Hydration and Microwave Curing Temperature Interactions of Repair Mortars

Microwave curing of repair patches provides an energy efficient technique for rapid concrete repair. It has serious economic potential due to time and energy saving especially for repairs in cold weather which can cause work stoppages. However, the high temperatures resulting from the combination of microwave exposure and accelerated hydration of cementitious repair materials need to be investigated to prevent potential durability problems in concrete patch repairs. This paper investigates the time and magnitude of the peak hydration temperature during microwave curing (MC) of six cement based concrete repair materials and a CEM II mortar. Repair material specimens were microwave cured to a surface temperature of 40-45 °C while their internal and surface temperatures were monitored. Their internal temperature was further monitored up to 24 hours in order to determine the effect of microwave curing on the heat of hydration. The results show that a short period of early age microwave curing increases the hydration temperature and brings forward the peak heat of hydration time relative to the control specimens which are continuously exposed to ambient conditions (20 °C, 60% RH). The peak heat of hydration of normal density, rapid hardening Portland cement based repair materials with either pfa or polymer addition almost merges with the end of microwave curing period. Similarly, lightweight polymer modified repair materials also develop heat of hydration rapidly which almost merges with the end of microwave curing period. The peak heat of hydration of normal density ordinary Portland cement based repair materials, with and without polymer addition, occurs during the post microwave curing period. The sum of the microwave curing and heat of hydration temperatures can easily exceed the limit of about 70 °C in some materials at very early age, which can cause durability problems.

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Difference in Strength Development between Cement-Treated Sand and Mortar with Various Cement Types and Curing Temperatures

Materials ◽

10.3390/ma13214999 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4999

Author(s):

Lanh Si Ho ◽

Kenichiro Nakarai ◽

Kenta Eguchi ◽

Yuko Ogawa

Keyword(s):

Portland Cement ◽

Ordinary Portland Cement ◽

Bound Water ◽

Curing Temperature ◽

Strength Development ◽

Early Age ◽

Cement Type ◽

A Value ◽

Water To Cement Ratio ◽

Novel Method

To improve the strength of cement-treated sand effectively, the use of various cement types was investigated at different curing temperatures and compared with the results obtained from similar mortars at higher cement contents. The compressive strengths of cement-treated sand specimens that contained high early-strength Portland cement (HPC) cured at elevated and normal temperatures were found to be higher than those of specimens that contained ordinary Portland cement (OPC) and moderate heat Portland cement at both early and later ages. At 3 days, the compressive strength of the HPC-treated sand specimen, normalized with respect to that of the OPC under normal conditions, is nearly twice the corresponding value for the HPC mortar specimens with water-to-cement ratio of 50%. At 28 days, the normalized value for HPC-treated sand is approximately 1.5 times higher than that of mortar, with a value of 50%. This indicates that the use of HPC contributed more to the strength development of the cement-treated sand than to that of the mortar, and the effects of HPC at an early age were higher than those at a later age. These trends were explained by the larger quantity of chemically bound water observed in the specimens that contained HPC, as a result of their greater alite contents and porosities, in cement-treated sand. The findings of this study can be used to ensure the desired strength development of cement-treated soils by considering both the curing temperature and cement type. Furthermore, they suggested a novel method for producing a high internal temperature for promoting the strength development of cement-treated soils.

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Thermal Properties of Calcium Sulphoaluminate Cement as an Alternative to Ordinary Portland Cement

Materials ◽

10.3390/ma14227011 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7011

Author(s):

Małgorzata Gołaszewska ◽

Barbara Klemczak ◽

Jacek Gołaszewski

Keyword(s):

