Use Of Lightweight Aggregates Research Articles

The Use of Lightweight Aggregates in Geopolymeric Mortars: The Effect of Liquid Absorption on the Physical/Mechanical Properties of the Mortar.

Geopolymers have been proposed as a green alternative to Portland cement with lowered carbon footprints. In this work, a geopolymeric mortar obtained using waste materials is studied. Fly ash, a waste generated by coal combustion, is used as one of the precursors, and waste glass as lightweight aggregates (LWAs) to improve the thermal performance of the mortar. The experimental study investigates the effect of varying the alkali activating solution (AAS) amount on the workability, compressive strength, and thermal conductivity of the mortar. Indeed, AAS represents the most expensive component in geopolymer production and is the highest contributor to the environmental footprint of these materials. This research starts by observing that LWA absorbs part of the activating solution during mixing, suggesting that only a portion of the solution effectively causes the geopolymerization reactions, the remaining part wetting the aggregates. Three mixes were investigated to clarify these aspects: a reference mix with a solution content calibrated to have a plastic consistency and two others with the activating solution reduced by the amount absorbed by aggregates. In these cases, the reduced workability was solved by adding the aggregates in a saturated surface dry state in one mix and free water in the other. The experimental results evidenced that free water addiction in place of a certain amount of the solution may be an efficient way to improve thermal performance without compromising the resistance of the mortar. The maximum compressive strength reached by the mortars was about 10 MPa at 48 days, a value in line with those of repair mortars. Another finding of the experimental research is that UPV was used to follow the curing stages of materials. Indeed, the instrument was sensitive to microstructural changes in the mortars with time. The field of reference of the research is the rehabilitation of existing buildings, as the geopolymeric mortars were designed for thermal and structural retrofitting.

Analysis of influence of concrete aggregate in evaluation of form removal time of concrete using ultrasonic pulse velocity methods

Recently, due to the increase in high-rise and large-scale buildings, the use of ordinary aggregates has increased, and research is continuously being conducted on the use of lightweight aggregates to reduce weight. However, because concrete exhibits different compressive strength due to material influences, it is believed that there will be a difference in the form demoulding time for ordinary aggregate and lightweight aggregate in the early age. In order to evaluate the characteristics of concrete in a quantitative manner, an experiment was conducted to predict the time of form demolding through correlation by measuring compressive strength and ultrasonic pulse velocity (UPV). In this study, the target strengths of normal aggregate concrete (NC) and lightweight aggregate concrete (LC) were set at 30 MPa, 45 MPa, and 60 MPa. To reach the target strength of each test specimen, the W/B ratio was set to 41.0%, 33.0%, and 28.0%. In addition, in order to meet the same mixing conditions, the mixing was carried out by setting the fine aggregate excluding aggregate, W/B ratio, and cement amount to the same level. In the case of compressive strength, NC30 was 13.4% higher than LC30 at 24 h, and NC45 and LC45 showed similar compressive strength. NC60 showed 29.9% higher compressive strength than LC60, and it can be seen that NC generally shows higher compressive strength than LC. It can be seen that as the target intensity increases, the difference between NC and LC at the same target intensity increases. At 24 h, UPV showed 21.9% and 11.9% lower rates for NC30 and NC45 compared to NC60. Additionally, compared to LC60, LC30 and LC45 showed 22.3% and 12.2% lower UPV, and it is believed that the timing of form demolding can be evaluated by utilizing the fact that UPV varies depending on aggregate and W/B ratio. The prediction models for NC and LC based on the correlation between compressive strength and UPV showed a coefficient of determination (R2) of 0.90 or higher. Although the cement content significantly impacts the UPV of concrete, UPV may vary depending on the porosity and density of the aggregate, thus making it necessary to consider these factors for strength estimation.

