Normal Weight Concrete Research Articles

On the Durability of Concrete under the Action of Ultra-Low (up to -196 °C) Technological Temperatures

The article presents the physical-chemical bases and as result – the technological bases of concrete resistance to ultra-low cryogenic (up to-196 °C) technical (engineering) temperatures, which is applied to the reinforced concrete structures of engineering constructions such as storage tanks for liquefied gases (in particular, liquid nitrogen and oxygen with cryogenic temperatures), as well as the enclosing structures of blocks (units) for air separation for various inert gases. The above-mentioned physical and chemical bases of concrete resistance to the ultralow cryogenic technical temperatures are developed, using the results of the analysis of modern ideas (hypotheses and theories) about the mechanism of low negative temperatures exposure on structural lightweight aggregate concrete and normal weight concrete due to the characteristics of their macro-and microstructure. The resistance of structural lightweight aggregate concrete in comparison with equal-strength normal weight concrete to the cyclic exposure of cryogenic temperatures was performed by the authors based on the results of the relevant analytical and experimental investigations. The results of these investigations are considered in the article as a modern scientific basis for the development of the main provisions for the manufacturing technology of structural lightweight aggregate concrete and normal weight concrete with high durability (frost resistance and water resistance) in conditions of cyclic exposure to cryogenic temperatures. The results of changes in strength and deformative characteristics of concrete in the process of cyclic freezing and thawing are accepted as evaluation criteria of the resistance of concrete, manufactured using the above-mentioned technologies, to such temperature exposure.

Flexural Resistance Factors for Structural Ultra Lightweight Engineered Cementitious Composite Slabs

Many problems associated with the use of normal weight concrete have been solved with the development of structural ultra-lightweight engineered cementitious composite (SULWECC) that has the capability to exhibit strain-hardening behavior prior to failure. However, the feasibility and standards that address the design of such engineered cementitious composites (ECC) in flexural slab systems are not available. In this study, reliability analysis and calibration process are carried out on three different SULWECC slab systems with the intention of estimating the potential flexural resistance factors. Although the high volume of randomly dispersed synthetic short fiber is considered the main reinforcement, SULWECC slab systems internally reinforced with carbon FRP mesh are also considered. The reinforcement ratio is selected so that the section is under-reinforced. Relevant load and resistance random variables are used, and appropriate statistical parameters are selected. The target reliability indices are chosen to be consistent with those used to develop current design code specifications. The nominal moment capacity is calculated based on a new model that consists of: elastic linear stress distribution in the compression zone and elastic-perfectly-plastic uniform stress distribution in the tension zone. The determined flexural resistance factors ranged from 0.59 to 0.69, although higher values are justifiable in special circumstances. The average slab thickness needed to satisfy the strength requirements ranged from 1/37 to 1/22 times the slab length. Flexural toughness to measure ductility is evaluated using load-deflection curves of experimentally tested SULWECC specimens.

Analytical Investigation of the Load-Bearing Behavior of Light Weight Hollow Core Composite Slabs*

Slabs are considered the most important structural member but also the heaviest one. Therefore, in the last few years a new type of slabs was introduced, hollow core slabs with steel decks. On the other hand, the use of light weight concrete that has got a density less than (1850 kg/m3 ) reduces the self-weight of structures considerably. This paper conducts an analytical study of the flexural behavior of five slabs, a solid slab that acts as a reference, a hollow core slab with elliptical voids, a composite slab and two hollow core composite slabs using normal weight and light weight concrete using ANSYS software. All the slabs share the same size (2600 x 1200 x 140) mm. The results show that the use of hollow core slabs increases the load carrying capacity by about 32% while using light weight concrete reduces it by about 34% but it also decreases the self- weight and the deformation considerably. The use of light weight hollow core slabs promises with a wide horizon of privileges and improvements in the construction and research domain

A Comprehensive Review on the Performance of Structural Lightweight Aggregate Concrete for Sustainable Construction

Lightweight aggregate concrete is an innovative building material used to reduce the self-weight of a high-rise building. Recently, the use of lightweight aggregate in construction is increasing immensely due to its performance during an earthquake. Lightweight aggregate concrete (LWAC) is a solution for the achievement of sustainability in the construction sector, which helps us cut down the overall cost of a project in massive construction work (tall buildings and bridges). Additionally, using various industrial by-products and waste instead of natural aggregate allows us to reduce the negative impact on the environment. The development of lightweight aggregate concrete with its relevance is still prominent. The performance of lightweight aggregate on various properties of concrete is explored in this study. This study shows that the lightweight aggregate and waste materials of less density can be used for structural applications with a strength equivalent to that of normal weight concrete. The application and advantages of LWAC are also discussed in this study. The paper’s overall finding reveals that LWAC can be used in sustainable construction growth and reduce waste by using it as natural aggregate in concrete to maintain environmental sustainability.

