scholarly journals Effects of Chemical Admixtures on the Working and Mechanical Properties of Ordinary Dry-Mixed Mortar

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Shu-Chun Zhou ◽  
Heng-Lin Lv ◽  
Ning Li ◽  
Jie Zhang
Keyword(s):  
Mechanical Properties ◽  
Water Retention ◽  
Cement Mortar ◽  
Setting Time ◽  
Methyl Cellulose ◽  
Cellulose Ether ◽  
Hydroxypropyl Methyl Cellulose ◽  
Chemical Admixtures ◽  
Retarding Effect ◽  
Mixed Mortar

The effects of hydroxypropyl methyl cellulose ether, starch ether, bentonite, and redispersion emulsoid powder on the working and mechanical properties of fresh dry-mixed mortar were studied. The results show that hydroxypropyl methyl cellulose ether has the greatest impact on the consistency and water retention of ordinary dry-mixed mortar and that redispersion emulsoid powder reduces the water action and starch ether has essentially no effect on water retention. It also shows that the time of mortar condensation when mixed with hydroxypropyl methyl cellulose ether is the longest, followed by redispersion emulsoid powder and bentonite. Starch ether can slightly, but not obviously, extend the setting time of cement mortar. Hydroxypropyl methyl cellulose ether has the greatest impact on the mechanical properties of ordinary dry-mixed mortar, followed by redispersion emulsoid powder, starch ether, and bentonite. As the water retention increases, the setting time of the mortar also increases. The use of water as a thickening material has a retarding effect on the mortar, increases the water-retention rate, and increases the retarding effect. Moreover, increasing the content of the chemical admixtures decreases the strength of cement mortar.

scholarly journals Water Retention Mechanism of HPMC in Cement Mortar

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2918 ◽  
Author(s):  
Ning Chen ◽  
Peiming Wang ◽  
Liqun Zhao ◽  
Guofang Zhang
Keyword(s):  
Network Structure ◽  
Water Retention ◽  
Fine Particles ◽  
Cement Mortar ◽  
Methyl Cellulose ◽  
Retention Mechanism ◽  
Plastic Viscosity ◽  
Cellulose Ether ◽  
3D Network ◽  
Migration Capacity

In this paper, the effect of HPMC (hydroxypropyl methyl cellulose ether) on the cement mortar water retention (WR) and composition was studied. The relationship between the plastic viscosity and water retention of cement mortar was revealed. The results showed that HPMC formed a colloidal film with a 3D network structure in water, which changed the ability of water to migrate. The HPMC colloid adsorbed on the surface of cement and sand particles and played a bridging role due to the influence of the spatial network structure of the thin film. Fine particles formed a grid-like distribution, and the hydration products formed a unique fibrous tree-like structure. A positive correlation was observed between the plastic viscosity and the water holding capacity of cement mortar. Finally, the mechanism responsible for the improved water retention of cement mortar by HPMC was analyzed using the changing water migration capacity, migration channels, and mortar cohesion.

Individual and combined effects of modified starch, bentonite and their composite powder with HPMC on the performance of cement mortars

2013 ◽  
Vol 33 (6) ◽  
pp. 551-555 ◽  
Author(s):  
Ke Yuan ◽  
Libing Liao ◽  
Yunhua Wang ◽  
Zepeng Zhang ◽  
Daimei Chen ◽  
...  
Keyword(s):  
Water Retention ◽  
Composite Powder ◽  
Cement Mortar ◽  
Methyl Cellulose ◽  
High Water ◽  
Cellulose Ether ◽  
Modified Starch ◽  
Water Retention Value ◽  
Combined Use ◽  
Cement Mortars

Abstract A series of acetate starch was synthesized and mixed with bentonite to prepare acetate starch/bentonite composite as a novel additive in order to improve the thixotropic property of cement mortar. The thixotropic index and water retention value of the fresh cement mortar containing acetate starch, bentonite, and acetate starch/bentonite composite, respectively, were measured with and without hydroxypropyl methyl cellulose ether (HPMC). Acetate starch with the degree of substitution (DS) of about 0.5 provided the largest increase in the thixotropic index of the cement mortar. Application of HPMC gave high water retention ability and viscosity to the mortar, but the thixotropic property was not improved. Adding acetate starch or starch/bentonite composite to the mortar can increase its thixotropic index, whereas no significant improvements on the water retention ability and viscosity of mortars were observed. By the combined use of acetate starch/bentonite composite with HPMC, the water retention value (WRV) of the mortar was as high as 98%, and its thixotropic index increased from 4.06 to 5.30, with a high value of viscosity.

