Lightweight Cement Composites Research Articles

Properties of a lightweight cement composite with an ecological organic filler

This study aimed to establish the properties of lightweight cement composites with organic fillers, such as common reed and conifer sawdust. The reed Phragmites australis is a notably common plant in Poland that grows on waterlogged lands, and sawdust is a waste product that appears during the mechanical processing of wood.The first step was to determine the influence of the mineralisation on the water absorbability of the organic filler. Next, the influences of the superplasticiser (SP) content and the method of mixture consolidation on cement composite properties, such as the compressive strength, the water absorbability, the density and the porosity structure, were established. The chemisorption abilities of the cement composite and of the organic filler were also determined.

Flexural performance of fiber-reinforced ultra lightweight cement composites with low fiber content

This paper presents an experimental study on flexural performance of ultra lightweight cement composites (ULCC) with 0.5vol% fibers. Low density of the ULCC is achieved by using cenospheres from coal-fired power plants as micro aggregates. Effects of shrinkage reducing admixture (SRA) and fiber types on compressive strength and flexural performance of the ULCC are investigated. ULCC with density of 1474kg/m3, compressive strengths of 68.2MPa, flexural strength of 8MPa, and deflection hardening behavior can be produced. Such good performance could be attributed primarily to the SRA which reduced entrapped air in paste matrix and densified fiber–matrix interface. The improvement on the flexural performance of the ULCC depends on fibers used and bond between fibers and matrix. Improvement of the flexural performance of the steel fiber (coated with brass) reinforced ULCC due to the densification effect by SRA was more significant than that of the PE fiber reinforced ULCC.

An Investigation on Adding Polypropylene Fibers to Reinforce Lightweight Cement Composites (LWC)

The influence of polypropylene fibers has been studied in different proportioning and fiber length to improve the performance characteristics of the lightweight cement composites. Fibers used in two different lengths (6mm and 12mm) and fiber proportions (0.15% and 0.35%) by cement weight in the mixture design. Hardened concrete properties such as: 7- and 28-day compressive strength, splitting tensile strength, flexural strength, water absorption, and shrinkage were evaluated. Fiber addition was seen to enhance the physical and mechanical properties of lightweight concrete. Compared to unreinforced LWC, polypropylene (PP) reinforced LWC with fiber proportioning 0.35% and 12 mm fiber length, caused 30.1% increase in the flexural strength and 27% increase in the splitting tensile strength. Increased fiber availability in the LWC matrix, in addition to the ability of longer PP fibers to bridge on the micro cracks, are suggested as the reasons for the enhancement in mechanical properties.

Transient Thermal Response of Lightweight Cementitious Composites Made with Polyurethane Foam Waste

The development of low-cost lightweight aggregate (LWA) mortars and concretes presents many advantages, especially in terms of lightness and thermal insulation performances of structures. Low-cost LWA mainly comes from the recovery of vegetal or plastic wastes. This article focuses on the characterization of the thermal conductivity of innovative lightweight cementitious composites made with fine particles of rigid polyurethane (PU) foam waste. Five mortars were prepared with various mass substitution rates of cement with PU-foam particles. Their thermal conductivity was measured with two transient methods: the heating-film method and the hot-disk method. The incorporation of PU-foam particles causes a reduction of up to 18 % of the mortar density, accompanied by a significant improvement of the thermal insulating performance. The effect of segregation on the thermal properties of LWA mortars due to the differences of density among the cementitious matrix, sand, and LWA has also been quantified. The application of the hot-disk method reveals a gradient of thermal conductivity along the thickness of the specimens, which could be explained by a non-uniform repartition of fine PU-foam particles and mineral aggregates within the mortars. The results show a spatial variation of the thermal conductivity of the LWA mortars, ranging from 9 % to 19 %. However, this variation remains close to or even lower than that observed on a normal weight aggregate mortar. Finally, a self-consistent approach is proposed to estimate the thermal conductivity of PU-foam cement-based composites.