Recycling potential in building energy renovation: A prospective study of the Dutch residential building stock up to 2050

Building energy and construction and demolition waste (CDW) are highly relevant but intertwined issues for the transition towards a carbon-neutral and circular built environment. Ongoing energy renovation uses an increasing number of emerging materials that pose a challenge for recycling. As a response, a novel technological system has been proposed to recycle CDW (including insulation mineral wool and lightweight concrete) for the manufacture of prefabricated concrete elements (PCEs) for use as façades for new (PCE-new) and retrofitting existing (PCE-refurbs) buildings. To explore how this novel system can improve recycling potential as part of building energy renovation efforts, the Dutch residential building stock was selected as a case study. Using a dynamic material flow analysis, we explore the supply-demand balance of secondary raw materials made from CDW (including normal-weight and lightweight concrete, glass, insulation mineral wool, and steel) and the secondary raw materials required for manufacturing PCEs in building energy renovation for the period 2015–2050. Our findings show that with advanced recycling technology, the secondary raw materials recovered from normal-weight concrete waste, glass waste, insulation mineral wool waste, and steel scrap will be more than sufficient to support the manufacturing of PCE-new walls, implying the possibility of closed-loop construction. However, for emerging materials such as lightweight concrete, the related waste will not be sufficient in the near future to meet the raw material demand for large-scale refurbishment with PCE-refurbs. Therefore, the Dutch case shows that the novel technology system offers a promising solution to CDW management problems in building energy renovation, but primary raw materials will still be needed for the increased use of emerging materials such as lightweight concrete.

Flexural performance of reinforced carbon nanofibers enhanced lightweight cementitious composite (CNF-LCC) beams

As a type of lightweight concrete, foam concrete is traditionally used for non-structural applications due to its poor mechanical properties. However, in recent years, there is a surge in interest in potential applications of foam concrete as structural components due to its low self-weight, homogenous foam bubble distribution, self-compacting, saving in raw materials, good thermal and acoustic insulation. The main challenge for foam concrete is to have high-performance pore walls to provide required mechanical properties, shrinkage resistance, and durability under reduced density. A new type of foam concrete termed as carbon nanofibers enhanced lightweight cementitious composite (CNF-LCC) was developed and reported to have excellent mechanical properties, bond strength with steel reinforcement, durability and shrinkage resistance compared with traditional foam concrete. In this paper, the flexural performance of 8 reinforced CNF-LCC beams was investigated. Test parameters included the amount of carbon nanofibers (CNFs), tension and compression reinforcement ratios, and steel link ratio. The flexural performance of reinforced CNF-LCC beams was comparable with that of normal weight concrete (NWC) and lightweight aggregate concrete (LWAC) and even exceeded traditional foam concrete. The usual reinforcement detailing for NWC beams can be equally employed on CNF-LCC beams. Incorporation of CNFs produced varying degrees of improvement on flexural response especially ductility of beams. Finally, predictions from standard codes and the proposed model agreed well with the test results.

Characteristics of lightweight concrete with different admixtures

Lightweight concrete (LWC) is the most needed material to be used in many applications due to its low density, accepted compression strength, and high thermal properties. This paper study the effect of using lightweight concrete in structural elements using three experimental variables such as (admixtures content, cement content and w/c ratio). For twenty-five different mix trial with different admixtures was used. The slump loss, slump flow, compaction factor, compressive strength at the ages of 7, 14, 28, and 56 days and tensile strength at the age of 28 days were obtained. Based on the results the slump ranged from 70 to 140 mm. Moreover, the average slump loss was as same as the average slump loss for the normal concrete(NC). Further, the average compressive strength of the lightweight plain concrete mixtures fluctuated from 70 to 75% of the compressive strength of normal weight concrete and using admixture improved this ratio. By using mineral admixtures, the compressive strength improved to 90 to 95% of the normal concrete compressive strength.

