the dissolution of pozzolanic materials and reformation of additional CSH.…”

Section: Literature Reviewmentioning

confidence: 99%

Effect of Curing Environment on the Strength Properties of Cement and Cement Extenders

Bediako¹,

Kevern²,

Amankwah³

2015

MSA

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Curing of cement based products such as concrete and mortar, is very important to achieve good strength and durable products. However the curing environment plays a pivotal role in the overall quality of cement based products in terms of strength development. ASTM C192 allows moist curing either in a fog room or under water. However, these must meet ASTM C511 which controls temperature, and specifically for water curing, the concentration of calcium ions in the curing solution. Unfortunately in many parts of the world, water curing literally means curing in tap water. This is done primarily because there is a lack of knowledge or ignorance regarding the mobility and roll of calcium hydroxide in the curing process. To illustrate the differences, in this study, straight ASTM Type I/II Portland cement and that mixed with powdered waste clay bricks as a cement extender were used to prepare two different batches of mortars. The chemical properties of the powdered waste clay brick met the ASTM C618 standard specifications for Class N pozzolans. Both mortar specimens were cured under two different environment comprising of either water and lime saturated water. Mortar specimens were tested for compressive strength at 3, 7, 14 and 28 days of either curing conditions. Test results indicated that mortar specimens cured in lime saturated water obtained higher strength than those cured in fresh water at all ages of curing. Statistical inference drawn from ANOVA testing showed that curing conditions had significant impact on strength development of the blended and unblended cement systems. The study recommends that testing of concrete and mortar samples and other research related works be performed in lime saturated water other than fresh water. * Corresponding author. M. Bediako et al. 34

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Effect of brief heat-curing on microstructure and mechanical properties in fresh cement based mortars

Cited by 20 publications

References 16 publications

Bond of steel reinforcement with microwave cured concrete repair mortars

Bond of steel reinforcement with microwave cured concrete repair mortars

Terahertz spectroscopy of concrete for evaluating the critical hydration level

Effect of Curing Environment on the Strength Properties of Cement and Cement Extenders

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