scholarly journals A New Microstructure Development Model for the Evaluation of Concrete Setting Time

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Ho-Jin Cho ◽  
Joo-Won Kang ◽  
Yong Han Ahn ◽  
Sunkook Kim ◽  
Xiao-Yong Wang
Keyword(s):  
Construction Material ◽  
Setting Time ◽  
Volume Ratio ◽  
Point Of View ◽  
Development Model ◽  
Mineral Admixtures ◽  
Strength Development ◽  
Hydration Reaction ◽  
Design Strength ◽  
High Durability

Concrete is an exceptionally attractive construction material, with stable material supply, adequate fire resistance, and high durability. Its plasticity can be both an advantage and a disadvantage from an engineering point of view, providing versatile shapes via casting and hardening but also requiring a relatively long period of time to reach its design strength. The setting time, or hardening period, needed before the freshly poured concrete can carry a load, which begins once the hydration reaction has commenced, is a key parameter for durability since it directly affects cracking resistance in early-aged concrete. The new analysis technique for calculating setting time that was developed for this study utilizes both percolation theory and the strength development model. To verify the analytical results obtained using the new model, a critical volume ratio of hydrates was determined and a series of final setting times in concrete were experimentally investigated for different temperatures, mineral admixtures (FA: fly ash; GGBFS: ground granulated blast furnace slag), and a chemical admixture (superplasticizer). The results were found to be in good agreement with the model predictions, confirming its potential utility.

scholarly journals Experimental Evaluation of Cement Mortars with End-of-Life Tyres Exposed to Different Surface Treatments

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 552
Author(s):  
Eduardo García ◽  
Bárbara Villa ◽  
Mauricio Pradena ◽  
Bruno Urbano ◽  
Víctor H. Campos-Requena ◽  
...  
Keyword(s):  
End Of Life ◽  
Construction Material ◽  
Cost Effective ◽  
Surface Treatments ◽  
Point Of View ◽  
Negative Effects ◽  
Design Strength ◽  
Cement Mortars ◽  
Concrete Mechanical Properties ◽  
Portland Pozzolana Cement

An end-of-Life Tyre (ELT) is a type of waste that can generate negative social and environmental impacts due to its disposal. Considering that rubber can improve concrete properties and the massive use of concrete as construction material, the addition of ELT rubber in concrete mixes is attractive. However, concrete mechanical properties are negatively affected due to the rubber-cementitious matrix interaction. Although rubber treatments have been developed to minimise the negative effects, the geo-dependency of the mix makes necessary to find cost-effective and practical solutions that will allow a real use of the ELT waste. Therefore, the objective of the present study is to characterise the properties of cement mortars with the addition of ELT rubber under three surface treatments: hydration, oxidation-sulphonation, and hydrogen peroxide. The results show that hydration is the most favourable treatment from a technical, practical, and economical point of view. In fact, with this treatment, it is possible to add up to 5% ELT rubber, with respect to the aggregate weight, and still exceed the design strength without adding more cement or additives as other investigations. The use of Portland Pozzolana Cement, with local fly ash waste, contributes as well to the promissory results obtained.

scholarly journals Effects of CNT Dosages in Cement Composites on the Mechanical Properties and Hydration Reaction with Low Water-to-Binder Ratio

2019 ◽  
Vol 9 (21) ◽  
pp. 4630 ◽  
Author(s):  
Sang-Hwa Jung ◽  
Sungwoo Oh ◽  
Sung-Wook Kim ◽  
Jae-Heum Moon
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Construction Material ◽  
Isothermal Calorimetry ◽  
Strength Development ◽  
Hydration Reaction ◽  
Cement Composites ◽  
Gravimetric Analysis ◽  
Binder Ratio ◽  
Water To Binder Ratio

This study aimed to investigate the potential use of carbon nanotubes (CNTs), which are an innovative construction material preferred by many researchers. Long-term microstructure enhancement and on-site application are major reasons to conduct research on CNT-cement composites; thus, a study on mechanical properties as well as the thermal conductivity of CNT-cement composites was carried out. As the CNT content increased, the thermal conductivity of CNT-cement composites was also enhanced. In addition, a couple of microstructure analyses such as isothermal calorimetry, thermal gravimetric analysis and SEM-EDS (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy) for observing hydration reaction rate and types of hydration products were conducted to establish the advantage of CNT use in cement composites. Strength development of CNT-cement composites at early ages was slow, although eventually CNTs containing water developed equivalent level of strengths at last as internal curing effects.

