scholarly journals RESISTÊNCIA A COMPRESSÃO EM TESTEMUNHO DE CONCRETO: INFLUÊNCIA DO FATOR DE ESBELTEZ, DIÂMETRO DA AMOSTRA E MÉTODO DE EXTRAÇÃO

2017 ◽  
Vol 13 (1) ◽  
Author(s):  
Marcelo Henrique Farias de Medeiros ◽  
Ana Paula Brandão Capraro ◽  
Giovana Costa Réus ◽  
Marcel Luiz Escobedo
Keyword(s):  
Compressive Strength ◽  
Slenderness Ratio ◽  
Extraction Procedure ◽  
Resistance Level ◽  
Curing Conditions ◽  
Standard Specimens ◽  
Strength Tests ◽  
Axial Compressive Strength ◽  
The Difference ◽  
Shape Ratio

RESUMO: Este trabalho tem como objetivo avaliar a influência dos fatores de forma nos ensaios de resistência à compressão em testemunhos de concreto. Para isso foram moldadas e extraídas amostras de concreto de 20 e 30 MPa. Variou-se o diâmetro da base das amostras (50 e 100mm) e sua esbeltez (de 1 a 3). Para verificar a diferença entre amostras moldadas e extraídas, no momento da fabricação do concreto foram moldados corpos de prova de 100 x 200 mm e dois blocos de 500 x 630 x 270 mm de onde os testemunhos foram extraídos. Os dados indicam que os valores de resistência à compressão obtidos em testemunhos de 50 mm de diâmetro tenderam a ser mais baixos do que os obtidos com 100 mm. A magnitude desta diferença é afetada pelo nível de resistência do concreto avaliado. Além disso, a resistência dos testemunhos extraídos foi menor ou igual à obtida em corpos de prova moldados, mesmo mantendo as condições de cura constantes entre o bloco e os corpos de prova normalizados. Dessa forma, o que pode ser concluído neste estudo é que, a resistência real da estrutura é minorada pelo procedimento da extração, sendo este influenciado por diversos fatores. Dentre as possíveis variáveis da extração, o diâmetro foi um fator que demonstrou influência significativa na propriedade do material ensaiado
 
 ABSTRACT: This study aims to evaluate the influence of shape ratio in compressive strength tests. Concrete specimens with 20 and 30 MPa was made and extracted. The diameter of the specimen’s base was 50 and 100mm and its slenderness ratio vary 1 to 3. To verify the difference between molded and samples taken at the time of manufacture of concrete molded bodies were evidence of 100 x 200 mm and two blocks of 500 x 630 x 270 mm where witnesses were extracted. The results indicated that the axial compressive strength values obtained with concrete cores extracted of 50 mm diameter tended to be lower than those obtained with 100 mm, and the magnitude of this difference is affected by the resistance level of the evaluated concrete. Furthermore, the resistance of concrete cores extracted was less than or equal to the obtained in the molded test specimens, while maintaining constant the curing conditions between the block and standard specimens. Thus, it can be concluded in this study is that the real strength of the structure is alleviated by the extraction procedure, which is influenced by several factors. Among the possible variables of extraction, the diameter was a factor that showed a significant influence on the property of the material tested.

scholarly journals Alkali-Activated Fly Ashes: Influence of Curing Conditions on Mechanical Strength

2018 ◽  
Vol 3 (2) ◽  
pp. 57-67
Author(s):  
Filipe Almeida ◽  
Nuno Cristelo ◽  
Tiago Miranda ◽  
Castorina S. Vieira ◽  
Maria De Lurdes Lopes ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Relative Humidity ◽  
Mechanical Strength ◽  
Research Groups ◽  
Fly Ashes ◽  
Curing Conditions ◽  
Alkaline Activation ◽  
Strength Tests ◽  
Higher Temperature ◽  
Alkali Activated

Alkaline activation of fly ashes is a procedure that enables an alternative binder which has been receiving much interest by several research groups particularly on the manufacturing of mortars and concretes. The properties of the materials that are developed during the alkaline activation are influenced by the curing conditions (temperature and relative humidity). Another relevant facet related to the curing procedures is the possibility of carbonation occur, which may have an impact on the mechanical strength of the alkaline cements. In this research, several sets of curing conditions were tested to understand which one results in a higher strength and reveals carbonation. Uniaxial compressive strength tests were conducted to assess mechanical behavior. The outcome suggests that higher temperature and low relative humidity yields higher mechanical strength.

