scholarly journals Effect of varying silica-limestone sand fines on the physical-mechanical performance of concrete

2021 ◽  
Vol 16 (59) ◽  
pp. 580-591
Author(s):  
Tarek Djedid ◽  
Mohammed Mani ◽  
Abdelkader Ouakouak ◽  
Abdelhamid Guettala
Keyword(s):  
Mechanical Characteristics ◽  
Mechanical Performance ◽  
Capillary Absorption ◽  
River Sand ◽  
Ordinary Concrete ◽  
Statistical Relationships ◽  
Limestone Sand ◽  
Limestone Fines ◽  
Mechanical Strengths ◽  
Crushed Limestone

The use of crushed limestone sand in the concrete industry will be quite possible and imperative for environmental reasons. Many researchers around the world have found that concrete based on 50% substitution of river sand by limestone sand gives better physico-mechanical characteristics. The main objective of this investigation is to search for an optimal percentage of silica-limestone fines resulting from the substitution of half in quantity of alluvial sand by crushed limestone sand in ordinary concrete. The proportions of fines that were tested in this work are 6%, 8%, 10%, 12% and 14%. The obtained results revealed that concrete based on silica-limestone sand and containing 14% of the same type of fines strongly improves the different mechanical strengths and participates in the reduction of 10% and 13%, of the coefficient of capillary absorption and of the porosity accessible to water, respectively, compared to the control concrete. In addition, good statistical relationships between the studied parameters were also found

Weldability - Behavior of Welded Reinforcement

2019 ◽  
Vol 70 (10) ◽  
pp. 3469-3472
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Mechanical Characteristics ◽  
Mechanical Performance ◽  
Current Work ◽  
Carbon Equivalent ◽  
Work Process ◽  
Ultimate Limit

Weldability involves two aspects: welding behavior of components and safety in operation. The two aspects will be reduced to the mechanical characteristics of the elements and to the chemical composition. In the case of steel reinforcing rebar’s, it is reduces to the percentage of Cech(carbon equivalent) and to the mechanical characteristics: the yielding limit, the ultimate limit, and the elongations which after that represent the ductility class in which the re-bars is framed. The paper will present some types of steel reinforcing rebar’s with its mechanical characteristics and the welding behavior of those elements. In the current work, process-related behavior of welded reinforcement, joint local and global mechanical properties, and their correlation with behavior of normal reinforcement and also the mechanical performance resulted in this type of joints. Keywords: welding behavior, ultimate limit, reinforcing rebar’s

Comparison of Superpave and Marshall Mixtures for Low-Volume Roads and Shoulders

1998 ◽  
Vol 1609 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Affan Habib ◽  
Mustaque Hossain ◽  
Rajesh Kaldate ◽  
Glenn Fager
Keyword(s):  
Mix Design ◽  
River Sand ◽  
Low Volume Roads ◽  
Superpave Gyratory Compactor ◽  
Asphalt Content ◽  
Low Volume ◽  
Project Site ◽  
Axle Loads ◽  
Crushed Limestone ◽  
Asphalt Film

Superpave and Marshall mix designs using local aggregates were done to study the suitability of the Superpave mix design as compared with the Marshall mix design for low-volume roads, especially shoulders. The project site was Kansas Route 177 in northeast Kansas. Three locally available aggregates, crushed limestone and coarse and fine river sands, were used in this study. Five blends with varying proportions of coarse and fine river sands were selected. Mix samples were compacted in the Superpave gyratory compactor with the applicable number of gyrations and were compacted with the Marshall hammer by using 50 blows per face. Bulk densities of the compacted samples and maximum specific gravities of loose samples also were measured for each blend. The results show that the Superpave mix design for low-volume roads and shoulders results in lower estimated asphalt content than does the Marshall method. The required asphalt content increases as the proportion of coarse river sand increases in the mix. Superpave requirements for the voids filled with asphalt (VFA) for low-volume traffic, that is, less than 0.3 million equivalent single-axle loads, appeared to be too high. High asphalt film thicknesses were computed for the mixtures that did not meet the Superpave VFA requirements. Lowering the design number of gyrations (Ndes) for compaction of samples would result in increased asphalt requirement for the Superpave mixture with a given gradation.