scholarly journals Comparing Properties of Concrete Containing Electric Arc Furnace Slag and Granulated Blast Furnace Slag

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1371 ◽  
Author(s):  
Jin-Young Lee ◽  
Jin-Seok Choi ◽  
Tian-Feng Yuan ◽  
Young-Soo Yoon ◽  
Denis Mitchell
Keyword(s):  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Setting Time ◽  
Electric Arc Furnace ◽  
Electric Arc ◽  
Strength Development ◽  
Hydration Reaction ◽  
Arc Furnace ◽  
Steel Making ◽  
Furnace Slag

For sustainable development in the construction industry, blast furnace slag has been used as a substitute for cement in concrete. In contrast, steel-making slag, the second largest by-product in the steel industry, is mostly used as a filler material in embankment construction. This is because steel-making slag has relatively low hydraulicity and a problem with volumetric expansion. However, as the quenching process of slag has improved recently and the steel making process is specifically separated, the properties of steel-making slag has also improved. In this context, there is a need to find a method for recycling steel-making slag as a more highly valued material, such as its potential use as an admixture in concrete. Therefore, in order to confirm the possibility of using electric arc furnace (EAF) oxidizing slag as a binder, a comparative assessment of the mechanical properties of concrete containing electric arc furnace oxidizing slag, steel-making slag, and granulated blast furnace (GBF) slag was performed. The initial and final setting, shrinkage, compressive and split-cylinder tensile strength of the slag concretes were measured. It was found that replacing cement with EAF oxidizing slag delayed the hydration reaction at early ages, with no significant problems in setting time, shrinkage or strength development found.

scholarly journals Alkali-activated laterite binders: Influence of silica modulus on setting time, Rheological behaviour and strength development

2021 ◽  
pp. 100175
Author(s):  
Cyriaque Rodrigue Kaze ◽  
Adeyemi Adesina ◽  
Gisèle Laure Lecomte-Nana ◽  
Thamer Alomayri ◽  
Elie Kamseu ◽  
...  
Keyword(s):  
Setting Time ◽  
Rheological Behaviour ◽  
Strength Development ◽  
Alkali Activated

The Effect on Cement Mortar and Concrete by Admixture of Spray Drying Absorption Products

1989 ◽  
Vol 178 ◽  
Author(s):  
Kirsten G. Jeppesen
Keyword(s):  
Grain Size ◽  
Fly Ash ◽  
Cement Mortar ◽  
Setting Time ◽  
Mineralogical Composition ◽  
Cement Clinker ◽  
Strength Development ◽  
Fall Meeting ◽  
Freeze Thaw ◽  
Spray Dried

AbstractSpray dried absorption products (SDA) having special characteristics are used as substitutes for cement in the preparation of mortars; the qualities of the resulting mixed mortars are described. Conditions are described for mortar mixes, data for which were presented at the MRS Fall Meeting 1987.The influence of the composition of the SDA on water requirement and setting time has been studied. A full scale project involving 3 precast, reinforced concrete front-elements containing 20 and 30 wt.% SDA is described. Strength development, mineralogical composition and corrosion were monitored for two years.A non-standard freeze-thaw experiment was performed which compares mortars containing SDA and fly ash (FA) and also shows the effect of superplasticizer.The possibility of improving the SDA by grinding has been tested and a limited improvement has been found. The strength of the mixed mortars seems slightly influenced by the grain size of SDAGypsum (CaSO4·2H2O), synthetic calcium-sulphite (CaSO3·½H2O) and 2 SDAs have been used as retarders for cement clinker. Mortar test prisms have been cast and comparative strengths after curing for 3 years are reported

scholarly journals Positive Influence of Liquid Sodium Silicate on the Setting Time, Polymerization, and Strength Development Mechanism of MSWI Bottom Ash Alkali-Activated Mortars

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1927
Author(s):  
Lei Jin ◽  
Guodong Huang ◽  
Yongyu Li ◽  
Xingyu Zhang ◽  
Yongsheng Ji ◽  
...  
Keyword(s):  
Sodium Silicate ◽  
Setting Time ◽  
Bottom Ash ◽  
Free Water ◽  
Polymerization Reaction ◽  
Liquid Sodium ◽  
Strength Development ◽  
Mswi Bottom Ash ◽  
Alkali Activated ◽  
Development Mechanism

