Lightweight Concrete Mixtures Research Articles

Flexural Strength of Structural Beams Cast Using Combined Normal-Weight and Lightweight Concrete Mixtures

Limited investigations have evaluated the potential of using layered sections of normal-weight and lightweight concrete (NWC and LWC) mixtures in structural beams and slabs. The main objective of this paper is to assess the flexural strength properties of layered reinforced concrete (RC) beams, which help conserve natural resources and reduce construction weight. Six RC beams cast with different NWC/LWC combinations are tested to determine the damage patterns, concrete strains, ultimate load, displacements at failure, and ductility. The test results showed that the LWC cast in the tension zone (and up to the neutral axis) has a negligible effect on the beam’s stiffness and ultimate load since the overall behavior remains governed by the yielding of tensile steel reinforcement. Nevertheless, the deflection at failure and ductility seem to gradually curtail when the NWC is partially replaced by LWC at different elevations across the beam’s cross-section. A finite element analysis using ABAQUS software 6.14 is performed, and the results are compared with experimental data for model validation. Such data can be of interest to structural engineers and consultants aiming for optimized design of slabs and beams using layered concrete casting, which helps reduce the overall construction weight while maintaining the structural integrity of members.

Effect of Recycled Concrete Aggregate Utilization Ratio on Thermal Properties of Self-Cleaning Lightweight Concrete Facades

In today’s environment, where energy is desired to be used more efficiently, it has been understood that the interest in the use of lightweight concrete with superior performance in terms of thermal insulation properties has increased. On the other hand, it has been stated that construction waste increases rapidly, especially after severe earthquakes. In this context, encouraging the use of recycled concrete waste and efficient disposal of construction and demolition waste is of great importance for the European Green Deal. It is also known that pollutants such as COx and NOx stick to facades over time, causing environmental pollution and visual deterioration. It has been reported that materials with photocatalytic properties are used in lightweight concrete facade elements to prevent such problems. This study examines the effect of using recycled concrete aggregates on the thermal properties of self-cleaning lightweight concrete mixtures (SCLWC). For this purpose, an SCLWC containing 1% TiO2 and 100% pumice aggregate was prepared. By replacing pumice aggregate with recycled concrete aggregate at the rates of 15%, 25%, 35%, 45% and 50%, four different SCLWCs with self-cleaning properties were produced. High-temperature resistance, thermal conductivity performance, microstructure analysis and photocatalytic properties of the produced mixtures were examined. It has been understood that the unit volume weight loss of SCLWC mixtures exposed to high temperatures generally decreases due to the increase in the recycled concrete-aggregate substitution rate. However, it was determined that the loss of compressive strength increased with the increase in the amount of recycled concrete-aggregate replacement. Additionally, it was determined that the thermal-conductivity coefficient values of the mixtures decreased with the use of pumice. After SCLWC mixtures were exposed to 900 °C, small round-shaped crystals formed instead of C–S–H crystals.

Physical and mechanical properties of lightweight concrete with the incorporation of waste disposal polyurethane foam as coarse aggregate

<p>Industrial waste in engineered concrete mixes is an enormous step towards sustainable development. Polyurethane foam waste (PUFW) is mainly generated by the refrigeration, automobile, and construction industries. Day by day, large amounts of PUFW are incinerated and disposed of in landfills, which not only affects the environment but also leads to the loss of land usage. On the other hand, with the improvement of financial benefits, environmental benefits, and structural style, the demand for lightweight concrete (LWC) is also increasing. This study investigated the incorporation of rigid PUFW as coarse aggregate in LWC. Various proportions of PUFW replacement by volume (40%, 50%, 60%, 70%, and 80%) were examined to formulate the LWC mixtures. The physical and mechanical properties of the LWC were tested and compared with conventional concrete. The results showed that the compressive strength reached more than 17 MPa when LWC was made with 40%, 50%, and 60% PUFW content, satisfying the compressive strength of structural LWC. At 70% PUFW content, the compressive strength was satisfactory for semi-load bearing strength, and at 80% PUFW content, it was suitable for insulation concrete. In all mix proportions, the density value was less than 2000 kg/m3, which was satisfactory for LWC.</p>