Long-Term Behavior Related to Water Ingress in Mortars Which Combine Expanded and Natural Cork Lightweight Aggregates and Eco-Friendly Cements

The water ingress plays an important role in building materials’ degradation. The use of lightweight aggregates is interesting in terms of sustainability, because they reduce the density of cement-based materials, among other advantages. The development and use of new lightweight aggregates, such as cork granulates, is a current research topic. In the present work, water ingress performance of sustainable mortars which combined expanded and natural cork aggregates and cements with slag, fly ash and limestone has been studied. Mortars produced with sand and expanded clay were also prepared. Bulk density, water absorption, drying capacity and gel and capillary pores were studied. Tests were carried out at 28 days and 1 year. A good behavior has been generally observed when an addition was incorporated to the binder, especially slag or fly ash. Regarding the new non-standardized lightweight cork aggregates, mortars with natural cork showed lower water absorption and lower volume of permeable pore space in the long term than mortars with expanded cork. At one year, natural cork mortars had an adequate water absorption performance compared to those with expanded clay, which may be due to the high volume of small capillary pores (100 nm–1 µm) in natural cork mortars.

Performance of resource saving agro-industrial wastes and their utilization in lightweight concrete -A review

The high demand for natural aggregates has created opportunities for the use of agro-industrial waste in the building sector brought on by rising urbanization and the disposal issue of agricultural and industrial waste. Numerous agricultural waste and industrial by-products are already employed in concrete in place of cement, fine aggregate, coarse aggregate and reinforcing elements. Furthermore, there is an increase in the use of Lightweight concrete (LWC) in civil structures such as high-rise buildings, off-shore structures, and long-span bridges owing to the need of concrete, lighter than the conventional one. Presence of natural aggregates makes the concrete dense and heavy, hence the use of lightweight aggregates (LWA), such as perlite, paper industry waste, expanded shale, volcanic pumice, slate, wood ash waste, and expanded polystyrene (EPS), in the production of LWC can effectively decrease the self-weight of a structure. In a comparable manner agricultural wastes, like oil palm shell (OPS), coconut shell (CS), rice husk ash (RHA) and industrial waste like fly ash, plastic aggregate, silica fume (SF), metakaolin (MK) have the potential of a LWA. This study reviewed the utilization of oil palm shells (OPS), coconut shells (CS), expanded polystyrene (EPS), and silica fume (SF) in concrete, among the numerous available agro-industrial wastes. For the past decade, research has been ongoing on aggregate processing to meet special concrete requirements such as low density, thermal insulation, and strength. These wastes exhibit similar properties to conventional concrete when used in combination with mineral additives like SF and RHA, among others. The study also highlights the eco-efficiency and functional benefits of using these wastes as lightweight aggregates (LWA).

Influence of silicon-dioxide nanoparticles in cementitious mortars: verification using x-ray diffraction, thermal analysis, physical, and mechanical tests

In recent years, nanotechnology has been applied to building materials, such as cementitious composites (e.g., mortar and concrete), to improve their properties. The aim of this study was to analyze the thermal, physical, and mechanical properties of mortars with and without silicon-dioxide (SiO2) nanoparticles. Experiments such as thermogravimetry and differential thermal analysis (TG-DTA), x-ray diffraction (XRD), fresh density, incorporated-air content, bulk density, capillary absorption, capillarity coefficient, flexural tensile strength, and compressive strength on prismatic specimens were performed on mortars and analyzed for different levels of nanosilica (nS). These levels were 1% and 3%, in addition to the reference mortar (0% nS). The TG-DTA curves showed an elevated content of chemically combined water and a lower content of calcium hydroxide (Ca(OH)2) in the 3% nS compositions, while the XRD curves presented a lower content of calcite and portlandite in the same mortar. These results indicate the fixation capacity of lime for the formation of calcium silicate hydrate (C-S-H), which is the primary cause of resistance in cementitious mortars. In addition, it was found that the use of nanosilica contributed to a fresh density increase of approximately 15%, which caused a minimum air-incorporated content decrease of 37% and a minimum bulk density increase of 10%. Higher densities resulted in a minimum water absorption reduction of 36%, owing to fewer pores in the mortars. Therefore, the capillarity coefficient decreased by a minimum of 41%. These nanoparticles also improved the minimum flexural tensile and compressive strengths by 88% and 158%, respectively, when using a 3% nS composition. These results can enable the use of lightweight aggregates in cementitious composites, improving their physical and mechanical characteristics and allowing greater reuse of these materials, including construction waste.

