Lightweight Concrete Mixtures Research Articles

Behavior of structural lightweight concrete produced with expanded clay aggregate and after exposure to high temperatures

The residual compressive strength of eight lightweight concrete mixtures containing three commercial grading (Liapor HD 5 N, Liapor HD 7 N, and Liapor 8F) of coarse lightweight aggregate (LWA) were determined after to expose at high temperatures. Eight mixes were produced, two by normal weight aggregate and the rest by different types of LWA. The produced concrete was analyzed after high temperature exposure and the effect of using LWA, the type of LWA, and compaction method was studied. To do so, visual inspection, residual compressive strength, crack pattern, spalling, and thermoanalytical analysis were conducted. Generally, it could be concluded that concrete formulations with LWA behave more advantageous up to 500 °C, compared to those with quartz gravel aggregates. Moreover, this study found that an ideal type of LWA to produce structural concrete was Liapor HD 5 N, which was used for producing the mixes L1 and L3.

Theoretical and computational modeling of thermal properties of lightweight concrete

There is an increasing interest in developing and utilizing lightweight concrete (LWC) due to its environmental, structural, and economic benefits. In addition, replacing natural sand with lightweight particles has a direct positive impact on the thermal properties of the concrete mix. While there are many experimental studies available on the thermal properties of LWC, limited predictive capabilities exist. In this work, we examine a number of analytical models and assess their capabilities of predicting the effective thermal conductivity (ETC) of LWC mixtures. Six different mixtures were prepared by replacing 0%, 20%, 40%, 60%, 80%, and 100% of natural sand by volume with expanded perlite (EP) aggregate. Experimental measurements were conducted to evaluate their thermal conductivities (TC), thermal diffusivities, and volumetric heat capacities. In addition, X-ray computed tomography (CT) images coupled with numerical simulations were employed to perform microstructure analysis and numerical simulations of the ETC. This paper presents a comparison between the experimental and analytical results, and it discusses the predictive capabilities of the analytical models. Experimentally, the use of EP reduced the ETC from 1.81 W. m-1. K-1 at 0% EP to 0.688 W. m-1. K-1 at 100% EP. Among the analytical models, the Woodside & Messmer model exhibited the best prediction of the experimental data with a maximum error of 18.7%. The numerical simulations provided predictions of the ETC at 0%, 60%, and 100% EP with an error up to 10.5%. Based on the concerned application, the incorporated EP percentage can be optimized emanate on the relationship between ETC and the unit weight of LWC. The analytical Woodside & Messmer model and the numerical simulations using of X-ray CT images model can be used in the design of LWC mixtures with desired thermal properties.

Replacement of Conventional Concrete by Light Weight Concrete

Abstract: Lightweight concrete (LWC) allows for larger spans, fewer piers, and longer bridge designs due to its lower weight and improved durability. Because superstructures with broader shoulders or additional lanes may be improved without requiring extensive work on the substructure, LWC is a particularly desirable construction material at the moment. The goal of this research was to determine the density (unit weight), splitting tensile strength, and elastic modulus of LWC mixtures under various curing circumstances in order to gain a better knowledge of LWC qualities that are critical for long-lasting and costeffective buildings. The researchers also looked at the relationship between the results of the fast chloride permeability test and the outcomes of other tests and the Werner probe surface resistance test to see if the latter may be used to forecast the permeability of LWC mixtures because it is faster and more convenient. Keywords: Light weight aggregate, pumice, compressive strength, density,

Investigating fracture characteristics and ductility of lightweight concrete containing crumb rubber by means of WFM and SEM methods

