Lightweight Concrete Mixtures Research Articles

Lightweight concrete with Algerian limestone dust. Part II: study on 50% and 100% replacement to normal aggregate at timely age

Abstract A control lightweight concrete (LWC) mixture made with 50% and 100% of limestone as a replacement of coarse aggregates in weight was prepared. Limestone is used for economical and environmental concern. The concrete samples were cured at 65% relative humidity at 20 ºC. The compressive and flexural tensile strengths, elastic modulus and Poisson's ratio of hardened concrete were measured. Laboratory compressive and tensile strength tests results showed that LWC can be produced by the use of limestone. The aim of this study is twofold: one is to design a lightweight concrete with the use of limestone that will provide an advantage of reduction in dead weight of a structure; and second is to obtain a more economical LWC mixture with the use of limestone.

Lightweight concrete masonry units based on processed granulate of corn cob as aggregate

A research work was performed in order to assess the potential application of processed granulate of corn cob (PCC) as an alternative lightweight aggregate for the manufacturing process of lightweight concrete masonry units (CMU). Therefore, CMU-PCC were prepared in a factory using a typical lightweight concrete mixture for non-structural purposes. Additionally, lightweight concrete masonry units based on a currently applied lightweight aggregate such as expanded clay (CMU-EC) were also manufactured. An experimental work allowed achieving a set of results that suggest that the proposed building product presents interesting material properties within the masonry wall context. Therefore, this unit is promising for both interior and exterior applications. This conclusion is even more relevant considering that corn cob is an agricultural waste product.

High-strength lightweight concrete mixtures based on hollow microspheres: technological features and industrial experience of preparation

The research results concerning dependencies between technological parameters and physical properties of structural lightweight concrete are presented in the article. High-strength lightweight concrete has unique performance characteristics: low average density (less than 1500 kg/m3) and high compressive strength (more than 70 MPa). Hollow alumina-silicate microspheres with nanoscale modifier are used for obtaining these properties. It is shown in the article that the preparation of high-strength lightweight concrete in industrial conditions must be implemented using a turbine mixer having six paddles and engine power more than 39.2 kW. Oscillation frequency of more than 3000 rpm, vibro-compacting time less than 15 seconds, heat-humid treatment temperature approximately 60-65 °C and heat-humid treatment time 6-7 hours are optimal for production. The results of industrial mixing-test are presented.

Effects of Low Volume Fraction of Polyvinyl Alcohol Fibers on the Mechanical Properties of Oil Palm Shell Lightweight Concrete

This paper presents the effects of low volume fraction(Vf)of polyvinyl alcohol (PVA) fibers on the mechanical properties of oil palm shell (OPS) high strength lightweight concrete mixtures. The slump, density, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity under various curing conditions have been measured and evaluated. The results indicate that an increase in PVA fibers decreases the workability of the concrete and decreases the density slightly. The 28-day compressive strength of oil palm shell fiber-reinforced concrete (OPSFRC) high strength lightweight concrete (HSLWC) subject to continuous moist curing was within the range of 43–49 MPa. The average modulus of elasticity (E) value is found to be 16.1 GPa for all mixes, which is higher than that reported in previous studies and is within the range of normal weight concrete. Hence, the findings of this study revealed that the PVA fibers can be used as an alternative material to enhance the properties of OPS HSLWC for building and construction applications.

혼화재를 다량 치환한 경량 및 보통중량 콘크리트의 압축피로 특성 평가

(Received December 20, 2014 / Revised December 24, 2014 / Accepted December 25, 2014)The objective of this study is to examine the fatigue behavior in compression of normal-weight and lightweight concrete mixture s withhigh volume supplementary cementitious material(SCM). The selected binder composition was 30% ordinary portland cement, 20% fly-ash, and 50% ground granulated blast-furnace slag. The targeted compressive strength of concrete was 40 MPa. For the cyclic loading, the constant maximum stress level varied to be 75%, 80%, and 90% of the static uniaxial compressive strength, whereas the constant minimum stress level was fixed at 10% of the static strength. The test results showed that fatigue life of high volume SCM lightweight concrete was lower than the companion normalweight concrete. The value of the fatigue strain at the maximum stress level intersected the descending branch of the monotonic stress-strain curve after approximately 90% of the fatigue life.키워드 : 다량치환 혼화재, 경량콘크리트, 압축 피로, 응력-변형률 관계Keywords : High volume SCM, Lightweight concrete, Fatigue in compression, stress-strain relationship* Corresponding author E-mail: whenwhere@kgu.ac.kr