Chloride Ingress Resistance, Microstructure and Mechanical Properties of Lightweight Mortars with Natural Cork and Expanded Clay Prepared Using Sustainable Blended Cements

The use of lightweight aggregates in construction materials is a good solution for increasing the contribution to sustainability of civil engineering works, such as maritime ones. In this regard, the possibility of using cork granulates and expanded clay is a current research topic. The combination of eco-friendly cements with lightweight aggregates could provide solutions for developing new building materials. In this work, it has been studied mortars prepared with sustainable cements and the lightweight aggregates of natural cork and expanded clay. These cements incorporated slag, limestone and fly ash. Reference mortars with only sand as aggregate were also made. The total porosity and pore size distributions were obtained. The non-steady-state chloride migration coefficient and compressive and flexural strengths were also determined. The tests were performed at 28 days and 1 year. The differences in the total porosity between the natural cork and expanded clay series were not high, depending on the binder. Natural cork mortars showed similar or slightly higher migration coefficients than the reference and expanded clay mortars at 1 year. This adequate chloride resistance and the low mechanical strengths observed for the natural cork mortars recommend the possible use of this new aggregate in non-structural cement-based materials for civil engineering works exposed to maritime environments.

Thermal behavior of pervious concrete in dry conditions

As the world becomes more urbanized, concerns are growing about the phenomenon of urban heat islands (UHIs). In addition to the environmental function of stormwater management, pervious concrete (PC) pavements are also a solution that can help mitigate increasing urban temperatures, through cooling by evaporation. Several studies in the literature have focused on the evaporative cooling effect of PC, which requires the presence of water either from precipitation or irrigation. However, in countries that have dry summers and where watering techniques are complicated to implement, in hot weather and dry conditions, PC can have a higher temperature than traditional impermeable concrete. The main objective of this paper is therefore to study the influence of thermophysical parameters on the surface temperature of PC, with a view to designing a mix that minimizes its surface temperature in dry conditions. The thermal behavior of PC and ordinary impermeable concrete (OC) in dry condition have been studied both analytically and experimentally. All heat fluxes involved in the energy balance at the surface of both pavements were analyzed. The results show that PC has a surface temperature up to 6 °C higher than OC during the day and up to 4 °C lower during the night. Increasing the thermal conductivity of the pervious concrete makes the surface temperature of PC lower during the day but higher at night. On the other hand, increasing albedo makes the surface temperature of the pavement lower both during the day and during the night. Finally, the sensitivity study shows that the albedo has a greater influence on the maximum surface temperature of the PC than does thermal conductivity. To decrease the maximum temperature of PC, it is recommended to avoid the use of lightweight aggregates and to use finer and lighter colored aggregates (to increase the albedo), having high thermal conductivity. This mix optimization may be limited by the hydraulic properties of the PC due to its influence on the open porosity.

Development of high strength & lightweight cementitious composites using hollow glass microsphere in a low water-to-cement matrix

It has been a challenge for structural concrete to satisfy both high strength and lightweight, since general lightweight properties have been achieved through the use of lightweight aggregates with inherently weak strength. In this study, a cement composite with high strength and lightweight was developed using very low-specific gravity material of hollow particles. A combination of a polycarboxylate-ether superplasticizer, filler materials, and a low water-to-cement ratio was selected to increase the viscosity of the cement matrix for minimizing floating of the hollow particles. As a result, the developed cementitious composites substantially outperformed the material performance of previously reported lightweight concretes. Compressive strength of 69 MPa and 97 MPa at 28 days were achieved with the density less than 1.5 g/cm3 from ambient and heat-treated curing, respectively. From a reaction perspective, the used hollow particles did not actively participate in the cement-based hydration reaction, which indicated that their role is limited to being very light inert fillers in the designed cementitious matrix.