The use of lightweight and recycled materials such as crumb rubber due to unknown behavior in concrete can change the cracking behavior and fracture parameters. On the other hand, nowadays, using waste materials as a substitute for natural aggregates in concrete is an effective solution to environmental problems. This study investigated the effect of crumb rubber on the main fracture characteristics and ductility of lightweight concrete (LWC). For this purpose, a part of aggregates replaced with crumb rubber in volume of 4 different percentages (5, 10, 15 and 20%). The main experiment in this research was three-point bending tests that were performed on notched beams. Fracture parameters were determined using two different methods, Work of Fracture Method (WFM) and Size Effect Method (SEM). The results show that by increasing the replacement percentage of crumb rubber instead of fine aggregates from 0 to 20%, the total fracture energy (GF) and characteristic length (Lch) in WFM increase by 63% and 99%, respectively. Also, By increasing the crumb rubber replacement up to 20% in LWC, the initial fracture energy (Gf), length of fracture process zone (Cf) and fracture toughness (KIC) in SEM has increased 1.92, 3.4 and 1.14 times, respectively, compared to lightweight concrete without rubber, while the brittleness number (β) decreased in SEM. Furthermore, the results showed that the fracture surface, the size of the plasticity zone of the crack tip decreases with the reduction of the crumb rubber content. Finally, the ratio of fracture energy obtained from WFM. GF, to initial fracture energy obtained from SEM, Gf, for lightweight concrete containing crumb rubber was approximately 2.8. On the other hand, this study can put a step forward in the fracture mechanics field for sustainable LWC mixtures.

Heat-insulating non-autoclaved lightweight concrete with hydraulic ash removal

The paper presents research results of natural hardening of lightweight concrete with aluminosilicate ash generated by the Thermal Power Plant in Seversk (Tomsk, Russia). Today, it is necessary to develop effective building materials with improved operational properties by using local natural and technogenic raw materials. The acceleration of the structure formation and required plasticity for a transportation and molding of lightweight concrete products are achieved by using finely dispersed aluminosilicate minerals and plasticizers for natural hardening of lightweight concrete. The concrete mixture and lightweight concrete are studied in the TSUAB laboratory accredited in accordance with national standard requirements. The optimum content of hydraulic ash in lightweight concrete mixture is 10–15 wt.%. the compressive strength lightweight concrete with D400 density increases by 26−66 % after 28-day curing, when adding the Relamix T-2 plasticizer and ash from the Thermal Power Plant. Its water absorption reduces by 30 wt.% with insignificant decrease in thermal conductivity. Technological solutions are developed for the production of lightweight concrete with ash ash and slag materials for wall structures in individual housing construction.

Fiber-reinforced lightweight concrete formulated using multiple residues

Waste from mineral extraction and the manufacturing industry can be used to produce lightweight concrete. Moreover, fiber-reinforcing lightweight concrete is capable of reducing structural weight and piece sections, resulting in a variety of applications such as flooring, shotcrete and precast concrete. This work aimed at studying fiber-reinforced lightweight concrete mixtures prepared with the combined addition of multiple residues, i.e., rubber, limestone and porcelain dust residues along with expanded clay. 0.2% to 0.6 vol% steel, polypropylene, glass and carbon fibers, were studied. A reference fiber-free lightweight mixture with compressive strength of 32 MPa was also produced. The physical characteristics of the mixtures were evaluated by consistency tests, void indices, water absorption and density measurements. The mechanical characterization was carried out by compressive, flexural and fracture strength in addition to toughness tests. The results indicated that the addition of fibers decreased the workability of the concrete, but improved flexural and fracture strength along with toughness. The effects of fiber volume and properties, such as shape factor, tensile stress and elastic modulus on the properties of the resulting materials were evaluated. Steel and carbon fibers resulted in the best fracture strength properties, due to their high modulus of elasticity and tensile strength.

Durability of Structural Lightweight Concrete Containing Different Types of Natural or Artificial Lightweight Aggregates

Different structural lightweight concrete mixtures of specific density and strength classes were produced by using various lightweight aggregates (LWAs) such as pumice, perlite, and rice husk ash. Their properties were evaluated in fresh and hardened states with regards to compressive strength and durability parameters such as water absorption (open porosity and capillary absorption), chloride’s penetration resistance, and carbonation depth. According to the results, most LWA concrete mixtures performed satisfactorily in terms of the designed strength and density and they could be used as structural LWA concrete mixtures. As far as the durability of LWA concrete was concerned, open porosity and resistance to the carbonation of LWA concrete were burdened with the porous nature of LWAs, while sorptivity in some mixtures and especially chlorides’ penetration resistance in all mixtures were reported to be significantly improved. The overall strength and durability performance of the designed LWA concrete mixtures could mitigate the concerns stemming from its vulnerability to extreme exposure conditions.

