Cellular lightweight concrete containing high-calcium fly ash and natural zeolite

Cellular lightweight concrete （CLC） with the controlled density of approximately 800 kg/m3 was made from a preformed foam, Type-I Portland cement （OPC）, fly ash （FA）, or natural zeolite （NZ）, and its compressive strength, setting time, water absorption, and microstructure of were tested. High-calcium FA and NZ with the median particle sizes of 14.52 and 7.72 μm, respectively, were used to partially replace OPC at 0, 10wt%, 20wt%, and 30wt% of the binder （OPC and pozzolan admixture）. A water-to-binder mass ratio （W/B） of 0.5 was used for all mixes. The testing results indicated that CLC containing 10wt% NZ had the highest compressive strength. The replacement of OPC with NZ decreased the total porosity and air void size but increased the capillary porosity of the CLC. The incorporation of a suitable amount of NZ decreased the setting time, total porosity, and pore size of the paste compared with the findings with the same amount of FA. The total porosity and cumulative pore volume decreased, whereas the gel and capillary pores increased as a result of adding both pozzolans at all replacement levels. The water absorption increased as the capillary porosity increased; this effect depended on the volume of air entrained and the type or amount of pozzolan.

Durability of Lightweight Concrete Using Oil Palm Shell as Aggregates

Oil Palm Shell (OPS) concrete can be used in different fields of construction. To determine more accurately the fields of application, it is important to know and understand the behaviour of OPS concrete over the long term and when it is in aggressive environments. This paper presents the results of studies conducted on the durability of OPS concrete. Water absorption capacity, electrical resistivity and apparent diffusion of chloride ions have been measured on different concrete samples. In addition, the behaviour of OPS concretes to carbonation was studied in an environment rich in carbon dioxide. Results show that OPS concrete has an absorptivity of 0.97 kg/m2·h1/2, an electrical resistivity of 64.37 Ω·m and an apparent diffusion coefficient of chloride ions of 3.84 × 10-12 m2/s after 90 days. All these results of OPS concrete are very close to those of concrete with normal aggregate and other lightweight concrete, which mean OPS concretes have globally good properties with regard to durability.

Strength of Lightweight Concrete Under Triaxial Compression

The strength of lightweight concrete under triaxial compressive stress is studied experimentally with the concrete triaxial apparatus designed by the authors, and is compared with that of normal concrete under the same stress state. Ninety-five 100 mm cubes under twenty stress ratios are tested. As compared with normal concrete, it is found that not only the multiaxial compressive strength of lightweight concrete is small, but also the ratio of the multiaxial compressive strength to the uniaxial compressive strength is small. The influence of the intermediate principal stress on the multiaxial strength of lightweight concrete is discussed. The strength criteria which are expressed in the principal stresses and the octahedral stresses respectively are proposed.

Bond Strength Degradation of Corrosive Reinforced Lightweight Concrete

The influence of reinforced bar corrosion on the bond degradation in lightweight concrete was studied. Accelerated constant current corrosion tests were performed on lightweight reinforced concrete samples, and the influential factors, such as protective layer thickness, reinforced bar diameter and corrosive level were investigated. The constant current step method was used to measure the electric resistance of the concrete protective cover, which was used to characterize the corrosion level of the rebar. Experimental results indicated that the corrosive resistance increased with increasing the cover dimension and decreasing the reinforced bar diameter, and the rate of decrease in the specimen impedance after cracking depended on the cover dimension. A new medium was offered for the further research on the performance degradation of corrosion lightweight concrete.

