Normal Weight Aggregate Research Articles

Performance of Lightweight Aggregate Concrete Containing Expanded Polystyrene, Cinder and Silica Fume

Lightweight aggregate concrete is developed by substituting normal weight aggregate either fully or partially based on required strength and density. Expanded polystyrene (EPS) bead is a type of low density material, which also has good energy-absorbing characteristics and can be used as light weight aggregate in concrete. In the present study, Structural lightweight aggregate concrete (SLWAC) was produced by fully replacing normal weight aggregate with combinations of EPS beads to Cinder by the ratio 20:80, 40:60, 60:40, 80:20 respectively and Silica fume was used as supplementary cementitious material. The resulting concrete had strength variation between 24.85 to 12.01 MPa, and the density variation of 1896 to 1664 kg/m3. Considering strength and density criteria 40:60 ratios was observed as the optimal mix. The Compressive strength acquired by concrete was inversely proportional to the volume of EPS beads. Effect of fibres on mechanical properties such as flexural strength, compressive strength, and split-tensile strength was investigated on optimal mix by using polypropylene fibres, it was observed that a 13.24% increase in flexural strength at 1% fibres, 8.41% increase in Compressive strength at 1% fibres and 23.11% increase in split-tensile strength at 1% fibres. Along with these, durability tests such as water absorption and permeability tests were performed, the performance of this concrete in water absorption test and permeability is well within the acceptable limits as the EPS ratio in the concrete increased, the absorption and depth of penetration values increased considerably. Microscopic observations were also made to study the interface amongst the cement paste and aggregates. It was revealed that silica fume has influenced significantly in bonding with EPS beads.

Effect of Mineral Admixture, W/B Ratio and Elevated Temperature on Strength of Lightweight Expanded Clay Aggregate Concrete

Abstract: The present paper focused on development ofstructural lightweight concrete by using light weight expandedclay aggregate (LECA) with unit weight of 1700 kg/m3 to 1900kg/m3 and compressive strength of 40 MPa. In this study,investigation was done using LECA as coarse aggregate inconcrete by replacing normal aggregate in three differingvolume fractions i.e., 30%, 40% and 50% with different w/bratios 0.40, 0.50 and 0.60 to produce lightweight expanded clayaggregate concrete (LECAC) with addition of chemicaladmixture. For that, concrete mix design was done using ISmethod and replacement of lightweight aggregate wascalculated based on volume batching. The effect of mineraladmixture (i.e., 10% microsilica) on the properties oflightweight expanded clay aggregate concrete and normalweight aggregate concrete such as workability of freshconcrete, compressive strength and flexural strength ofconcrete were compared. The studies also include the effect ofelevated temperature on light weight expanded clay aggregateconcrete and normal weight aggregate concrete.Index Terms: Normal weight aggregate concrete (NWAC),Light weight expanded clay aggregate (LECA). Light weightexpanded clay aggregate concrete (LECAC), Elevatedtemperature.

A review on concrete filled tubular sections using self compacting concrete

Concrete filled tubular section (CFT’s) is a composite column of hollow steel and concrete filled into it. This composite action of concrete and steel gives better performance under service. CFT’s carries higher loads as compared to steel column and conventional reinforced concrete, due to this property CFT’s are highly recommended for tall structures. CFT’s can provide more carpet area as compared to the RCC column due to cross section reduction in CFT’s. Study shows that for high rise buildings composite construction is economical. CFT’s are filled with normal concrete where the filling problems arise due to dense reinforcement or smaller cross section or the distance between two profiles are less, self compacting concrete (SCC) can be recommended due to its workability. The previous researcher shows a comparison between normal concrete, SCC and light weight aggregate concrete inside CFT’s with L/D and D/t ratios and different curing techniques for SCC.