Investigating the mechanical and physical properties of lightweight geopolymer concrete

Using waste materials and by-products from various building sectors is gaining popularity because natural resources are quickly depleting. Geopolymer concrete is made from by-product material and is a relatively new environmental material that does not require the presence of ordinary Portland cement as a binder. This study involves producing lightweight geopolymer concretes using a slag binder and replacing the conventional fine and coarse aggregates with two types of locally available lightweight aggregate (thermostone and montmorillonite). Several sequential steps were used to process the aggregates, along with a series of tests conducted to evaluate the concrete properties in different states. The fresh state test includes the slump test, while the hardened concrete tests involve compressive strength, flexural strength, density, thermal conductivity, and water absorption. This study reveals the suitability of lightweight concrete mixtures for various constructional applications. The most reliable mixture was the GMM, which consisted of coarse montmorillonite (5–25 mm) and fine montmorillonite aggregates. This mixture exhibited the highest compressive strength of 23.3 MPa, a flexural strength of 3.25 MPa compared to other LWGC mixtures, and a low density of 1785 kg/m3. The GMM density was 23.97% lower than the reference mixture, whereas the thermal insulation significantly improved by 65.58%. Consequently, this improvement was evident in the thermal conductivity coefficient, which measured as approximately 0.349 W/m.K. In addition, the GTT mixture containing thermostone aggregate (5-25 mm) yielded the most optimal thermal insulation and lowest density of 0.267 W/m.K and 1552 kg/m3, respectively. In general, the strength and density of the LWGC mixtures in this study meet the requirements of lightweight structural applications.

PENGARUH SERAT BAMBU TERHADAP KAPASITAS LENTUR PELAT BETON CAMPURAN STYROFOAM DEGAN PERKUATAN TULANGAN WIREMESH

Lightweight concrete is a concrete technology innovation that is currently developing. The advantage of lightweight concrete is that it uses less time and costs compared to concrete in general but has the disadvantage of lower strength. This research aims to determine the effect of adding bamboo fiber on the flexural capacity of lightweight concrete slabs mixed with Styrofoam. The lightweight concrete mixture used is Styrofoam at 50% of the weight of the mixed aggregate. Variations in adding bamboo fiber with a diameter of 1 mm and a length of 40 mm are 0% and 0.5% of the cement weight. The test object consists of a lightweight concrete plate measuring 50 cm x 150 cm x 8 cm with wire mesh reinforcement with a diameter of 8 mm. Tests were carried out when the concrete was 28 days old by applying an even load gradually until the slab collapsed. From the test results, at a loading of 300 kg, the average deflection value for lightweight concrete slabs with reinforcement reinforcement with 0% bamboo fiber was 1.18 mm and for lightweight concrete slabs with 0.5% bamboo fiber was 1.57 mm. Lightweight concrete slabs mixed with bamboo fiber have a greater deflection than lightweight concrete slabs without a mix of bamboo fiber. This shows that the addition of bamboo fiber to lightweight concrete slabs does not increase the flexural capacity of the slab. The difference between theoretical calculations and testing is due to the theoretical calculation formula used in this research not taking into account the content and properties of Styrofoam in the plates. The two variations of concrete slabs used in the test did not experience any cracks and met the maximum allowable deflection requirements at loads reaching 300 kg.

Machine learning-based compressive strength estimation in nanomaterial-modified lightweight concrete