Activation Energy ◽

Portland Cement ◽

Apparent Activation Energy ◽

Thermal Behaviour ◽

Ordinary Portland Cement ◽

Isothermal Calorimetry ◽

Heat Of Hydration ◽

Curing Temperature ◽

Cement Pastes ◽

Calcium Sulphoaluminate

This paper presents the results of research into the heat of hydration and activation energy of calcium sulphoaluminate (CSA) cement in terms of the dependence on curing temperature and water/cement ratio. Cement pastes with water/cement ratios in the range of 0.3–0.6 were tested by isothermal calorimetry at 20 °C, 35 °C and 50 °C, with the evolved hydration heat and its rate monitored for 168 h from mixing water with cement. Reference pastes with ordinary Portland cement (OPC) were also tested in the same range. The apparent activation energy of CSA and OPC was determined based on the results of the measurements. CSA pastes exhibited complex thermal behaviour that differed significantly from the thermal behaviour of ordinary Portland cement. The results show that both the w/c ratio and elevated temperature have a meaningful effect on the heat emission and the hydration process of CSA cement pastes. The determined apparent activation energy of CSA revealed its substantial variability and dependence, both on the w/c ratio and the curing temperature.

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Sustainable cementitious materials: The effect of fly ash percentage as a part replacement of portland cement composite (PCC) and curing temperature on the early age strength of fly ash concrete

MATEC Web of Conferences ◽

10.1051/matecconf/201925801001 ◽

2019 ◽

Vol 258 ◽

pp. 01001

Author(s):

Gidion Turuallo ◽

Harun Mallisa

Keyword(s):

Fly Ash ◽

Portland Cement ◽

Cement Composite ◽

Cementitious Materials ◽

Curing Temperature ◽

Early Age ◽

Water Tank ◽

Lower Strength ◽

Fly Ash Concrete ◽

Lower Temperature

This research aims to determine the effect of fly ash percentage as a part replacement of Portland cement and curing temperatures to the early age strength of concrete. The percentages of fly ash used were 0, 10 and 15% by cement weight. The cured temperatures were 25, 30 dan 50°C. The concrete specimens were cubes of 150 x 150 x 150 mm3. The cubes, which were cured at 25°C, placed in water tank, while those cured at 30 and 50°C cured in oven until 7 days and then continued in water. The testing was conducted at ages 3, 7, 14 dan 28 days. The results showed that at early ages, the strength of concrete without fly ash cured at 25°C were higher than that of fly ash concrete. The higher level replacement of cement with fly ash, the lower strength of concrete obtained. The higher the curing temperature at earlier age resulted the higher the strength of concrete. The strength of concretes with 10% of fly ash cured at 25, 30 and 50°C at age three days were 15.111, 15.481 and 16.296 MPa respectively. Conversely, the strength of concrete that of cured at higher temperatures at ages 28 days, were lower than that of concretes cured at lower temperature. The results of this research also showed that fly ash could improve the workability of concrete.

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Numerical Simulation of Autogenous Shrinkage of Eco-Friendly Blended Portland Cements Using a Multi-Component Hydration Model

Materials Science Forum ◽

10.4028/www.scientific.net/msf.569.261 ◽

2008 ◽

Vol 569 ◽

pp. 261-264 ◽

Cited By ~ 3

Author(s):

Xiao Yong Wang ◽

Han Seung Lee ◽

Seung Min Lim

Keyword(s):

Fly Ash ◽

Portland Cement ◽

Ordinary Portland Cement ◽

Autogenous Shrinkage ◽

Heat Of Hydration ◽

Curing Temperature ◽

Portland Cements ◽

Influence Of Water ◽

Hydration Model ◽

Numerical Program

Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry. Due to excellent durability, low heat of hydration, energy-saving, resource-conserving, and generally less expensive than ordinary Portland cement, blends Portland cements is used increasingly in construction industry. Both ecology benefit and economic benefit can be achieved by using blended Portland cement. Addition of blended components to cement, especially such as fly ash or silica fume, will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, based on the multi-component hydration model, a numerical program is built to predict autogenous shrinkage of ordinary Portland cement and blended Portland cement. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