Assessment of the Effect of Replacing Normal Aggregate by Porcelinite on the Behaviour of Layered Steel Fibrous Self-Compacting Reinforced Concrete Slabs under Uniform Load

In this research, an attempt has been made to study the effect of replacing all normal-weight aggregate “NWA” by lightweight aggregate “LWA” (having a volume equal to 60% of the volume of normal-weight aggregate) on the behaviour of layered steel fibrous self-compacting reinforced concrete slabs with various volume fractions of steel fiber under uniform area load using fine sand technique. The experimental work consists of two groups “NWA” and “LWA,” each group consists of three slab specimens (having an aspect ratio equal to the golden ratio, i.e., 1.618), the thickness of each slab is divided into two equal layers, the top layer is free from steel fibers, while the steel fibers exist only in the bottom layer with three volume fractions (0%, 0.4%, and 0.8%). Ultimate uniform load of the slabs decreases with the increase in steel fiber content, while the percentage of decrease in the bulk density remains rather constant. It was also found that the ultimate uniform load of the slabs in each group is significantly improved with increasing steel fiber content, and the percentage of this improvement is higher in lightweight concrete “LWC” than in normal-weight concrete “NWC” Finally, it was noticed that when steel fiber increased, the flexural strength of slabs increased higher than shear strength; therefore, the mode of failure has been changed from bending to shear mode for slabs of both groups “NWC” and “LWC.”

Lightweight aggregate concrete produced with crushed stone sand as fine aggregate

Lightweight aggregate concrete mixtures incorporating 0, 10, 20, and 30 weight percent replacement of normal-weight aggregate with lightweight aggregate and crushed stone as fine aggregate were tested at 7, 28, 56, and 90 days for various strength and durability characteristics of hardened concrete. Test results indicated that compressive, flexural, and split tensile strengths and static modulus of elasticity of concrete mixtures reduced with an increase in the percent replacement of normal-weight aggregate with lightweight aggregate. Furthermore, the volume of permeable voids and hence moisture sorption in lightweight aggregate concrete reduced as the lightweight aggregate content was increased pointing at the enhanced durability of the lightweight aggregate concrete mixtures. A significant reduction in dry density of hardened concrete was recorded due to the inclusion of lightweight aggregate in concrete mixtures. Considering the strength and reduction in dry mass, 20 wt.% replacement of normal-weight aggregate with lightweight aggregate is considered to be an optimum level. Reduced density of lightweight aggregate concrete mixtures is viewed as a major source of economical design of structural members as the lower concrete density will result into a reduction of self-weight of the structural members, which will allow the economical structural design of such members with smaller cross-sections. Test results of this work also showed the viability of 100% replacement of desert sand with crushed stone sand as fine aggregate towards the production of lightweight aggregate concrete.

Appropriate drying shrinkage prediction models for lightweight concrete containing coarse agro-waste aggregate

Oil palm shell (OPS) agro-waste aggregate was successfully employed to produce lightweight aggregate concretes. However, the high rate of drying shrinkage for this type of concrete can impair the intended functionality of the structures or reduce service life. In this study, drying shrinkage strain behaviour of normal-weight and lightweight aggregate concretes was compared with prediction models. Twelve different mix proportions were designed by using of crushed granite (NWA) and OPS aggregates as replacement of the NWA at increasing intervals of 20%. Actual drying shrinkage at early and long-term ages (275 days) was compared against theoretical results from drying shrinkage prediction models such as ACI209R, EN1992, GL2000, B3 and SAK. Comparison between the test results and predicted results indicated that the EN1992 was the most precise model at early-ages as well as GL2000 at long-term ages. In contrast, B3 was found the least precise model at both early and long-term ages.

Influence of artificial aggregate on mechanical properties, fracture parameters and bond strength of concretes

The paper presented herein investigates the mechanical performance of concrete involving lightweight and normal weight aggregates with similar compressive strength. For this, two compressive strength values, 25 and 45 MPa, were considered for the concretes produced by normal and lightweight aggregates. Therefore, four concrete mixtures were designed at different water-to-cement ratios and cement contents. The lightweight aggregate utilized in this study was produced through cold bonding pelletization of fly ash and cement at ambient temperature in a specially designed tilted pan. The artificial lightweight aggregate used as a substitution of natural aggregate had similar particle size distribution to that of natural aggregate. The same mixing procedure was adopted to produce concrete and the testing specimens attained from each mixture were cured at the same circumstances. After the 28-day curing period, the specimens were tested for compressive strength and modulus of elasticity, splitting tensile and flexural strengths. Moreover, advanced mechanical properties such as fracture parameters, bond strength between embedded reinforcement and the concrete were also investigated. The test results indicated that it is possible to produce the lightweight aggregate concrete having similar compressive strength with the natural aggregate concrete, however, the utilization of artificial lightweight aggregates significantly influenced the investigated mechanical and fracture properties of the concretes despite having the similar compressive strengths. But, it was also observed that the utilization of lightweight aggregate made the concrete more ductile.