Numerical Study of Fire and Energy Performance of Innovative Light-Weight 3D Printed Concrete Wall Configurations in Modular Building System

3D Printed Concrete (3DPC) technology is currently evolving with high demand amongst researches and the integration of modular building system (MBS) with this technology would provide a sustainable solution to modern construction challenges. The use of lightweight concrete in such innovative construction methods offers lightweight structures with better heat and sound insulation compared to normal weight concrete. It is worth noting that fire and energy performance has become central to building design. However, there are limited research studies on the combined thermal energy and fire performance of 3DPC walls. Therefore, this study investigates fire performance of 20 numbers of varying 3DPC wall configurations using validated finite element models under standard fire conditions. The fire performance analysis demonstrated that 3DPC non-load bearing cavity walls have substantial resistance under standard fire load and its performance can be further improved with Rockwool insulation. There is significant improvement in terms of fire performance when the thickness of the walls increases in a parallel row manner. Previous thermal energy investigation also showed a lower U-value for increased thickness of similar 3DPC walls. This research concludes with a proposal of using 3DPC wall with Rockwool insulation for amplified combined thermal energy and fire performance to be used in MBS.

Post-peak Behaviour of Composite Column Using a Ductile Lightweight Aggregate Concrete

Oil palm shell (OPS) concrete filled steel tube (CFT) columns are acknowledged to be a new type of sustainable composite column. In this type of column, the conventional coarse aggregate was partially replaced with OPS lightweight aggregate to provide a green composite column. This type of CFT column showed higher energy absorption and flexibility compared to CFT columns with normal weight concrete. This research studied the effect of the strength of OPS concrete on the axial compressive behaviour of CFT columns for two grades of OPS concretes. The behaviour was comparable to that of CFT columns with two grades of normal concrete. The results showed that the CFT columns with OPS concrete achieved a new post-peak behaviour. The experimental results of the axial compressive load were compared with the estimation of two international standards. EC4-1994 and ACI318-14 showed a reliable and conservative estimation of the axial load capacity of CFT columns, respectively.

Characterizing debonding strain in sand-lightweight high strength concrete T beams strengthened with CFRP sheets

The premature debonding of Fiber Reinforced Polymer (FRP) sheets has been well studied and understood for normal weight concrete. This type of failure mode can be averted by keeping the maximum FRP strain below the debonding strain of FRP as specified by ACI 440.2R-17. However, the debonding strain in lightweight concrete has not been addressed or evaluated yet. Accordingly, this paper investigates the debonding strain in lightweight concrete using full-scale reinforced concrete T beams strengthened with different layers of carbon fiber reinforced polymer (CFRP). These beams were prepared and strengthened in two series. The first series included three T beams that were cast with normal weight concrete. The second series consisted of another group of three T beams using lightweight concrete. Both series had identical geometry, reinforcement, and span lengths. Furthermore, they had almost identical concrete properties and the same FRP material to effectively examine the deboning strain difference in both types of concrete. The debonding strains of the lightweight and normal weight concrete are compared and the reduction factor is addressed in light of the current design equation in ACI 440.2R-17.

Evaluation of Mechanical and Shielding Properties of Normal Weight Concrete by Incorporating Iron Cutting Waste (ICW)

We fabricated samples of different percentage of iron cutting waste (ICW) and evaluated mechanical & shielding properties of concrete by Gamma ray attenuation. For shielding, linear γ-ray attenuation coefficient and mean-free path length were measured. Cs-137 (0.668 meV) and spectrum was used to measure attenuation coefficient of concrete. NAI (TI) Detector was used to detect the radiation coming from the source. Calculated linear attenuation coefficient from semi log graph of transmission and thickness of shields. Compressive, flexural and split tensile strengths were increased 32.2%, 10.3% and 36%, respectively, with 10% replacement of sand with ICW. The attenuation coefficient of mix with 20% replacement was increased 10.5% from the control mix. The mix with 20% of ICW as a sand replacement took less distance to attenuate the same amount of radiation than the control mix. The difference in mean free path length of control mix and mix with 20% ICW was about 0.5 cm. Maximum mass attenuation was achieved on 15% replacement of sand which was 7.5% of the control mix. Fine ICW, increased both mechanical and shielding properties of concrete compared to the control specimen. Shielding of radiation is highly dependent on the size, orientation and particle distribution in a concrete matrix.

The The Effects of Structural Lightweight Concrete on Energy Performance and Life Cycle Cost in Residential Buildings

Energy efficiency in the construction industry is crucial to reducing increased energy consumption. A significant portion of the energy is consumed in residential buildings. Thermal properties of the materials used in the building envelope can reduce the energy consumed in the buildings and thus contribute to the building economy. For this purpose, in the study, structural lightweight concretes (SLWC) with a lower thermal conductivity than normal weight concrete (NWC) were produced and energy efficiency and life cycle costs were compared between these concretes on a 1 + 1 reference flat. The compressive strength, unit weights and thermal conductivity coefficients of SLWCs and NWC were determined experimentally. Heating and cooling energy consumption and life cycle costs for the flat were calculated using the DesignBuilder simulation program according to the different concrete types produced. The results indicate that the thermal conductivity coefficients of all SLWCs produced were about 37–45 % lower than those of NWC. All mixes of the SLWCs provided energy saving by about 18–25 % compared to the NWC and two SLWCs reduced the life cycle cost by 4 %. In addition, the results showed that the best SLWC about energy was not the best SLWC about life cycle cost.

