INFLUENCE OF COARSE AGGREGATES AND MORTAR MATRIX ON PROPERTIES OF LIGHTWEIGHT AGGREGATE CONCRETES

2020 ◽  
Vol 19 (75) ◽  
Author(s):  
Hoang Vinh Long
Keyword(s):  
Lightweight Aggregate ◽  
Coarse Aggregates ◽  
Mortar Matrix

scholarly journals Influence of Coarse Aggregate Gradation on the Mechnical Properties of Concrete, Part I: No-Fines Concrete

2019 ◽  
Vol 9 (5) ◽  
pp. 4612-4615 ◽  
Author(s):  
Z. A. Tunio ◽  
F. U. R. Abro ◽  
T. Ali ◽  
A. S. Buller ◽  
M. A. Abbasi
Keyword(s):  
Coarse Aggregate ◽  
Lightweight Concrete ◽  
Lightweight Aggregate ◽  
Fine Sand ◽  
Minimum Size ◽  
Unit Weight ◽  
Lightweight Aggregate Concrete ◽  
Total Load ◽  
Aggregate Gradation ◽  
Coarse Aggregates

It is well-accepted fact that in concrete construction, the self-weight of the structure is a major part of its total load. Reduction in the unit weight of the concrete results in many advantages. The structural lightweight aggregate concrete (LWAC) of adequate strength is now very common in use. In frame structures, the partition walls are free of any loading, where the construction of these non-structural elements with lightweight concrete of low strength would lead to the subsequent reduction of the overall weight of the structure. No-fines concrete is one of the forms of lightweight concrete and it is porous in nature. It can be manufactured similarly as normal concrete but with only coarse aggregates and without the sand. Thus, it has only two main ingredients; the coarse aggregates and the cement. The coarse aggregates are coated with a thin cement paste layer without fine sand. This is a detailed experimental study carried on NFC with fixed cement to the aggregate proportion of 1:6 with w/c 0.40 ratio. In this study, coarse aggregate of  various gradations (7-4.75) mm, (10-4.75) mm, (10-7) mm, (13-4.74) mm, (10-7) mm, (13-4.75) mm, (13-10) mm, (13-7) mm, (20-4.75) mm, (20-7) mm, (20-10) mm, (20-13) mm, are used, where prefix and suffix show the maximum and minimum size of the aggregate. The cube and cylinder specimens of standard sizes are cast to determine the compressive strength and splitting tensile and the specimens are cured in water up to the age of testing (28 days).

scholarly journals Lightweight concrete with Algerian limestone dust: Part I: Study on 30% replacement to normal aggregate at early age

Cerâmica ◽  
2013 ◽  
Vol 59 (352) ◽  
pp. 600-608 ◽  
Author(s):  
S. Kitouni ◽  
H. Houari
Keyword(s):  
Tensile Strength ◽  
Lightweight Concrete ◽  
Concrete Strength ◽  
Young Modulus ◽  
Lightweight Aggregate ◽  
Coarse Aggregates ◽  
Flexural Tensile Strength ◽  
Strength Tests ◽  
Mechanical Performances ◽  
Limestone Dust

The mechanical characteristics of the lightweight aggregate concretes (LWAC) strongly depend on the proportions of aggregates in the formulation. In particular, because of their strong porosity, the lightweight aggregates are much more deformable than the cementations matrix and their influence on concrete strength is complex. This paper focuses on studying the physical performance of concrete formulated with substitution of 30% of coarse aggregates by limestone dust. In this article an attempt is made to provide information on the elastic properties of lightweight concrete (LWC) from tests carried out under uniaxial compression conditions. The results of Young modulus, Poisson's ratio, and compressive and flexural tensile strength tests on concrete are presented. The concretes obtained present good mechanical performances reaching 34.99 MPa compressive strength, 6.39 MPa flexural tensile strength and in front of 36 MPa Young modulus.

scholarly journals Assessment of Engineering Properties of Artificial Aggregate Prepared From Canal Silt