Mechanical Properties of lightweight Concrete Produced using Pottery Waste as Aggregate

Structures built using lightweight concrete have feature of the lower own weight than that of the conventional concrete, where this property contributes to reducing the construction cost. This paper study recycling of pottery waste (PW) to use it as aggregate to develop structural lightweight concrete. To achieve this aim, six concrete mixtures were prepared. Five mixes developed using PW of 20%, 40 %, 60%, 80%, and 100% as a partially and wholly replacement of normal weight aggregate, while the control mix produced using normal weight aggregate of dolomite. The properties; consistency, dry density, water absorption, compressive, tensile and flexural strengths were studied and compared with the same properties of the control mix. Experimental results indicate that using 40, 60, 80, and 100% of PW as dolomite replacement can produce lightweight concrete, also all concrete mixtures containing PW aggregate can classified as structural concrete where their compressive strengths are more than 17 Mpa.

The strength of lightweight aggregate in concrete – A Review

Concrete elements are the heaviest weight in structure, and it is the main component of the dead load in structure. Lightweight concrete is used to minimize overall dead load in structures, and also has a remarkable fire resistance quality more than normal weight aggregate concrete. Lightweight concrete can be characterized as a concrete consists of normal and artificial lightweight aggregate such as lightweight expanded clay aggregate (LECA). LECA produced in a rotary kiln which is approximately 50% lighter than normal aggregate, which is a new method in minimizing concrete self-weight. The main purpose of concrete in structure is to resist the compression stresses, the tests need to prove the effectiveness of using LECA in concrete to produce acceptable compression strength. For this reason, many attempts has been made to discuss and review the strength of structural element using LECA. This paper reviews several tests for the strength of LECA concrete by determining the mechanical properties such as flexural strength and compressive strength. The LECA concrete compressive strength is found to be slightly lower than normal weight aggregate concrete. It can be seen from researches results that LECA concrete produced medium strengths, both in compressive and flexural.

Neutral Axis Depth versus Ductility and Plastic Rotation Capacity on Bending in Lightweight-Aggregate Concrete Beams.

This article presents an experimental study on the evolution of the neutral axis depth at failure in the critical section with the flexural ductility and plastic rotation capacity of reinforced concrete (RC) lightweight-aggregate concrete (LWAC) beams. For this, the results of a previous experimental program involving RC LWAC beams tested in flexure until failure are used. The variable studies were the concrete compressive strength (between 22.0 and 60.4 MPa and dry density between 1651 and 1953 kg/m3) and the longitudinal tensile reinforcement ratio (between 0.13% and 2.69%). The flexural ductility and the plastic rotation capacity of the RC LWAC beams are characterized by a ductility index and a plastic trend parameter, respectively. The influence of the variable studies, as well as the relation of the flexural ductility and plastic rotation capacity with the values for the neutral axis depth at failure are analyzed and discussed. Some conclusions are drawn which can be useful for the design of RC LWAC beams for flexure. In particular, it is shown that the practical rule of limiting the neutral axis depth at failure to ensure ductile behavior, as used in normal-weight aggregate concrete beams, is also valid for RC LWAC beams.

Study of the suitability of a new structural concrete manufactured with carbon fiber reinforced lightweight aggregates sintered from wastes

The suitability of three new lightweight aggregates containing carbon fiber residues (CAs) as components in structural lightweight concrete has been studied. Prismatic concrete specimens were prepared using these CAs as a coarse fraction. Additional specimens of normal-weight aggregate, commercial lightweight aggregate and mortar were prepared for comparison. The CA-concrete samples (CACs) have yielded compressive strength values between 35 and 55 MPa as well as low density and thermal conductivity results. Furthermore, the CACs have displayed the highest ratios of mechanical strength over density and the thermal conductivity, which means that there is a better balance between their mechanical and physical properties than in the other samples studied. These results indicate that the new CAs could have great potential for use in structural lightweight concrete, also complying with the principles of the Circular Economy.