scholarly journals Characteristics of Metakaolin-Based Geopolymer with Cathode Ray Tube Glass

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1149
Author(s):  
Marcin Górski ◽  
Natalia Wielgus ◽  
Krzysztof Loska ◽  
Michał Kozioł ◽  
Marcin Landrat ◽  
...  
Keyword(s):  
Compressive Strength ◽  
High Strength ◽  
Optimal Composition ◽  
Curing Conditions ◽  
Temperature Changes ◽  
Strength Tests ◽  
Cathode Ray Tube ◽  
New Material ◽  
Curing Regime ◽  
Mass Loss Temperature

Geopolymers can be treated as an environmentally friendly alternative for concrete and enables utilization of various wastes. This paper focuses on the possibility of application of discarded cathode ray tube (CRT) glass inside a metakaolin-based geopolymer in the form of an aggregate, providing an ecological method of recycling of this hazardous material. The main goal of this paper was to develop an optimal composition of a new geopolymer and to describe its behavior under varying curing conditions. A geopolymer made of different mixtures was subjected to flexural and compressive strength tests. The density, mass loss, temperature changes, and metals leaching were determined as well. The results demonstrated that neither the content of CRT glass nor the curing regime has a significant influence on the mechanical behavior. However, the strength of the geopolymer containing 50% CRT glass by mass increased with time in contrast to a geopolymer with a higher CRT glass content. The development of temperature inside the mixture was dependent on the amount of metakaolin. The concentration of toxic metals in an aqueous extract decreased considerably after the encapsulation of CRT glass inside the geopolymer. The presented results indicate that discarded CRT glass can be considered an aggregate for a metakaolin-based geopolymer. The new material shows high strength and makes the CRT glass safe for the environment.

scholarly journals Effect of Addition of Alccofine on the Compressive Strength of Cement Mortar Cubes

2021 ◽  
Vol 5 (2) ◽  
pp. 155-170
Author(s):  
Balamuralikrishnan R. ◽  
Saravanan J.
Keyword(s):  
Compressive Strength ◽  
Cement Mortar ◽  
River Sand ◽  
Mix Proportion ◽  
Strength Tests ◽  
The Difference ◽  
Glass Wastes ◽  
Cement Strength ◽  
Modern Era

In the modern era, many research works are going on throughout the world for finding suitable cementitious material for the replacement of cement since it causes environmental pollution. In this order Fly ash, Silica fume, GGBS, Metakaolin, Micro materials, Quartz powder, etc. are tried out for replacing partially or fully the cement in concrete. A new ultrafine material called Alccofine (AF) which is manufactured from glass wastes is tried out for replacing partially in this research. Compressive strength is one of the important properties of cement. Strength tests are not made on neat cement paste because of difficulties of excessive shrinkage and subsequent cracking of neat cement. Cement mortar of 1:3 mix proportion is used to cast the cubes having an area of 50 cm2 are used for the determination of compressive strength of cement as per IS: 4031-1988 (Part-6). The graded Indian Standard sand (Ennore Sand -ES) confirming to IS: 650-1991 is used for preparing the cubes. In the same mix proportion, the same size cubes are cast with the River Sand (RS) to study the difference of the compressive strength between the Indian standard sand and river sand. Ordinary Portland cement (OPC) and Portland Pozzolana Cements (PPC) are used. The present study is the influence of Alccofine on cement mortar cubes by replacing the cement by Alccofine with various proportions like 5%, 10%, 15%, 20% were cast and tested in the laboratory as per Indian Standard 4301-1988 (Part-6) and the results were analysed and presented in the form of charts and graphs. It is observed that the early age strength is obtained for all the combinations but 10 percent of Alccofine yields more strength than other dosages. Doi: 10.28991/esj-2021-01265 Full Text: PDF

Experimental Study on Size Effect of Compressive Strength and Deformation Properties of Large Size Fly Ash Concrete

2011 ◽  
Vol 477 ◽  
pp. 319-324 ◽  
Author(s):  
Xi Xi He ◽  
She Yong Lin ◽  
Xue Cheng Zhen
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Size Effect ◽  
Failure Modes ◽  
Slenderness Ratio ◽  
Ultimate Strain ◽  
Fly Ash Concrete ◽  
Deformation Properties ◽  
Axial Compressive Strength ◽  
Strength And Deformation

