Effect of SRA on the Course of Hydration of Cement Composites

2019 ◽  
Vol 296 ◽  
pp. 35-40
Author(s):  
Lucia Osuská ◽  
Martin Ťažký ◽  
Milan Meruňka ◽  
Rudolf Hela
Keyword(s):  
Liquid Phase ◽  
Chemical Reaction ◽  
Cement Hydration ◽  
Cement Composites ◽  
Mechanical Parameters ◽  
Curing Time ◽  
Volume Changes ◽  
Cement Pastes ◽  
Binder Component ◽  
The Impact

Cement hydration is a chemical reaction that is associated with the development of hydration heat and changes in the volume of input components that transit from the solid and liquid phase to one homogeneous whole. In order to eliminate the volume changes already occurring during the hydration process, several principles can be applied, such as the use of active or inert admixtures as partial cement substitute or special shrinkage reducing additives. The experiment verifies the effect of anti-shrinkage additives on the course of hydration of cement pastes in terms of the development of hydration temperatures and elimination of volume changes of cement pastes. Volume changes will be monitored for the first 30 hours of cement mixing with water, i.e. in the time when the major changes occur due to this chemical reaction. Due to the expected hydration deceleration of the binder component by the effect of SRA, the impact of the use of these additives on the curing time of the composite and consequently on the mechanical parameters of the concrete will be verified.

scholarly journals Effect of Graphene Oxide on Mechanical Properties of Cement Mortar and its Strengthening Mechanism

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3753 ◽  
Author(s):  
Yahui Wang ◽  
Jiawen Yang ◽  
Dong Ouyang
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Cement Hydration ◽  
Strengthening Mechanism ◽  
Cement Composites ◽  
Working Mechanism ◽  
Cement Pastes ◽  
Cement Mortars ◽  
Binder Ratio ◽  
Growth Space

The effects of the water–binder ratio and different graphene oxide (GO) sizes on the mechanical properties of GO-cement composites were systematically studied by preparing GO-cement mortars. The scanning electron microscopy observation (SEM) of the surface and fracture surface of cement pastes was carried out to study the morphology of cement hydration crystals in GO-cement systems under different space conditions. It was found that GO nanosheets significantly improved the compressive, flexural, and tensile strengths of cement mortars. When the dosage of GO nanosheets was 0.03% by weight of cement, the compressive, flexural, and tensile strengths at 28 days increased by 21.37%, 39.62%, and 53.77%, respectively, but GO was not found to be able to regulate the formation of flower-like cement hydration crystals. It was only shown that the growth space had an important influence on the morphology of hydrates. A possible working mechanism was proposed by which GO nanosheets prevented the expansion of microcracks in the cement pastes via a shield effect, thus enhancing the strength and toughness of the cement composites.

scholarly journals Biodeterioration mechanisms and kinetics of SCM and aluminate based cements and AAM in the liquid phase of an anaerobic digestion

2018 ◽  
Vol 199 ◽  
pp. 02003 ◽  
Author(s):  
Marie Giroudon ◽  
Matthieu Peyre Lavigne ◽  
Cédric Patapy ◽  
Alexandra Bertron
Keyword(s):  
Organic Matter ◽  
Anaerobic Digestion ◽  
Liquid Phase ◽  
Biological Activities ◽  
Concrete Durability ◽  
Slag Cement ◽  
Cement Pastes ◽  
The Impact ◽  
Kinetics Of ◽  
Aluminate Cement

In biogas structures, concrete faces aggressive media during anaerobic digestion. Biological activities allow the conversion of organic matter into biogas, leading to a medium characterized by a variability of composition in time and space. In order to ensure the sustainability of this expanding industry, solutions for increasing concrete durability are needed. This study aims to analyse the deterioration mechanisms of different binders focusing on the impact of the binder nature on the medium (biochemical composition) during the digestion. Binders with favourable composition to chemically aggressive media were tested: slag cement (CEM III/B), calcium aluminate cement (CAC) and metakaolin-based alkaliactivated material (MKAA), and a reference binder: OPC (CEM I). They were exposed to three anaerobic digestion cycles in liquid phase in laboratory bioreactors. The organic acids and ammonium concentrations of the liquid phase were monitored by GC and HPIC. For OPC and slag cement pastes, the chemical and mineralogical changes were characterized by SEM/EDS and XRD. Locally, the presence of binder materials has an impact on the kinetics of the digestion reaction, and therefore on the quantities of gas produced. Ammonium concentrations were above the XA3 class range. Under the conditions explored, biodeterioration mainly led to the carbonation of cement pastes.

