Properties Of Lightweight Aggregate Concrete Research Articles

Experimental investigation on the mechanical and chemical properties of lightweight aggregate concrete with CO2 curing

In the cement and concrete industry, enormous amounts of Carbon Dioxide (CO2) are emitted during their production processes. Carbon dioxide emission significantly contributes to the global climate change, which has been one of the biggest challenges of our times. Some novel solutions have been proposed for CO2 capture and storage, as well as reducing CO2 emission in concrete production. Carbonation curing is an effective alternative for conventional water curing for concrete. It can store CO2 in the hardened concrete and meanwhile improve early mechanical properties of concrete. Partial replacement of cement with fly ash shows environmental benefits, such as reducing greenhouse gas emissions and industrial waste destined for landfills. There has been some previous research studying on the effect of carbonation curing on normal Portland concrete in the past decade. Nevertheless, few studies have focused on the CO2 curing for lightweight aggregate concrete (LWAC). In this paper, the influence of early carbonation curing on LWAC is studied. LWAC specimens with two different water-to-cement ratios are cast and cured for a series of experimental investigations. The mechanical and chemical properties including the 1-day compressive strength, 28-day compressive strength, flexural strength, CO2 uptake, heat development, and pH level are investigated. Specimens with ordinary Portland cement are also tested as references in terms of compressive strength and CO2 uptake.

Mechanical Properties of Barchip Polypropylene Fibre-reinforced Lightweight Concrete Made With Recycled Crushed Lightweight Expanded Clay Aggregate

Concrete is one of the broadly used construction materials in the construction industry. This research intends to recommend the replacement of conventional coarse aggregates with recycled lightweight expanded clay aggregate (LECA) which offers several advantages such as lightweight, low cost, and easy availability. Lightweight concrete (LWC) offers numerous benefits; therefore, many researchers are using lightweight aggregate to produce lightweight structural composites concrete to compensate heavy loads by reducing the concrete self-weight due to lower density of lightweight concrete, improving in thermal properties and fire resistance, saving the cost of transportation and handling of precast units in the site. Different percentages (0, 0.15, 0.30, and 0.45%) of volume fraction of barchip polypropylene (BPP) fibre have been incorporated to improve the mechanical properties of lightweight aggregate concrete (LWA) concrete. In this study, the mixture of crushed lightweight expanded clay aggregate (CLECA) and barchip polypropylene (BPP) fibre have been used to achieve compressive strength between 28 and 37 MPa at 28-days with an oven-dry density ranged between 1900 and 2000 kg/m3. It is found that the inclusion of BPP fibres at an optimum volume fraction concrete enhances the compressive strength, splitting tensile strength and modulus of rupture. The compressive strength of the lightweight aggregate concrete containing 0.45% volume fraction of BPP fibre (CLLWAC-BPP0.45%) had achieved the highest compressive strength of 37 MPa at 28-days with a significant increment of about 31% compared to plain concrete. Hence, the findings of this research showed that the development of eco-friendly lightweight structural composites can be used as an alternative solution for conventional lightweight concrete, infrastructure and marine fields application.

Review of the Properties of Lightweight Aggregate Concrete Produced from Recycled Plastic Waste and Periwinkle Shells

As the world population continues to increase, so does the demand for raw materials to produce basic needs of the human race. One of the areas where this pressing demand for means of production is evident is in the production of concrete materials for building construction and infrastructure. The source of constitutive materials for concrete production, such as cement and aggregates are fast shrinking across the nations of the earth, and there is an urgent need for substitutes that will guarantee the availability of this essential material to the built environment sector of the economy. One of the trending approaches is the adoption of waste materials as a replacement for some of the constitutive materials of concrete. This research reviews past works on the use of recycled plastic waste and periwinkle shells for the production of lightweight aggregate concrete. The results of this review showed that the adoption of a reduced percentage of waste plastic in concrete leads to acceptable strengths for lightweight concrete, economy, efficient energy and excellent crack resistance. The use of periwinkle shell is beneficial for satisfactory strengths for normal aggregate concrete and for lightweight aggregate concrete, excellent resistance to heat and economy. This approach is sustainable as a means of recycling and will facilitate the actualization of the sustainable development goal “Responsible Production and Consumption”, (SDGs 12). There is a perspective that combining these two waste materials will lead to improvement towards achieving sustainable concrete.

