Ultra-lightweight Concrete Research Articles

Assessing the equivalent spring modelling method of CFS elements encased in ultra-lightweight concrete

An efficient finite element approach was recently developed to analyse encased cold-formed steel (CFS) structures. This new technique replaced encasing material with unidirectional springs, analogous to the Winkler foundation concept, to shorten the analysis time while ensuring accuracy and reliability in predicting the structural behaviour of encased CFS components. In this paper, the validity, and limitations of the simplified spring model to represent outstanding plates were assessed. The investigation demonstrated that the simplified spring model could effectively predict the ultimate load for a wide range of ultra-lightweight concrete moduli (50-250 MPa) with an acceptable error. The analysis indicated that plate elements initially in cross-section class 4 without encasing material become at least class 3, or better as a consequence of encasing. Previously reported experiments were used to evaluate the performance of the ESM. The analysis demonstrated that the ESM can accurately predict the local failure ultimate load of encased CFS sections with an acceptable error percent and significantly less computational effort than a 3D solid model.

Lower Carbon Footprint Concrete Using Recycled Carbon Fiber for Targeted Strength and Insulation.

The production of concrete leads to substantial carbon emissions (~8%) and includes reinforcing steel which is prone to corrosion and durability issues. Carbon-fiber-reinforced concrete is attractive for structural applications due to its light weight, high modulus, high strength, low density, and resistance to environmental degradation. Recycled/repurposed carbon fiber (rCF) is a promising alternative to traditional steel-fiber reinforcement for manufacturing lightweight and high-strength concrete. Additionally, rCF offers a sustainable, economical, and less energy-intensive solution for infrastructure applications. In this paper, structure-process-property relationships between the rheology of mix design, carbon fiber reinforcement type, thermal conductivity, and microstructural properties are investigated targeting strength and lighter weight using three types of concretes, namely, high-strength concrete, structural lightweight concrete, and ultra-lightweight concrete. The concrete mix designs were evaluated non-destructively using high-resolution X-ray computed tomography to investigate the microstructure of the voids and spatially correlate the porosity with the thermal conductivity properties and mechanical performance. Reinforced concrete structures with steel often suffer from durability issues due to corrosion. This paper presents advancements towards realizing concrete structures without steel reinforcement by providing required compression, adequate tension, flexural, and shear properties from recycled/repurposed carbon fibers and substantially reducing the carbon footprint for thermal and/or structural applications.

Current Developments in Ultra-Light Weight Concrete

Günümüzün en önemli yapı malzemelerinden biri olan betonun farklı özel çeşitleri bulunmaktadır. Bunlardan biride hafif betonlardır. Hafif betonlar (HB) üzerinde yapılan çalışmalarla birim ağırlıkları azaltılmakta ve üretilen betonlara ultra hafif beton denilmektedir (UHB). Birim ağırlıkları azaltılmaya çalışılırken basınç dayanımı, ses emme özelliği, ısıl iletkenlikleri, yangına ve dona dayanıklılıkları gibi özellikleri iyileştirilmeye çalışılmaktadır. Ultra hafif betonların (UHB) üretiminde kullanılan agregalarda zamanla değişime uğramaktadır. Atık malzemelerin değerlendirilerek sürdürülebilir ve doğa dostu UHB çalışmaları devam etmektedir. Doğal kaynakların kullanılması yerine atıkların değerlendirilerek kullanılması UHB’lere karşı ilginin ve talebin artmasını sağlamaktadır. Böylece UHB’lerin ekonomik, çevreci ve sürdürülebilirliği dikkat çekmektedir. Kullanılan agregaların türlerine ve boyutlarına göre UHB’ler sadece binalarda ısı ve ses yalıtım malzemesi olarak kullanılmasının yanı sıra dayanım özellikleri arttırılarak yapının kendi yükünü azaltarak deprem kuvvetlerinin etkilerini de azaltması amaçlanmaktadır. Bu çalışmada literatür kaynakları incelenerek UHB’lerle ilgili son gelişmeler incelenmiştir. UHB’ler arasında karşılaştırmalar yapılmakla birlikte avantaj ve dezavantajları değerlendirilmiştir.