Abstract The development of nanotechnology has led to the creation of materials with unique properties, and in recent years, numerous attempts have been made to include nanoparticles in concrete in an effort to increase its performance and create concrete with improved qualities. Nanomaterials are typically added to lightweight concrete (LWC) with the goal of improving the composite’s mechanical, microstructure, freshness, and durability qualities. Compressive strength is the most crucial mechanical characteristic for all varieties of concrete composites. For this reason, it is essential to create accurate models for estimating the compressive strength (CS) of LWC to save time, energy, and money. In addition, it provides useful information for planning the construction schedule and indicates when the formwork should be removed. To predict the CS of LWC mixtures made with or without nanomaterials, nine different models were proposed in this study: the gradient-boosted trees (GBT), random forest, tree ensemble, XGBoosted (XGB), Keras, simple regression, probabilistic neural networks, multilayer perceptron, and linear relationship model. A total of 2,568 samples were gathered and examined. The most significant factors influencing CS during the modeling process were taken into account as input variables, including the amount of nanomaterials, cement, water-to-binder ratio, density, the content of lightweight aggregates, type of nano, fine and coarse aggregate content, and water. The performance of the suggested models was assessed using a variety of statistical measures, including the coefficient of determination (R 2), scatter index, mean absolute error, and root-mean-squared error (RMSE). The findings showed that, in comparison to other models, the GBT model outperformed the others in predicting the compression strength of LWC mixtures enhanced with nanomaterials. The GBT model produced the best results, with the greatest value of R 2 (0.9) and the lowest value of RMSE (5.286). Furthermore, the sensitivity analysis showed that the most important factor influencing the prediction of the CS of LWC enhanced with nanoparticles is the water content.

Effect of fiber type, size, and utilization rate on mechanical and thermal properties of lightweight concrete facade panels

AbstractIt was understood that various studies were carried out on the strength, permeability, durability, increasing the thermal performance of lightweight concrete facade panels, and sustainable and energy‐efficient concepts. It was observed that fiber was added to the mixture to improve the properties in question. However, it was determined that contradictory results were obtained due to the large number of active parameters and whether the fiber was distributed homogeneously in the matrix. In this study, the effects of fiber type, length and usage rate on the strength, energy absorption capacity, elasticity modulus, water absorption, and thermal performance of lightweight concrete mixtures were investigated. For this purpose, three different types of fibers of different lengths: polypropylene (3, 6, and 12 mm), glass (13 and 25 mm) and polyamide (6 and 12 mm) were used at 0%, 0.25%, 0.50%, and 0.75% of the total volume. It was determined that the mixture containing 0.25% polypropylene fiber with a length of 3 mm exhibited the best performance in terms of both mechanical and thermal properties. In terms of these features, it was understood that the mixtures with 12 mm polypropylene with a usage rate of 0.75% and 6 mm polyamide fibers with a usage rate of 0.50% had the weakest performance.

Flowability and Cracks Patterns of Lightweight Concrete Subjected to Compression and Tension Loading

AbstractConcrete is one of the most widely used buildings materials in construction. One of the concrete types used is foam concrete which is produced by adding liquid foam (a foam agent) to water in the concrete design mix. The purpose of the foam agent is to stabilize air bubbles during the concrete hardening process. This study aims to analyse the flowability and crack patterns of lightweight concrete subjected to compressive and tensile loadings. A lightweight concrete specimen was made using foam, fine aggregate, and Portland Composite Cement. Foam agent and water are combined in a 3:10 ratio to produce lightweight concrete. There were three different foam volume variations namely 15.7 litres, 25.12 litres, and 37.68 litres. The specimens were prepared using cylinders with dimensions of 10 cm by 20 cm. Flowability testing was carried out when lightweight concrete is still in fresh condition. Cracks in foam concrete were examined after compressive and tensile strength tests were performed at 3, 7, and 28 days of age. The research results show that the fresh lightweight concrete mixture from each mixture is sticky, which could prevent the segregation or bleeding. The crack patterns for the compressive and indirect tensile strength tests were essentially identical; namely parallel to the load direction at the age of 3, 7, and 28 days. The cracks were categorized as columnar crack patterns. It could also be noted that the concrete became more resistant as it ages, as the number of cracks decreased.

Fly Ash Substitution in Lightweight Concrete for Rigid Pavement Construction on Low-Bearing-Capacity Soil

Peatlands are more likely to be affected by intense precipitation and soil erosion, thus requiring modifications for stabilized soil and subgrade protection. This experimental study aimed to find a suitable pavement type using fly ash, an unutilized byproduct from coal burning processes, for peatland areas with a low bearing capacity. We designed lightweight concrete specimens using 15% fly ash substitution to be incorporated into rigid pavement construction. The concrete quality was assessed through compressive and flexural strength tests performed at the ages of 7, 14, and 28 days in order to shorten the project durations and prevent further traffic delay. The obtained results suggested that the substitution of fly ash in 15% of the lightweight concrete mixture can be taken into account to achieve a mixture of a lightweight concrete that meets the general specification criteria for cement-treated subbases (CTSBs). Furthermore, the utilization of fly ash as a new material is considered substantial in managing existing waste-related environmental problems, as well as soil stabilization and subgrade protection problems for low-bearing-capacity soil areas.