Effects of carbon nanotubes on expanded glass and silica aerogel based lightweight concrete

This study is aimed to investigate the effect of carbon nanotubes on the properties of lightweight aggregate concrete containing expanded glass and silica aerogel. Combinations of expanded glass (55%) and hydrophobic silica aerogel particles (45%) were used as lightweight aggregates. Carbon nanotubes were sonicated in the water with polycarboxylate superplasticizer by ultrasonication energy for 3 min. Study results show that incorporating multi-wall carbon nanotubes significantly influences the compressive strength and microstructural performance of aerogel based lightweight concrete. The addition of carbon nanotubes gained almost 41% improvement in compressive strength. SEM image of lightweight concrete shows a homogeneous dispersal of carbon nanotubes within the concrete structure. SEM image of the composite shows presence of C–S–H gel surrounding the carbon nanotubes, which confirms the cites of nanotubes for the higher growth of C–S–H gel. Besides, agglomeration of carbon nanotubes and the presence of ettringites was observed in the transition zone between the silica aerogel and cementitious materials. Additionally, flowability, water absorption, microscopy, X-ray powder diffraction, and semi-adiabatic calorimetry results were analyzed in this study.

Dynamic Properties Test and Constitutive Relation Study of Lightweight Aggregate Concrete under Uniaxial Compression

For the purpose of studying the dynamic properties of lightweight aggregate concrete, dynamic performance tests under uniaxial compression were conducted by considering 10 different strain rates ranging from 10−5/s to 10−1/s, from which the stress‐strain curves under various compressive loads were obtained. From the stress‐strain curves, parameters including peak stress, peak strain, and elastic modulus of lightweight aggregate concrete, as well as the concrete failure mode, were determined and examined. By reviewing the relevant literature on ordinary concrete, the dynamic properties of lightweight aggregate concrete were analyzed accordingly. Meanwhile, by applying the dynamic elastoplastic damage constitutive model, the effect of dynamic rate on lightweight aggregate concrete was calculated. The experimental results showed that the damage mode of lightweight aggregate concrete under the static and dynamic strain rates belonged to shear failure, which is different from that of ordinary concrete (binding material failure). On the other hand, it was also found that the peak stress and elastic modulus of lightweight aggregate concrete could be increased by 54.48% and 28.75%, respectively, with the increase of strain rate, suggesting that the loading strain rate has a stronger influence on lightweight aggregate concrete than on ordinary concrete. Based on the experimental data, both the peak stress and nondimensionalized elastic modulus are in linear relationship with the logarithm of the nondimensionalized strain rate. Moreover, the established constitutive model had been verified as an effective and reliable tool for simulating the dynamic rate effect of lightweight aggregate concrete.

Comparative Analysis of Young’s Modulus Predictions for Lightweight Aggregate Concrete

Many experimental and numerical works are attempting to predict the elastic properties of Lightweight Aggregate Concrete (LWAC). The purpose of this paper is to estimate the Young’s modulus of Lightweight Aggregate Concrete utilizing two-phase composite models. However, results of experimental data published in the literature were used as a platform, upon which, two-phase composite models had been utilized. The outcomes of this comparative analysis show that neither of the two-phase analytical models could be directly utilized for predicting Young’s modulus of LWAC. The Hashin-Hansen composite model provides a good prediction of experimental Young’s modulus of all LWAC tested with a maximum error percentage equal to 16.94%. This model provides an upper bound whereas the Counto2 model provides the lower bound of experimental Young’s modulus of LWAC.

Improving Compressive strength of Lightweight Aggregate Concrete

This work aims to improve the strength of Lightweight Aggregate Concrete (LWAC) developed in Egypt using available local materials. The Crushed Sand Brick (CSB) was used with (50, 60, and 70 percent) replacement ratios of crushed dolomite by volume in two options, once without surface coating another time after coating its surface with cement mortar before mixing. It is recommended to use uncoated CSB with a replacement ratio of 60 percent which provided optimum compressive strength/density ratio. Expanded Polystyrene (EP) was cut manually and used with of 60 % replacement ratio of crushed dolomite by volume by study the effect of type of Lightweight Aggregate (LWA) on properties and strength of LWAC, finally Expanded Polystyrene Granules (EPG) with particle size less than 4.75 mm was used as 60% replacement of sand by volume. Cement content was increased from 350 Kg/m3 to 450 Kg/m3, Silica Fume (SF) was added with different doses (10, 20, and 30) % of cement by weight, and High Range Water Reducer (HRWR) was used with different doses (2, 3, and 4) % of binder materials by weight to improve compressive strength and properties of LWAC. The type of LWA was found to be the most effective factor on the strength of LWAC.