Effect of waste glass powder and liquid glass on the Physico-Chemistry of Aluminum-Based Ultra-Lightweight concrete

The research aims to utilize waste glass powder in aluminum-based ultra-lightweight concrete (ULWC). It is a cheaper alternative to autoclaved aerated concrete. The study proposed obtaining glass powder and liquid glass from municipal solid waste. It was discovered that waste glass powder at the early hydration stage is not an active pozzolanic material. However, it helps to accelerate the Portland cement hydration process. Furthermore, a combination of waste glass powder and liquid glass can replace up to 30 % of Portland cement and increase almost twice the compressive strength of ULWC. The study aligns with the EU waste policy, which motivates extracting valuable resources from the dumpsite and converting them to functional materials, thus reducing global CO2 emissions.

Utilization of glass shards from municipal solid waste in aluminium-based ultra-lightweight concrete

• Glass powder react with portlandite and form an additional amount of low basicity CSH. • Glass powder increase dissolution of clinker mineral. • Glass shards from municipal solid waste can replace up to 30% of Portland cement. • Cleaned glass shards can be utilized in most types of concrete. • Glass shards without cleaning process can be utilized in aluminium-based ultra-lightweight concrete. The research proposed a method on how to prepare glass shards from municipal solid waste and utilize it in aluminium-based ultra-lightweight concrete (density ≤800 kg/m 3 ). In the research glass from municipal solid waste is prepared in two different ways: 1) washed under running water, dried, and milled in a ball mill (referred to as washed waste glass powder); 2) milled in a ball mill without washing (referred to as unwashed waste glass powder). In the research, Portland cement 42.5 R was used as the binder, aluminium powder was used as a foaming agent, β-calcium sulphate hemihydrate was used as early-strength agent, and sodium hydroxide was used as neutralizer of organic and other impurities. The aluminium powder showed good synergy with elemental aluminium found in unwashed waste glass powder. Sodium hydroxide also increases the dissolution of elemental aluminium. Additionally, polypropylene fibres were used to increase the integrity of hardened concrete structure. The main aim of the research is to utilize glass shards from municipal waste in ultra-lightweight concrete. The experiment was performed with and without CO 2 curing. The research revealed that it is possible to replace up to 30 % of Portland cement with waste glass powder without a decrease in compressive strength and to create ULWC with the density of ∼600 kg/m 3 , compressive strength of 3–6 MPa, and total porosity of ∼50 %–60 %. Experimental results confirmed that waste glass from municipal waste has pozzolanic and cementing properties, and therefore can replace some portion of Portland cement. The research is in line with the EU waste policy, which motivates extracting valuable resources from the dumpsite, converting them to beneficial raw materials, and thus reducing global CO 2 emissions. The proposed method is suitable to create ultra-lightweight concrete, which is a cheaper alternative for autoclaved aerated concrete.

Shear connection of prefabricated ultra-lightweight concrete slab systems (PUSSTM)

This paper reports a detailed computational study of a recently developed novel steel–concrete composite flooring system (PUSS) with two different types of shear connectors: (i) web-welded shear stud connectors (WWSS), and (ii) web-welded shear stud with dowels (WWSS with dowels). In addition, different types of concrete, (normal and lightweight,) are used. A nonlinear FE model is developed and validated against two sets of full-scale push-out tests of the novel steel–concrete composite flooring system reported in a companion paper. The FE model replicated the experimentally determined failure loads, ultimate slips, and observed failure modes. Parametric studies are conducted to obtain the failure loads and ultimate slips of these PUSS untis with different types of concrete: normal weight concrete, light weight concrete and ultra light weight concrete (NWC, LWC and ULWC), and various diameters and heights of shear connectors (WWSS, WWSS with dowels). The concrete strength varied between 20 N/mm2 to 35 N/mm2, the shear connectors’ diameter varied between 16 mm, 19 mm, 20 mm and 22 mm, and the height of the shear studs between 75 mm and 100 mm. In conclusion, load-slip curves obtained from the FE parametric studies demonstrated that FE models with same diameter of shear connectors can result to different slip stiffnesses, while the failure loads and slips varied with the concrete strengths. The slip results were also compared with different shear connection systems’ dimensions at concrete strengths of 20, 30 and 35 N/mm2.