Mechanical and shrinkage performance of steel fiber reinforced high strength self-compacting lightweight concrete

This study investigated the effects of mixture proportion on the mechanical and shrinkage behaviors of steel fiber reinforced high strength self-compacting lightweight concrete (SHSLC) mixtures incorporating bottom ash aggregates for internal curing. In this study, different types of fine aggregates, fine aggregate ratios, supplementary materials such as silica fume (SF) and colloidal nano-silica (CNS), and four types of steel fibers were considered to develop SHSLC. The self-compacting characteristics of concrete were evaluated by means of slump flow, J-ring flow, and V-funnel tests. The test results indicate that incorporation of SF and CNS had a positive effect on the mechanical properties, but 4% incorporation of CNS decreased workability and strength due to the agglomeration of mixture. The addition of steel fibers improved compressive strength, and flexural toughness of SHSLC, but reduced the flowability and passing ability with increased fiber contents. Due to the internal curing from coarse bottom ash, significant reduction of autogenous shrinkage up to 33% was observed, whereas 7% for drying shrinkage. The incorporation of fibers reduced the autogenous and drying shrinkage up to 31% and 22% compared with non-fiber reinforced concrete, respectively. Finally, the autogenous shrinkage behavior was simulated with several models in the literature, and a model for high strength self-compacting lightweight concrete with and without fibers considering equivalent age was proposed.

The Influence of Waste Plastic Fiber on the Characteristics of Light Weight Concrete with Expanded Polystyrene (EPS) as Aggregate

This research aims to create lightweight concrete mixtures containing waste from local sources, such as expanded polystyrene (EPS) beads and waste plastic fibers (WPFs), all are cheap or free in the Republic of Iraq and without charge. The modern, rigid, and mechanical properties of LWC were investigated, and the results were evaluated. Three mixtures were made, each with different proportions of plastic fibers (0.4%, 0.8%, 1.2%), in addition to a lightweight concrete mixture containing steak fibers (0.4%, 0.8%, 1.2%), in addition to a lightweight concrete mixture. It contains 20% EPS. The study found that the LWC caused by the addition of WPFs reduced the density (lightweight) of the concrete mixtures because EPS tends to form more blocks, absorb water, and dry the mixture. While the increase in WPF content increased in compressive strength, as the compressive strength of the concrete mix containing (EPS) was only 13.6 MPa, the compressive strength increased to 17.6 MPa when WPFs were added. The addition of plastic also increased the bending resistance, where the bending resistance of the concrete mix containing (EPS) was only 2.26 MPa and increased to 2.66 MPa when (WPFs) were added.

Perlite and Rice Husk Ash Re-Use As Fine Aggregates in Lightweight Aggregate Structural Concrete—Durability Assessment

In this paper, perlite mining and rice production by-products, namely run-of-mine perlite and rice husk ash, are used as fine aggregates in combination with pumice and calcareous aggregates to produce lightweight concrete. Their use is evaluated mainly in terms of the durability of the concrete, by comparing four optimized lightweight concrete mixtures of similar density and strength with a reference one of normal weight. The sorptivity due to capillary sorption, open porosity, chloride migration, penetration resistance, and freeze and thaw response were studied to evaluate the durability of the lightweight concrete. According to the experimental results, the examined mixtures developed an adequate strength in order to be classified into strength classes greater than LC25/28 and, therefore, be used in structural applications. The durability of the mixtures was also sufficient, especially as far as the chlorides’ penetration resistance is concerned, which was found to be up to 39% lower compared to the reference mixture. The sorptivity and open porosity of the LWC mixtures increased due to the porous nature of the lightweight aggregates, and the mixtures were also found to be susceptible to freeze and thaw cycles. Exceptionally, the lightweight concrete mixtures comprising pumice and perlite exhibited a lower sorptivity and resistance to chloride penetration than the standard concrete and a promising tolerance to freezing and thawing. Thus, the optimized combination of pumice and perlite is a sustainable recommendation for structural lightweight concrete production and use, promoting the wider exploitation of natural aggregates with an acceptable compromise on strength and durability.