scholarly journals Preparation of Electric- and Magnetic-Activated Water and Its Influence on the Workability and Mechanical Properties of Cement Mortar

2021 ◽  
Vol 13 (8) ◽  
pp. 4546
Author(s):  
Kaiyue Zhao ◽  
Peng Zhang ◽  
Bing Wang ◽  
Yupeng Tian ◽  
Shanbin Xue ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Cement Paste ◽  
Cement Mortar ◽  
Environmental Issues ◽  
Chemical Admixtures ◽  
Untreated Water ◽  
Alternating Voltage

Cement-based materials prepared with activated water induced by a magnetic field or electric field represent a possible solution to environmental issues caused by the worldwide utilization of chemical admixtures. In this contribution, electric- and magnetic-activated water have been produced. The workability and mechanical properties of cement mortar prepared with this activated water have been investigated. The results indicate that the pH and absorbance (Abs) values of the water varied as the electric and magnetic field changed, and their values increased significantly, exhibiting improved activity compared with that of the untreated water. In addition, activated water still retains activity within 30 min of the resting time. The fluidity of the cement paste prepared with electric-activated water was significantly larger than that of the untreated paste. However, the level of improvement differed with the worst performance resulting from cement paste prepared with alternating voltage activated water. In terms of mechanical properties, both compressive strength and flexural strength obtained its maximum values at 280 mT with two processing cycles. The compressive strength increased 26% as the curing time increased from 7 days to 28 days and flexural strength increased by 31%. In addition, through the introduction of magnetic-activated water into cement mortar, the mechanical strength can be maintained without losing its workability when the amount of cement is reduced.

Effect of Hardening Accelerators and other Chemical Admixtures on the Properties of a Quick-Setting Mixture

2018 ◽  
Vol 276 ◽  
pp. 116-121 ◽  
Author(s):  
Alsu Khamatova ◽  
Grigory Ivanovich Yakovlev ◽  
Vadim Khozin ◽  
Grigory Nikolaevich Pervushin
Keyword(s):  
Mechanical Properties ◽  
Setting Time ◽  
Physicomechanical Properties ◽  
Electric Steelmaking ◽  
Steelmaking Slag ◽  
Strength Gain ◽  
Short Term ◽  
Fine Grained ◽  
Chemical Admixtures ◽  
Gypsum Content

The physicochemical and physicomechanical properties of quick-setting compositions based on fine-grained electric steelmaking slag (ESS) produced by Izhstal PJSC, Russia, have been examined. The study also focuses on the processes of interaction of the components of the compositions based on ESS in combination with hardening accelerators (Li2CO3, K2SO4) and plasticizing additives (SP-1, Melflux 2651F). It has been found that mechanoactivation of the composition improves the hydration in comparison with chemical admixtures. This can be proved by the obtained results of the setting and testing timing of the mechanical properties of the mixture. Plasticizers being added, the setting time increases at the average by 2.3 times, and accelerators being added, by 2 times compared with the mechanically activated composition. The influence of mechanoactivation on the strength of the compositions has been described. In comparison with the plasticized composition, the strength increases by 10%, while using accelerators – by 30%. Thus, the most effective way of producing a dry mixture with the properties of quick setting and hardening is a short-term mixed grinding of all its components, which makes it possible to exclude accelerating chemical admixtures and plasticizing additives in the mixture. Also, grinding positively affects the strength gain of quick-setting compositions while reducing the gypsum content to 5%.

Preparation of Coal Gangue Cement Mortar

2013 ◽  
Vol 684 ◽  
pp. 159-162
Author(s):  
Wen Xia Li ◽  
Dong Li Wang ◽  
Ji Shou Niu ◽  
Xian Wei Ma
Keyword(s):  
Cement Mortar ◽  
Methyl Cellulose ◽  
Coal Gangue ◽  
Cellulose Ether ◽  
Low Strength

Many researches on coal gangue are aimed at increasing its activity by many methods together such as thermal, mechanical and chemical. The methods are so complex that they are difficult to be adopted by some companies. In this paper, considering the low-strength requirement of cement mortar, the activity of coal gangue is more evidently shown by Ca(OH)2 activator. The 28-days strength of coal gangue cement mortar can reach 18MPa and the hydrated mortar shows and keeps an expansive behavior by adding methyl cellulose ether and CaSO4•2H2O at all the ages.