Behavior of novel hybrid lightweight concrete composites under drop-weight impact loading

This investigation evaluated the feasibility of combining lightweight concrete (LWC) and engineered cementitious composite (ECC) in specific configurations to develop a lightweight hybrid composite with improved impact resistance. In this study, three mixtures were investigated: one LWC mixture fully produced with lightweight fine and coarse expanded slate aggregates; one ECC mixture developed with polyvinyl alcohol fibers (ECCP); and one ECC mixture developed with steel fibers (ECCS). For testing, cylindrical specimens and small-scale beams were constructed in a two-layer composite system having different configurations (i.e., different arrangements and depths). Additional specimens fully cast with LWC, ECCP, and ECCS were tested for comparison. The interface bond strength between LWC and either ECCP or ECCS was also evaluated. The performance of the developed composites was assessed under static flexural loading and drop-weight impact. The results showed that both ECCP and ECCS could achieve a good bonding with LWC substrate, i.e., above 90% of that measured for the monolithic LWC specimens, even with no surface preparations (i.e., roughening or using shear keys). Combining LWC with either ECCP or ECCS generated novel lightweight hybrid composites that can offer superior performance for different structural lightweight members exposed to high impact loading. For given arrangement and depth, the LWC-ECCS composite exhibited higher mechanical and impact performance whereas the LWC-ECCP was distinguished by achieving an excellent impact resistance at a lighter self-weight.

Life cycle assessment multi-objective optimization and deep belief network model for sustainable lightweight aggregate concrete

There has been rapidly growing demand for manufacturing structural lightweight concrete (LWC) owing to its reduced gravity and seismic loads. Concrete is required to meet increasingly more stringent eco-efficiency and sustainability requirements. Therefore, an experimental study on 30 LWC mixtures (S1 to S30) was conducted. The experimental variables included the percentage of lightweight expanded clay aggregate (LECA), water-to-cement ratio, cement content, and silica fume dosage. The effects of the test variables on the compressive and tensile strengths of LWC were assessed. The resulting experimental database was used to train and test deep belief network models for accurate prediction of the mechanical properties of LWC. Moreover, life cycle assessment based multi-objective optimization was deployed for optimizing sustainable LWC mixture proportions with minimized environmental footprint and life cycle cost, while maximizing the mechanical strength. The genetic algorithms approach was furtherly used to determine optimal LECA replacement levels for natural aggregates by minimizing the economic cost and environmental life cycle impact and maximizing the compressive and tensile strengths. The compressive and tensile strengths of LWC specimens ranged from 14.9 to 50.1 MPa and from 1.62 to 3.9 MPa, respectively, with the lowest and highest values belonging to mixtures S23 and S7, respectively. The LWC mixture S9 achieved the least environmental impact, while mixture S18 induced the highest environmental burden. The cost increased with increasing mechanical strength, life cycle, and LECA replacement level. Overall, the computational approach allows the user to accurately predict the mechanical strength of LWC and optimize sustainable LWC mixtures for specific target performance objectives, tailored economic cost, and eco-efficiency performance.

Change in effective viscosity and level of synergism of cement-containing mechanoactivated suspension

The article considers the influence of prescription factors (ground chamot, superplasticizer C-3) on the change of the effective viscosity of mechanically activated cement-containing suspensions used in the technology of lightweight concrete mixtures. The synergistic effect of reducing the viscosity of cement-containing suspensions during their activation in high-speed mixers of turbulent type in the presence of C-3 was revealed. Optimized modes of mechanical activation of suspensions that provide the maximum reduction of their effective viscosity.

Automating the mixture design of lightweight foamed concrete using multi-objective firefly algorithm and support vector regression

Lightweight concrete (LWC) is widely used in the construction industry due to a variety of advantages. However, compared with traditional normal-weight concrete, more influencing variables (e.g. types of lightweight aggregates) must be considered to optimize multiple properties including uniaxial compressive strength (UCS), density and cost. This makes the mixture design of LWC more difficult or sometimes impossible using laboratory experiments. To address this issue, this study proposes a multi-objective optimization (MOO) method using machine learning and metaheuristic approaches for LWC mixture design through a two-step approach. In the first step, a least squares support vector regression (LSSVR) model is constructed to predict multiple properties of LWC. The hyper-parameters of the LSSVR model are tuned using the firefly algorithm (FA). A dataset containing a large number of different mixtures of LWC is compiled from published literature. High prediction accuracy (0.97 for UCS and 0.90 for density) is achieved on the test dataset (including 30% of all the instances). In the second step, a newly developed multi-objective FA (MOFA) model is used to optimize the LWC mixture, while satisfying the constraints. The Pareto fronts of the triple objectives (UCS, cost and density) are successfully obtained. The proposed MOO method is powerful and efficient in finding optimal LWC mixtures with conflicting objectives and therefore decision making can be facilitated in early phases of construction.