Characteristic of Polymeric Lightweight Aggregate with Coal Fly Ash and Epoxy Resin for Manufacturing the Lightweight Concrete

Concrete is an essential element and is widely used in various industrial construction works. However, concrete is weak in its specific gravity range of 2200 – 2500 kg/m³. Using lightweight aggregates is one way to reduce the weight of concrete. In Indonesia, the availability of coal fly-ash (CFA) is easy to obtain and abundant, while the utilization rate is still low. To overcome this problem, CFA mixed with epoxy resin (ER) is used as a binder to manufacture polymer lightweight aggregates (PLA). The manufacturing process uses a simple mixing method using three different compositions. The ratio composition of coal fly-ash and epoxy resin proposed in this study are 90:10 (PLA_90:10), 80:20 (PLA_80:20), and 70:30 (PLA_70:30). From the results of testing the compressive strength and specific gravity of the three aggregate compositions, it was found that PLA_70:30 had a compressive strength of 74.60 MPa and a specific gravity of 1668 kg/m³ at an aggregate age of 28 days. The aggregate microstructure is shown by scanning electron microscope (SEM) photo of each composition. The greater the composition of the epoxy resin on the lightweight polymer aggregate, the better the bond between the aggregate particles. The coal fly-ash is improperly bound and the aggregate becomes more fragile when there is less epoxy resin used. Furthermore, PLA_70:30 aggregate, which has become crushed aggregate, is inserted into a lightweight concrete mixture with a design quality of f'c = 17.5 MPa, following the requirements for lightweight concrete quality. The result is lightweight concrete with a compressive strength of 18.38 at 28 days, and specific gravity that varies between 1918.87 kg/m³ - 1928.93 kg/m³. According to the ASTM, the results of the compressive strength and specific gravity tests show that PLA_70:30 meets the standards specified as lightweight aggregates for lightweight structural concrete.

Evaluation of Thermal Conductivity of Sustainable Concrete Having Supplementary Cementitious Materials (SCMs) and Recycled Aggregate (RCA) Using Needle Probe Test

The evaluation of thermal properties is commonly conducted to characterize non-structural materials, such as lightweight concrete, that are used for thermal insulation. Such materials are designed for thermal resistivity applications. Due to the increased demand to adopt sustainable practices in the construction industry, municipalities in the United Arab Emirates (UAE) emphasize the use of sustainable materials in construction, such as green concrete. The cement in green concrete is partially replaced with supplementary cementitious materials (SCMs); these materials are by-product waste from other industries. The SCMs can contribute to sustainability by reducing the concrete carbon footprint. They can also help in extending concrete durability and service life. However, there is still a lack in the literature regarding the effects of these materials on the thermal properties of concrete. This paper investigates the thermal properties of sustainable concrete mixes incorporating various types of SCMs. The SCMs that are considered in this investigation are fly ash, ground granulated blast-furnace slag (GGBS), and microsilica. Another way to improve the sustainability of the concrete is to partially replace the natural aggregates with recycled aggregates. Thus, a group of the concrete mixes in this investigation were prepared by replacing 40% of natural aggregates with recycled aggregates to investigate the effects of recycled aggregate on the thermal properties of concrete. Further, the thermal properties of three lightweight concrete mixtures commonly used in construction were evaluated. All concrete mixtures were examined for thermal conductivity and resistivity in accordance with ASTM D5334. The results of this investigation showed that SCMs and recycled aggregates have a significant impact on the thermal properties of concrete. The high replacement of ground granulated blast-furnace slag (GGBS) resulted in a remarkable increase in thermal conductivity. This investigation provides significant conclusions and recommendations that are of practical importance to the construction industry in the UAE to promote sustainability. This research aims at formulating recommendations for the effective use of SCMs in the construction industry in the UAE based on their effects on the thermal properties of concrete.