Contribution of lightweight self-consolidated concrete (LWSCC) to shear strength of beams reinforced with basalt FRP bars

To date, the shear contribution of lightweight self-consolidating concrete (LWSCC) members reinforced with basalt fiber-reinforced polymer (BFRP) bars (LWSCC-BFRP) has not yet been investigated. Therefore, the anticorrosion properties of BFRP bars combined with the advantages of LWSCC motivated this research to assess the behavior of such members under shear. Eight beams cast using LWSCC and normal-weight concrete (NWC) reinforced with BFRP or steel bars were prepared and tested up to failure. The specimens had a total length of 3100 mm and concrete cross section of 200 mm in width and 400 mm in depth. The influence of two different types of BFRP bars of comparable quality and commercially available (sand-coated basalt and helically grooved basalt) on shear capacity was assessed. The tested beams included five beams reinforced with BFRP bars, one beam reinforced with steel bars, and two beams constructed using NWC for comparison purposes. The experimental results indicate that the adoption of LWSCC allowed for decreasing the self-weight of the reinforced concrete (RC) beams (density of 1800 kg/m3) compared to NWC. Test results show that the concrete shear capacity of the LWSCC beams increased as did the axial stiffness of the longitudinal BFRP reinforcing bars. The test results were compared with the shear capacities predicted using the provisions in several standards. Using a 0.75 concrete density reduction factor in the CSA 2012 shear equation to consider the influence of concrete density yielded a more accurate value for the concrete shear capacity. In addition, using a 0.8 concrete density reduction factor in the ACI 2015 design equation yielded an appropriate degree of conservatism compared to the NWC beams.

Long-term behavior of normal weight concrete containing hybrid nanoparticles subjected to gamma radiation

Since a lot of medical facilities are made from normal weight concrete (NWC), it became an important task to improve the radiation shielding properties of such concrete in a confrontation to radiation with special emphasis on gamma radiation type. Therefore, an experimental program was conducted to investigate the effect of nanoparticles addition on gamma radiation shielding, physical properties, and mechanical properties of NWC. Nano silica (NS), nano hematite (NH), nano titania (NT), and their hybridization were added to NWC with four different percentages of 0.5, 0.75, 1.0, and 2.0% from the cement weight. A total of sixteen concrete mixes with nanoparticles in addition to a control mix were made. The long-term effects of gamma radiation on samples representing all concrete mixes were studied to find out the consequence of exposure to gamma rays over long periods (250 and 500 days) on their mechanical properties. The experimental results showed that the single addition of each of NS, NH, or NT particles and their combination up to 2.0% improved the physical properties, compressive strength, and attenuation coefficient of NWC. The results of the hybrid nano addition showed that the synergistic phenomenon occurred in some cases. Furthermore, the scanning electron microscopy technique (SEM) was used to prove the enhancement in the microstructure of NWC as a result of the addition of NS, NH, NT, and their combination.

Structural lightweight aggregate concrete exposed to marine environment for 5 years

The present paper characterises the chloride penetration into a large array of structural lightweight aggregate concrete (LWAC), after a 5-year exposure period to aggressive marine conditions. The chloride profiles, chloride diffusion coefficients and surface chloride contents were determined and the influence of the main composition parameters and exposure conditions was assessed. Current service life models were evaluated through the estimation of chloride profiles. The results suggest that LWAC can present the same durability as normal weight concrete (NWAC). However, despite having the same chloride diffusion coefficients, the surface chloride content of LWAC tended to be greater than that of NWAC, leading to higher chloride penetration at a given depth. In general, the estimated chloride profiles from existing models did not fit the real results.

Behaviors of novel sandwich composite beams with normal weight concrete

The ultimate strength behaviour of sandwich composite beams with J-hooks and normal weight concrete (SCSSBJNs) are studied through two-point loading tests on ten full-scale SCSSBJNs. The test results show that the SCSSBJN with different parameters under two-point loads exhibits three types of failure modes, i.e., flexure, shear, and combined shear and flexure mode. SCSSBJN failed in different failure modes exhibits different load-deflection behaviours, and the main difference of these three types of behaviours exist in their last working stages. The influences of thickness of steel faceplate, shear span ratio, concrete core strength, and spacing of J-hooks on structural behaviours of SCSSBJN are discussed and analysed. These test results show that the failure mode of SCSSBJN was sensitive to the thickness of steel faceplate, shear span ratio, and concrete core strength. Theoretical models are developed to estimate the cracking, yielding, and ultimate bending resistance of SCSSBJN as well as its transverse cross-sectional shear resistance. The validations of predictions by these theoretical models proved that they are capable of estimating strengths of novel SCSSBJNs.