Effects of air entraining admixture on the properties of lightweight aggregate concrete

In Lightweight Aggregate Concrete manufacturing, there is a stratification of lightweight aggregate during construction process, because bulk density of lightweight aggregates is much smaller than that of cement mortar. This paper presents some research results about the effect of air entrainment additive on the properties of lightweight aggregate concrete. When adding air entrainment admixture into lightweight concrete components with the amount of 0.02 – 0.08% by mass of binder, the stratification and bulk density of fresh concrete reduce, and strength of hardened concrete is also significantly reduced. Therefore, this result indicates that we should only use the air entrainment additive in small amounts (less than 0.02% by mass).

Influence of mortar matrix on properties of light weight concrete with foam glass granules

Foam glass granule (FGG) is commonly used as an aggregate for light weight aggregate concrete (LWAC). Because bulk gravity of FGG is much less than that of mortar matrix, segregation is tended to occur in LWAC mixtures. Mortar plays an important role in properties of LWAC with FGG. Therefore, this paper presents research results of influence of mortar matrix to properties of this type of concrete. In the study, the raw materials were FGG, But Son PC40 cement, Pha Lai fly ash and Sikament plasticizer named R4. The experimental results showed that with FGG content of 40% by volume and flow of mortar at 21- 22 cm, the LWC mixture was homogeneous and its slump was at 3.5- 5.5 cm. Simultaneously, the LWAC’s density was 1400-1500 kg/m3 and its compressive strength at 28 days was over 11 MPa.

Residual Mechanical Properties of Fiber-Reinforced Lightweight Aggregate Concrete after Exposure to Elevated Temperatures

In this study, the effects of individual and mixed fiber on the mechanical properties of lightweight aggregate concrete (LWC) after exposure to elevated temperatures were examined. Concrete specimens were divided into a control group (ordinary LWC) and an experimental group (fiber-reinforced LWC), and their compressive strength, elastic modulus, and flexural strength after heating to high temperatures of 400–800 °C were investigated. The four test parameters included concrete type, concrete strength, fiber type, and targeted temperature. The test results show that after exposure to 400–800 °C, the variation in mechanical properties of each group of LWC showed a trend of increasing first and then decreasing. After exposure to 400 °C, the residual mechanical properties of all specimens did not attenuate due to the drying effect of the high temperature and the more sufficient cement hydration reaction. However, after exposure to 800 °C, the residual mechanical properties significantly reduced. Overall, the mixed fiber-reinforced LWC showed a better ability to resist the loss of mechanical properties caused by high temperature. Compared with the loss of compressive strength, the flexural strength was relatively lost.

Mechanical Properties of Chopped Basalt Fiber-Reinforced Lightweight Aggregate Concrete and Chopped Polyacrylonitrile Fiber Reinforced Lightweight Aggregate Concrete.

In this study, an experimental investigation was conducted on the mechanical properties of lightweight aggregate concrete (LWAC) with different chopped fibers, including basalt fiber (BF) and polyacrylonitrile fiber (PANF). The LWAC performance was studied in regard to compressive strength, splitting tensile strength and shear strength at age of 28 days. In addition, the oven-dried density and water absorption were measured as well to confirm whether the specimens match the requirement of standard. In total, seven different mixture groups were designed and approximately 104 LWAC samples were tested. The test results showed that the oven-dried densities of the LWAC mixtures were in range of 1.819–1.844 t/m3 which satisfied the definition of LWAC by Chinese Standard. Additionally, water absorption decreased with the increasing of fiber content. The development tendency of the specific strength of LWAC was the same as that of the cube compressive strength. The addition of fibers had a significant effect on reducing water absorption. Adding BF and PANF into concrete had a relatively slight impact on the compressive strength but had an obvious effect on splitting tensile strength, flexural strength and shear strength enhancement, respectively. In that regard, a 1.5% fiber volume fraction of BF and PANF showed the maximum increase in strength. The use of BF and PANF could change the failure morphologies of splitting tensile and flexural destruction but almost had slight impact on the shear failure morphology. The strength enhancement parameter β was proposed to quantify the improvement effect of fibers on cube compressive strength, splitting tensile strength, flexural strength and shear strength, respectively. And the calculation results showed good agreement with test value.