Mechanical behaviour and environmental benefit of eco-friendly steel fibre-reinforced dry UHPC incorporating high-volume fly ash and crumb rubber

This study evaluates the impact of high-volume fly ash (HVFA) and waste crumb rubber (CR) on the mechanical property and environmental benefit of steel fibre-reinforced dry UHPC (FR-DUHPC) designed in a previous study. FA was introduced at 20–60% by mass substitution for cement with fibre dosage of 1.5 vol. %. Then, waste CR with different meshes were added as partial/completed replacements of coarse and medium sand with three volume contents of fibres (0.5%, 1.0% and 1.5%). Test results indicated that in the case of 1.5% fibre reinforcement, the increase in FA content and the addition of CR aggregate markedly reduced the density, modulus of elasticity and strength behaviour, whereas had minimal effect on the post-peak ductility of the assessed mixtures under compression and bending loads. Owing to the adopted moist/steam curing and the continuous pozzolanic reaction, the contribution of FA effect to both strengths at various ages was apparently increased and 50% of cement substitution was considered to be the most suitable FA addition in this study. For rubberized concrete reinforced with 0.5–1.5% steel fibres, the mechanical properties increased gradually with fibre dosage and curing age. However, the effect was evidently weakened with the addition of finer CR aggregate, and increasing the fibre dosage contributed to more positive impact on ductility rather than the load-carrying capacity. In summary, the flexural property benefits derived from the inclusion of steel fibre, FA and waste CR, as well as the eco-friendly benefits derived from the cost saving, energy conservation and carbon emission reduction, render the developed lightweight concrete mixture to be broadly used in dry concrete applications with different strength requirements that are mainly subjected to bending loads during serviceability.

ДИСПЕРСНО–АРМОВАНИЙ ЛИТИЙ КЕРАМЗИТОБЕТОН НА МЕХАНОАКТИВОВАНОМУ ШЛАКОПОРТЛАНДЦЕМЕНТІ

The paper examines the properties of dispersed-reinforced cast expanded clay concrete on mechanically activated slag Portland cement with the addition of Super-PC polycarboxylate superplasticizer. Experimental studies have established the possibility of obtaining lightweight concrete based on high-mobility lightweight concrete mixtures with a diameter of a cone of at least 50 cm. It has been experimentally confirmed that the hydrophobization of expanded clay gravel helps to increase the spreading of the cone of the concrete mixture, and also increases the viability of the concrete mixture. The expediency of mechanical activation of slag Portland cement in the presence of Super-PC to obtain light concrete with increased characteristics in terms of frost resistance, abrasion and impact strength is shown. The results of research are presented, which indicate that the introduction of basalt fiber into slag Portland cement together with the mechanical activation of the binder allows to reduce the abrasion of concrete from 0.44 to 0.13 g/cm2, as well as to increase the impact strength of concrete by almost 2 times (compared to with control). The proposed complex of recipe-technological influences allows to ensure frost resistance of concrete not less than 350 cycles of alternating freezing and thawing. It was established that the mechanical activation of the binder causes an increase in the strength of concrete at the age of 3 days from 11.3 to 16.2 MPa, that is, by more than 40% compared to the control. The introduction of basalt fiber in the amount of 1% of the mass of the binder ensures an increase in the strength of concrete by 10-15%. The joint effect on slag Portland cement of mechanical activation, additives of poly-carboxylate Super-PC and basalt fiber causes an increase in the strength of concrete at the age of 28 days (compared to the control) from 11.3 to 29.5 MPa, i.e. more than 2.5 times. In general, the combined use of the listed recipe-technological factors ensures an increase in the main physical and mechanical characteristics of lightweight concrete.