EXPERIMENTAL AND THEORETICAL RESEARCH ON REINFORCED LIGHTWEIGHT CONCRETE FLEXURAL ELEMENTS / ARMUOTOJO LENGVOJO BETONO LENKIAMŲJŲ ELEMENTŲ EKSPERIMENTINIAI IR TEORINIAI TYRIMAI

The paper deals with analysis of structural lightweight concrete. New lightweight concrete mixture made with expanded clay aggregate has been proposed and applied for experimental rein-forced concrete beams. Totally 8 beams with different rein-forcement ratios (0.309%, 0.557%, 0.895% and 1.255%) were tested under short-term four point bending loading. Stress-strain behavior of the beams under considerations has been investigated. Average strains at 4 different levels of pure bend-ing zone and vertical displacements at 12 different points of the beam were measured. During the test, deformations and crack-ing of the pure bending zone were additionally observed using high-speed digital video cameras. The data obtained by cameras were analyzed using digital image correlation technique. Applying the test data bending moments and curvature diagrams were derived for each beam. The obtained relationships were compared with theoretical results calculated using design code methods LST EN and STR. Using the inverse algorithm developed by VGTU, tension reinforced lightweight concrete stress and strain diagrams were obtained, which were adapted to numerical modeling by software ATENA. Moment and curvature diagrams obtained by finite elements program were compared with experimental moment and curvature diagrams. Good agreement between both diagrams has been obtained. Straipsnyje aprašytas naujai sukurtas konstrukcinis lengvasis betonas ir jo panaudojimas eksperimentinių armuotojo lengvojo betono sijų gamybai. Atlikti trumpalaike apkrova veikiamų plieniniais strypais armuotų lengvojo betono sijų eksperimentiniai tyrimai, kuriuose nagrinėtas sijų įtempių ir deformacijų būvis. Laboratorijoje išbandyti 8 lenkiamieji elementai, kurių armavimo procentai: 0,309 %, 0,557 %, 0,895 % ir 1,255 %. Tyrimų metu matuotos vidutinės elemento deformacijos grynojo lenkimo zonoje 4 skirtinguose lygmenyse bei sijų poslinkiai ties atramomis, jėgos pridėjimo vietose ir viduriniame pjūvyje (iš viso 12 matavimo taškų). Bandymo metu grynojo lenkimo zonos deformacijos bei pleišėjimas papildomai stebėti greitaeige vaizdo kamera. Gauti rezultatai panaudoti sudarant eksperimentines lenkimo momentų ir kreivių diagramas, kurios palygintos su teoriškai apskaičiuotomis taikant Lietuvoje galiojančių LST EN ir STR projektavimo normų metodikas. Taikant VGTU sukurtą atvirkštinio uždavinio algoritmą, gautos tempiamo armuotojo lengvojo betono įtempių ir deformacijų diagramos, kurios pritaikytos atliekant skaitinį modeliavimą baigtinių elementų programa ATENA. Gautos momentų ir kreivių diagramos baigtinių elementų programa palygintos su eksperimentų metu gautomis momentų ir kreivių diagramomis. Gautas geras šių diagramų sutapimas.

Alkali-silica reactivity of expanded glass granules in structure of lightweight concrete

Main component in the lightweight concrete, which provides its properties, is aggregate. A lot of investigations on alkali silica reaction (ASR) between cement and lightweight aggregates have been done with their results published in the academic literature. Whereas expanded glass granules, which is relatively new product in the market of building materials, has not been a frequent research object. Therefore lightweight granules made from waste glass and eight types of cement with different chemical and mineralogical composition were examined in this research. Expanded glass granules used in this research is commercially available material produced by Penostek. Lightweight concrete mixtures were prepared by using commercial chemical additives to improve workability of concrete. The aim of the study is to identify effect of cement composition to the ASR reaction which occurs between expanded glass granules and binder. Expanded glass granules mechanical and physical properties were determined. In addition, properties of fresh and hardened concrete were determined. The ASR test was processed according to RILEM AAR-2 testing recommendation. Tests with scanning electron microscope and microstructural investigations were performed for expanded glass granules and hardened concrete specimens before and after exposing them in alkali solution.