Development of Lightweight Concrete Using Industrial Waste Palm Oil Clinker

Concrete is a major material used in the construction of buildings and structures in the world.Gravel and sand are the major ingredients of concrete but are non-renewable natural materials.Therefore,the utilisation of palm oil clinker(POC),a solid waste generated from palm oil industry is proposed to replace natural aggregate in this research to reduce the demand for natural aggregates.One mix of ordinary concrete as control concrete;while four mix proportions of oil palm clinker concrete were obtained by replacing 25%,50%,75%,and 100%of gravel and sand of control concrete with coarse and fine oil palm clinker respectively by volume,with same cement content and water cement ratio.Compressive strength test was carried out of concretes with different percentages of oil palm clinker;whereas water absorption tests according to respective standard,were carried out to determine the durability properties of various mixes.Based on the results obtained,the study on the effect of percentage of clinker on strength and durability properties was drawn.According to ACI classification of light weight concrete only the 100 percentage replacement can achieve the definition of light weight concrete since its density is less than 1,900 kg/m3 and strength larger than 17 MPa.Eventually the 25%replacement of the normal aggregate by the OPC will improve the strength and durability of the concrete.

Size Variation of Palm Kernel Shells as Replacement of Coarse Aggregate for Lightweight Concrete Production

The utilization of palm kernel shells (PKS) as an alternative to conventional materials for construction is desirable to promote sustainable development. The purpose of this study is to investigate the properties of lightweight concrete produced with different sizes of PKS of 6, 8, 10, 12 mm and mix (consisting of 25% each of the four sizes). RPK sizes were used to replace coarse aggregate in the concrete and cured for 7, 14, 21 and 28 days. The tests performed on the concrete are dry density, compressive strength, flexural strength, EDS and SEM. It was revealed that the densities of the concrete specimens were all less than 2000 kg/m3, which implies that the PKS concrete satisfied the requirement of lightweight concrete for structural application. The compressive strength of the 12 mm PKS concrete specimens at 28-day of curing was 10.2 MPa which was 4% to 15.9% better than the other PKS sizes concrete. The flexural strength of the 12 mm PKS concrete specimens at 28-day of curing was 2.85 MPa which was also 3.2% to 57.07% better than the other PKS sizes concrete. It was also revealed by the SEM analysis that there was a good bond between the palm kernel shells and the mortar. A high calcium-silicate content was found in the concrete which resulted in a Ca/Si ratio of 1.26 and Al/Si ratio of 0.11. The study therefore concludes that size variations of PKS as replacement of coarse aggregate have an influence on the properties of the lightweight concrete and recommends 12 mm PKS for use by construction practitioners for lightweight concrete structural application.

A Research on the Usage of Corn Cob in Producing Lightweight Concrete

In this study, the possibility of using corn cobs as an organic aggregate in producing lightweight concrete has been investigated. First, some important physical properties of corn cob have been determined in the laboratory. These properties are as follows: weight to volume ratio (unit weight), water absorption rate and granulometric analysis. Later on, 4 concrete mixtures have been prepared according to the workability of concrete and standards specified in Turkey. After that, unit weight, heat transmissibility coefficient and 28-day pressure strength of these 4 concrete samples have been determined using machines measuring these properties. The 28-day pressure endurance value has been found between 1.4 - 56.25 kgf/cm2, heat transmissibility coefficient has been found between 0.19 - 0.35 Kcal/m∙h∙˚C and unit weight of samples have been found between 800 - 1520 kg/m3. Lastly, these properties of concrete samples have been compared with other lightweight materials being used in the construction of buildings.

Simulation of Fracture Process of Lightweight Aggregate Concrete Based on Digital Image Processing Technology