Magnesium Potassium Phosphate Cement-Based Derivatives for Construction Use: Experimental Assessment.

The presented research is focused on the development and testing of the magnesium potassium phosphate cement-based materials (MKPC-based). Firstly, the fresh state properties of the pastes consisting of dead burned magnesia powder, potassium dihydrogen phosphate, setting retarder borax applied in the range of 0–10 wt.%, and batch water were investigated. The aim of testing was to characterize the hydration process in dependence on the borax content. The properties of raw MgO powder were described by chemical composition and particle size distribution. The properties tested in fresh state included shear stress (viscosity), Young’s modulus of elasticity, and temperature; their time dependence was observed. The measurements started immediately after the mixing process. At the age of 14 days, basic structural and mechanical properties of the hardened pastes were obtained. The mixture with 5 wt.% of borax proved to be the most advantageous in terms of setting time, sample integrity, and mechanical strength; therefore, it was chosen as the binder for the following part of the study—MKPC-based mortar development. In the next step, the MKPC paste containing 5 wt.% of borax was supplemented by silica sand aggregate, and the resulting material was marked as a reference. Subsequently, three other mixtures were derived by replacing 100% of quartz sand by lightweight aggregate; namely by expanded glass aggregate, waste rubber from tires, and combination of both in ratio 1:1. The aggregates were characterized by chemical composition (except for the rubber granulate), and loose and compacted powder density. For the resulting hardened composites, basic structural, hygric, strength, and thermal parameters were investigated. The use of lightweight aggregates brought in a considerable decrease in heat transport parameters and low water permeability while maintaining sufficient strength. The favorable obtained material properties are underscored by the fact that magnesia-phosphate is considered to be a low-carbon binder. The combination of magnesia-phosphate binder and recycled aggregate provides a satisfying, environmentally friendly, and thermally efficient alternative to traditional Portland cement-based materials.

Effect of Aggregate and Binder Type on the Functional and Durability Parameters of Lightweight Repair Mortars

The subject matter of the work presented here is the development and evaluation of novel lightweight mortars that meet the functional and technical criteria imposed on repair mortars. In a broad experimental campaign, lime, natural hydraulic lime, and lime–cement mortars were designed and tested. Lightweight aggregate, expanded perlite, granules from expanded glass and zeolite were used as full replacements for quartz sand. The hardened mortars were tested at the ages of 28 days and 90 days. The conducted tests and analyses were focused on the assessment of structural, mechanical, hygric and thermal parameters. The salt crystallization resistance and effect of salt presence on the hygroscopicity of the investigated mortars were also investigated. The use of lightweight aggregates in the composition of mortars resulted in their high porosity, low density, satisfactory mechanical parameters, improved water vapor transmission capability and water absorption. The mortars with expanded perlite and glass granulate were ranked among thermal insulation mortars of classes T1 and T2, respectively. The use of lightweight aggregates enabled the development of mortars with great durability in terms of salt action, which was almost independent of binder type. The ability to accommodate water vapor was increased by the effect, i.e., the use of lightweight aggregates and the presence of salt in mortars increased porous space. Taking into account the compatibility, functional, and technical criteria, lime- and natural hydraulic lime-based lightweight mortarswere classified as repair mortars, providing improved thermal performance. The lime–cement lightweight plasters can be recommended only for repair of building structures where cement and lime–cement materials were original applied.