Properties of fly-ash lightweight aggregate concretes

Lightweight concrete with sintered fly-ash aggregates was compared with that of normal weight concrete with granite aggregates for various water/binder ratios starting from 0·30 to 0·50. They both had the same mixture proportion by volume and the only difference between them was the coarse aggregate used. Test results indicated that when granite aggregates have been replaced completely with lightweight aggregates, a reduction of 20% in the density of concretes was observed. Lightweight concrete exhibited higher workabilities than the corresponding normal weight concrete mixtures. With the exception of the elastic modulus all the other properties such as compressive strength, splitting tensile strength and chloride permeability of the lightweight concrete mixtures were comparable with normal weight concrete mixtures at water/binder ratios of 0·45 and 0·50. The ratios of splitting tensile strength to compressive strength of lightweight concrete were found to be similar to that of normal weight concrete.

Mechanical Behavior of White Concrete

In this study, possibility of the use of WPC 42.5 containing pyrophyllite in the production of white concrete was investigated. Normal and light-weight concrete samples were produced with WPC. In normal-weight concrete mixture, WPC and white aggregate were used. In light-weight concrete mixtures, WPC, FA, SF and SP were used. Setting time and soundness of cement paste specimens and compressive strength of light and normal weight white concrete specimens were determined. According to the test results, normal weight white concrete can be used in the construction of frames and light-weight white concrete can be used in the production of concrete/reinforce concrete panels.

Ultimate Behavior of Lightweight High Strength Concrete Filled Steel Tube (LWHCFST)

Strength and ductility of concrete members can be significantly improved with lateral confinement, usually achieved by using a steel tube casing. The concrete confinement can be utilized to make bridge lighter and have longer spans. In addition, a significant portion of the load carried concrete bridge girders is the self- weight of the girders and deck. If all or part of the girder and deck can be made using high strength lightweight concretes, there is a potential for appreciable economic savings since the self-weight could be reduced by as much as 15-20%. The study described herein investigates the static nonlinear behavior of lightweight high strength concrete filled steel tube (LWHCFST) bridges up to failure. The current study had two specific goals. The first was to experimentally determine the static modulus of elasticity of confined high strength lightweight concrete mixture. The second was to develop a nonlinear finite element computer program to study the ultimate behavior of a filled tube (LWHCFST) example bridge. The nonlinear stress-strain behavior of confined high strength lightweight concrete is evaluated experimentally by the authors and is used to help establish a comparison between the ultimate behavior of the bridge using confined normal weight concrete and confined high strength lightweight concrete. The ultimate strength of the bridge is related to the occurrence of an equivalent failure mechanism. The study indicated that the use of (LWHCFST) is beneficial for extending bridge girder lengths.

Performance Studies of Lightweight Concrete Mixtures Made with Rigid Polyurethane Foam Wastes

This paper describes the results of some studies on the properties of lightweight expanded concrete mixtures made with rigid polyurethane foam waste. Experimental study on the mechanical properties of polyurethane foam waste mixed with concrete shrinkage performance and the relationship between packing density and absolute density. The results showed that: Polyurethane foam plastic waste can be used in the preparation of lightweight concrete, the strength with the state standards, and packing density and concrete absolute density with reference line between sex. Drying shrinkage comply with Selih and Bremner lightweight concrete water content to evolution.

Influence of elevated temperatures on the mechanical properties and microstructure of self consolidating lightweight aggregate concrete

Self consolidating lightweight concrete (SCLWC) mixtures were prepared by using two different lightweight coarse aggregates and by replacing normal weight crushed coarse limestone aggregate at a constant water/powder ratio. One of the SCLWC mixtures was also prepared at different water/powder ratios. All the mixtures were exposed to 300, 600 and 900°C, respectively. Lightweight aggregate type and water/powder ratio affect water transport characteristics and resistance of the mixtures to elevated temperatures. The microstructural investigation findings are consistent with thermal strain and residual mechanical properties of the mixtures after exposure to high temperatures.