The mechanical properties and failure mechanism of lightweight aggregate concrete(LWAC)is a hot topic in the engineering field,and the relationship between its microstructure and macroscopic mechanical properties is also a frontier research topic in the academic field.In this study,the image processing technology is used to establish a micro-structure model of lightweight aggregate concrete.Through the information extraction and processing of the section image of actual light aggregate concrete specimens,the mesostructural model of light aggregate concrete with real aggregate characteristics is established.The numerical simulation of uniaxial tensile test,uniaxial compression test and three-point bending test of lightweight aggregate concrete are carried out using a new finite element method-the base force element method respectively.Firstly,the image processing technology is used to produce beam specimens,uniaxial compression specimens and uniaxial tensile specimens of light aggregate concrete,which can better simulate the aggregate shape and random distribution of real light aggregate concrete.Secondly,the three-point bending test is numerically simulated.Thirdly,the uniaxial compression specimen generated by image processing technology is numerically simulated.Fourth,the uniaxial tensile specimen generated by image processing technology is numerically simulated.The mechanical behavior and damage mode of the specimen during loading were analyzed.The results of numerical simulation are compared and analyzed with those of relevant experiments.The feasibility and correctness of the micromodel established in this study for analyzing the micromechanics of lightweight aggregate concrete materials are verified.Image processing technology has a broad application prospect in the field of concrete mesoscopic damage analysis.

Utilization of Basalt Saw Mud as a Spherical Porous Functional Aggregate for the Preparation of Ordinary Structure Concrete

To promote the production and application of artificial aggregates,save natural sand resources and protect the ecological environment,we evaluated the feasibility of using spherical porous functional aggregates(SPFAs) formed by basalt saw mud under autoclave curing in ordinary structural concrete.In our work,two types of prewetted functional aggregates were taken as replacements for natural aggregates with different volume substitution rates(0%,5%,10%,15%,20%,25%,and 30%) in the preparation of ordinary structural concrete with water-to-binder ratios(W/B) of 0.48 and 0.33.The effects of the functional aggregate properties and content,W/B,and curing age on the fluidity,density,mechanical properties and autogenous shrinkage of ordinary concrete were analyzed.The experimental results showed that the density of concrete declined at a rate of not more than 5%,and the 28 d compressive strength could reach 31.0-68.2 MPa.Low W/B,long curing age and high-quality functional aggregates were conducive to enhancing the mechanical properties of SPFAs concrete.Through the rolling effects,SPFAs can optimize the particle gradation of aggregate systems and improve the fluidity of concrete,and the water stored inside SPFAs provides an internal curing effect,which prolongs the cement hydration process and considerably reduces the autogenous shrinkage of concrete.SPFAs exhibits high strength and high density,as well as being more cost-effective and ecological,and is expected to be widely employed in ordinary structural concrete.

Thermal performance of lightweight concrete applications in building envelopes in Lebanon

Innovative building materials are being used in building envelopes for reducing their heating and cooling needs.This paper aims to assess the thermal impact of using lightweight concrete in Lebanese building constructions by pouring an 8 cm thickness of lightweight concrete on the roof and the slab and replacing traditional hollow concrete block by lightweight concrete blocks.Thermal properties of two different samples were experimentally determined:the first one(558 kg/m^(3))used for the roof and the slab and the second one(1074 kg/m^(3))used for the walls.Then numerical simulations were carried out for a Lebanese traditional detached house using the characteristics of these two samples.The thermally improved Light Weight Concrete building(LWC)was compared to a traditional Lebanese house base case(BC)using a dynamic building energy simulation tool in the four different Lebanese climate zones:coastal,mid-mountain,mountain,and inland zones.The results highlight the effectiveness of integrating LWC to building envelopes by reducing energy consumption and improving thermal comfort in both winter and summer climate conditions and in the different Lebanese climatic zones.The paper demonstrates that the use of LWC in the vertical walls replacing the traditional hollow blocks can reduce the heating needs by up to 9%and by up to 13%for cooling needs.On the other hand,adding a LWC roof screed has a very high impact on cooling and heating energy consumption,which can reach up to 74%in cooling energy savings and up to 24%in heating energy savings.

