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Nanomaterials-Based Self-Healing Cementitious Materials
Published in Ghasan Fahim Huseien, Iman Faridmehr, Mohammad Hajmohammadian Baghban, Self-Healing Cementitious Materials, 2022
Ghasan Fahim Huseien, Iman Faridmehr, Mohammad Hajmohammadian Baghban
In the past, polycarboxylates (PCE) nanomaterials have been utilized in concrete [52]. PCE is a polymer-based compound that is obtained from methoxy-polyethylene glycol co-polymer. It functions in the secondary or side reactions which are reinforced to methacrylic acid co-polymer as the major element. Usually, the carboxylate group is comprised of a water molecule, rendering a negative charge alongside the backbone of PCE. The polyethylene oxide group provides a non-uniform electron cloud distribution and chemical polarities to the secondary or side reactions. The number and the length of secondary or side groups are can easily be changed. In case the secondary or side reactions possess numerous electrons, it lowers the large molar mass and alters the polymer density, resulting in reduced performance of cement suspension [11, 53]. For both chains to combine and pair simultaneously, longer side groups and strong charge density from one to another reaction end must form. Usually, polycarboxylate is used in concrete as high range water reducer (HRWR). Inclusion of PCE allows in controlling the concrete workability better at lower water-to-cement ratios.
Admixtures
Published in Peter Domone, John Illston, Construction Materials, 2018
These basic chemicals can be used alone or blended with each other or lignosulphonates to give products with a wide range of properties and effects. A particular feature is that polycarboxylates in particular can be chemically modified or tailored to meet specific requirements, and much development work has been carried out to this end by admixture suppliers in recent years. This has undoubtedly led to improvements in construction practice, but a consequence is that the websites of the major suppliers contain a confusing plethora of available products, often with semi-scientific sounding names.
Admixtures
Published in Marios Soutsos, Peter Domone, Construction Materials, 2017
These basic chemicals can be used alone or blended with each other or lignosulphonates to give products with a wide range of properties and effects. A particular feature is that polycarboxylates in particular can be chemically modified or tailored to meet specific requirements, and much development work has been carried out to this end by admixture suppliers in recent years. This has undoubtedly led to improvements in construction practice, but a consequence is that the websites of the major suppliers contain a confusing plethora of available products, often with semi-scientific sounding names.
A new insight into the mode of action between cement containing montmorillonite and polycarboxylate superplasticizer
Published in Journal of Sustainable Cement-Based Materials, 2023
Shengnan Sha, Lei Lei, Yihan Ma, Dengwu Jiao, Zhiqiang Xiao, Caijun Shi
Polycarboxylate (PCE) superplasticizer has the characteristics of high-water reduction rate at low dosage, improved workability of the fresh concrete at a given water/cement (W/C) ratio, enhanced mechanical properties of the hardened concrete by lowering the W/C ratio without sacrificing workability [1]. However, its effectiveness in concrete is substantially weakened by the presence of clay contaminants which exist on the surface of sand and stone, especially montmorillonite (MMT) with the chemical formula of Mx (Mg, Al, Fe)2 (OH)2 [Si4O10]·nH2O [2]. MMT is a typical 2:1 layered mineral which is made up of two silicate tetrahedral sheets and one aluminate octahedral sheet. Oxygen atoms connect the silicon oxygen tetrahedron with the aluminum oxide octahedron [3]. The expanding lattices of MMT caused by the absorbing water molecules in its layers easily allow swelling and cation exchange [4]. It is well recognized that polyethylene glycol (PEO) side chains of the PCE polymer possess a high affinity to the interlayer of MMT, resulting in decreased dispersion capability of PCEs [5].
Definition of mode-I fracture behaviour of plain and fiber reinforced various grades of concretes by digital image analysis
Published in Mechanics of Advanced Materials and Structures, 2023
Muhammed Gümüş, Abdussamet Arslan, Hüseyin Kalkan
Fine and coarse aggregates were added into the mixture of low and moderate strength concrete, while only the silica sand with a grain size of 0–1 mm was utilized in the mixture of high strength concrete. Grading curves of each aggregate used in this work are comparatively given in Figure 1. Water to binder ratios of the mixtures were 0.6, 0.5, and 0.2 for the low, moderate, and high strength concrete, respectively. Due to decreased water to binder ratio of high strength concrete, a high amount of polycarboxylate-based superplasticizer was included to compensate for decreased workability. According to the manufacturer, the density and pH of the superplasticizer used were 1.07 kg/L and 5, respectively. The compressive strength of each mixture at the 28 days was given in Table 1 as the average of three cube specimens in dimensions of 100 mm. Hooked-end steel fibers, Dramix 3D 65/35 BG, were used in varying amounts in order to examine the effect of the volume fraction of steel fibers as well as the concrete strength on some fracture parameters of notched beams. According to the manufacturer, some geometrical and mechanical properties of the hooked-end steel fibers are given in Table 2.
Nonlinear models to predict stress versus strain of early age strength of flowable ordinary Portland cement
Published in European Journal of Environmental and Civil Engineering, 2022
Wael Emad, Ahmed Salih, Rawaz Kurda, Panagiotis G. Asteris, Aram Hassan
Two types of polymeric admixtures were used in this study as a desperation agent (surfactant). The first one (Polymer A) is a Polycarboxylate ether-based polymer, consisting of one main linear backbone with groups of side carboxylate and ether (Sarwar et al., 2019). The groups of carboxylates are the anchoring groups by which these admixtures are added to cement particles (Duran et al., 2018; Erzengin et al., 2018). The second polymer (Polymer B) belongs to the sulphonated melamine formaldehyde condensate family. Each repeating unit contains one sulphonate group in this synthetic polymer. The solid content of both polymers (A and B) is greater than 97%. The pH value ranged between 6 and 8 for polymer A and ranged between 9 and 11 for polymer B. To modify the mechanical properties of cement from 0 to 0.06% (% wt) of polymers with interval-based addition, every 0.02% was used. Due to the segregation of cement particles, which will occur, higher dosages were not included in this study (Brückner et al., 2016; Sarwar et al., 2019).