Compressive stress-strain behavior of CFRP-confined lightweight aggregate concrete reinforced with hybrid fibers

The axial compressive stress-strain behavior of CFRP-confined lightweight aggregate concrete (LWAC) with short carbon fiber and/or polypropylene fiber was investigated. Thirty cylinders with different concrete types (normal weight concrete and LWAC), fiber types (carbon fiber, polypropylene fiber, and mixture of these two fibers), volume faction of fibers (from 0% to 0.4% for each fiber type in single and hybrid form), and spacing between CFPR straps (0 mm, 30 mm, and 50 mm) were experimentally studied. The compressive strengths of CFRP-confined LWAC were improved to 1.01–1.51 times the unconfined strength, and LWAC showed less enhancement in compressive strength provided by confining pressure compared with normal weight concrete. The increase in spacing between CFRP straps declined the confining effect. Addition of carbon fiber in both single and hybrid form positively affected the toughness of CFRP-confined LWAC, while the polypropylene fiber showed few influences on properties of LWAC. Models for the peak stress and corresponding strain were established by collected and present test data. Then theoretical stress-strain model was developed by combining iterative calculation of ascending portion and close-form formula of descending branch. The proposed model showed good match to the test results.

Alternative Estimation of Effective Young’s Modulus for Lightweight Aggregate Concrete LWAC

The prediction of effective mechanical properties of composite materials using analytical models is of significant practical interest in situations in which tests are impossible, difficult, or costly. Many experimental and numerical works are attempting to predict the elastic properties of Lightweight Aggregate Concrete (LWAC). In order to choose the optimized prediction composite model, the purpose of this paper is to appraise the effective Young’s modulus of LWAC using two-phase composite models. To this effect, results of previous experimental research have used as a platform, upon which, 07 two-phase composite models were applied. The outcomes of this comparative analysis show that not all two-phase analytical models can be directly used for predicting Young’s modulus of LWAC. The Hashin-Hansen and Counto2 models are in close concordance with the experimental Young’s modulus of all LWAC used for comparison in this study. Thus, the precision of this prediction model demonstrates its effectiveness and potential application as a model for Lightweight Aggregate Concrete. They were found more appropriate for reasonable prediction of elasticity modules of the LWAC.

Study on Mechanical Properties of Light Aggregate Concrete for Filled Core Assembly

This paper mainly explores the mechanical properties of lightweight aggregate concrete used for core-filled assembly members. Through the design adjustment of the mix ratio, the results show that the concrete slump is about 100mm, its workability is good, and its compressive strength is lower than ordinary concrete, but it meets the strength design requirements of prefabricated components. By analyzing the tensile and compression ratio and elastic strength ratio, the crack resistance and ductility of light aggregate concrete are better than ordinary concrete, which can provide reference for light aggregate concrete engineering applications.

Properties of Lightweight Aggregate Concrete Reinforced with Carbon and/or Polypropylene Fibers.

The impact of carbon and polypropylene fibers in both single and hybrid forms on the properties of lightweight aggregate concrete (LWAC), including the slump, density, segregation resistance, compressive strength, splitting tensile strength, flexural strength, and compressive stress–strain behavior, were experimentally investigated. The toughness ratio and ductility index were introduced for quantitatively evaluating the energy-absorbing capacity and post-peak ductility. A positive synergistic effect of hybrid carbon and polypropylene fibers was obtained in terms of higher tensile strength, toughness, and ductility. The toughness ratio and ductility index of hybrid fiber-reinforced LWAC were increased by 26%–37% and 12%–27% compared with plain LWAC, respectively. The fiber in both single and hybrid forms had a smaller effect on the linearity ascending branch of the stress–strain curves, whereas the post-peak patterns in terms of the toughness and ductility for the hybrid fiber-reinforced LWAC were significantly improved when the fiber in hybrid form.

Predicting the mechanical properties of lightweight aggregate concrete using finite element method

Abstract The compressive strength (fc) and Young’s modulus (Ec) of concretes are properties of great importance in civil engineering problems. To this day, despite the relevance of the subject, concretes are still designed based on charts and empirical formulae. This scenario is even more imprecise for lightweight aggregate concretes (LWAC), which contain less design methodologies and case studies available in the literature. In this sense, the present work presents a numerical simulation for predicting the properties of LWAC’s specimens using the Finite Element Method. The material was considered as biphasic, comprising lightweight aggregates and the enveloping mortar. Each phase was modelled with its own compressive strength, tensile strength and Young’s modulus. The achieved numerical results for fc and Ec were compared with their experimental counterparts, obtained from the literature. In total, 48 concrete formulations were assessed. Numerical results showed fair agreement with the experimental data. In general, the Mean Absolute Percentage Error (MAPE) was lower for the shale aggregates for both Young's modulus (1.75% versus 4.21% of expanded clay) and compressive strength (4.19% versus 9.89% of expanded clay). No clear trend of error was identified in relation to the aggregate proportion or to the mortar types, in which the MAPE varied from 2.36% to 8.13%. In conclusion, the simplification to spherical aggregates has shown satisfactory results, as has the adoption of a 2D model, which require less computational resources. Results encourage further applications with more complex geometrical aspects to improve the mix design and safety of LWAC.