The Effectiveness of Basalt Fiber in Lightweight Expanded Clay to Improve the Strength of Concrete Helicoidal Staircase

Staircase is a very important structural element found in mostly buildings of more than a floor. The properties of materials and designs used in constructing this structural element are very important. This study addresses the development of ultra-lightweight concrete. How ultra-lightweight concrete can effectively work in helicoidal structure. The flexural strength of this staircase was analysed on a finite element software SCAD. The designed lightweight aggregates concrete is targeted to be used in staircase of a structure having the shape of helicoid. In the concrete, chopped basalt fiber portion was added to each concrete mixture specimen reinforced as reinforcement. The basalt fiber percentages used are 0, 0.45, 0.9, 1.2 and 1.6. The developed lightweight expanded clay basalt fiber concrete showed significant increase in the flexural strength. The loads applied on this helicoidal concrete staircase in SCAD were derived from the laboratory experiments conducted on the concrete specimens on the 28 days curing period. This combination of values exceeds, to the researchers' knowledge, the performance of all other lightweight building materials. Furthermore, the developed lightweight concrete possesses excellent durability properties.

Influence of ultra-lightweight foamed glass aggregate on the strength aspects of lightweight concrete

Foamed glass aggregate is a special type of ultra-lightweight aggregate which can be easily used to enhance the properties of concrete. Foamed glass aggregate is completely prepared from waste glass available from various sources where the waste glass from industries is dumped at regular intervals. Here in this present study foamed glass was used as part as well as a full replacement of natural fine Aggregate to modify and enhance the properties of the normal concrete to prepare lightweight concrete. This study was taken into more advanced aspect by taking different sizes of the foamed glass aggregate to predict the optimum size as well as the optimum replacement percentage of the foamed glass aggregate. The foamed glass was replaced from 0% to 100% at an interval of 20% each. Overall three sizes of foamed glass were taken into consideration for the study. Different types of tests such as compressive strength test, Flexural strength test, water absorption test, and at last scanning electron microscopy was performed over the prepared specimen to compare the properties of the lightweight concrete and the normal concrete. All these aspects improve the strength as well as durable properties of concrete to a new extent. The concept of lightweight concrete, as well as the ultra-lightweight concrete, is not very much implemented in modern aspects but it one must not forget its importance as lighter will the concrete lighter will be the dead load of the structure. Although the use of this concept is implemented over lightweight structures only but with the size variation in the study it can also be used for the medium weight structures. Foamed glass aggregate usage also took the load of the waste glass from the earth and it is needed environmental point of view .

Evaluating the effects of nanosilica on the material properties of lightweight and ultra-lightweight concrete using image-based approaches

