Two Options of Self-Curing of High Performance Concrete

2018 ◽  
Vol 272 ◽  
pp. 88-93 ◽  
Author(s):  
David Pytlík ◽  
Vlastimil Bilek
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Internal Curing ◽  
Cement Matrix ◽  
High Dose ◽  
Negative Effects ◽  
Cement Ratio ◽  
Polymer Curing ◽  
The Matrix ◽  
Mixing Water

Some effects of self-curing on the mechanical properties of High Performance Concrete (HPC) are discussed in this paper. The matrix of HPC is very dense and it is very difficult to deliver the curing water into the cement matrix. Two different materials in different dosages were selected to examine self-curing. Polymer curing agent (PCA) was selected as the first, and 0.2% 0.4% 0.6% and 0.8% of PCA were added by weight of cement. This additive should allow the physicochemical binding of a larger portion of the mixing water and then release it slowly for better hydration without negative effects on the products. Pre-soaked slag of 0/4 mm was tested as another source of water for internal curing. The slag was also dosed in 10%, 15%, 20% and 30% volume of sand with the fraction 0/4 mm. Referential HPC was a high-dose cement that consumes a large amount of water for hydration. The water/cement ratio was 0.2. Metakaolin was added to improve the properties of fresh and hardened HPC.

Morphology and Strength of Cement Paste from Clay as Nanomaterial

2014 ◽  
Vol 490-491 ◽  
pp. 19-24 ◽  
Author(s):  
M.S. Muhd Norhasri ◽  
M.S. Hamidah ◽  
A. Mohd Fadzil
Keyword(s):  
Cement Paste ◽  
High Performance ◽  
High Performance Concrete ◽  
Human Life ◽  
Sol Gel ◽  
Hydration Product ◽  
Strength Properties ◽  
Cement Matrix ◽  
The Matrix ◽  
Early Strength

Now days the application of nanomaterials was vastly growing in the development of new material to improve the quality of human life. Particles of nanomaterials which are in nanoscale helps to improve to the characteristics of the existing micro based materials. The application of nanomaterials in the construction were started since in the early 90s when during those time micro based materials was very demanding especially when dealing with High Performance Concrete (HPC). The utilization of nanobased materials improves and reinforces the cement matrix system and performs early strength and also enhances tensile properties of concrete. In this research, two types of clay were used which nanometakaolin and nanometaclay. nanometakaolin were made from sol gel process thats involved milling technique and nanometaclay were supplied by Sigma Aldrich. The mix proportion for clay based cement paste also includes metakaolin as cement replacement material. nanometakaolin and nanometaclay was added as additives from 0, 1, 3, 5, 7, 9 percent (%) from weight of cement and will be compared to OPC as control specimen. nanometakaolin and nanometaclay inclusion in cement paste will be evaluated for morphology effect by using Scanning Electron Microscope (SEM), chemical composition by using X-Ray Fluorescent (XRF) technique and strength properties. From morphology evaluation, the shape of the particles and particularisation of the matrix observed on the nanometakaolin, nanometaclay and plain cement paste were compared. Similarly, the strength of the plain cement paste shows was compared with those of nanometakaolin and nanometaclay. From the results, shows that inclusion of nanometakaolin at 7% additives generates early strength of cement paste and at 28 days of age addition of 1% of nanometakaolin was found to be the optimum addition level. The addition of 1% nanometakaolin acts as an ultra-filler and refines the microstructure of concrete. Furthermore, nanometakaolin also produces a secondary hydration product by optimizing the remaining calcium hydroxide which was not fully removed during the hydration period.

scholarly journals Materials for Production of High and Ultra-High Performance Concrete: Review and Perspective of Possible Novel Materials

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4304
Author(s):  
Markssuel Teixeira Marvila ◽  
Afonso Rangel Garcez de de Azevedo ◽  
Paulo R. de de Matos ◽  
Sergio Neves Monteiro ◽  
Carlos Maurício Fontes Vieira
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Review Article ◽  
Cement Matrix ◽  
Bibliographic Databases ◽  
Future Research ◽  
Chemical Additives ◽  
Ultra High Performance Concrete ◽  
Conventional Concrete ◽  
Essential Components