Mechanical Characterization of Rhecktophyllum Camerunense (RC) Fiber Reinforced Concrete

This work presents the development and mechanical characterization of a concrete reinforced with plant fiber extracted from Rhecktophyllum Camerunense (RC), a plant found in the regions of Center and South Cameroon. A comparative study between ordinary concrete and concrete reinforced with RC fiber at different percentages (0.1%, 0.2% and 0.3%) was carried out. The mechanical characterization of the material consisted in studying the flexural, compressive and splitting tensile strength by using cylindrical specimens of dimensions 160 × 320 in accordance with standards EN 12390-3 and EN 12390-6. The study of the mechanical properties was completed by the three-point bending test using prismatic test specimens of dimension 40 × 40 × 160 made according to the EN 196 standard. It emerges from this work that the addition of RC fiber improves the mechanical properties of concrete up to 0.2% with a peak at 0.1% of fiber corresponding to respective increases of 9%, 16% and 6% of the values of mechanical resistance to compression, flexion and tension after 28 days. From 0.3% of fiber, the values of the mechanical characteristics of the composite drop to values lower than those of ordinary concrete. The density reduction rate at 28 days is about 10% compared to the mass of ordinary concrete. These results allow us to conclude that the RC fiber could be valorized for the production of lightweight concrete.

Mechanical Characterization of Rhecktophyllum Camerunense (RC) Fiber Reinforced Concrete

This work presents the development and mechanical characterization of a concrete reinforced with plant fiber extracted from Rhecktophyllum Camerunense (RC), a plant found in the regions of Center and South Cameroon. A comparative study between ordinary concrete and concrete reinforced with RC fiber at different percentages (0.1%, 0.2% and 0.3%) was carried out. The mechanical characterization of the material consisted in studying the flexural, compressive and splitting tensile strength by using cylindrical specimens of dimensions 160 × 320 in accordance with standards EN 12390-3 and EN 12390-6. The study of the mechanical properties was completed by the three-point bending test using prismatic test specimens of dimension 40 × 40 × 160 made according to the EN 196 standard. It emerges from this work that the addition of RC fiber improves the mechanical properties of concrete up to 0.2% with a peak at 0.1% of fiber corresponding to respective increases of 9%, 16% and 6% of the values of mechanical resistance to compression, flexion and tension after 28 days. From 0.3% of fiber, the values of the mechanical characteristics of the composite drop to values lower than those of ordinary concrete. The density reduction rate at 28 days is about 10% compared to the mass of ordinary concrete. These results allow us to conclude that the RC fiber could be valorized for the production of lightweight concrete.

The Testing Strength Curves of Lightweight Aggregate Concrete by Rebound Method and Ultrasonic-rebound Combined Method

The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound combined method.The results show that the common measured strength curves tested by above two methods can not satisfy the required accuracy of LWAC strength test.In addition,specified compressive strength curves of testing LWAC by rebound method and ultrasonic-rebound combined method are obtained,respectively.

Autogenous Shrinkage of High Strength Lightweight Aggregate Concrete

The characteristic of autogenous shrinkage（AS） and its effect on high strength lightweight aggregate concrete（HSLAC） were studied.The experimental results show that the main shrinkage of high strength concrete is AS and the amount of cement can affect the AS of HSLAC remarkably,At the early stage the AS of HSLAC is lower than that of high strength normal concrete,but it has a large growth at the later stage.The AS of high strength normal concrete becomes stable at 90d age,but HSLAC still has a high AS growth .It is found that adjusting the volume rate of lightweight aggregate,mixing with a proper dosage of fly ash and raising the water saturation degree of lightweight aggregate can markedly reduce the AS rate of HSLAC.

Influence of Polymer Addition on Performance and Mechanical Properties of Lightweight Aggregate Concrete

The influence of polymer addition on microstructure, performance and mechanical properties of lightweight aggregate concrete was investigated. It was found that the addition of polymer improved the performance and mechanical properties of lightweight aggregate concrete. It was ascertained that the modification of microstructural uniformity and densification with the addition of polymer is responsible for the enhancement of mechanical properties. With respect to compressive strength and bending strength, the lightweight aggregate concrete added with 13% ethylene-acetate ethylene interpolymer (EVA) exhibits preferred mechanical properties. Key words lightweight aggregate concrete - polymer - microstructure - mechanical properties CLC number TU 528.2 Foundation item: Supported by the National Nature Science Foundation of China (50272045)Biography: Jiang Cong-sheng (1963-), male, Ph. D candidate, Associate professor, research direction: advanced architectural materials.