Enhance the properties of concrete using pre-developed burnt clay chips as internally curing concrete aggregate

Materials of internal curing concrete have been developed in many countries. Some of those materials are superabsorbent polymers, light weight aggregate (LWA), normal weight aggregate, recycled aggregate, bentonite clay, furnace slag and bottom ash. The most popular internal curing material is LWA. LWA are not available in most countries. Thus, the production of internal curing concrete (ICC) was limited for few countries. Consequently, this research was focused on the utilization of burnt clay chips as a new material to enhance the properties of ICC. Furthermore, water–cement (w/c) ratio and workability of ICC were investigated to develop high strength internal curing concrete (SICC). The water absorption and desorption capacity of porous aggregates are basically depends on the capillary interaction between water and the pore structure. Thus, formation of an effective pore structure within the burnt clay chips becomes the most important thing. Thus, Red clay was selected and different pore structures were developed within the clay mass by heating trough furnace. The heating temperature ranged from 800 to 1300 °C. The burnt clay chips produced at 900 °C was identified as an effective ICC aggregate. Afterwards, the pre-developed burnt clay chips (DBCC) were produced in larger scale. During the production of burnt clay chips, clay blocks (150 × 250 × 14 mm) were produced and heated at 900 °C using industrial furnace. Subsequently, heated clay blocks were crushed and sifted through 4.75 mm sieve to obtain fine clay chips. The water absorption capacity and the dry apparent density of DBCC was recorded as 15.5% and 1.8 g/cm3 respectively. Finally, grade 25, 30 and 35 concretes were prepared to study the effect of workability and w/c ratio. Moreover, three different concrete samples were prepared from each concrete grade; external curing concrete (ECC), ICC and SICC. ICC samples increased the slump value in 12%. Furthermore, the compressive strength of ICC and ECC were almost same for all three concrete grades. SICC sample increased the compressive strength in 9% while maintaining the required workability and same cement content of ECC sample. Thus, it is concluded that, DBCC can be used as an effective internal curing agent to increase the compressive strength and workability of ICC.

Prediction Model for Mechanical Properties of Lightweight Aggregate Concrete Using Artificial Neural Network.

The mechanical properties of lightweight aggregate concrete (LWAC) depend on the mixing ratio of its binders, normal weight aggregate (NWA), and lightweight aggregate (LWA). To characterize the relation between various concrete components and the mechanical characteristics of LWAC, extensive studies have been conducted, proposing empirical equations using regression models based on their experimental results. However, these results obtained from laboratory experiments do not provide consistent prediction accuracy due to the complicated relation between materials and mix proportions, and a general prediction model is needed, considering several mix proportions and concrete constituents. This study adopts the artificial neural network (ANN) for modeling the complex and nonlinear relation between constituents and the resulting compressive strength and elastic modulus of LWAC. To construct a database for the ANN model, a vast amount of detailed and extensive data was collected from the literature including various mix proportions, material properties, and mechanical characteristics of concrete. The optimal ANN architecture is determined to enhance prediction accuracy in terms of the numbers of hidden layers and neurons. Using this database and the optimal ANN model, the performance of the ANN-based prediction model is evaluated in terms of the compressive strength and elastic modulus of LWAC. Furthermore, these prediction accuracies are compared to the results of previous ANN-based analyses, as well as those obtained from the commonly used linear and nonlinear regression models.

TRM-to-Masonry Bond under Elevated Temperatures: Lightweight versus Normalweight Matrices

In the last decade, Textile Reinforced Mortar (TRM) systems have increasingly been gaining ground as a means of strengthening damaged or seismically deficient masonry structures, in addition to counterpart reinforced concrete ones. The existing experimental data on the behavior of TRM materials (used as externally bonded reinforcement on masonry – or concrete – substrates) under elevated temperatures still remains scarce. This work aims at enriching the existing data on the influence of elevated temperatures on the TRM-to-masonry bond conditions. The applied TRM systems consisted of a cementitious mortar with normalweight (limestone) or lightweight (pumice) aggregates. Shear bond tests on single-lap/single-prism specimens were conducted after the exposure of the specimens at different temperature levels. All specimens (masonry prisms with ridge-faced fired clay bricks) were unilaterally furnished with a dry AR glass TRM comprising a single textile layer; TRM bond length was kept constant for all specimens tested. Tests were carried out by varying both the type of matrix employed (normalweight vs. lightweight) and the exposing temperature. The experimental results provide an insight on the effect of mortar type (comprising either normalweight or lightweight sand) on the TRM-to-masonry bond capacity as a function of the exposure temperature.