Lightweight concrete incorporating volcanic materials

This paper describes properties of lightweight concrete obtained by incorporating volcanic-materials-based blended cements and pumice aggregates. Blended cements are produced by replacing ASTM Type I Portland cement with 20% volcanic ash and finely ground pumice. Properties of fresh lightweight concrete mixtures (such as slump and air content) along with their mechanical properties (such as density, compressive/tensile strength and modulus of elasticity) are described. The durability and microstructural characteristics are investigated by drying shrinkage, water permeability, mercury intrusion porosimetry, differential scanning calorimetry and microhardness tests. The investigation suggests that volcanic-materials-based blended cements in combination with pumice aggregates can be used for the production of lightweight concrete for structural applications, having satisfactory strength and durability characteristics. The use of volcanic ash/pumice-based blended cements induces the beneficial effect of reducing drying shrinkage and water permeability as well as refinement of pore structures and better interfacial transition zone. Development and use of such inexpensive and environmentally friendly lightweight concretes can be extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.

Mechanical and thermal properties of novel lightweight concrete mixtures containing recycled glass and metakaolin

The aim of this study was to investigate the behaviour of a new type of lightweight concrete which would be suitable for use as a load-bearing concrete masonry unit. Different ratios of by-product materials which consist of metakaolin (MK) and recycled glass were used in conjunction with expanded clay to produce the lightweight concrete mixtures. The short and long-term mechanical properties and thermal criteria were measured using a total of 208 specimens with different geometries. Some statistical analysis was conducted and the obtained results were compared with the standard expressions.The tests results showed that it is possible to produce a structural lightweight concrete possessing good thermal properties using by-product materials. Compressive and splitting tensile strengths, as well as the modulus of elasticity, increased with an increase in the metakaolin content, whilst a counteractive behaviour was recorded for the density. Clear improvements in thermal conductivity and insulation criteria were observed in comparison with conventional lightweight concrete mixtures. The measured thermal conductivity values ranged from 0.092W/mK to 0.177W/mK, and the insulation criterion reached up to 110.25min for 29mm concrete member thickness.

Effect of pre-conditioning on CO 2 curing of lightweight concrete blocks mixtures

It is a common practice to use steam to cure precast concrete products and concrete masonry blocks after casting. Steam curing is an energy extensive process and contributes significantly to the production costs. This study investigated the effects of pre-conditioning on the CO 2 curing of lightweight concrete block mixtures. The results indicated that there was an optimum moisture loss at which the specimens demonstrated the highest strength and CO 2 consumption after CO 2 curing. However, the moisture evaporation rate had to be controlled so to avoid plastic shrinkage cracking. CO 2 curing was an exothermal process, which raised the temperature of specimens very quickly within a short period of time. Traditional steam curing of concrete blocks took 18–24 h, CO 2 curing could be completed with 4–8 h including pre-conditioning to achieve strength equivalent to that steam curing, This means that the use of CO 2 curing technology has advantages not only in reducing and/or utilizing greenhouse gas emissions, but also in decreasing the curing time and increasing productivity of plain and non-steel reinforced concrete products.

Effect of steel fiber on the mechanical properties of oil palm shell lightweight concrete

This paper reports the results of a study conducted to investigate the effect of low volume content of steel fiber on the slump, density, compressive strength under different curing conditions, splitting tensile strength, flexural strength and modulus of elasticity of a grade 35 oil palm shell (OPS) lightweight concrete mixture. The results indicate that an increase in steel fiber decreased the workability and increased the density. All the mechanical properties except the modulus of elasticity (E) improved significantly. The 28 day compressive strength of steel fiber OPS lightweight concrete in continuously moist curing was in the range of 41–45 MPa. The splitting tensile/compressive and the flexural/compressive strength ratio for plain OPS concrete are comparable with artificial lightweight aggregate. The (E) value measured in this study was about 15.5 GPa on average for all mixes, which is higher than previous studies and is in the range of normal weight concrete. Steel fiber can be used as an alternative material to reduce the sensitivity of OPS concrete in poor curing environments.