Use of Spongilites as Pozzolanic Additives in Cement Mortars

2021 ◽  
Vol 325 ◽  
pp. 65-70
Author(s):  
Martin Vyšvařil ◽  
Patrik Bayer ◽  
Tomáš Žižlavský
Keyword(s):  
Mechanical Properties ◽  
Bulk Density ◽  
Frost Resistance ◽  
Water Retention ◽  
Cement Mortar ◽  
Partial Replacement ◽  
Fine Grained ◽  
Natural Pozzolans ◽  
Cement Mortars ◽  
Pozzolanic Additives

In this study, the utilization of two types of spongilites in various addition in cement mortars has been investigated with the purpose of exploring a new application of this natural pozzolans as cement mortar additives. The influence of the addition of spongilites on the physico-mechanical properties, frost-resistance, and microstructure of cement mortars as a function of time was studied. The results revealed that the rising proportion of spongilites in cement mortars causes increase in water retention of mortars, reduction of their bulk density, increase in porosity of mortars due to the growing predominance of capillary pores maintaining sufficient mortars strengths, and slightly increase in the frost-resistance of mortars. After initial tests, partial replacement of cement in fine-grained cement mortars with hitherto unexploited spongilites seems to be very promising. Based on the achieved results, a 20% cement replacement can be recommended as optimal.

scholarly journals Retarding effect of grinding dust and its influence on the physical-mechanical and rheological properties of cementitious matrices

2019 ◽  
Vol 12 (3) ◽  
pp. 486-508
Author(s):  
R. D. MARIANO ◽  
J. S. ANDRADE NETO ◽  
M. R. MORELLI ◽  
D. V. RIBEIRO
Keyword(s):  
Mechanical Properties ◽  
Rheological Properties ◽  
Setting Time ◽  
Squeeze Flow ◽  
Retarding Effect ◽  
Finishing Process ◽  
Flow Table ◽  
Hardened State

Abstract The present study evaluated the feasibility of the use of grinding dust (GD), a waste generated in the clutch disc finishing process, as a retardant additive in cementitious matrices. For this, the waste was added in contents of 5%, 10% and 15%, relative to the cement weight, and the setting time was determined by the Vicat method. In addition, the influence of this material on rheology (flow table, squeeze-flow and rotational rheometry) and on the physical-mechanical properties of the hardened matrices was analyzed. The results indicated an increase in setting time and a reduction in the fluidity of the mortars as a function of the addition of GD and the best results for the hardened state properties were verified for the cementitious matrices containing a 5% addition. Therefore, it was observed that GD is effective in retarding the setting time, presenting great potential for use in civil construction, without impairing its properties.

scholarly journals Experimental Investigation of the Physical and Mechanical Properties of Cassava Starch Modified Concrete

2019 ◽  
Vol 13 (1) ◽  
pp. 331-343 ◽  
Author(s):  
Daniel Oluwabusayo ONI ◽  
John Mwero ◽  
Charles Kabubo
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Setting Time ◽  
Research Work ◽  
Physical And Mechanical Properties ◽  
Cassava Starch ◽  
Split Tensile Strength ◽  
Chemical Admixtures ◽  
Mix Proportion ◽  
Hot Weather

Background: Concrete is a widely used material in construction, which has given rise to innovations in terms of modifying some of its properties to meet desired requirements. The use of chemical admixtures is important in this regard, which has necessitated the search for new materials which can serve as a substitute. Objective: This research work investigates the use of Cassava Starch (CS) as an admixture for improving the physical and mechanical properties of concrete. Methodology: The physical and mechanical properties of concrete were studied by adding CS by weight of cement at 0.4, 0.8, 1.2, 1.6 and 2.0%, respectively. Concrete cubes and cylinders were cast and cured for a test period of 7, 14, 28, 56 and 90 days, respectively. Unreinforced beams of size 150 x 150 x 530 were cast and cured for 28 days. A total of 6 mix proportion was used, five out of which were used to examine the effect of CS on the properties of concrete. Results: The workability of concrete reduced as the percentage of CS increased due to its viscosity modifying properties. CS increased the initial and final setting time of concrete for every increase in percentage addition. An improvement in the compressive strength, split tensile strength, flexural strength and elastic modulus of concrete were noticed for cassava starch-modified concrete over the control for some of the mixes at all days of curing. The density of concrete was found to decrease at 1.6 and 2.0% addition of CS in concrete. Conclusion: From the results of this investigation, CS improved the compressive, split tensile, flexural and elastic modulus of concrete at an optimum of 0.8 percentage addition of CS. The setting time of concrete was also increased, which makes CS suitable to be used as a retarding admixture in hot weather concreting. Based on the findings of the work, CS can be considered as an admixture to be used as a substitute for retarders and viscosity modifying admixtures for improved concrete properties.

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