This review article proposes the identification and basic concepts of materials that might be used for the production of high-performance concrete (HPC) and ultra-high-performance concrete (UHPC). Although other reviews have addressed this topic, the present work differs by presenting relevant aspects on possible materials applied in the production of HPC and UHPC. The main innovation of this review article is to identify the perspectives for new materials that can be considered in the production of novel special concretes. After consulting different bibliographic databases, some information related to ordinary Portland cement (OPC), mineral additions, aggregates, and chemical additives used for the production of HPC and UHPC were highlighted. Relevant information on the application of synthetic and natural fibers is also highlighted in association with a cement matrix of HPC and UHPC, forming composites with properties superior to conventional concrete used in civil construction. The article also presents some relevant characteristics for the application of HPC and UHPC produced with alkali-activated cement, an alternative binder to OPC produced through the reaction between two essential components: precursors and activators. Some information about the main types of precursors, subdivided into materials rich in aluminosilicates and rich in calcium, were also highlighted. Finally, suggestions for future work related to the application of HPC and UHPC are highlighted, guiding future research on this topic.

scholarly journals تأثير إستخدام خبث أفران مجموعة جياد الصناعية على جودة الخرسانة

2021 ◽  
Vol 9 (2) ◽  
pp. 1-6
Author(s):  
علي حسين محمد علي ◽  
الطيب عبداللطيف أحمد حبيب
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Hardened Concrete ◽  
Gradual Reduction ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Artificial Materials ◽  
Percent Increase ◽  
And Performance ◽  
Furnace Slag

The need to produce high performance concrete led the researchers to try to exploit the potentialities of natural or artificial materials so as to improve the properties and performance of concrete. Slag is an industrial disposal which considered as a secondary product of pig-iron, these disposal will cause a severe harm to the environment in case of not get rid of it. In this investigation iron furnace slag which is produced at Giad Group - Iron Factory has been used as an alternative of proportion on cement after being processed, since its main oxides are similar to those of cement. In the practical part of our research slag has been added to the concrete mix in two ways, first by using it to replace as cement by weight as a substitutions of cement in different percent [10, 20, 30]% without changing in water-cement ratio [W/C], second by using the slag with the same previous percentage in addition to [15, 25]% to replace cement with reducing in water-cement ratio [W/C], and in addition superplasticizer [SP 901] has been added as percent from cement used in the mixture. The effect of slag was studied on the properties of fresh and hardened concrete including slump test and compressive strength in [7, 14, 28] days were investigated. The results show improvement in all concrete specimens for the added percentage of the slag as replacement materials and the addition of superplasticizer in the production of concrete and improvement in its properties. However, there is a gradual reduction in slump measurements due to slag percent increase in case of the two methods.  

Research Progress on Early Autogenous Shrinkage of Cement-Based Cementitious Materials

2013 ◽  
Vol 634-638 ◽  
pp. 2738-2741
Author(s):  
Wei Huang ◽  
Tao Zhang ◽  
Yun Yun Xu
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Research Work ◽  
Autogenous Shrinkage ◽  
Cementitious Materials ◽  
Mineral Admixtures ◽  
Research Progress ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Improvement Measures

Concrete autogenous shrinkage phenomenon would adversely affect the mechanical properties and durability of concrete, this phenomenon is important. Autogenous shrinkage problem of low water-cement ratio of the with high mineral admixtures, cement-based cementitious materials was introduced. The main reason for high-performance concrete early cracking being autogenous shrinkage was pointed out. Based on the home and abroad research status of low water cement ratio of the cement paste and concrete autogenous shrinkage, especially for early autogenous shrinkage phenomenon, the mechanism of autogenous shrinkage and the measure method is presented, and the improvement measures and the possible problems the need for further research work is presented.