Influence of aggregate type on workability of self-consolidating lightweight concrete

In this study, the effects of aggregate type on the workability of self-consolidating concrete produced with lightweight aggregate (self-consolidating lightweight concrete – SCLC) were investigated. In experiments, three coarse lightweight aggregate (LWA) types, namely pumice, volcanic tuff and diatomite, were used. Different combinations of water/powder ratio and superplasticiser dosage levels were prepared for the self-consolidating lightweight concrete mixtures. The total powder content (cement and mineral additives) was constant in the experiments. Workability tests such as slump flow, restricted slump flow, filling-box, V-funnel, GTM screen stability, L-box and U-box were performed to characterise accurately the flow ability, passing ability and segregation resistance of self-consolidating lightweight concrete in fresh condition. The results, in general, showed that self-consolidating lightweight concrete with lightweight aggregate in low unit weight has higher flow ability and passing ability. The segregation of self-consolidating lightweight concrete was prevented by use of air-entraining admixture in high water/powder ratios. As a result, it was observed that the aggregate type and water/powder ratio has significant influence on the workability properties of self-consolidating lightweight concrete.

Lightweight Concrete Incorporating Volcanic Ash-Based Blended Cement and Pumice Aggregate

This paper presents the workability, mechanical, durability, and microstructural properties of lightweight concrete (LWC) incorporating pumice aggregate, normal-weight gravel aggregate, ASTM type I portland cement, and volcanic ash (VA)–based ASTM Type I blended cement (PVAC). Workability and mechanical properties of LWC mixtures such as slump, air content, compressive strength, tensile strength, density, and modulus of elasticity are described. The durability and microstructural characteristics are investigated by drying shrinkage (DS), water permeability, mercury intrusion porosimetry (MIP), differential scanning calorimetry (DSC), and microhardness tests. The variables in the study include percent replacement (0, 50, 75, and 100% by volume) of coarse gravel aggregate (GA) by coarse volcanic pumice aggregate (VPA), water-to-binder ratio (W/B) by mass, aggregate-to-binder ratio (A/B) by mass, total binder content, and cement types (ASTM type I cement and PVAC). The investigation suggests the production o...

Contribution of fibres to the properties of EPS lightweight concrete

The effect of different fibres on the workability, mechanical properties, drying shrinkage and water adsorption was investigated on expanded polystyrene (EPS) lightweight concrete of high strength and workability. The results showed that the addition of fibres to the EPS lightweight concrete mixture during mixing substantially reduced the sedimentation of EPS beads and improved the uniformity of the mix as well. Compared with normal EPS concrete, fibres were demonstrated to have greatly increased strength, especially splitting tensile strength. It was also demonstrated that fibres restrained the long-term drying shrinkage. However, no significant effect was found of fibres on the water adsorption of EPS concrete.

Self-compacting lightweight aggregate concrete: design and experimental study

This study focuses on the production of self-compacted lightweight structural concrete. For this purpose, lightweight concrete was produced by replacing normal aggregate with pumice aggregate obtained from the Kayseri region. Three series of mixtures were prepared to obtain the proper self-compacting lightweight concrete (SCLC) mixture. The D series included normal-weight, self-compacting concrete (SCC) mixtures and the H series included SCLC mixtures having 100% lightweight coarse aggregate and different air contents. Fresh concrete test results obtained from these mixtures were used as a basis for the T series containing different amounts of lightweight and normal-weight coarse aggregate. Some mechanical and fresh concrete properties were obtained from the T series. It was found that the loss of strength owing to lightweight aggregate addition is higher than the decrease of unit weight of the mixture. Furthermore, the decrease in flexural tensile strength owing to addition of lightweight aggregate is less than the reduction in compressive strength and splitting tensile strength. The percentage of entrained air and paste content are important factors to avoid segregation problems in lightweight SCC mixtures. There is a good relationship between 28-day compressive strength and unit weight data obtained from the H and T series.