İKİ FARKLI POMZA AGREGASI İÇEREN CAM TOZU KATKILI BETONLARIN FİZİKSEL VE MEKANİK ÖZELLİKLERİNİN İNCELENMESİ

In this study, the physical and mechanical properties of concretes produced using basaltic and acidic pumice at different rates were investigated. Pumice aggregates have been replaced by 50% and 100% of normal-weight aggregates. In addition, in order to produce a more environmentally friendly concrete, 5 different mixtures were produced by replacing waste glass powder from cement at the rate of 10%. Unit volume weight, water absorption, porosity, ultrasonic pulse velocity and compressive strength tests were applied to the produced samples. As a result of the study, while the 100% substituted acidic pumice aggregate gave the lowest density, ultrasonic sound transmission velocity and compressive strength values, the water absorption and porosity values were the highest. Except for the concrete mixture containing 100% acidic pumice aggregate, all of the other lightweight concrete mixtures have higher compressive strength values than the compressive strength value of the structural light-weight concrete (17,2 MPa) specified in the TS 2511 standard.

Effects of Using Pumice Sand as A Partial Replacement of Fine Aggregate in Lightweight Concrete Mixtures

Purpose: The advantage of lightweight concrete is to reduce the weight, which is considered the dead load on the structure. This study aims to determine the effect of replacing sand with pumice sand as fine aggregate in lightweight concrete. The substitution affects the compressive strength, split tensile strength, and weight. 
 Design/methodology/approach: The research method is through testing in the laboratory, where the test specimens are cylindrical following SNI with a height of 30 cm and a diameter of 15 cm totaling 50 pieces. The composition ratio between regular and pumice sand is 75%:25%, 50%:50%, 25%:75%, and 0%:100%, respectively. Control of the test object using 100% regular sand.
 Findings: This research shows that adding pumice sand into the mixture decreases the volume weight. The weight of the volume of concrete produced is < 1,900 kg/m3, which is classified as a lightweight one.
 Research limitations/implications: The resulting compressive strength of 56.63 kg/cm2 decreased against the control test object by 81.10%. At the same time, the split tensile strength is 1.13 kg/cm2, or a decline of 52.05% from the control test object.
 Originality/value: This paper is an original work.
 Paper type: Research paper

Investigation on optimal lightweight expanded clay aggregate concrete at high temperature based on deep neural network

AbstractThis study explores the effects of mixture design parameters on the residual mechanical properties of lightweight expanded clay aggregate (LECA) concrete exposed to elevated temperatures. A total of 30 lightweight concrete mixtures were cast and exposed to three elevated temperatures, namely 250°C, 500°C, and 700°C. The test variables comprised the LECA percentage used as partial volume substitution for natural sand (0%, 25%, 50%, 75%, and 100%), silica fume partial replacement for cement by weight (5%, 7.5%, 10%, 12.5%, and 15%), cement content (300, 400, 500, 600, and 700 kg/m3), and different water‐to‐cement (W/C) ratios (0.25, 0.313, 0.375, 0.438, and 0.5). The compressive and indirect tensile strengths were measured before and after exposure to elevated temperatures. The results indicate that the lightweight concretes incorporating higher contents of cement and silica fume and made with lower W/C ratio exhibited higher initial mechanical properties yet incurred more significant drop in mechanical properties after exposure to 500°C and 750°C.

Segmentação de imagens microtomográficas tridimensionais de concretos leves usando técnicas de limiarização automática para cálculo de porosidade aparente

Construction industry demands sustainable processes and the addition of lightweight aggregates presents as an effective solution to obtain different concrete mixtures by recycling production outputs from other industries, as the Ethylene-Vinyl Acetate (EVA), raw material mostly utilized at footwear industry. Despite all the sustainable appeal in the recycle of EVA or other lightweight aggregates into the concrete mixtures, the loss of resistance is a frequent issue that can be prevented by adding natural fibers, such as piaçava, to the composition. Aiming the usage of these new materials, it is necessary to know their characteristics. In materials science the techniques of non-destructive tests stand out for maintaining the integrity of the material in question promoting savings and sustainability. In this work, X-ray computerized microtomographic images from samples of different lightweight concrete compositions were analyzed. These analyzes were carried out by image processing techniques, such as the Otsu and k-means, aiming to characterize the microstructure of the cementitious matrix of lightweight concrete mixture with EVA and piaçava fiber. The three-dimensional analysis of the microtomographic images offers descriptors that make it possible to characterize these samples. The results were satisfactory when compared with mercury porosimetry tests performed on the samples.