3D printable lightweight cementitious composites with incorporated waste glass aggregates and expanded microspheres – Rheological, thermal and mechanical properties

One of the fields in the construction industry where 3D printing of cementitious composites can play a significant role is associated with manufacturing of lightweight structures. Thanks to 3D printing, structural self-weight can be reduced by topology optimization of printed elements. Moreover, further decrements of self-weight and improvement of thermal insulating properties can be achieved by the mixture design and introduction of materials of low thermal conductivity. To date, limited knowledge on lightweight printable mixtures is available. The main objective of this study is to develop 3D printed lightweight concrete (3DPLWC) mixture, with the intention of replacing natural aggregate with waste glass (WG) by 50 vol.-% and 100 vol.-%. Moreover, expanded thermoplastic microspheres (ETM) were incorporated into the mixture. This led to a reduction in density of the mixtures as well as the thermal conductivity by up to 40%. Comprehensive evaluation of material's fresh properties revealed that the addition of ETM results in 3D printable material with lower yield shear stress and higher plastic viscosity by 28% and 66%, respectively, compared to the mixes without ETM. Moreover, improvement of shape retention, flowability, setting times, and early-hardened mixtures' properties was observed. The mechanical properties of 3DPLWC showed that the replacement of natural aggregate by 50 vol.-% WG led to enhanced flexural and compressive strength of the composite, while full replacement resulted in retaining or slight reduction of the mechanical properties.

PENGARUH LIMBAH ABU ALUMUNIUM SEBAGAI SUBTITUSI AGREGAT HALUS DENGAN FAKTOR AIR SEMEN YANG BERBEDA PADA BETON RINGAN TERHADAP KUAT TEKAN DAN ABSORBSI

Lightweight concrete is concrete containing light aggregate and has a density less than 1900 kg / m3 (SNI-03-2847-2002). The purpose of this thesis is to examine the effect of the utilization of aluminum ash waste for fine aggregate substitution with variations in the water cement ratio of 0.40, 0.50 and 0.60 in terms of concrete compressive strength, absorption power and production cost of making lightweight concrete with fine aggregate substitution using aluminum ash waste compared to lightweight concrete without a mixture. Using the ash as a substitution material of sand in concrete by 10% and the variation of water cement ratio of 0.40, 0.50 and 0.60, identifying the physical properties of aluminum ash, aggregate physical properties, hard concrete performance including concrete compressive strength and absorption. Hard concrete performance testing is carried out at the age of 7, 14, 21 and 28 days. Test objects for W/C ratio 0.4 as many as 15 pieces, for FAS 0.5 as many as 15 pieces and for FAS 0.6 as many as 15 pieces with a total of 45 test specimens. The results of the study are as follows: performance of concrete with 10% aluminum ash mixed concrete with a water cement ratio of 0.4 produces a concrete compressive value of 3.83 MPa with a weight of 1553 kg / m3. The compressive strength does not meet the target compressive strength of 17.24 MPa and the cost used to make 1 m3 of concrete mixture is cheaper Rp. 22,930.05 of concrete without alumunium ash mixed. Based on the analysis used, the use of aluminum waste ash requires another method when making the mix design and the use of light aggregate needs to be studied beforehand so that the target concrete compressive strength is as planned and aluminum waste ash mixture is preferred for non-structural concrete or lightweight concrete mixtures

The effect of pozzolanic mineral additives on the strength and durability properties of structural lightweight concrete