A review of lightweight aggregate concrete fiber reinforcement

Despite its numerous benefits, lightweight aggregate concrete (LWAC) has not been extensively utilized in the construction industry due to its greater brittleness and poorer mechanical characteristics when compared to normal weight concrete (NWC) at the same compressive strength. Fibers in LWAC have been proven in studies to be an effective option for resolving such issues. This study examines the effects of fiber addition on the characteristics of several kinds of LWAC. Workability, compressive strength, stress-strain behaviour, tensile strength, modulus of elasticity, and compressive and flexural toughness are some of these characteristics. In general, adding fibers to LWAC, whether in single or hybrid forms, improves mechanical characteristics and increases toughness, ductility, and energy absorption while reducing workability, especially when steel fiber is included in the concrete mixture. The efficacy of fiber in LWAC is greater than NWC when it comes to splitting tensile and flexural strengths.

Flexural strength of Lightweight geopolymer concrete using sisal fibres

Lightweight concrete is usually chosen for structural purpose where its use will lead to a lower overall cost of a structure than normal weight concrete by reducing its dead weight. This weight will make it an uneconomical structural material. Attempts have been made in the past to reduce the self-weight of concrete to increase the efficiency of concrete as a structural material. In this research, bamboo sticks are used in the form of coarse aggregate at different proportions to reduce the self-weight of concrete. Also, naturally available fibre named sisal fibre is into the reinforcement to study its properties. The influence of sisal fibres and bamboo sticks on the strength of light weight geopolymer concrete is taken as the main objective of this experimental study. In recent years, a great deal of interest has been created worldwide on the potential applications of light weight concrete and utilization of natural fibres reinforced cement-based composites. In this work, it is also aimed to investigate the strength properties of concrete by casting light weight geopolymer concrete by replacing bamboo aggregates with 10%, 20% and 30% of coarse aggregate. Also, Sisal fibres are added at different proportions as 0.25%, 0.5%, 0.75% and 1.0% by volume of concrete respectively. Evaluation of flexural bending strength for M25 geopolymer concrete specimens was done. Totally 9 number of 500×100×100 mm flexural members are cast and tested under M25 grade of concrete. The 12 M NaOH, ratio of NaOH:Na2SiO3 as 2.5 and ratio of flyash to alkaline activator solution as 0.6 are considered as various parameters for designing the mix of geopolymer concrete. Ambient curing condition is applied for evaluating strength properties. The flexure strength was tested with replacement of coarse aggregate with bamboo sticks and by adding different percentage of sisal fibres. The test results indicated that the sisal fibres were effective in improving the strength of concrete.

Subject Review: A Comparison of Lightweight Concrete Made With Sawdust

Lightweight concrete is a very useful and advantageous material in the modern civil industry. It is lighter than normal-weight concrete. This paper investigates the review of the significant applications and advantages of using lightweight concrete in the area of civil engineering. Also, therefore, the use of lightweight concrete has a great impact on developing countries as it permits design flexibility and substantial saving in the cost of construction. In this paper, the background for many experimental studies of lightweight concrete made with sawdust is provided and a comparison between these studies.

Structural behavior of shear connectors embedded in different types of concrete

Push-out tests are used to determine shear connectors’ properties where two small reinforced concrete walls are attached to the top and bottom flanges of an I-section through four shear studs located on both its flanges. In this study, the structural behavior of shear connectors was examined by testing a total of 36 push-out specimens. In these specimens, various test parameters were used. The types of shear connectors and their strengths, their connection types, and the strength of the concrete in which they were embedded were all investigated. Headed, L-shaped, and C-shaped studs were selected in this experimental study to represent different types of shear connectors. These shear connectors were assumed to be either ordinary or high strength steel-embedded in three different types of concrete: ordinary, high strength, and reactive powder concretes. In these tests, the shear connectors were connected through welding or epoxy bonding. The objective of this study was to investigate the structural behaviors of these different types of shear connectors by focusing on their shear force capacities and slip values. The test results indicate that the reactive powder concrete increased the mechanical properties of concrete as the concrete age increased. The specimens with C-shaped studs made of high-strength steel with welded studs embedded in normal weight, high strength and reactive powder concretes, generated the maximum shear resistance values.