Liquid nitrogen effect on the fresh concrete properties in hot weathering concrete

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Iman Kattoof Harith ◽  
Maan S. Hassan ◽  
Shatha S. Hasan
Keyword(s):  
Liquid Nitrogen ◽  
Fresh Concrete ◽  
Nitrogen Effect ◽  
Concrete Properties

scholarly journals The Effect of Accelerator Dosage on Fresh Concrete Properties and on Interlayer Strength in Shotcrete 3D Printing

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 374 ◽  
Author(s):  
Inka Dressler ◽  
Niklas Freund ◽  
Dirk Lowke
Keyword(s):  
3D Printing ◽  
Yield Stress ◽  
Fresh Concrete ◽  
Testing Machine ◽  
Image Correlation ◽  
Early Age ◽  
Stress Evolution ◽  
Functional Interaction ◽  
Concrete Properties ◽  
Instantaneous Increase

Recently, the progress in 3D concrete printing has developed enormously. However, for the techniques available, there is still a severe lack of knowledge of the functional interaction of processing technology, concrete rheology and admixture usage. For shotcrete 3D printing technology, we present the effect of accelerator dosages (0%, 2%, 4% and 6%) on fresh concrete properties and on interlayer strength. Therefore, early yield stress development up to 90 min is measured with penetration resistance measurements. Deformation of layers under loading is investigated with digital image correlation and a mechanical testing machine. One point in time (10 min after deposition) is examined to quantify vertical buildability of elements depending on the accelerator dosage. Four different interlayer times (0, 2, 5 and 30 min), which occur for the production of small and large elements as well as due to delay during production, are investigated mechanically as well as quantitatively with computed tomography regarding the formation of cold joints. With increased accelerator dosage, an instantaneous increase in early age yield stress and yield stress evolution was observed. An increase in interlayer time leads to a reduced strength. This is mainly attributed to the observed reduced mechanical interlocking effect of the strands. Finally, a model to describe interlayer quality is presented. In the end, advantages as well as limitations of the findings are discussed.

Monitoring of Self Compacting Concrete Characteristics Development

2014 ◽  
Vol 1054 ◽  
pp. 128-131
Author(s):  
Klára Křížová ◽  
Petr Novosad ◽  
Denisa Orsáková
Keyword(s):  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Fresh Concrete ◽  
Raw Material ◽  
Self Compacting Concrete ◽  
Concrete Properties ◽  
New Concepts ◽  
Basic Characteristics ◽  
Characteristics Development

The paper presents obtained results of self-compacting concretes with various compositions with focus on basic characteristics development. Firstly the fresh concrete properties are summed and self-compactness classes are categorised and subsequently the values of compressive strength, static and dynamic modulus of elasticity of hardened concretes are compared. All the stated parameters were monitored during different ages of the concrete and therefore they provide a view of its development in time. With still enlarging scale of concrete types and development of their application it is necessary to monitor common parameters which due to the application of new concepts in raw material compositions and use of higher amounts of additives may notably differ compared to applied orthodox concrete parameters.

scholarly journals Comparative Study of Self-Compacting Concrete Containing Lightweight and Normal Aggregates

2019 ◽  
Vol 27 (2) ◽  
pp. 1-8
Author(s):  
Ramamohanrao Pannem ◽  
Padmaja P. Kumar
Keyword(s):  
Fly Ash ◽  
Fresh Concrete ◽  
Void Content ◽  
Self Compacting Concrete ◽  
Simple Method ◽  
Coarse Aggregates ◽  
Concrete Properties ◽  
Round Shape ◽  
Fine Aggregates ◽  
Ash Aggregates

AbstractBased on the available literature, a simple method was adopted to calculate the packing density of aggregates and thereby reduce their void content by optimising their packing aggregates and by using two different sizes of coarse aggregates and fine aggregates. This study provides an understanding of the way in which the shape of aggregates affects the properties of self-compacting concrete (SCC). The fresh, hardened, and durable properties of SCC with normal and lightweight fly ash coarse aggregates are found at the corresponding age of the curing. Their values were compared with respect to SCC containing normal aggregates. A mix with fly ash aggregates was found to have better fresh concrete properties due to the round shape of the aggregates. After the packing of the aggregates, this mix was found to have better mechanical and durability properties than all the other concrete mixes.