scholarly journals Effect of Mineral Aggregates and Chemical Admixtures as Internal Curing Agents on the Mechanical Properties and Durability of High-Performance Concrete

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2090 ◽  
Author(s):  
Francisco Javier Vázquez-Rodríguez ◽  
Nora Elizondo-Villareal ◽  
Luz Hypatia Verástegui ◽  
Ana Maria Arato Tovar ◽  
Jesus Fernando López-Perales ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
High Performance ◽  
High Performance Concrete ◽  
Chloride Ions ◽  
Internal Curing ◽  
Fine Aggregate ◽  
Pumice Stone ◽  
Chemical Admixtures ◽  
Mineral Aggregates

In the present work, the effect of mineral aggregates (pumice stone and expanded clay aggregates) and chemical admixtures (superplasticizers and shrinkage reducing additives) as an alternative internal curing technique was investigated, to improve the properties of high-performance concrete. In the fresh and hardened state, concretes with partial replacements of Portland cement (CPC30R and OPC40C) by pulverized fly ash in combination with the addition of mineral aggregates and chemical admixtures were studied. The physical, mechanical, and durability properties in terms of slump, density, porosity, compressive strength, and permeability to chloride ions were respectively determined. The microstructural analysis was carried out by scanning electronic microscopy. The results highlight the effect of the addition of expanded clay aggregate on the internal curing of the concrete, which allowed developing the maximum compressive strength at 28 days (61 MPa). Meanwhile, the replacement of fine aggregate by 20% of pumice stone allowed developing the maximum compressive strength (52 MPa) in an OPC-based concrete at 180 days. The effectiveness of internal curing to develop higher strength is attributed to control in the porosity and a high water release at a later age. Finally, the lowest permeability value at 90 days (945 C) was found by the substitutions of fine aggregate by 20% of pumice stone saturated with shrinkage reducing admixture into pores and OPC40C by 15% of pulverized fly ash. It might be due to impeded diffusion of chloride ions into cement paste in the vicinity of pulverized fly ash, where the pozzolanic reaction has occurred. The proposed internal curing technology can be considered a real alternative to achieve the expected performance of a high-performance concrete since a concrete with a compressive strength range from 45 to 67 MPa, density range from 2130 to 2310 kg/m3, and exceptional durability (< 2000 C) was effectively developed.

scholarly journals Fluorescence Microscopic Investigations of the Retarding Effect of Superplasticizers in Cementitious Systems of UHPC

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1057 ◽  
Author(s):  
Johannes Arend ◽  
Alexander Wetzel ◽  
Bernhard Middendorf
Keyword(s):  
Molecular Structure ◽  
High Performance ◽  
High Performance Concrete ◽  
Ultra High Performance Concrete ◽  
Adsorption Characteristic ◽  
Beneficial Effects ◽  
Retarding Effect ◽  
Cementitious Systems ◽  
Mixing Water

The adsorption of superplasticizer molecules to particle surfaces in cementitious systems is a very important aspect for the desired liquefaction of pastes and concretes. This way, the comb shaped polymers shield attractive forces between the particles and induce a well-dispersed, homogeneous suspension. These admixtures allow the usage of fine fillers even in combination with low amounts of mixing water, and thus, are the basis for modern high performance concretes. However, the adsorption does not cause beneficial effects only: The polymer covered particle surfaces, especially clinker, are hindered to interact with water, thus hydration is retarded. This is the reason for lower early strength and is very disadvantageous for certain applications. Today it is known that the molecular structure of the polymers, for instance the chain length and charge density, affects the retardation strongly. The complexity and diversity of cementitious systems is the main reason why research in this field is quite empiric and time as well as cost intensive. To investigate the adsorption of superplasticizers in various systems in-situ, a fluorescence microscopic approach was applied: By staining the polymers with fluorescent dye they become localizable and the adsorption quantifiable. This work shows the influence of molecular structure to adsorption characteristic of different polymers and the correlation to the retarding effect of superplasticizers, especially concerning the presence of silica fume, which is indispensable for ultra-high performance concrete (UHPC).

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