scholarly journals Investigations on Flexural and Compressive Strengths of Mortar Dedicated to Clinker Units—Influence of Mixing Water Content and Curing Time

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 347
Author(s):  
Jan Kubica ◽  
Iwona Galman
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Laboratory Tests ◽  
Bending Strength ◽  
Mechanical Parameters ◽  
Curing Time ◽  
The Impact ◽  
Mixing Water

The article presents laboratory tests on the impact of the mixing water content used in the preparation of fresh mortar on the flexural and compressive strength of one of the dry-mix mortars produced by a leading European producer and dedicated to bricklaying with clinker elements. The development of these parameters in relation to curing time was also analyzed. The mortar samples were prepared from a factory-made mortar mix using 4.0 L (the value recommended by the mortar manufacturer), 4.5 L, and 5 L of water per 25 kg bag of ready-made, pre-mixed dry mortar mix. All samples were tested in five series after 5, 9, 14, 21, and 28 days of sample curing. The results of these tests showed that the use of 6 and 18% more mixing water than recommended by the manufacturer (4.5 and 5 L per bag) adversely affected the basic mechanical parameters of the tested mortar. Moreover, it was found that the highest compressive strength values were obtained after 21 days of curing and not after 28 days as usual. It was also found that hardening time and higher than recommended water content adversely affected the bending strength of the mortar.

The Influence of Shrinkage-Reducing Additives on Volume Changes and Mechanical Parameters of a Concrete Composite

2021 ◽  
Vol 325 ◽  
pp. 125-130
Author(s):  
Milan Meruňka ◽  
Lucia Ťažká ◽  
Rudolf Hela
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
High Performance ◽  
Cement Hydration ◽  
Heat Of Hydration ◽  
The Other ◽  
Cement Stone ◽  
Mechanical Parameters ◽  
Volume Changes ◽  
Significant Development

Cement hydration is a process during which the setting and hardening of cement stone occur. This process is linked to the significant development of heat of hydration, which is accompanied by volume changes of concrete composite (i.e. shrinkage). Due to this, cracks in a concrete composite can arise and influence not only its durability, mechanical parameters or aesthetics but, in the case of water-tight concretes (e.g. the so-called white boxes), also its function. The extent of volume changes can be influenced not only by the composite structure itself or the selection and amount of cement but also by using suitable active additions, e.g. high-temperature fly ash. As a result, it is possible to reduce the amount of cement required while maintaining identical mechanical parameters of concrete and, at the same time, slow down the progress of heat of hydration during cement hydration. One of the other options to eliminate volume changes in concrete composites is the use of shrinkage-reducing additives (SRA). This article focuses on the SRA influence on volume changes of high-performance concretes and their impact on the development of hydration temperatures and mechanical parameters of composites.

scholarly journals LONG-TIME INVESTIGATION OF CEMENT PASTES WITH MICRONIZED OLD CONCRETE, INFLUENCE OF DIFFERENT TYPE OF MIXING APPROACH ON MECHANICAL PROPERTIES

2020 ◽  
Vol 26 ◽  
pp. 71-75
Author(s):  
Zdeněk Prošek ◽  
Pavel Tesárek
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Resonance Method ◽  
Dynamic Shear Modulus ◽  
Cement Composites ◽  
Cement Pastes ◽  
Long Time ◽  
The Individual ◽  
The Impact ◽  
Non Destructive

The article focuses on the impact of different type of mixing approach on resulting mechanical properties of cement composites. The monitored parameters of the mixing approach were the speed of mixing and the method of mixing the individual components of the fresh mixture. The mechanical properties of the resulting composites were the main comparative parameter. The determined mechanical properties were dynamic modulus of elasticity, dynamic shear modulus, flexural strength and compressive strength. Dynamics moduli were detected using non-destructive resonance method during the whole experiment and compressive and flexural strength were determined by destructive method for 28 and 129 days old samples. Testing samples had dimensions equal to 40×40×160 mm.

scholarly journals Nanofluid flow containing carbon nanotubes with quartic autocatalytic chemical reaction and Thompson and Troian slip at the boundary

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Muhammad Ramzan ◽  
Jae Dong Chung ◽  
Seifedine Kadry ◽  
Yu-Ming Chu ◽  
Muhammad Akhtar
Keyword(s):  
Mathematical Model ◽  
Carbon Nanotubes ◽  
Drag Force ◽  
Chemical Reaction ◽  
Slip Velocity ◽  
Volume Fraction ◽  
Surface Drag ◽  
Nanofluid Flow ◽  
Velocity Parameter ◽  
The Impact

