Recent advance of MgO expansive agent in cement and concrete

Zhang, Jian

doi:10.1016/j.jobe.2021.103633

Cited by 26 publications

(8 citation statements)

References 71 publications

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“…The resulting products build up in the crack, sealing it. This includes the addition of fly ashes, silica fume, blast furnace slag and many others [7][8][9][10][11]. Another method is the addition of bacteria.…”

Section: Methods Used In the Self-healing Of Cementitious Materialsmentioning

confidence: 99%

Self-Healing of Cracks in Cementitious Materials as a Method of Improving the Durability of Pre-Stressed Concrete Railway Sleepers

Dudek,

Stryszewska

2024

Materials

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The article presents research results regarding the possibility of modifying pre-stressed concrete railway sleepers to improve their durability. The cracks that appear in these elements are one of the reasons for shortening the period of safe use. They do not have a significant impact on the load-bearing capacity of these elements, but on their durability. The resulting scratches become an easy way for the external environment to migrate inside the element, including the reinforcement area. Despite efforts to eliminate the possibility of cracking, this phenomenon still occurs in railway sleepers. In order to reduce the negative effects of cracking the cement matrix, a technology for modifying a prefabricated concrete element with resin-filled tubes towards its autonomous self-healing was developed and tested. The tests were divided into three stages, including laboratory tests carried out on cement mortar beams, semi-technical tests carried out on reinforced concrete beams, and industrial tests carried out on pre-stressed concrete and prefabricated railway sleepers. All research conducted on a laboratory and semi-technical scale, preceding the target stage, was intended to ultimately enable the development of tube application technology on an industrial scale while verifying the effectiveness of self-healing at the laboratory level. The use of self-healing cementitious materials potentially reduces the negative effects of cracking railway sleepers, as shown by observations conducted during the research.

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Section: Methods Used In the Self-healing Of Cementitious Materialsmentioning

confidence: 99%

Self-Healing of Cracks in Cementitious Materials as a Method of Improving the Durability of Pre-Stressed Concrete Railway Sleepers

Dudek,

Stryszewska

2024

Materials

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“…NanoMgO is another nanomaterial used to reduce the surface cracking of concrete caused by autogenous shrinkage and thermal stresses [ 121 ]. On the other hand, microMgO [ 122 ] functions as an agent that limits concrete cracking caused by thermal shrinkage in mass concrete and self-desiccation from utilizing a low w/c ratio and fine material. However, Wang et al [ 123 ] reported that excessive amounts of microMgO can deteriorate compressive strength, tensile strength, and abrasion resistance in concrete.…”

Section: Surface Abrasion Resistance Of Concrete Optimised With Nanom...mentioning

confidence: 99%

An Elucidative Review of the Nanomaterial Effect on the Durability and Calcium-Silicate-Hydrate (C-S-H) Gel Development of Concrete

Al-saffar,

Wong,

Paul

2023

Gels

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Concrete as a building material is susceptible to degradation by environmental threats such as thermal diffusion, acid and sulphate infiltration, and chloride penetration. Hence, the inclusion of nanomaterials in concrete has a positive effect in terms of promoting its mechanical strength and durability performance, as well as resulting in energy savings due to reduced cement consumption in concrete production. This review article discussed the novel advances in research regarding C-S-H gel promotion and concrete durability improvement using nanomaterials. Basically, this review deals with topics relevant to the influence of nanomaterials on concrete’s resistance to heat, acid, sulphate, chlorides, and wear deterioration, as well as the impact on concrete microstructure and chemical bonding. The significance of this review is a critical discussion on the cementation mechanism of nanoparticles in enhancing durability properties owing to their nanofiller effect, pozzolanic reactivity, and nucleation effect. The utilization of nanoparticles enhanced the hydrolysis of cement, leading to a rise in the production of C-S-H gel. Consequently, this improvement in concrete microstructure led to a reduction in the number of capillary pores and pore connectivity, thereby improving the concrete’s water resistance. Microstructural and chemical evidence obtained using SEM and XRD indicated that nanomaterials facilitated the formation of cement gel either by reacting pozzolanically with portlandite to generate more C-S-H gel or by functioning as nucleation sites. Due to an increased rate of C-S-H gel formation, concrete enhanced with nanoparticles exhibited greater durability against heat damage, external attack by acids and sulphates, chloride diffusion, and surface abrasion. The durability improvement following nanomaterial incorporation into concrete can be summarised as enhanced residual mechanical strength, reduced concrete mass loss, reduced diffusion coefficients for thermal and chloride, improved performance against sulphates and acid attack, and increased surface resistance to abrasion.

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“…Additionally, when cured under temperature C, the compressive strength at 14 days decreased by 1.5 MPa, 4.2 MPa, and 10.1 MPa for HPC samples containing 6%, 8%, and 10% MEA content, respectively, in comparison to samples without MEA. These findings align with previous studies that indicate the addition of MEA has a detrimental effect on concrete compressive strength because MEA partially replaces cement in the binding material., leading to a reduction of calcium hydroxide and other essential materials that contribute to strength [27][28][29][30]. Furthermore, the weakened mechanical properties of the MEA HPC composite system could be attributed to the relatively diminutive crystal phase of the hydrated MgO products, shown in Equation ( 1), which possess inferior strength when compared to the cement hydration products.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Effect of Working Temperature Conditions on the Autogenous Deformation of High-Performance Concrete Mixed with MgO Expansive Agent

et al. 2023

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Currently, mass concrete is increasingly utilized in various engineering projects that demand high physical properties of concrete. The water-cement ratio of mass concrete is comparatively smaller than that of the concrete used in dam engineering. However, the occurrence of severe cracking in mass concrete has been reported in numerous engineering applications. To address this issue, the incorporation of MgO expansive agent (MEA) in concrete has been widely recognized as an effective method to prevent mass concrete from cracking. In this research, three distinct temperature conditions were established based on the temperature elevation of mass concrete in practical engineering scenarios. To replicate the temperature increase under operational conditions, a device was fabricated that employed a stainless-steel barrel as the container for concrete, which was enveloped with insulation cotton for thermal insulation purposes. Three different MEA dosages were used during the pouring of concrete, and sine strain gauges were placed within the concrete to gauge the resulting strain. The hydration level of MEA was studied using thermogravimetric analysis (TG) to calculate the degree of hydration. The findings demonstrate that temperature has a significant impact on the performance of MEA; a higher temperature results in more complete hydration of MEA. The design of the three temperature conditions revealed that when the peak temperature exceeded 60 °C in two cases, the addition of 6% MEA was sufficient to fully compensate for the early shrinkage of concrete. Moreover, in instances where the peak temperature exceeded 60 °C, the impact of temperature on accelerating MEA hydration was more noticeable.

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Recent advance of MgO expansive agent in cement and concrete

Cited by 26 publications

References 71 publications

Self-Healing of Cracks in Cementitious Materials as a Method of Improving the Durability of Pre-Stressed Concrete Railway Sleepers

Self-Healing of Cracks in Cementitious Materials as a Method of Improving the Durability of Pre-Stressed Concrete Railway Sleepers

An Elucidative Review of the Nanomaterial Effect on the Durability and Calcium-Silicate-Hydrate (C-S-H) Gel Development of Concrete

Effect of Working Temperature Conditions on the Autogenous Deformation of High-Performance Concrete Mixed with MgO Expansive Agent

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