Stress-strain relationship for plain and fibre-reinforced lightweight aggregate concrete

Lightweight aggregate concrete (LWAC) shows good performance in structural applications owing to its expected lower contribution to the deadweight of a structure, it nonetheless exhibits significant reduction in certain mechanical properties compared with the normal weight aggregate concrete. The inclusion of fibres could provide some positive changes to its mechanical properties and stress–strain behaviour. This study experimentally investigated the mechanical properties and full stress–strain curve of LWAC reinforced with steel and carbon fibres, involving specimens of strength classes ranging from LC40 to LC60 and fibre volume fractions from 0% to 0.9%. The test results showed that steel fibres could significantly improve the flexural strength and splitting tensile strength. Both the steel and carbon fibres strengthened the crack resistance of LWAC, while the compressive strength was not obviously enhanced. A general stress–strain model adapted to both plain LWAC and fibre-reinforced LWAC was proposed by comparing and modifying the existing models, and a statistically stochastic damage constitutive model was derived. The validity of the proposed models was examined by experimental results and test data from other studies.

Radiation shielding performance of heavy-weight concrete mixtures

In the present work, an experimental investigation was carried out to evaluate the radiation shielding performance of heavy-weight concrete mixtures prepared using different high-density coarse aggregates that included steel slag, steel shot, and iron ore. Normal-weight limestone aggregate was also used in control mixture as well as for partial replacement of the high-density aggregates in some of the heavy-weight concrete mixtures. Considering different combinations of the normal and high-density coarse aggregates and keeping cement content and water/cement ratio constant, a total of nineteen heavy-weight concrete mixtures were prepared and tested for their dry-density, compressive strength, and nuclear radiation response through gamma-ray intensity measurement. Except the control mixture containing normal-weight limestone aggregate, all eighteen heavy-weight concrete mixtures achieved 28-day dry unit weight in the acceptable range of 2600–3563 kg/m3. The compressive strength of the mixtures varied in the range of 26–45 MPa, all satisfying the requirements of a structural concrete. Radiation shielding performance was influenced by the unit weight of the concrete mixtures regardless of the type of coarse aggregates and the strength class of the concrete mixture. Based on the experimental data, correlations between indicator of the radiation shielding performance and unit-weight of concrete was obtained with a high degree of fit.

The Structural Characteristics of Lightweight Aggregate Concrete Beams

This paper aims to investigate the structural behavior of reinforced lightweight concrete beams. Attapulgite aggregate and crushed clay brick aggregate were used as coarse lightweight aggregate to produce structural lightweight aggregate concrete with 25 Mpa and 43.6 Mpa cube compressive strength and 1805 Kg/m3 and 1977 Kg/m3 oven dry density respectively. The result of reinforced lightweight concrete beams compared with reinforced normal weight concrete beams, which have 50.5 Mpa cylinder compressive strength and 2317 Kg/m3 oven dry density. For each type of concrete two reinforced concrete beams with (1200 mm length × 180 mm height × 140 mm width), one of them tested under symmetrical two-points load STPL (a/d = 2.2) and another one tested under one-point load OPL (a/d=3.3) at 28 days. The experimental program shows that a structural lightweight aggregate concrete can be produced by using Attapulgite aggregate with 25 MPa cube compressive strength and 1805 Kg/m3 oven dry density and by using crushed clay brick aggregate with 43.6 MPa cube compressive strength and 1977 Kg/m3 oven dry density. The weight of Attapulgite aggregate concrete and crushed clay bricks aggregate concrete beam specimens were lower than normal weight aggregate concrete beams by about 20.56% and 13.65% respectively at 28 days. As for the ultimate load capacities of beam specimens, the ultimate load of Attapulgite aggregate concrete beams tested under STPL were lower than that of crushed clay bricks aggregate concrete beams and normal weight aggregate concrete beams by about 4.85% and 5% respectively. While the ultimate load capacities of reinforced Attapulgite concrete beams tested under OPL were lower than that of reinforced crushed clay bricks aggregate concrete beams and reinforced normal weight aggregate concrete beams by about 10.3% and 10.5% respectively. Finally, Attapulgite aggregate concrete and crushed clay bricks aggregate concrete showed ductility and toughness less than that of Normal weight aggregate concrete.