Abstract A mathematical model is envisioned to discourse the impact of Thompson and Troian slip boundary in the carbon nanotubes suspended nanofluid flow near a stagnation point along an expanding/contracting surface. The water is considered as a base fluid and both types of carbon nanotubes i.e., single-wall (SWCNTs) and multi-wall (MWCNTs) are considered. The flow is taken in a Dacry-Forchheimer porous media amalgamated with quartic autocatalysis chemical reaction. Additional impacts added to the novelty of the mathematical model are the heat generation/absorption and buoyancy effect. The dimensionless variables led the envisaged mathematical model to a physical problem. The numerical solution is then found by engaging MATLAB built-in bvp4c function for non-dimensional velocity, temperature, and homogeneous-heterogeneous reactions. The validation of the proposed mathematical model is ascertained by comparing it with a published article in limiting case. An excellent consensus is accomplished in this regard. The behavior of numerous dimensionless flow variables including solid volume fraction, inertia coefficient, velocity ratio parameter, porosity parameter, slip velocity parameter, magnetic parameter, Schmidt number, and strength of homogeneous/heterogeneous reaction parameters are portrayed via graphical illustrations. Computational iterations for surface drag force are tabulated to analyze the impacts at the stretched surface. It is witnessed that the slip velocity parameter enhances the fluid stream velocity and diminishes the surface drag force. Furthermore, the concentration of the nanofluid flow is augmented for higher estimates of quartic autocatalysis chemical.

The impact of Fe dosage on the ettringite formation during high ferrite cement hydration

2020 ◽  
Author(s):  
Dawei Wan ◽  
Wenqin Zhang ◽  
Yong Tao ◽  
Zonghua Wan ◽  
Fazhou Wang ◽  
...  
Keyword(s):  
Cement Hydration ◽  
Ettringite Formation ◽  
The Impact

The Study of Underfill Epoxy Hardness in Reducing Curing Process Time for Flip Chip Packaging

2011 ◽  
Vol 462-463 ◽  
pp. 1194-1199
Author(s):  
Zainudin Kornain ◽  
Azman Jalar ◽  
Rozaidi Rashid ◽  
Shahrum Abdullah
Keyword(s):  
Thermal Expansion ◽  
Flip Chip ◽  
Ball Grid Array ◽  
Process Time ◽  
Curing Process ◽  
Curing Time ◽  
Hold Temperature ◽  
Flip Chip Packaging ◽  
Time Cycle ◽  
The Impact

Underfilling is the vital process to reduce the impact of the thermal stress that results from the mismatch in the co-efficient of thermal expansion (CTE) between the silicon chip and the substrate in Flip Chip Packaging. This paper reported the pattern of underfill’s hardness during curing process for large die Ceramic Flip Chip Ball Grid Array (FC-CBGA). A commercial amine based underfill epoxy was dispensed into HiCTE FC-CBGA and cured in curing oven under a new method of two-step curing profile. Nano-identation test was employed to investigate the hardness of underfill epoxy during curing steps. The result has shown the almost similar hardness of fillet area and centre of the package after cured which presented uniformity of curing states. The total curing time/cycle in production was potentially reduced due to no significant different of hardness after 60 min and 120 min during the period of second hold temperature.

Assessment of Hydration Degree of Cement in the Fly Ash-Cement Pastes Based on the Calcium Hydroxide Content

2014 ◽  
Vol 875-877 ◽  
pp. 177-182 ◽  
Author(s):  
Xiang Li ◽  
Hua Quan Yang ◽  
Ming Xia Li
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Cement Hydration ◽  
Ash Content ◽  
Content Increase ◽  
Hydration Degree ◽  
Equilibrium Calculation ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio

The hydration degree of fly ash and the calcium hydroxide (CH) content were measured. Combined with the equilibrium calculation of cement hydration, a new method for assessment of the hydration degree of cement in the fly ash-cement (FC) pastes based on the CH content was developed. The results reveal that as the fly ash content increase, the hydration degree of fly ash and the CH content decrease gradually; at the same time, the hydration degree of cement increase. The hydration degree of cement in the FC pastes containing a high content of fly ash (more than 35%) at 360 days is as high as 80%, even some of which hydrates nearly completely. The effect of water-cement ratio to the hydration degree of cement in the FC pastes is far less distinct than that of the content of fly ash.

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