Mechanical Performance of Steam-Cured Self-Compacting Concrete Incorporating Silica Fume and Limestone Powder

2021 ◽  
Vol 56 ◽  
pp. 111-122
Author(s):  
Youcef Ghernouti ◽  
Bahia Rabehi ◽  
Sabria Malika Mansour
Keyword(s):  
Heat Treatment ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Limestone Powder ◽  
Maximum Temperature ◽  
Self Compacting Concrete ◽  
Curing Period ◽  
Heat Treated ◽  
Binder Ratio ◽  
Mechanical Strengths

In this paper, influence of heat treatment on evolution of mechanical strengths at early age, less than 24hours of self-compacting concretes containing limestone powder and silica fume as fine materials was investigated experimentally. Two compositions of self-compacting concrete have been studied; the first is elaborated with silica fume addition and the second with limestone powder, each mixture were prepared with a constant water/binder ratio of 0.39. Concrete samples were either cured in water at (23±1°C), or steam cured at 65°C maximum temperature over six hours (6h) curing period. Tests of mechanical strengths were performed on specimens cooled down slowly to room temperature after heating.The obtained results show that all self-compacting mixtures exhibited satisfying fresh properties and check EFNARC specifications of self-compacting concrete (slump flow diameter higher than 650mm, L-box ratio higher than 80% and sieve stability less than 17%).Mechanical strengths of concrete containing limestone addition are slightly lower than those of concrete based on silica fume at all ages. Moreover, heat treatment generates an improvement of compressive and flexural strength. Interesting compressive strengths are obtained. At 24 hours, after heat treatment, the strengths are already greater than 35 MPa. The values ​​are 37 MPa and 40 MPa for self-compacting concrete containing limestone powder and silica fume respectively compared to 40 MPa and 46 MPa obtained at 7 days for the corresponding non-heat treated concretes. Compressive strength gain of SCCs mixtures with limestone powder and with silica fume, undergoing heat treatment at the age of 24hours is 85% and 75% respectively compared to SCCs mixtures cured in water.

scholarly journals Adherence between steel bars and lightweight concrete with EPS beads

2017 ◽  
Vol 10 (1) ◽  
pp. 122-140
Author(s):  
A. L. SARTORI ◽  
L. M. PINHEIRO ◽  
R. M. DA SILVA ◽  
S. B. FREITAS ◽  
T. G. CESAR
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Mechanical Characteristics ◽  
Lightweight Concrete ◽  
Monotonic Loading ◽  
Adherence Behavior ◽  
Ordinary Concrete ◽  
Cylinder Test ◽  
Pull Out ◽  
Steel Bars

Abstract This paper describes the adherence behavior of a structural lightweight concrete with EPS beads (SLCEB) in a monotonic loading, based in a bibliographic review and in pull-out tests. The results of these SLCEB tests were compared with those of an ordinary concrete (OC) and with the values based in indications of the Brazilian code ABNT NBR 6118:2014 - Design of concrete structures. The pull-out tests of two batches of SLCEB and one of OC were analyzed, in a total of 60 tests. Mechanical characteristics were determined too, such as: compressive strength and tensile strength in split cylinder test. The calculated results according to the above mentioned standard were very different from those obtained in the tests, indicating that the theoretical values are more conservative than the experimental ones. It was also verified that it is possible to use SLCEB in structures with respect to the adequate adherence of reinforcement in the concrete.

scholarly journals Thermal and mechanical behavior of composite mortars containing natural sorptive clays and fly ash

2019 ◽  
Vol 51 (1) ◽  
pp. 39-56 ◽  
Author(s):  
Anja Terzic ◽  
Lato Pezo ◽  
Ljiljana Milicic ◽  
Nevenka Mijatovic ◽  
Zagorka Radojevic ◽  
...  
Keyword(s):  
Fly Ash ◽  
Mechanical Behavior ◽  
Mechanical Performance ◽  
Thermal Characteristics ◽  
Principal Component ◽  
Effective Dosage ◽  
Factor Space ◽  
Ann Model ◽  
River Sand ◽  
Mineral Additives

Mineral additives are extensively applied as cement replacement materials in both construction concrete and mortar. Fly ash is one of the most commonly utilized additives which improve rheological properties, as well as thermal and mechanical behavior of mortar, and as such it has been widely investigated. This industrial byproduct comprises heavy metals in its composition; therefore further research is needed to optimize its effective dosage. Moreover, certain sorptive clays, such as natural zeolite and bentonite, can prevent migration of toxic elements from fly ash by immobilizing them in their structure. Ten experimental mortars are prepared with Portland cement, river sand and addition of fly ash, zeolite and/or bentonite in accordance with chemometric experimental design rules. The aim of the study was to investigate the effect of mineral additives on thermal and mechanical performances of mortar. Thermal characteristics were monitored via dilatometric analysis and DTA method. Principal component analysis was used on the results of physico-mechanical testing (workability, bulk density, water absorption, shrinkage, compressive and flexural strength) to enable the divisions of the observed samples into groups in the factor space. The performance of Artificial Neural Network was compared with the experimental data in order to develop rapid and accurate method for prediction of mechanical parameters of mortar. The ANN model showed high overall prediction accuracy (r2 = 0.989, during training cycle). The test results indicate that incorporation of the mineral additives gave cost effective mortars with sufficiently good properties. However, tools of analytical modeling highlighted mortar with zeolite and fly ash as the optimal composition regarding its mechanical performance.