Brittleness Generation Mechanism and Failure Model of High Strength Lightweight Aggregate Concrete

The brittleness generation mechanism of high strength lightweight aggregate con-crete(HSLWAC) was presented, and it was indicated that lightweight aggregate was the vulnerable spot, initiating brittleness. Based on the analysis of the brittleness failure by the load-deflection curve, the brittleness presented by HSLWAC was more prominent compared with ordinary lightweight aggregate concrete of the same strength grade. The model of brittleness failure was also established.

Properties Evaluation of Concrete using Local Used Bricks as Coarse Aggregate

With time concrete / reinforced concrete has become the popular material for construction. Modern industry utilizes this material a lot and has produced various beautiful, eye catching and amazing structures. Due to modern requirements for living and developed construction industries, the old buildings (usually constructed with brick masonry) are demolished and are replaced with new modern buildings. Demolition of buildings results in waste materials which can create waste related problems and environmental issues. By using recycled aggregates weight of concrete can also be reduced, which can also solve problems related to self-weight of concrete. In this paper attempt has been made to use local used bricks from vicinity of Nawabshah, Pakistan, as coarse aggregate. Concrete cubes made with local recycled bricks are cast and tested for overall weight of concrete, moisture content, dynamic modulus of elasticity and compressive strength (nondestructive and destructive methods). The results showed that concrete derived from recycled aggregates attained lower strength than regular concrete. More detailed elaborated work is recommended with different mix ratios and different proportions recycled aggregates for better conclusions.

Preparation of Novel Core-shell Non-sintered Lightweight Aggregate and Its Application in Wallboard for Better Properties

Due to the relatively high density of conventional non-sintered lightweight aggregate(NLA),a low-density core-shell NLA(CNLA) was developed.Moreover,two types of porous lightweight aggregate concrete (PLAC) for wallboard were designed,using both foam and lightweight aggregates.The effects of LA on lightweight concrete workability,compressive strength,dry shrinkage,and thermal conductivity were studied and compared.The bulk density of CNLA can be lowered to 500 kg/m^(3),and its cylinder crushing strength is 1.6 MPa.PLACs also have compressive strengths ranging from 7.8 to 11.8 MPa,as well as thermal conductivity coefficients ranging from 0.193 to 0.219 W/(m·K^(-1)).The CNLA bonds better to the paste matrix at the interface transition zone,and CNLA concrete has a superior pore structure than SLA concrete,resulting in a 20% improvement in fluidity,a 10% increase in strength,a 6% reduction in heat conductivity,and an 11% decrease in drying shrinkage.

Alkali-Silica Reactivity and Strength of Mortars with Expanded Slate, Expanded Glass or Perlite

Lightweight aggregates are increasingly used in concrete construction. They reduce concrete selfweight furnishing a structural advantage. In contrast, the mechanical properties and durability of lightweight concrete can become the governing factor on lightweight aggregate replacement ratios. Alkali-Silica Reactison (ASR) and compressive strength of mortar samples with expanded slate, expanded glass or perlite, covering the spectrum of internal porosity and weight of lightweight aggregates, were evaluated. Scanning electron microscopy was utilized to evaluate the contribution of the aggregates’ porosity and chemical composition in inhibiting ASR. Perlite, owing to its highly porous microstructure and lower matter excelled in ASR expansion while chemical composition and denser microstructure of the heavier expanded slate resulted in more signified late ASR expansion and higher compressive strength. An attempt in visual inspection of ASR attack of alkali metal ions on silica-rich expanded glass using an ultra-accelerated exposure to sodium hydroxide solution was made.

Experimental study of lightweight aggregate concrete under multiaxial stresses

Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A "plastic flow plateau" area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.