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Factors Affecting Early-Age Hydration of Ordinary Portland Cement Studied by NMR: Fineness, Water-to-Cement Ratio and Curing Temperature

Applied Magnetic Resonance ◽

10.1007/s00723-007-0019-y ◽

2007 ◽

Vol 32 (3) ◽

pp. 385-394 ◽

Cited By ~ 18

Author(s):

M. Alesiani ◽

I. Pirazzoli ◽

B. Maraviglia

Keyword(s):

Portland Cement ◽

Ordinary Portland Cement ◽

Curing Temperature ◽

Early Age ◽

Factors Affecting ◽

Cement Ratio ◽

Water To Cement Ratio ◽

Early Age Hydration

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Performance of Portland Cement-Based Rapid-Patching Materials with Different Cement and Accelerator Types, and Cement Contents

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198119852330 ◽

2019 ◽

Vol 2673 (11) ◽

pp. 172-184 ◽

Cited By ~ 1

Author(s):

Shayan Gholami ◽

Jiong Hu ◽

Yong-Rak Kim ◽

Miras Mamirov

Keyword(s):

Portland Cement ◽

Cement Content ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

High Heat ◽

Heat Of Hydration ◽

Early Age ◽

Type I ◽

Concrete Durability ◽

Aggregate Gradation

Because of the requirements of opening pavement to traffic after placing repair concrete, it is essential for that concrete to achieve high early strength. To ensure this, a high cement content is generally used in Portland cement-based rapid-patching materials. Besides its associated high cost, high cement content tends to result in a less stable mix with high drying shrinkage, high autogenous shrinkage, high heat of hydration, and cracking potential. In addition, using chloride-based accelerators has adverse effects on concrete durability. Therefore, this paper presents an experimental assessment to improve rapid-patching concrete mixtures by reducing cement content through optimizing aggregate gradation. A non-chloride-based accelerator was also sought to replace the chloride-based accelerator when the accelerators are associated with two different series of patching materials using Type I and III cement, respectively. Fresh, early-age, mechanical, and permeability tests were conducted on each specific mixture design. As an important outcome, patching materials employing lower cement content together with an optimized aggregate gradation can meet the general requirements, which were found from the observation of several key parameters, including early-age strength, setting times, surface resistivity, and heat of hydration. Furthermore, the non-chloride-based accelerator showed promising behavior as an alternative accelerator when it is blended with the proper cement type and content.

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Effect of Curing System on Mechanical Property of Slag-Based Geopolymer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.250-253.3372 ◽

2011 ◽

Vol 250-253 ◽

pp. 3372-3376 ◽

Cited By ~ 1

Author(s):

Qing Wang ◽

Xin Tu ◽

Zhao Yang Ding ◽

Zhi Tong Sui

Keyword(s):

Mechanical Properties ◽

Mechanical Property ◽

Compressive Strength ◽

Portland Cement ◽

Curing Temperature ◽

Early Age ◽

Curing Time ◽

Commercial Applications ◽

The Ideal

Geopolymer has been gradually attracting world attention as a potentially revolutionary material that is one of the ideal substitutes of Portland cement, and fundamental studies on geopolymer are increased rapidly because of its potential commercial applications. However, little work has been done in the field of curing system of geopolymer. In this paper, influence of curing temperature, curing time and curing humidity on the mechanical properties of slag-based geopolymer was studied by using the compressive strength as benchmark parameter. Results have shown that the early age compressive strength of geopolymer increased and the long-term compressive strength decreased at first and then increased as the curing temperature increased, 80°C was the best curing temperature. With prolonging the curing time, it was found that the compressive strength of early age of geopolymer reached the maximum ( 116.3 MPa for 1d, 97.5 MPa for 3d) as the curing time was 12h, and that of 28d geopolymer was 91.3 MPa as the curing time was 10h. It was also found that the compressive strength of geopolymer reduced evidently as the humidity increased.

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