2019 ◽  
Vol 8 (II) ◽  
Author(s):  
Safdar Iqbal ◽  
Beenish Jehan ◽  
Fasih Ahmed Khan ◽  
Hassan Nasir
Keyword(s):  
Polyvinyl Alcohol ◽  
Cement Content ◽  
Lightweight Aggregate ◽  
Dry Weight ◽  
Engineering Properties ◽  
Coarse Aggregates ◽  
Particles Size Distribution ◽  
Index Terms ◽  
Natural Aggregates ◽  
Aggregate Shape

In this research the canal silt from the Kabul River Canal was recycled to manufacture artificial aggregate. For making artificial aggregates three batches were prepared each of dry weight of 100kg. The composition of artificial aggregate is Polyvinyl Alcohol (PVA), Ordinary Portland Cement (OPC) and Silt was mixed in different proportions (by weight). Three batches were made having values of PVA varying from 0, 1 and 2 percent, cement content was 20, 19 and 18 percent respectively, and the quantity of silt used was kept constant (80%) in each batch. Samples were prepared from these three different batches and were cured for 28 days. After completion of the curing time, they were crushed to get the desired course aggregate. A number of tests were performed to check the viability of artificial aggregates for being used as a lightweight aggregate. Shape and particles size distribution properties of artificial aggregates were as that of the natural aggregate but not satisfactory at high silt content. The reductions in the specific gravity of the artificial aggregate were also observed compared to natural aggregates.   Index Terms— Artificial Aggregates, Canal Silt, Coarse Aggregates, Lightweight Aggregates, Polyvinyl Alcohol (PVA).

The Relationship between Mechanical Properties and Shrinkage of the Concretes Used in Florida

2012 ◽  
Vol 204-208 ◽  
pp. 3799-3804
Author(s):  
Yan Jun Liu ◽  
Mang Tia
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Empirical Relationship ◽  
Lightweight Aggregate ◽  
Shrinkage Strain ◽  
Coarse Aggregates ◽  
Concrete Mixtures ◽  
The Relationship ◽  
Mineral Additives

This paper investigated the mechanical strength and shrinkage properties of the concrete mixtures frequently used in Florida. The concrete mixtures were proportioned with three different types of coarse aggregates, such as Miami Oolite limestone, Georgia granite and Stalite lightweight aggregate, and two mineral additives, including fly ash and slag. And fourteen concrete mixtures were evaluated on their characteristics of compressive strength, elastic modulus and shrinkage for 91 days. The empirical relationship between the mechanical properties of concretes and shrinkage strain was analyzed mathematically. The results indicate that the compressive strength and elastic modulus of concrete are exponentially related the shrinkage strain of concrete. The finding from this study is agreeable with that by Troxell et al [5]. Also, the effectiveness of ACI 209 and CEB-FIP models on predicting the shrinkage behavior of concretes used frequently in Florida was evaluated. The result indicates that CEB-FIP model gives more reliable prediction than ACI 209 model does.

Effect of Coarse Aggregate Type on the Residual Velocity of Rigid Projectile Perforating Concrete Target

2014 ◽  
Vol 527 ◽  
pp. 7-12
Author(s):  
Zhao Jun Zhang ◽  
Xiao Ming Wang ◽  
Wen Bin Li
Keyword(s):  
Finite Element ◽  
Coarse Aggregate ◽  
Interfacial Transition Zone ◽  
Finite Element Code ◽  
Residual Velocity ◽  
3D Finite Element ◽  
Coarse Aggregates ◽  
Rigid Projectile ◽  
Concrete Model ◽  
Mortar Matrix

Algorithms for generating and distributing random 3D sphere coarse aggregates were proposed. The 3D finite element mesoscale concrete model, which consists of mortar matrix and coarse aggregates, was established based on the theory of background element and material identification. The interfacial transition zone was simplified as a kind of contact between elements. Based on this model, continuous finite element code was used to simulate the process of rigid projectiles perforating concrete targets and the effect of 3 different coarse aggregate types on residual velocities was analyzed. This work indicates that the strength and density of coarse aggregates affects the residual velocity under lower and higher impact velocity respectively.