The authors experimentally studied the size effect of axial compressive properties of concrete cube and slenderness ratio of 2:1 prism with cross-section side length of 100mm to 800mm in this paper. Commercial concrete was used for test specimens. Specimens were cast and cured outdoors. To highlight the size factors, accumulation of sand on the end surface of the specimen was used to eliminate the end cyclo-hoop effect. The test results show that, in the case of eliminating the end restraint, failure modes of the prism and the cube are the same. There isn’t determined relationship between the cubic compressive strength and cylinder axial compressive strength of concrete, in the case of the specimen slenderness ratio not more than 2 to 1. However, the decline trend of cylinder axial compressive strength with size is slightly greater than the cubic strength. Fly ash concrete, ordinary concrete without fly ash and fiber reinforced fly ash concrete show different size effects. Size effect for concrete with 40% fly ash replacement of cement significantly reduced. The experimental results also show that, strength, elastic modulus and ultimate strain of concrete are all size-dependent. But there are different size effect trends between strength and deformation properties. Ultimate strain of concrete decreases as size increases, and more attention should be taken to this point.

scholarly journals Influence of Specimen Size and Shape on the Uniaxial Compressive Strength Values of Rocks

2021 ◽  
Author(s):  
Tatiana Durmeková ◽  
Martin Bednarik ◽  
Petra Dikejová ◽  
Renáta Adamcová
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Rock Specimen ◽  
Slenderness Ratio ◽  
Factors Affecting ◽  
Size And Shape ◽  
Strength Tests ◽  
Ucs Test ◽  
Variable Impact ◽  
Significant Factors

Abstract The most significant factors affecting the results of Uniaxial Compressive Strength (UCS) test are the size, slenderness ratio h/d (ratio of height to diameter), and the shape of the rock specimen. The proposed experimental study shows the variable impact of these parameters on UCS values by implementing several lithological types. Standard strength tests were performed on four lithological types: granodiorite, limestone, sandstone and andesite. Cylindric and cube-shaped test specimens of different sizes were prepared from each rock. Cylindric specimens with diameter 20 mm, 35 mm, 50 mm and 70 mm with height to diameter ratio of 1:1 and 2:1, and cubic and prismatic specimens with an edge dimension of 50 mm were tested and analyzed. Obtained results of strength tests confirmed a high variability of current research opinions on how the size and shape of specimens influence the strength values of rocks. The study revealed the impossibility of conclusive correlations between the UCS and specimens to be generally applicable for all lithological types. Of the observed effects on the strength, the aspect of the specimen slenderness ratio was the most pronounced on all studied rocks.

scholarly journals Study of the influence of jigging of recycled coarse aggregate on the compressive strength of concrete

2020 ◽  
Vol 13 (5) ◽  
Author(s):  
Gabriela Nunes Malysz ◽  
Denise Carpena Coitinho Dal Molin ◽  
Angela Borges Masuero
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Local Market ◽  
Recycled Coarse Aggregate ◽  
Strength Tests ◽  
Before And After ◽  
Axial Compressive Strength ◽  
Selection Of

ABSTRACT: The composition heterogeneity of this type of aggregate is indicated as one of the main restrictions to its potential utilization since it generates great variability in the performance of the types of concrete produced with recycled aggregate. To reduce the use limitations of recycled coarse aggregate (RCA), this study aimed to analyze the use of a jig, a type of equipment used in mining, which performs density separation through air sprinkling in the selection of large aggregates of CDW crushing. To evaluate the equipment performance in the selection of RCA materials, specimens of concrete with recycled aggregate of three different sources were molded before and after selection in the jig, as well as reference concrete with natural aggregate. To measure the performance of the types of concrete produced, axial compressive strength tests were performed. Additionally, a statistical and comparative analysis of the results was performed to seek a better basis for possible conclusions. Analysis of the results of the axial compression strength tests showed that the variability of the recycled aggregates reflected in the inconstancy of the behavior of the concrete produced with them; it was not possible to perceive a common or uniform performance between the three sources of recycled aggregate for the mix design produced. Although some studies point to good separation results with jigging, it was found that with the use of recycled aggregates available in the local market, for the three studied sources, the selection was not able to minimize the variability of the properties of the recycled types of concrete produced with the selected aggregates.