Structural lightweight concretes have the potential to be used in road pavements and bridge decks due to their properties such as sufficient wear resistance, high impermeability, superior freeze-thaw resistance and ductile behavior. However, road pavements are directly exposed to nitric acid and sulfuric acid solutions created by the exhaust gases of transportation vehicles in humid environments. Therefore, the concrete to be used in road pavements must be resistant to these acid effects. In addition, sufficient strength must be guaranteed when used as pavement material. The aim of this study is to produce lightweight concrete suitable for road pavements and other structures exposed to acid effects. For this, the effect of silica fume (SF) and fly ash (FA) on acid resistance and strength development of lightweight concrete with perlite aggregates was investigated. Five different lightweight concrete mixtures were produced by substituting 0%, 5%SF, 10% SF, 10%FA, 20% FA instead of cement by weight. Natural perlite rock has been used as an aggregate source in order to provide high strength and lightness. The cylindrical samples produced were kept in lime saturated water cure for 120 days and their compressive strength was measured on the 28th, 56th, 90th and 120th days. In addition, in order to monitor the acid resistance, the strength changes of the samples exposed to 5% sulfuric acid and 5% nitric acid solution after 28 days of standard curing were followed until the 120th day. Results show that, SF and FA additives increase the compressive strength especially at older ages. In case of 10% SF, the 120-day strength value increased by 18.6% and reached 34.5 MPa. Also, lightweight perlite concrete is highly resistant to nitric acid and sulfuric acid effects. In the case of 92 days of nitric acid and sulfuric acid exposure, the strength losses are only 5.2% and 13.4%, respectively. In order to fully benefit from SF and FA, concretes must be adequately cured before acid attack. It has been concluded that it is possible to produce high-strength and acid-resistant lightweight concretes suitable for road pavements and many other structural elements by using natural perlite aggregate.

Experimental Study of Compressive Strength of Lightweight Concrete Using Wood Charcoal

The use of lightweight concrete materials in Indonesia, especially in the Merauke Regency area can be an alternative amid the rapid development of the housing sector. In this experimental study, the author took the initiative to replace coarse aggregate with wood charcoal as light coarse aggregate. The purpose of this study was to determine the value of compressive strength and to determine whether the wood charcoal material met the standard of lightweight concrete coarse aggregate. Planning the proportion of lightweight concrete mixture in this study using a volume ratio between cement, sand and wood charcoal of 1: 2, 1: 2: 2.5 and 1: 2: 5 with variations of test days at 3, 7, 14, 21 and 28 day. From the results of the compressive strength test of lightweight concrete, the use of wood charcoal aggregate as coarse aggregate in concrete causes the value of the compressive strength of concrete to decrease.

The Use of Nutmeg Shell as a Lightweight Concrete Material

Lightweight concrete is concrete that has a lighter density than concrete in general. Nutmeg shell utilization as coarse aggregate is expected to be the added material in the lightweight concrete mixture. The purpose of this study is to determine characteristics of the concrete aggregate and the compressive strength of the concrete design based on the DOE (Department of Environment) method and the SNI Standard. In this research, the use of nugmet shell was varied as follows: 10%, 20%, 30%, 40% and 50% of the concrete weight. The research result shows that the amount of nugmet shell used into the concrete mixture affects the compressive strength of the concrete characteristics (fck’). The compressive strength of the concrete characteristics increases with the increase in the amount of nutmeg shell used in the concrete mixture. The compressie strength increases consecutively from 28.42 kg /cm2, 31.65 kg / cm2 to 32.68 kg /cm2 with the increase in the amount of nutmeg shell: 10%, 20% and 30%. Then, it decreases into 29 , 09 kg /cm2 and 27.38 cm2 with further increasing 40% and 50% nutmeg shell of the concrete weight. The average weight of the concrete mixture using nutmeg shell was 1202 kg/m3with the maximum compressive strength value of 3.2 MPa, thus it could be categorized as the lightweight concrete.