scholarly journals GGBS based alkali activated fine aggregate in concrete - Properties at fresh and hardened state

2021 ◽  
Vol 13 (1) ◽  
pp. 47-53
Author(s):  
G. Lizia Thankam ◽  
T.R. Neelakantan ◽  
S. Christopher Gnanaraj
Keyword(s):  
Mechanical Properties ◽  
Alkaline Solution ◽  
Elevated Temperatures ◽  
Fresh Concrete ◽  
Hardened Concrete ◽  
Fine Aggregate ◽  
River Sand ◽  
Complete Replacement ◽  
Concrete Properties ◽  
Fine Aggregates

Abstract Scarcity of the construction materials, peculiarly the natural river sand has become a serious threat in the construction industry. Though many researchers of developed and developing countries are trying to find alternative sources for the same, the complete replacement of the fine aggregate in concrete is crucial. Geopolymer sand developed from the Industrial waste (Ground granulated blast furnace slag - GGBS) is an effective alternative for the complete replacement of the natural sand. The GGBS based geopolymer sand (G-GFA) was tested for physical and chemical properties. Upon the successful achievement of the properties in par with the natural river sand, the fresh properties (fresh concrete density & slump) and hardened properties (compressive strength, tensile strength & flexural strength) of the concrete specimens developed with G-GFA were studied. The G-GFA is obtained by both air drying (AD-G-GFA) and oven drying (OD-F-GFA) after the dry mixing of the alkaline solution and GGBS for about 10 min. Thus, developed fine aggregates were studied separately for the fresh and hardened concrete to optimize the feasible one. Superplasticizer of 0.4% is included in the concrete mix to compensate the sightly hydrophilic nature of the fine aggregates produced. The mechanical properties of the concrete with G-GFA are observed to be more than 90% close to that of the concrete developed with natural river sand. Thus, both the fresh and mechanical properties of the G-GFA concrete specimens resulted in findings similar to those of the control specimen developed with natural river sand reflecting the plausibility of G-GFA as a complete replacement choice to the fine aggregate in the concrete industry. The flaky GGBS particles merge well with the alkaline solution at room temperature itself since the former gets dried at elevated temperatures. Thus, more feasible fresh concrete properties and mechanical properties were recorded for the AD-G-GFA than the OD-G-GFA.

scholarly journals EVALUATION OF SUITABILITY TO USE PLASTIC WASTE IN CONCRETE PRODUCTION

2018 ◽  
Author(s):  
Rytis SKOMINAS ◽  
Linas ZVINAKEVIČIUS ◽  
Vincas GURSKIS ◽  
Raimondas ŠADZEVIČIUS
Keyword(s):  
Compression Strength ◽  
Fresh Concrete ◽  
Strength Loss ◽  
Plastic Waste ◽  
Hardened Concrete ◽  
Coarse Aggregates ◽  
Concrete Properties ◽  
Concrete Production ◽  
Negative Effect ◽  
Water Absorbability

Nowadays one of the main tasks of environmental protection is the management and recycling of plastic waste. Plastic occupy the major part of all public waste and with this material is polluted all earth. In natural condition plastic decompose in 400 or even in 500 years. Therefore, it is important to solve this problem reusing plastic waste. One of the possible areas is construction industry. In the present paper were estimated how plastic waste impact the properties of concrete. During the research the part of coarse aggregates were changed with polyethylene (PE) pellets and cut polypropylene (PP) particles. The change of fresh concrete density, workability and hardened concrete density, compression strength, water absorbability were evaluated. The results show, that plastic waste has a positive effect on fresh concrete properties: the concrete become more workable and lighter. Unfortunately, on the main hardened concrete properties the increase plastic waste amount has the negative effect: the compression strength was decreasing and the water absorbability was increasing. However, generalizing all results, can be stated, that keeping the same level of concrete workability there are possibilities to reduce water and cement ratio and it will give strength loss and water absorbability growth compensation.

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