Evaluation of Stress-Strain Behavior of Self-Compacting Rubber Lightweight Aggregate Concrete under Uniaxial Compression Loading.

The recycling of waste tires in lightweight aggregate concrete (LC) would achieve huge environmental and societal benefits, but the effects of rubber particles on the partial properties of LC are not clear (e.g., the stress–strain relationship). In this paper, uniaxial compressive experiments were conducted to evaluate the stress–strain relationship of self-compacting rubber lightweight aggregate concrete (SCRLC). Rubber particles were used to replace sand by volume, and substitution percentages of 0%, 10%, 20%, 30%, 40%, and 50% were set as influence factors. Experimental results indicate that with increased rubber particles substitution percentage, the cubic compressive strength and axial compressive strength of SCRLC decreased, while the failure modes of SCRLC prism specimens gradually changed from brittle to ductile failure. As the rubber particles substitution percentage increased from 0% to 50%, the peak strain of SCRLC increased whereas peak stress, elastic modulus, and peak secant modulus of SCRLC deceased, the descending stage of stress–strain curves became softer. The rubber particles substitution percentage of 30% was the critical point at which an obvious change in the properties of SCRLC occurred. Based on the data collected from experimental studies, a predictive model for SCRLC was established and a further prediction of the SCRLC stress–strain relationship was given.

Experimental and analytical study on uniaxial compressive fatigue behavior of self-compacting rubber lightweight aggregate concrete

In view of the excellent deformation capacity and energy absorption capacity, rubber particles had potential possibility to improve the fatigue properties of lightweight aggregate concrete (LC). However, the fatigue properties of LC containing rubber particles were not adequately understood. This paper focused on the effect of rubber particles on the uniaxial compressive fatigue properties of self-compacting rubber lightweight aggregate concrete (SCRLC). The results of uniaxial compressive fatigue tests indicated that fatigue life and fatigue strain of SCRLC added generally with increase of rubber particles substitution percentage, fatigue strain of SCRLC also raised with number of cycles increased. Analyses results indicated that the fatigue life of SCRLC conformed to two-parameter Weibull distribution. Based on the experimental results, fatigue equation of SCRLC was established by double logarithmic fatigue equation. From the curves of lgS-lgNf of SCRLC, it could be discovered that increasing of rubber particles substitution percentage in SCRLC resulted in a decrease of fatigue limit strength, but the stress level at fatigue life of 2 × 106 increased firstly and then decreased. The highest stress level of SCRLC would be obtained as rubber particles substitution percentage was 30%. By comprehensive consideration, under the same strength level, the fatigue properties of SCRLC was better than that of LC.

Prediction Model for Mechanical Properties of Lightweight Aggregate Concrete Using Artificial Neural Network.

The mechanical properties of lightweight aggregate concrete (LWAC) depend on the mixing ratio of its binders, normal weight aggregate (NWA), and lightweight aggregate (LWA). To characterize the relation between various concrete components and the mechanical characteristics of LWAC, extensive studies have been conducted, proposing empirical equations using regression models based on their experimental results. However, these results obtained from laboratory experiments do not provide consistent prediction accuracy due to the complicated relation between materials and mix proportions, and a general prediction model is needed, considering several mix proportions and concrete constituents. This study adopts the artificial neural network (ANN) for modeling the complex and nonlinear relation between constituents and the resulting compressive strength and elastic modulus of LWAC. To construct a database for the ANN model, a vast amount of detailed and extensive data was collected from the literature including various mix proportions, material properties, and mechanical characteristics of concrete. The optimal ANN architecture is determined to enhance prediction accuracy in terms of the numbers of hidden layers and neurons. Using this database and the optimal ANN model, the performance of the ANN-based prediction model is evaluated in terms of the compressive strength and elastic modulus of LWAC. Furthermore, these prediction accuracies are compared to the results of previous ANN-based analyses, as well as those obtained from the commonly used linear and nonlinear regression models.

설계 압축강도가 다른 경량골재 콘크리트의 역학적 특성에 대한 천연모래 양의 영향

설계 압축강도가 다른 경량골재 콘크리트의 역학적 특성에 대한 천연모래 양의 영향