This work is aimed at characterizing the effects of nanosilica (NS) on the properties of lightweight aggregate concretes with different densities. Lightweight aggregate concrete (LWAC) and ultra-lightweight aggregate concrete (ULWAC) with targeted oven-dry densities of 850 kg/m3 and 450 kg/m3, respectively, were produced. The mixtures were modified by replacing cement with nanosilica, in concentrations of 1, 2, 5 and 10 wt-%. For comparison purposes, control specimens containing either cement alone or cement with silica fume (SF) were also produced. Their mechanical properties, including flexural and compressive strengths and transport characteristics, were evaluated by measuring the water accessible porosity and water absorption coefficients of the concretes. In addition, the thermal conductivity and drying shrinkage, being important parameters of lightweight concrete, were characterized. The pore structure characteristics of the concretes were assessed using 2D and 3D image analysis techniques; namely, using an automated air void analyser and micro-computed tomography (micro-CT), respectively. The experimental results show that NS has a significant effect on improving the mechanical and transport properties of lightweight concretes and that the efficiency of NS is much higher than that of SF. Moreover, depending on dosage, NS was found to have a negligible or decreasing influence on the drying shrinkage of concrete, after 28 days of curing. Microstructural studies confirmed that NS significantly affects the pore characteristics of concretes, thus resulting in concretes with denser and stronger microstructures.

Development of flowable ultra-lightweight concrete using expanded glass aggregate, silica aerogel, and prefabricated plastic bubbles

Low energy consumption buildings is one of effective responses to the challenge of climate change. Lightweight cement-based composites with excellent thermal insulation and mechanical properties are sustainable building materials for energy-efficient buildings. In this study three different types of lightweight thermal insulating materials, namely expanded glass aggregates, silica-aerogel, and prefabricated plastic bubbles, were tested as aggregates and fine fillers. Four different series of concrete samples were prepared using expanded glass aggregates, fly ash, prefabricated plastic bubbles, and aerogel to investigate the mechanical properties of lightweight/ultra-lightweight concrete. Scanning microscopy, thermography, semi-adiabatic calorimetry tests and XRD analysis of concrete samples were performed to analyse the effect of aerogel particles on the hydration process of lightweight/ultra-lightweight concrete. The results show that replacement of up to 15% of cement by aerogel particles cause the compressive strength of concrete to drop by more than 42%. Less than 800 kg/m3 density of concrete can be reached when a higher content of aerogel particles is used in combination with expanded glass aggregate. Separation gaps observed between the aerogel and surrounding cementitious materials indicate lower bonding of aerogel particles. Fly ash and prefabricated plastic bubbles were found to be very beneficial for the production of flowable lightweight/ultra-lightweight concrete.

Experimental study on flexural and shear behaviour of sandwich panels using glass textile reinforced concrete and autoclaved aerated concrete

Textile-reinforced concrete (TRC) is a new composite material made of high-strength textiles embedded within fine grained concrete (FGC). The application of TRC leads to the design of thin and slender structures or for repairing and strengthening of existing structural members. Autoclaved aerated concrete (AAC) is an ultra-lightweight concrete, which can be combined with high strength TRC to form some kinds of precast curtain panels in construction. The concept of the TRC-AAC panel is based on the theory of sandwich construction with strong and stiff skins, like TRC layers, bonded to a lightweight AAC core. The resulting hybrid TRC-AAC panel can be used as structural or non-structural member for the housing construction. In this paper, the flexural and shear performance of hybrid TRC-AAC sandwich panels is presented by means of experimental results. The sandwich panels use three layers of different materials: TRC for the tensile layer, AAC for the core material and FGC for the compressive layer. Three different types of glass textile were used as reinforcements in the TRC layers.

基于正交试验设计制备超轻质泡沫混凝土

基于正交试验设计制备超轻质泡沫混凝土

Effect of Expanded Perlite Aggregate Size on Physical and Mechanical Properties of Ultra Lightweight Concrete Produced with Expanded Perlite Aggregate

