Effects of triethanolamine on autogenous shrinkage and drying shrinkage of cement mortar

2021 ◽  
Vol 304 ◽  
pp. 124620
Author(s):  
Hui Liu ◽  
Hui Lin ◽  
Xiaoyong Liu ◽  
Jian Wang ◽  
Xiaofan Pang ◽  
...  
Keyword(s):  
Cement Mortar ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage

scholarly journals Reinforcing Mechanisms of Coir Fibers in Light-Weight Aggregate Concrete

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 699
Author(s):  
Xiaoxiao Zhang ◽  
Leo Pel ◽  
Florent Gauvin ◽  
David Smeulders
Keyword(s):  
Cement Hydration ◽  
Natural Fibers ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Hydration Reaction ◽  
Light Weight ◽  
Limited Information ◽  
Aggregate Concrete ◽  
Coir Fibers ◽  
Light Weight Aggregate

Due to the requirement for developing more sustainable constructions, natural fibers from agricultural wastes, such as coir fibers, have been increasingly used as an alternative in concrete composites. However, the influence of coir fibers on the hydration and shrinkage of cement-based materials is not clear. In addition, limited information about the reinforcing mechanisms of coir fibers in concrete can be found. The goal of this research is to investigate the effects of coir fibers on the hydration reaction, microstructure, shrinkages, and mechanical properties of cement-based light-weight aggregate concrete (LWAC). Treatments on coir fibers, namely Ca(OH)2 and nano-silica impregnation, are applied to further improve LWAC. Results show that leachates from fibers acting as a delayed accelerator promote cement hydration, and entrained water by fibers facilitates cement hydration during the whole process. The drying shrinkage of LWAC is increased by adding fibers, while the autogenous shrinkage decreases. The strength and toughness of LWAC are enhanced with fibers. Finally, three reinforcement mechanisms of coir fibers in cement composites are discussed.

scholarly journals Calcined Oyster Shell Powder as an Expansive Additive in Cement Mortar

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1322 ◽  
Author(s):  
Joon Ho Seo ◽  
Sol Moi Park ◽  
Beom Joo Yang ◽  
Jeong Gook Jang
Keyword(s):  
Compressive Strength ◽  
Cement Mortar ◽  
Autogenous Shrinkage ◽  
Oyster Shell ◽  
Heat Of Hydration ◽  
Strength Development ◽  
Flow Loss ◽  
Hardened Properties ◽  
Oyster Shell Powder ◽  
Shell Powder

The present study prepared calcined oyster shell powder having chemical composition and crystal structure of calcium oxide and lime, respectively, and investigated the fresh and hardened properties of cement mortar incorporating calcined oyster shell powder as an additive. The test results indicated that the hydration of calcined oyster shell powder promoted the additional formation of Ca(OH)2 at the initial reaction stage, thereby increasing the heat of hydration. In particular, the volumetric increase of calcined oyster shell powder during hydration compensated the autogenous shrinkage of mortar at early ages, ultimately leading to a clear difference in the shrinkage values at final readings. However, an excessive incorporation of calcined oyster shell powder affected the rate of C–S–H formation in the acceleratory period of hydration, resulting in a decrease in the compressive strength development. Meanwhile, the degree of flow loss was inconsequential and rapid flow loss was not observed in the specimens with calcined oyster shell powder. Therefore, considering the fresh and hardened properties of cement mortar, the incorporation of calcined oyster shell powder of approximately 3% by weight of cement is recommended to enhance the properties of cement mortar in terms of compressive strength and autogenous shrinkage.

scholarly journals Synthesis of Pectiniform Polyurethane-Modified Polycarboxylate and Its Preliminary Application in Ultrahigh-Performance Concrete

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Shuncheng Xiang ◽  
Yingli Gao
Keyword(s):  
Silica Fume ◽  
Negative Impact ◽  
Raw Materials ◽  
Synthesis Method ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Isophorone Diisocyanate ◽  
Initiation System ◽  
Dry Shrinkage ◽  
Preliminary Application

In this paper, modified polyurethane prepolymer was synthesized by the segmental synthesis method using isophorone diisocyanate (IPDI), hydroxyl-terminated silicone, and polyether glycol dimethylolpropionic acid as raw materials. After that, pectiniform polycarboxylate, of which side chains were in roughly the same polymerization degree and main chains were in different lengths, was synthesized at normal temperature in the complex initiation system of H2O2, APS, sodium bisulfite, and Vc. Then, compared with commercial Sika polycarboxylate, their applications in ultrahigh-performance concrete (HUPC), including flowability, strength, drying shrinkage, and autogenous shrinkage, were investigated. The results showed that, due to the molecular structure of polyorganosiloxane, the synthesized polycarboxylate could be better dispersed. Dosage of silica fume could effectively improve the compressive strength of UHPC, while slag had a certain negative impact on its strength. Incorporation of slag and silica fume could effectively reduce the dry shrinkage of UHPC.