Cleaner Design and Production of Lightweight Aggregates (LWAs) to Use in Agronomic Application

This research focused on the obtainment of sustainable lightweight aggregates (LWAs) for agronomic application. The cleaner production is based on saving matter through the valorization of waste available in industry as a substitute of clays into the formulation of the lightweight aggregates (LWAs). Three different types of clays (white, black, and red) and alternative raw materials were blended. Cattle bone flour ash (CBA) and a fertilizer glass (FG) were used to introduce K and P into the mixture in amounts suitable for fertilizer application, and a sewage sludge from a brewery wastewater treatment plant was used as pore forming agent. For the production of the LWAs, we mixed different percentage of waste in two different clay mixtures, which were thermally treated at 1000 °C for 1 h. Technological parameters such as loose bulk and oven dry density, total porosity, water absorption capacity, pH, and electrical conductivity were determined to evaluate the potential use of LWAs as a growing media. Moreover, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) techniques were used, and leaching tests were performed to complete the samples’ characterization. The results indicated the potential for manufacturing high-quality LWAs for the agronomic field by using energy-saving and matter-processing involving low temperatures with respect to the conventional process.

High strength lightweight concrete with expandable perlite as the aggregate

Lightweight concrete has been an interest due to its advantages compared to normal concrete. Lightweight concrete can be produced by the use of lightweight aggregates. In this study lightweight concretes were made with the composition of expandable perlite combined natural sand with each volume is 50% and concrete with 100% expandable perlite as the aggregates. The volume of the aggregates was varied from 80% up to 89%. The concretes were measured for their density and tested for the mechanical and absorption properties. As the results, expandable perlite obviously has the effect in reducing the concrete density. Nevertheless, the strength decrease as the expanded perlite aggregate increase. The optimum lightweight concrete that acceptable as the international standard is with the aggregates of expandable perlite combined natural sand having the 50% of each volume with the aggregates composition is 80%.

Design of tools for treatment lightweight mortars in supporting construction materials in Banyuwangi

The development of the construction industry in Banyuwangi has very rapid. This can be seen from the high-rise building construction projects such as hotels and others. Banyuwangi has located in a coastal area, this gives a signal that consideration of lateral loads that may occur is necessary. One of them is earthquake load which has a higher concept and building weight, so the greater the earthquake load received. So, we need the use of lightweight structural elements such as the use of lightweight aggregates. This requires innovation, which in this case was used fly ash in making lightweight mortars that were applied to non-structural elements such as lightweight bricks. Proportion that has been done in previous studies. In this follow-up research focused on the design of tools used to treat mortars in order to have good quality. Results of this study found the design of the steam curing device and the results of the mortar test. The mortar test results with tools could be have compression test a maximum of 7.47 MPa, with treatment on 70 degree C for six hours. These results have a better value when compared to the value of mortar on lightweight bricks on the market.

Self-Healing Concrete by Biological Substrate.

At present, the commonly used repair materials for concrete cracks mainly include epoxy systems and acrylic resins, which are all environmentally unfriendly materials, and the difference in drying shrinkage and thermal expansion often causes delamination or cracking between the original concrete matrix and the repair material. This study aimed to explore the feasibility of using microbial techniques to repair concrete cracks. The bacteria used were environmentally friendly Bacillus pasteurii. In particular, the use of lightweight aggregates as bacterial carriers in concrete can increase the chance of bacterial survival. Once the external environment meets the growth conditions of the bacteria, the vitality of the strain can be restored. Such a system can greatly improve the feasibility and success rate of bacterial mineralization in concrete. The test project included the microscopic testing of concrete crack repair, mainly to understand the crack repair effect of lightweight aggregate concrete with implanted bacterial strains, and an XRD test to confirm that the repair material was produced by the bacteria. The results show that the implanted bacterial strains can undergo Microbiologically Induced Calcium Carbonate Precipitation (MICP) and can effectively fill the cracks caused by external concrete forces by calcium carbonate deposition. According to the results on the crack profile and crack thickness, the calcium carbonate precipitate produced by the action of Bacillus pasteurii is formed by the interface between the aggregate and the cement paste, and it spreads over the entire fracture surface and then accumulates to a certain thickness to form a crack repairing effect. The analysis results of the XRD test also clearly confirm that the white crystal formed in the concrete crack is calcium carbonate. From the above test results, it is indeed feasible to use Bacillus pasteurii in the self-healing of concrete cracks.