Topography studies of concrete abraded with ice

Topography studies of concrete-ice abrasion were made to proceed in our understanding of the mechanisms of concrete wear by ice on Arctic offshore structures. The effects on various initial surfaces of a B75 normal-weight concrete (smooth, rough, sawn) and on the sawn surface of a LB60 lightweight concrete were studied during concrete-ice abrasion experiments. The degradation of a concrete surface appears mainly as valley formation resulting from air voids opening, or aggregate protrusion and cutting of peaks. The various initial roughness conditions were found to lead to an evolution with both increasing (at both meso- and microscale) and converging roughness. Protrusions from both lightweight and normal-weight aggregates were observed on sawn surfaces. Greater abrasion is seen on lightweight concrete and its initial roughness was much affected by the porous aggregate.

Lightweight Self-compacting Concrete Incorporating Oil Palm Shell

This paper presents the results of an experimental research on the fresh concrete properties, density, compressive and tensile strength of lightweight self-compacting concrete (LWSCC) incorporating oil palm shell (OPS) as coarse aggregates. Three aspects of fresh concrete properties including passing ability, filling ability and segregation resistance of the mixtures have been investigated experimentally and tests were carried out in accordance with the procedures stated in European Federation of National Associations Representing for Concrete (EFNARC) guidelines. LWSCC with OPS as aggregates fulfils the fresh concrete properties requirements of the EFNARC guidelines. In this study, the compressive and tensile strengths have also been compared with granite based self-compacting concrete (SCC). It is observed that OPS based SCC achieved comparable compressive strength with granite based SCC. This research provides basic framework to develop mix design of lightweight self-compacting concrete by using OPS as aggregates. Other properties such as durability and fire resistance of the developed concrete are not considered in the present study and are recommended for future research. The experimental studies show that LWSCC, with the use of OPS as full replacement to normal weight aggregates (NWA), is potentially a sustainable alternative construction material. Its use also provides a cleaner and more beneficial solution in OPS disposal for oil palm industry. This research demonstrated that OPS can be successfully used to develop lightweight self-compacting concrete. This research will benefit the oil palm industry and the environment as a whole.

Properties of Ambient-Cured Normal and Heavyweight Geopolymer Concrete Exposed to High Temperatures.

Ambient-cured heavyweight geopolymer concrete (HWGC) is a new type of concrete that combines the benefits of both heavyweight concrete (HWC) and geopolymer concrete (GC). HWGC provides proper protection from the sources that emit harmful radiations in medical and nuclear industries. Furthermore, HWGC may also be used in offshore structures for pipeline ballasting and similar underwater structures. In this study, heavyweight aggregates (magnetite) have been used and replaced by normal-weight coarse aggregates in GC at volume ratios of 50, 75, and 100% to attain heavyweight classification according to British standards. This study investigates the impacts of high temperatures on standard ambient-cured geopolymer concrete and ambient-cured HWGC through its residual properties regarding compressive and tensile strengths, mass loss, spalling intensity, and flexural strength. The residual properties were examined by heating 100 × 200 mm cylinder specimens to 100, 300, 600, and 900 °C. The results indicated that the maximum compressive strengths of 40.1 and 39.0 MPa were achieved by HWGC at 300 and 100 °C, respectively. The overall result shows that the strength of HWGC increases by increasing magnetite aggregate proportion, while the mass loss, intensity of spalling, and loss of strengths is proportional to temperature after a certain point. Minor spalling with holes and cracking was observed only at 900 °C in HWGC.