MESOSCALE MODELING OF CONCRETE UNDER DYNAMIC SPLIT TENSION

2013 ◽  
Vol 07 (03) ◽  
pp. 1350028 ◽  
Author(s):  
XIAO-QING ZHOU ◽  
YONG XIA
Keyword(s):  
Coarse Aggregate ◽  
Mesoscale Model ◽  
Aggregate Size ◽  
Concrete Specimen ◽  
Generation Process ◽  
Concrete Material ◽  
Aggregate Distribution ◽  
Coarse Aggregates ◽  
Wave Distribution ◽  
Mortar Matrix

In this paper, a mesoscale model is adopted to simulate concrete behavior under dynamic split tension. The concrete material is assumed to comprise coarse aggregates, mortar matrix, and an interfacial transition zone (ITZ). In the mesh generation process, random coarse aggregate particles are generated from a certain aggregate size distribution and then placed into the mortar matrix with ITZ between the coarse aggregate edge and the mortar matrix. Different aggregate shapes, such as circular, oval, and polygons are modeled to analyze the gravel and crushed stone aggregates. Numerical simulation is used to model the dynamic damage responses of a typical cylinder concrete specimen and a cube specimen under split tension. Velocity boundary is added as the dynamic loading. Reasonable tensile stress–strain relationships are obtained at the macroscale level; and the detailed stress wave distribution and the crack pattern are obtained at the mesoscale level. These numerical results agree well with conventional experimental results. It also shows that cracks are affected by aggregate distribution.

LWA as Internal Curing Agent to Control Availability of Internal Curing Water in Concrete

2013 ◽  
Vol 1612 ◽  
Author(s):  
Luis Emilio Rendon ◽  
Montserrat Rendon ◽  
Norma Ramirez
Keyword(s):  
Lightweight Aggregate ◽  
Normal Weight ◽  
Internal Curing ◽  
Appreciable Effect ◽  
Curing Agent ◽  
Concrete Compressive Strength ◽  
Concrete Shrinkage ◽  
Coarse Aggregates ◽  
Paste Content ◽  
High Absorption

ABSTRACTThe effectiveness of lightweight aggregate (LWA) as an internal curing agent (ICA) to reduce concrete shrinkage is evaluated for repair concrete used in cultural heritage works (RCCHW) using curing periods of 30 days. Normal weight aggregate is replaced by LWA at volume replacement levels ranging from 10 to 14%. The mixtures contain Portland cement maintaining the paste content at approximately 24.1% of concrete volume. Comparisons are made with mixtures containing low-absorption granite and high-absorption limestone normal weight coarse aggregates. At the replacement levels used in this study, LWA results in a small reduction in concrete density, no appreciable effect on concrete compressive strength, and a decrease in concrete shrinkage for drying periods up to 30 days. With a curing period of 14 days, all mixtures with LWA exhibited less shrinkage than the mixtures with either low- or high-absorption normal weight aggregates.

scholarly journals Mechanical and Electrical Characteristics of Lightweight Aggregate Concrete Reinforced with Steel Fibers

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6505
Author(s):  
Se-Hee Hong ◽  
Jin-Seok Choi ◽  
Tian-Feng Yuan ◽  
Young-Soo Yoon
Keyword(s):  
Electrical Conductivity ◽  
Lightweight Aggregate ◽  
Steel Fibers ◽  
Lightweight Aggregate Concrete ◽  
Electrical Characteristics ◽  
Shielding Effectiveness ◽  
Aggregate Concrete ◽  
Conductive Materials ◽  
Coarse Aggregates ◽  
Steel Rebars