scholarly journals Experimental Study on Deformation Behavior and Compressive Strength of Concrete Cast in Steel Tube Arches under Low-Temperature Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Tuo Shi ◽  
Nianchun Deng ◽  
Xiao Guo ◽  
Wen Xu ◽  
Shi Wang
Keyword(s):  
Compressive Strength ◽  
Low Temperature ◽  
Performance Test ◽  
Large Diameter ◽  
Test Site ◽  
Steel Tube ◽  
Design Strength ◽  
Curing Conditions ◽  
Expansive Agent ◽  
Arch Bridges

Taking the construction of a concrete-filled steel tube (CFST) arch bridge (part of the Sichuan-Tibet Railway) in low temperatures as the test site, firstly the deformation performance test of concrete was carried out. Following this initial testing, measurement of compressive strength and shrinkage performance was conducted in large-diameter CFSTs under a variety of curing conditions. Experimental results showed that the expansion effect of Ca-Mg composite expansive agent in concrete was better than that of other expansive agents at any stage. Under low-temperature curing (0°C), the sampling strength of the large-diameter CFSTs reached 73.5% of the design strength at 28 d in the presence of a nonthermal curing system. The design strength itself was reached, when a curing system involving a thermal insulation film was applied, and use of this film also led to improvements in concrete shrinkage. The results suggested that a Ca-Mg composite expansive agent, combined with an insulation film curing system, should be the technique selected for concrete pumping construction of CFST arch bridges in Tibet.

scholarly journals Strengthening Effect of the External Prestressing Method That Simulated a Deterioration Bridge

2021 ◽  
Vol 11 (6) ◽  
pp. 2553
Author(s):  
Sang-Hyun Kim ◽  
Jong-Sup Park ◽  
Woo-Tai Jung ◽  
Jae-Yoon Kang
Keyword(s):  
Compressive Strength ◽  
Strengthening Effect ◽  
Reinforcement Effect ◽  
Loading Test ◽  
Yield Load ◽  
Existing Structures ◽  
External Prestressing ◽  
The Difference ◽  
Existing Structure ◽  
Strengthening Method

Various methods for strengthening existing structures have been developed owing to the increase in human and property damages caused by the deterioration of structures. Among the various reinforcing methods, the external prestressing method increases the usability and safety of a structure by directly applying tension to the weak tensile area that suffers the greatest deflection during the structure usage. The external prestressing method is advantageous in reducing cracks caused by the introduced tension and restoration of the deflection. Since the strengthening method is applied to deterioration bridges, the strengthening effect is affected by the condition of the existing structure. However, studies on the strengthening effect according to the degree of deterioration are insufficient. Therefore, the behavior according to the strengthening status was analyzed, and the strengthening effect was identified in this study by simulating the deteriorated bridge, reducing the compressive strength and reinforcement quantity, and conducting a four-point loading test. As a result of the experiment, a reinforcement effect of 215% crack load, 161% yield load, and the difference in behavior according to the reinforcement parameters were confirmed.

Measurement of high-alumina cement-calcium carbonate reactions using DTA

Clay Minerals ◽  
1984 ◽  
Vol 19 (5) ◽  
pp. 857-864 ◽  
Author(s):  
H. G. Midgley
Keyword(s):  
Compressive Strength ◽  
Calcium Carbonate ◽  
High Alumina ◽  
Curing Time ◽  
Lower Strength ◽  
Alumina Cement ◽  
High Alumina Cement ◽  
Strength Tests ◽  
The Stability

AbstractHydrating high-alumina cement will react with calcium carbonate to form the complex mineral calcium carboaluminate hydrate, 3CaO.Al2O3.CaCO3.12H2O. This mineral is reported to be capable of providing strength in concrete and so may provide an alternative to the minerals normally found in the hydration of high-alumina cement, which may under certain conditions convert to other minerals with a loss in strength. Some doubt has been cast on the stability of calcium carboaluminate hydrate and it has been found that in hydrated high-alumina cement, calcium carboaluminate hydrate decomposes at temperatures in excess of 60°C. Cube compressive strength tests on high-alumina cement and high-alumina cement-calcium carbonate pastes have shown that the latter have a lower strength than pastes made with high-alumina cement alone. When cured at 50°C the high-alumina cement-calcium carbonate pastes show a loss in strength with curing time. Cements made with the high-alumina cement-calcium carbonate mixture always have a lower strength than those made with high-alumina cement alone and so no advantage is gained from their use.

Sign in / Sign up

Export Citation Format

Share Document