scholarly journals Mitigating the Drying Shrinkage and Autogenous Shrinkage of Alkali-Activated Slag by NaAlO2

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3499
Author(s):  
Bin Chen ◽  
Jun Wang ◽  
Jinyou Zhao
Keyword(s):  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Nitrogen Adsorption ◽  
Partial Substitution ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
Na2o Content ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

The shrinkage of alkali-activated slag (AAS) is obviously higher than ordinary Portland cement, which limited its application in engineering. In this study, the effects of NaAlO2 in mitigating drying shrinkage and autogenous shrinkage of AAS were studied. To further understand the shrinkage mechanism, the hydration products and microstructures were studied by X-ray diffraction, scanning electron microscopy and nitrogen adsorption approaches. As the partial substitution rate of NaAlO2 for Na2SiO3 increased, the drying shrinkage and autogenous shrinkage reduced significantly. The addition of NaAlO2 could slow down the rate of hydration reaction and reduce the porosity, change the pore diameter and the composition of generated paste and cause more hydrotalcite and tetranatrolite generated—which contributed to reduced shrinkage. Additionally, raising the Na2O content rate caused obvious differences in drying shrinkage and autogenous shrinkage. As the Na2O content elevated, the drying shrinkage decreased and autogenous shrinkage increased. A high Na2O content would cause complete hydration reactions and provoke high autogenous shrinkage. However, incomplete hydration reactions left more water in the paste, and the evaporated water dramatically influenced drying shrinkage. The results indicate that addition of NaAlO2 could greatly mitigate the drying shrinkage and autogenous shrinkage of AAS.

scholarly journals Effect of Shrinkage Reducing Admixture on Drying Shrinkage of Concrete with Different w/c Ratios

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5721 ◽  
Author(s):  
Mahdi Kioumarsi ◽  
Fazel Azarhomayun ◽  
Mohammad Haji ◽  
Mohammad Shekarchi
Keyword(s):  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Hardened Concrete ◽  
Free Shrinkage ◽  
Water Penetration ◽  
Concrete Shrinkage ◽  
Different Types ◽  
Shrinkage Reducing Admixture ◽  
Shrinkage Reducing Admixtures ◽  
Liquid Propylene

The reduction of the moisture content of concrete during the drying process reduces the concrete’s volume and causes it to shrink. In general, concrete shrinkage is a phenomenon that causes concrete volume to dwindle and can lead to durability problems. There are different types of this phenomenon, among them chemical shrinkage, autogenous shrinkage, drying shrinkage including free shrinkage and restrained shrinkage, and thermal contraction. Shrinkage-reducing admixtures are commercially available in different forms. The present study investigates the effect of liquid propylene glycol ether on mechanical properties and free shrinkage induced by drying at different water-cement (w/c) ratios. Furthermore, the effect of shrinkage-reducing admixtures on the properties of hardened concrete such as compressive and tensile strength, electrical resistivity, modulus of elasticity, free drying shrinkage, water absorption, and depth of water penetration was investigated. The results indicated that shrinkage reducing agents performed better in a low w/c ratio and resulted in up to 50% shrinkage reduction, which was due to the surface reduction of capillary pores. The prediction of free shrinkage due to drying was also performed using an artificial neural network.

Research on Polymer Latex Modify Comprehensive Properties of Cement Mortar

2011 ◽  
Vol 225-226 ◽  
pp. 457-460
Author(s):  
Wei Li
Keyword(s):  
Mechanical Properties ◽  
Cement Mortar ◽  
Drying Shrinkage ◽  
Mix Design ◽  
Cement Ratio ◽  
Comprehensive Properties ◽  
Before And After ◽  
Overall Performance ◽  
Styrene Butadiene ◽  
Polymer Latex

Aimed for current situation that most scholars concerned with mechanics, deformation, flow performance of modified cement mortar, the paper selected carboxyl styrene-butadiene latex as the modified material, researched on cement mortar’ water reducing effect, wear resistance, corrosion resistance-mechanical properties, drying shrinkage before modifing and after modifing. Compared cement fine mortar’s properties with cement mechine-made mortar’s properties before and after modification. Research results showed that the addition of carboxyl SB latex, the overall performance of cement mortar is greatly improved, and with the increase of polymer cement ratio, this improvement trend is more obvious, those changes especially are suitable for extra-fine cement mortar. The results clarify the properties variation law of cement mortar before and after modification, this provides scientific guidance for polymer latex modified cement mortar mix design.

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