In this study, ultra-light weight concrete (ULWC) with heat-insulating properties is produced by using different size expanded perlite aggregates and various admixtures. The compressive strength, 4 point bending strength, freezing and thawing resistance, water absorption, dry unit weight, ultra sound velocities and thermal conductivity of the samples were determined by applying appropriate tests. The effect of different size expanded perlite aggregate on the properties of ULWC were also investigated in this study and it was found that as the expanded perlite aggregate diameter increased, the void volume uniformity, water absorption percentage and freezing-thawing resistance increased while the unit volume weight of ULWC samples, ultrasound speed velocities, thermal conductivity and compressive strength were decreased. The changes in the masses and compressive strength of ULWC samples subjected to freezing and thawing cycles were examined. The compressive strength loss was found to be between 5 % and 47 % while the weight loss was between 1 % and 3.5 % after 15 freezing and thawing cycles. Finally, the effects of the admixtures on the fresh properties of ULWC were examined and it was determined that the use of 4.5 kg of air-entraining material in one cubic meter of concrete mix is the most ideal ratio and the use of more than 0.01 % by volume of polypropylene fiber is caused settlements in fresh concrete mixtures.

Investigation on Bond Stress-slip Behavior of Concrete Containing Poly-lactic Acid Aggregate

The performance of Composites Structural Assemblies (CSAs) depends on the bond strength of the embedded components, namely composite panels and infill materials. A new type of eco-friendly ultra-lightweight concrete with Expanded Poly-Lactic Acid (EPLA) was prepared to assess the possibility of using biopolymer concrete as a replacement for expanded polystyrene (EPS) lightweight concrete. The bond properties of EPLA and EPS concrete for the parameters compressive strength, strip locking patterns, as well as elastic and inelastic interlocking areas were assessed. The results indicate that the application of biopolymers significantly changed the mechanical and bond properties of concrete. The chemical reactivity of EPLA and its degradation in the alkaline environment of cement causes bond failure at the interfacial transition zone of the aggregate-paste. Two different failure modes consisting of splitting cracks and pullout failure were observed. A bond stress-slip model for EPS and EPLA concrete was found to give a reasonable estimation of experimental results of bond-slip behaviour. Also, a new method is proposed to estimate the elastic and inelastic length of embedded components in ultra-lightweight concrete.

Waste of granite dust utilization in ultra-light weight concrete

In the article possibility to utilize granite dust in production of ultra-light weight concrete (≤800 kg/m3) is researched. Granite dust is a by-product of crushed granite, has very fine particles and high surface area. Due to very fine particles and high surface area, applicability of granite dust in concrete is limited. Mainly because granite dust increases W/C ratios and thus mechanical and durability properties tends to decrease. Ultra-light weight concrete, usually has very high W/C ratios, therefore in this type of concrete utilization of granite dust has favourable opportunity. In the research ultra-light weight concrete based on aluminium powder was created. Main mechanical and microstructure properties were researched and thermal conductivity coefficient was calculated. During experiment ultra-light weight concrete with 700 kg/m3 and up to 3.33 MPa was created. According to the experiment results, waste of granite dust can be properly utilised in production of ultra-light weight concrete blocks suited for one or two storages individual houses.

Ultra-lightweight Concrete Containing Expanded Poly-lactic Acid as Lightweight Aggregate

The environmental impact of using petroleum products has become a serious issue nowadays. This paper is about the possibility of producing ultra-lightweight concrete by using bio-polymer aggregate as a replacement for petroleum polymer. Expanded poly-lactic acid (EPLA) and Expanded Vermiculite (EV) are used as aggregate in producing biopolymer concrete. In total, five concrete mixtures are designed with varying EPLA and EV contents. The cement content and effective water-cement ratio are kept constant. The EV aggregate was replaced with EPLA aggregate in the ratio of 20%, 40%, 60% and 80%. Three types of curing conditions were used. The mechanical properties, thermal properties, electrical properties of biopolymer concrete were assessed and analysed. The microstructure of concrete was assessed after 28-days and one year. It was found that the properties of EPLA concrete are mainly influenced by the volume of EPLA and curing conditions. The chemical reactivity of EPLA significantly changes the hydration products of concrete and causes concrete carbonation as well as the conversion of hydration products to more calcium carbonate. However, at the long-term investigation (after a year) the more C-S-H gel was found. Furthermore, EPLA aggregates shrunk and lost their strength in the alkaline environment of cement.