Effect of the curing type on the mechanical properties of lightweight concrete with polypropylene and steel fibres

This study assessed the effect of steel and polypropylene fibres at various volume contents on concrete incorporating lightweight expanded clay aggregate (LECA) and water/binder (W/B) ratios of 0.37 and 0.42. The concrete specimens were cured under six curing conditions: wet, 3-day wet, 14-day wet, air-dry controlled, air-dry uncontrolled, and 90 °C vapour. The use of lightweight aggregates in the construction industry has drawn the attention of researchers and, on the other hand, fibres with a high strain-hardening response can be used as an appropriate addition in concrete materials. In this study, the mechanical properties of lightweight concrete containing steel or polypropylene fibres were evaluated by means of compressive strength, splitting tensile strength and modulus of elasticity tests at 3, 7, 28 and 60 days. According to the results, fibre reinforced concrete mixes containing LECA, cured under 90 °C vapour curing, achieved the highest mechanical strength. In addition, the optimum contents of steel fibres to obtain the highest compressive and splitting tensile strengths of lightweight concrete were 1% and 3%, respectively.

Lightweight Self-Compacting Concrete Incorporating Perlite, Scoria, and Polystyrene Aggregates

Self-compacting concrete (SCC) is a highly fluid form of concrete that can consolidate under its own weight, thereby reducing the need of any mechanical compaction processes. Lightweight concrete (LWC), which incorporates the use of lightweight aggregates, can reduce the density of the concrete and therefore the potential associated dead loads. In recent decades, there have been numerous studies in the production of lightweight self-compacting concrete (LWSCC) that aim to combine the benefits of both SCC and LWC. Due to the various lightweight aggregates and their different material characteristics, it is imperative to assess whether the properties of both concretes still apply when using different lightweight aggregates. This paper aims to develop information about the fresh and hardened properties of lightweight self-compacting concrete using perlite, scoria, and polystyrene lightweight aggregates at varying replacement percentages. The fresh properties were investigated using the slump flow, T500, and J-ring tests. Hardened properties include 7- and 28-day compressive and tensile strengths, and compressive stress-strain behavior at 28 days.

Influence of microstructure on fluid transport and mechanical properties in structural concrete produced with lightweight clay aggregates

The use of lightweight aggregates (LWA) in concrete is an interesting alternative to simultaneously reduce the total structure weight and provide both appropriate resistance and concrete’s performance. This paper studies the influence of LWA on concrete, comparing the changes in the mechanical properties, pore structure and fluid transport related to the increase of LWA content. Results reveal that although LWA reduces the mechanical properties of the studied samples does not significantly affect the fluid transport properties. Total porosity rises with LWA content whereas open porosity remains nearly invariable. LWA pores do not totally participate in the fluid transport through the concrete and, consequently, fluid transport through lightweight concrete is limited by the continuity and accessibility of the LWA pores and is dominated by the properties of the mortar matrix.

Engineering Properties of Self-Consolidating Lightweight Aggregate Concrete and Its Application in Prestressed Concrete Members

Self-consolidating lightweight aggregate concrete (SCLC) is a highly flowable and lightweight concrete. In this study, the properties of SCLC and prestressed SCLC members were tested and compared with those made of normal-weight self-consolidating concrete (SCC). The test results show that SCLC can be used for prestressed concrete members. The use of lightweight aggregates with a particle density larger than 1100 kg/m3 can avoid the serious segregation of fresh concrete. In addition, the SCLC designed in this study can meet most of the SCC Rank 2 test standards, except for the V-funnel test. The water contained in the lightweight aggregates supplied sustained curing, so the level of drying shrinkage of the SCLC was lower than that of the conventional SCC. However, the level of creep of the SCLC was higher than that of the conventional SCC, because normal-weight aggregates are more able to inhibit the change of the concrete’s volume. On-site test results show that after 180 days of prestressing, the prestress loss was about 5.35–6.83% for the full-size SCLC members, which was smaller than that for the conventional SCC members (about 8.19–9.06% loss).