There is increased interest in applying electromagnetic (EM) shielding to prevent EM interference, which destroys electronic circuits. The EM shielding’s performance is closely related to the electrical conductivity and can be improved by incorporating conductive materials. The weight of a structure can be reduced by incorporating lightweight aggregates and replacing the steel rebars with CFRP rebars. In this study, the effects of lightweight coarse aggregate and CFRP rebars on the mechanical and electrical characteristics of concrete were investigated, considering the steel fibers’ incorporation. The lightweight coarse aggregates decreased the density and strength of concrete and increased the electrical conductivity of the concrete, owing to its metallic contents. The steel fibers further increased the electrical conductivity of the lightweight aggregate concrete. These components improved the EM shielding performance, and the steel fibers showed the best performance by increasing shielding effectiveness by at least 23 dB. The CFRP rebars behaved similarly to steel rebars because of their carbon fiber content. When no steel fiber was mixed, the shielding effectiveness increased by approximately 2.8 times with reduced spacing of CFRP rebars. This study demonstrates that lightweight aggregate concrete reinforced with steel fibers exhibits superior mechanical and electrical characteristics for concrete and construction industries.

scholarly journals Performance and Microstructural Analysis of Lightweight Concrete Blended with Nanosilica under Sulfate Attack

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Paola Vargas ◽  
Natalia A. Marín ◽  
Jorge I. Tobón
Keyword(s):  
Compressive Strength ◽  
Porous Structure ◽  
Magnesium Sulfate ◽  
Lightweight Concrete ◽  
Microstructural Analysis ◽  
Lightweight Aggregate ◽  
Sulfate Solution ◽  
Pore System ◽  
Coarse Aggregates ◽  
Strength And Durability

The influence of two lightweight aggregates (LWA) on concrete and the effects of cement substitution for nanosilica (NS) on the interfacial transition zone (ITZ) and cementitious matrix of concrete in resistance to attacks by magnesium sulfate (MgSO4) are researched in this work. The aggregates evaluated were perlite, which is a lightweight aggregate of open porous structure, and expanded clay (aliven) with closed porous structure. The variables included in the study were replacement percentage of coarse aggregates by lightweight coarse aggregates (0 and 100% by volume) and replacement percentage of cement by nanosilica (0 and 10% by weight). In the dosage of the mixtures, water/cementitious-material ratio constant of 0.35 was used. The LWA were characterized by XRD, XRF, and SEM techniques. Compressive strength, water absorption, and volume change in magnesium sulfate solution (according to ASTM C1012 for a period of 15 weeks) of lightweight concretes were evaluated. It was found that the nanosilica had effect on refinement in the pore system; however, the main incidence on the compressive strength and durability of lightweight concrete (LWC) was defined by the characteristics of lightweight aggregate used in its preparation.

Study of Prediction Model for Compressive Strength of Lightweight Aggregate Concrete

2011 ◽  
Vol 335-336 ◽  
pp. 1204-1209 ◽  
Author(s):  
H. Z. Cui
Keyword(s):  
Compressive Strength ◽  
Prediction Model ◽  
Volume Content ◽  
Particle Density ◽  
Lightweight Aggregate ◽  
Shape Index ◽  
Lightweight Aggregate Concrete ◽  
Crushing Strength ◽  
Aggregate Concrete ◽  
Mortar Matrix

This paper presents studies of prediction of compressive strength of lightweight aggregate concrete (LWAC). In order to choose the optimized prediction model, the prediction models based on different parameters, which included compressive strength of mortar matrix, volume content of lightweight aggregate (LWA), crushing strength of LWA, particle density of LWA and shape index of LWA, were analyzed and compared. For LWAC, due to the effect of LWA on LWAC is more obvious than the effect of mortar matrix, therefore, a prediction model that just used LWA properties to serve as parameters of prediction model can predict LWAC strength. The LWA properties included volume content, crushing strength, particle density and shape index. As long as the LWA properties are known, the advantage of the model is that LWAC strength can be predicted. The best prediction discrepancy of 12.9% compared with the experimental results.

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