Integrated life cycle cost method for sustainable structural design by focusing on a benchmark office building in Australia

Cost has been traditionally known as a key factor that needs to be considered in the decision making process. Recent awareness in environmental problems has highlighted the need for considering environmental impacts into the process of making choices. However, far too little attention has been paid to reflect the environmental impact and the building cost into the decision making process. As such, this study proposed a method that integrates and considers the environmental cost and building cost in the structural design process. This method takes into account the cost associated with building materials, construction methods and amount of embodied carbon emission during the life cycle of buildings. The current study analysed the effects of two construction systems (Flat slab and waffle slab) and two structural materials (Normal concrete and Ultra-lightweight concrete) on overall costs of a typical high rise concrete structure (15-story office building) in Australia (NS11401.1 2014). The results show that the office building designed with lightweight construction method (waffle slab) and normal concrete (Normal weight) has a lower life cycle cost (50 year lifespan) in comparison with the other design alternatives. It was found that an appropriate selecting of construction forms and type of concrete can save up to 7% of the cost of material consumption, 5% of the total energy consumption expense, and 5% of the CO2-e emissions of the building across all five major cities. This study demonstrates a method to quantify the potential impact of Ultra-lightweight concrete has on the life cycle cost and carbon emissions of commercial buildings. The proposed methodology to assess life cycle cost and environmental impact can be used as a supporting tool in selection of efficient construction methods and structural materials over the lifetime of building.

Experimental Investigation of Thin-walled Column-end Joints Encased in Ultra-lightweight Concrete

A novel thin-walled structural system is under development which aims to utilise the beneficial effect of continuous bracing achieved by encasing CFS elements in ultra-lightweight-concrete. This paper deals with the experimental analysis of column-end joints. Altogether six types of end connection and four cross-sections were tested by 18 unbraced and 48 braced specimens. Based on the results four main zones of the load-displacement curves were defined which represent the behaviour of the different types. The failure modes and ultimate loads were identified and were found to be in close correlation with the results of previous tests on compression members. The experimental test helped to identify the main parameters of thin-walled column-end joints which affect the behaviour of the structural detail.

Ultra-lightweight concrete: Energy and comfort performance evaluation in relation to buildings with low and high thermal mass

Ultra-lightweight concrete (ULWC) was recently introduced as a novel building material that combines moderate thermal insulation properties with load-bearing capacity. Its intended use as monolithic building envelope brings new opportunities in building physics, by merging characteristics of both heavyweight and lightweight construction types. This paper investigates the potential of ULWC building envelopes in terms of energy efficiency and thermal comfort. The dynamic thermal characteristics of a monolithic structure of ULWC were first compared to more conventional constructions using EN-ISO-13786 calculation methods. The main contribution of this article lies in the subsequent development and application of a simulation strategy for predicting the energy and comfort performance of ULWC on the whole-building level. The quality of the simulations in EnergyPlus was first ensured in an analytical validation study, and then applied to assess the performance of ULWC for commercial and residential case studies in the Netherlands. Results show that ULWC constructions are comparable to heavyweight buildings in long-term behaviour, whereas they resemble the performance of lightweight building envelopes for short-term heating periods. ULWC can therefore be a suitable construction type in buildings with intermittent operation, but in other cases it can get outperformed by conventional constructions with low or high thermal mass.

Ultra-lightweight concrete: Conceptual design and performance evaluation

The present study presents a methodology to design ultra-lightweight concrete that could be potentially applied in monolithic concrete structures, performing as both load bearing element and thermal insulator. A particle grading model is employed to secure a densely packed matrix, composed of a binder and lightweight aggregates produced from recycled glass.The developed ultra-lightweight concrete, with a dry density of about 650–700kg/m3, shows excellent thermal properties, with a thermal conductivity of about 0.12W/(mK); and moderate mechanical properties, with a 28-day compressive strength of about 10–12N/mm2. Furthermore, the developed concrete exhibits excellent resistance against water penetration.