Porosimetric, Thermal and Strength Tests of Aerated and Nonaerated Concretes

The paper presents the results of porosimetry tests of lightweight concretes, obtained with three research methods. Impact of different porosity structures on the basic thermal and strength properties was also evaluated. Tests were performed, using the pressure gauge method on fresh concrete mixes, as well as using the mercury porosimetry test and optic RapidAir method on specimens prepared from mature composites. The study was conducted on lightweight concretes, based on expanded clay aggregate and fly ash aggregate, in two variants: with non-aerated and aerated cement matrix. In addition, two reference concretes, based on normal aggregate, were prepared, also in two variants of matrix aeration. Changes in thermal conductivity λ and volumetric specific heat cv throughout the first three months of curing of the concretes were examined. Additionally, tests for compressive strength on cubic samples were performed during the first three months of curing. It was found that the pressure gauge method, performed on a fresh mix, gave lowered values of porosity, compared to the other methods. The mercury porosity tests showed high sensitivity in evaluation of pores smaller than 30μm. Unfortunately, this technique is not suitable for analysing pores greater than 300μm. On the other hand, the optical method proves good in evaluation of large pores, greater than 300μm. The paper also presents results of correlation of individual methods of porosity testing. A consolidated graph of the pore structure, derived from both mercury and optical methods, was presented, too. For the all of six tested concretes, differential graphs of porosity, prepared with both methods, show a very broad convergence. The thermal test results indicate usefulness of aeration of the cement matrix of the composites based on lightweight aggregates for the further reduction of the thermal conductivity coefficient λ of the materials. The lowest values of the λ coefficient were obtained for the aerated concretes based of fly ash aggregate. A diminishing influence of aeration on the volumetric heat capacity cv is clearly seen. Simultaneous aeration of the matrix and use of lightweight aggregates brought about also a significant decrease in the average compressive strength fcm of the tested composites.

A comparative study on the thermal conductivities and mechanical properties of lightweight concretes

Thermal conductivity of the materials used in buildings is one of the major factors affecting the heat transfer. Higher thermal conductivity of building walls results in higher heat losses, and in order to maintain the same temperature inside a building, energy consumption for heating or cooling increases. To reduce the heat loss, thus decrease the energy usage, materials with lower thermal conductivities should be preferred. Lightweight concretes can be used for this purpose. However, the properties of these concretes may vary depending on the materials used. The main objective of this experimental study is to compare the properties of lightweight concretes produced with different lightweight aggregates. Lightweight concretes in a wide range of unit weights from approximately 300–1800kg/m3 were prepared in the experimental program. Some properties of the concretes containing pumice and expanded polystyrene beads were obtained. Properties of concretes with expanded perlite and autoclaved aerated concrete determined in previous studies are also included in comparisons and discussion. The test results showed that, depending on the amount and type of lightweight aggregate, unit weight of concrete can be reduced and concretes with various physical and mechanical properties of can be achieved. Thermal conductivity was reduced with the use of lightweight aggregates and for all the lightweight concretes considered, a good relationship was obtained between thermal conductivity and unit weight of concrete. Reductions in the compressive strength and modulus of elasticity of concretes have been obtained with decreasing concrete unit weights. The reduction in strength was more for the concrete containing expanded polystyrene beads.Results showed that strong relationships exist between modulus of elasticity and unit weight of concrete. Results showed that strong relationships exist between modulus of elasticity and unit weight of concrete.