Non-Destructive Tests as Durability Indicators in Cement Mortars with Pozzolanic Substitutions

2017 ◽  
Vol 902 ◽  
pp. 9-13
Author(s):  
Rosalía Ruiz Ruiz ◽  
Elia Mercedes Alonso Guzmán ◽  
Wilfrido Martínez Molina ◽  
Hugo Luis Chávez García ◽  
Judith Alejandra Velázquez Perez
Keyword(s):  
Mechanical Characteristics ◽  
Ultrasonic Pulse Velocity ◽  
Good Alternative ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Industry ◽  
Capillary Absorption ◽  
Pozzolanic Material ◽  
Cement Mortars ◽  
Non Destructive

Cement industry is responsible of 5-7% of CO2 emissions to the atmosphere. This is preoccupant because this is one of the greenhouse effect gases which cause global warming. Pozzolanic material incorporation in cement mortars elaboration represents a good alternative to partially substitute cement, since its chemical composition could contribute to improvement of its durability and mechanical characteristics. In this research, mortars with pozzolanic substitutions are evaluated through non-destructive tests as: capillary absorption, electrical resistivity, and ultrasonic pulse velocity to the age of 1000 days. The results suggested that the incorporation of pozzolanic material as partial substitutes of Portland cement increases the mortars properties mainly in substitutions of CBC 20%, PN 10, and 30%.

Mechanical Performance Research on Modified Cement Concrete with Recycled Plastic Particles

2012 ◽  
Vol 450-451 ◽  
pp. 650-654
Author(s):  
Jian Hong Di ◽  
Zhan Liang Liu ◽  
Jun Jun Li
Keyword(s):  
Bending Strength ◽  
Mechanical Performance ◽  
Research Result ◽  
Basic Material ◽  
Fine Aggregate ◽  
Cement Concrete ◽  
Performance Indexes ◽  
Mechanical Strengths ◽  
Performance Research ◽  
Addition Amount

In order to improve the concrete performance and research the greenmaterial, the recycled ABS/PC plastic particles will be added into the cement concrete as a modifier. In this research, the C30 cement concrete was taken as the basic material, the fine aggregate in cement concrete was substituted by different amounts of recycled plastic particles. The change law of mechanical performance indexes（including cubic compressive strength. Splitting tensile strength，bending strength）were researched. The research result showed the recycled plastic particles, as a modifier, can improve mechanical performance of the cement concrete greatly. In the five addition amounts，including 0%, 2%, 5%, 8%, 11%，the three mechanical strengths will all increases at first then decreases with the addition amount increasing. When the addition amount is 5%, the three mechanical strength indexes will all reach the maximum.

Development of Bio-Based Foams With Improved Acoustic and Mechanical Performance

2012 ◽  
Author(s):  
Shahrzad Ghaffari Mosanenzadeh ◽  
Hani E. Naguib ◽  
Chul B. Park ◽  
Noureddine Atalla
Keyword(s):  
Mechanical Characteristics ◽  
Mechanical Performance ◽  
Water Soluble ◽  
Huge Amount ◽  
Open Cell ◽  
Acoustic Performance ◽  
Foam Morphology ◽  
Open Cell Foams ◽  
Weak Structure ◽  
Highly Porous

Interest in noise control has been growing in recent years and efforts are under way to improve the acoustic performance of existing sound absorbers and also to replace the non-recyclable ones with environmentally friendly materials. Present study describes the research on fabrication, improvement of acoustic absorption and enhancement of mechanical strength of bio-based open-cell foams. Through this study, highly porous open-cell Polylactide (PLA) foams were fabricated by a new fabrication method combining particulate leaching technique and compression molding. Foamed structures were fabricated with PLA and Polyethylene glycol (PEG) with salt as the particulate. Pore size of the foam was controlled by salt particulates and higher interconnectivity was achieved by the co-continuous blending morphology of PLA matrix with water-soluble PEG. As a result of novel secondary porous structure, acoustic performance of PLA foams was successfully improved. One issue with application of bio-based open-cell foams is the weak structure. To improve mechanical characteristics of PLA foams, different polymer composites of PLA and Polyhydroxyalkanoate (PHA) were foamed and characterized in terms of acoustic performance, mechanical properties and foam morphology. Polymers used in this study are bio-based which is of great importance considering huge amount of foams used as acoustic absorbers in various industries.

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