Setting time and mechanical properties are key metrics needed to assess the properties of municipal solid waste incineration (MSWI) bottom ash alkali-activated samples. This study investigated the solidification law, polymerization, and strength development mechanism in response to NaOH and liquid sodium silicate addition. Scanning electron microscopy and X-ray diffraction were used to identify the formation rules of polymerization products and the mechanism of the underlying polymerization reaction under different excitation conditions. The results identify a strongly alkaline environment as the key factor for the dissolution of active substances as well as for the formation of polymerization products. The self-condensation reaction of liquid sodium silicate in the supersaturated state (caused by the loss of free water) is the major reason for the rapid coagulation of alkali-activated samples. The combination of both NaOH and liquid sodium silicate achieves the optimal effect, because they play a compatible coupling role.

The Influence of Purification of Ethyl Acrylate on the Properties of Cement Matrix

2010 ◽  
Vol 150-151 ◽  
pp. 1143-1151
Author(s):  
Chau Lee ◽  
Nian Fu Wang ◽  
Meng Xun Xiem
Keyword(s):  
Hydrogen Peroxide ◽  
Early Stage ◽  
Setting Time ◽  
Ethyl Acrylate ◽  
Cement Matrix ◽  
Strength Development ◽  
Final Setting Time ◽  
Before And After ◽  
Analysis Of Performance ◽  
Acrylate Polymer

This research mainly probes into the analysis of performance and assessment that ethyl acrylate polymer is applied to the cement matrix. The result shows that, before and after the purification, ethyl acrylate can increase the flowability of modified mortar, and with the increasing the dosage of polymer, the flowability is getting better. But if the dosage of hydrogen peroxide used to remove the residua alcohol is excessive, it is easy to cause high mortar viscosity, and that is unfavorable to the flowability. According to the setting time of the mortar under normal consistency, the result shows that the ethyl acrylate before the purification, has retarding effects on both initial and final setting time. With the increasing the dosage of polymer, it takes longer for both setting time. Besides, because hydrogen peroxide has accelerative effect, the purified ethyl acrylate can shorten the setting time of initial and final setting time. However, over dosage of hydrogen peroxide can easily lead to poor strength development in later stage. Using purified ethyl acrylate can overcome the shortcoming of lower strength of 3、7- day early stage. when hydrogen peroxide consumption is 0.5% of the total amount of acid and alcohol, the ethyl acrylate has the positive effect on improving the compressive strength. Finally, among the comprehensive assessments of the mortar testing results, EH0.5-0.1 has the significant effect of modification.

scholarly journals Influence of Steam Curing Method on the Performance of Concrete Containing a Large Portion of Mineral Admixtures

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Mengyuan Li ◽  
Qiang Wang ◽  
Jun Yang
Keyword(s):  
Chloride Ion ◽  
Mineral Admixtures ◽  
Strength Development ◽  
Steam Curing ◽  
Chloride Permeability ◽  
Curing Conditions ◽  
Volume Stability ◽  
Ettringite Formation ◽  
The Impact ◽  
Reaction Degree

A comparison was made between the impact of raising the thermostatic temperature and the impact of prolonging the thermostatic time on the performance of steam-cured concrete containing a large portion of fly ash (FA) or ground granulated blast furnace slag (GGBS) by analysing the form removal strength, chemically combined water content, reaction degree, strength development, chloride permeability, and volume stability. For the materials and test conditions reported in this study, raising the thermostatic temperature is more favourable for concrete containing FA, as indicated by the significantly higher form removal strength and the higher growth of reaction degree of FA compared with prolonging the thermostatic time. With an increase in the thermostatic temperature, the hydration degree of a binder containing FA or GGBS initially increases and subsequently decreases. Although concrete containing FA can obtain satisfactory form removal strength with steam curing at 80°C, the late strength development of concrete containing FA is slow for the same curing conditions. The effect of the late performance of resistance to chloride ion permeability improved by FA is better than the effect improved by GGBS. The risk of destroying the structure of concrete containing a large portion of FA or GGBS due to delayed ettringite formation (DEF) is minimal when specimens were steam-cured at 80°C.

Sign in / Sign up

Export Citation Format

Share Document