Lightweight Cellular Hollow Concrete Blocks Containing Volcanic Tuff Powder, Expanded Clay and Diatomite for Non-Load Bearing Walls

Lightweight cellular hollow concrete (LCHC) block is a type of masonry unit manufactured by precast technique. LCHC blocks are produced by the mixing of Portland cement, volcanic tuff, expanded clay and diatomite for building applications. LCHC blocks are lightweight, and the frequent cellular holes provide excellent thermal and acoustic performance, fire resistance and resistance to harsh environmental conditions. In this research work, LCHC blocks with 28 different mix proportions were cast into a mould with vibro-compacting, de-moulded immediately and transferred to a storage area for curing up to 120 days in standard air condition at room temperature. The blocks were designed with 21 cellular spaces of 10 mm width. For each mixture, twenty four block specimens were prepared and tested in the air dry condition for compressive strength and water absorption in accordance with BS 1881: Part 116. This paper initially examines how volcanic tuff powder affects the characteristics of lightweight concrete masonry mixtures and investigates the use of quaternary blends containing volcanic tuff, expanded clay, diatomite and Portland cement to produce LCHC blocks for partitioning walls.

Development length of prestressing strands cast in lightweight self-consolidating concrete

This paper investigates the development length of 0.6 in. (15.2 mm) diameter prestressing strands. Fifty flexural tests were conducted on twenty-five pretensioned concrete beam specimens, which had a cross-section of 6.75 in. by 12 in. (170 mm by 305 mm) and were 18 ft (5.5 m) long. The specimens were cast with two normal weight and four lightweight self-consolidating concrete mixtures with compressive strengths of 4000 psi (27.6 MPa) at prestress transfer and 6000 psi (41.4 MPa) at 28-day of age or 6000 psi (41.4 MPa) at prestress transfer and 7000 psi (48.3 MPa) at 28-day of age. The measured development length was approximately half the value predicted using the ACI 318 and AASHTO equations. Shear cracking leading to shear and bond failures at short embedment lengths made determination of the true development length difficult for lightweight specimens, but embedment lengths resulting in pure flexural failure were similar for all specimen types.

Mechanical Properties of Lightweight Concrete Using Class F Fly Ash as a Partial Replacement for Ordinary Portland Cement

This study shows the mechanical properties of lightweight concrete (LWC) made by partially replacing ordinary Portland cement (OPC) with class F fly ash (FFA). Natural sand and pumice were used as the fine aggregate and coarse aggregate, respectively. Five LWC mixtures, M1, M2, M3, M4, and M5, were made by replacing, by weight, of 0%, 10%, 20%, 30 %, and 40% OPC with FFA, respectively. The mix proportion of LWC, by weight, was 1.00 binder: 3.24 fine aggregate: 1.19 coarse aggregate, and the water-binder ratio was 0.32. Tests of the LWC mechanical properties were conducted at the hydration time of 28 and 56 days using 150 by 300 mm cylindrical specimens. The results indicate that the use of FFA as a partial replacement for OPC improved the development of the mechanical properties of LWC. The compressive strength and the modulus of elasticity of the LWC increased in all the mixtures during the hydration time. The optimal proportion of FFA for replacing OPC in LWC is about 20%. With this optimal proportion and after 56 days of hydration, the compressive strength and the modulus of elasticity are, respectively, about 113% and 105% of those produced by LWC made with 100% OPC.

Prediction of mechanical properties of lightweight basalt fiber reinforced concrete containing silica fume and fly ash: Experimental and numerical assessment

As a building material, concrete has its own advantages and disadvantages. One of the weaknesses of concrete is its very low tensile strength and strain as well as brittleness under flexural or compressive loading, which results in sudden failure of the concrete structures during earthquakes. On the other hand, low strength of lightweight aggregates and their fragility lead to poor performance of the lightweight concrete against ductility. Therefore, this study investigated mechanical properties of the lightweight structural concrete containing expanded clay aggregate and different amounts of basalt fibers (0–0.5%). Hence, pozzolanic materials of silica fume and fly ash were used to modify some of the concrete properties in lightweight concrete mixtures as a substitute of part of the cement weight. In total, 21 mix designs were made and their fresh and hardened properties were tested at different ages of 7, 28, and 90 days. Results indicated that the presence of basalt fibers reduced slump and compressive strength by 37% and 13%, respectively. It was also found that all mixtures had a “good” level of water absorption quality and thus were placed in the category of “structural concrete”. Results also indicated that addition of fibers improved tensile, flexural strength, and shrinkage. In order to predict empirical results, an adaptive neuro-fuzzy inference system (ANFIS) was used as a reliable method for evaluating and estimating the results and numerical analysis outputs showed accurate estimation of the empirical results.