Effect of recycled cellulose fibres on the properties of lightweight cement composite matrix

This paper discusses the results from an experimental investigation conducted to study the effect on using cellulose fibres as cement replacement on the properties of lightweight cement composite. The fibres were recycled from waste paper and packaging and the content in the composite was ranged from 0% to 16% by mass of cement. The prepared specimens were tested after 28day of curing in order to investigate compressive and tensile strengths, density and thermal conductivity. Also, Scanning Electron Microscopy (SEM) examination was carried out.Results revealed that although there was general reduction in the compressive strength of concrete with the increase of fibre content, the thermal insulation properties of concrete were improved. Results from SEM examination showed a homogenous distribution of fibres in the matrix when using adequate water–cement ratio for different fibre contents. It may be concluded from this study that it is possible to use this material for the construction of non-load bearing walls and partitions, ceilings, and roofs.

Stability of cenospheres in lightweight cement composites in terms of alkali–silica reaction

This paper presents an experimental study on characteristics and stability of cenospheres used in lightweight cement composites. ASTM C227 and C1260 tests were used to evaluate if cenospheres are potentially deleterious due to alkali–silica reaction (ASR). Natural sand was used as control. Examination by scanning electron microscope with energy-dispersive X-ray spectroscopy and analyses by X-ray diffractometer and thermogravimetry were conducted on samples with cenospheres after 9-month C227 and C1260 tests to better understand the behavior of cenospheres exposed to high alkaline environments and higher temperatures in these tests. Results indicate that cenospheres are not potentially deleterious due to ASR. Expansion of the mortar specimens tested to ASTM C227 and C1260 seems to be affected by the pozzolanic reactivity of cenospheres. Fine cenospheres showed limited pozzolanic reactivity at 28–30°C and 38°C, but exhibited significant pozzolanic reactivity at 80°C with aluminum tobermorite [Ca5Si5Al(OH)O17∙5H2O] identified as the main reaction product.

Utilization of recycled post consumer carpet waste fibers as reinforcement in lightweight cementitious composites

Purpose – A large amount of post‐consumer carpet waste is discarded into landfills. The need to recycle this waste is increasing due to the lack of available landfill spaces in many parts of the world, environmental concerns, and resource conservation. The purpose of this paper is to explore the use of this waste for a low‐cost, high‐volume application.Design/methodology/approach – Fibers from carpet waste have been successfully used as reinforcement in concrete, typically at 0.1‐1 per cent volume fraction (fractions by weight are even lower), for enhanced toughness. In this study, lightweight cementitious composites were fabricated that were reinforced with recycled carpet fibers at up to 20 per cent fiber to cement weight ratios. Flexural, toughness, and impact properties of the lightweight cementitious composites were characterized.Findings – The density of the composites decreases with the increase of fiber content. In the three‐point bending test, lightweight cementitious composites exhibited a ducti...

Polymer–cement composite based on recycled expanded polystyrene foam waste

AbstractA new polymer–cement composite based on a recycled expanded polystyrene (EPS) resin has been developed as an effective method for EPS foam wastes management. The liquefied polymer is prepared by dissolving the foam waste in acetone, then in toluene at the ratio 113:2:1 per volume, respectively. The composite is made by incorporating the resulting resin into cement‐paste at selected water:cement ratios. At the end of defined curing periods, the physical, mechanical, and thermal characterizations of the obtained composite were evaluated under variable factors e.g., Acetone: toluene ratio, water:cement ratio (w/c), curing periods. Compressive strength, apparent porosity, bulk density, and specific gravity were determined for the composite under the various stated conditions. FT‐IR, XRD, thermal analysis, and scanning electron microscope (SEM) were performed for the hard blocks to study the effect of the added recycled EPS resin on the microstructure of the end products. Based on the data so far obtained it can be concluded that the candidate dissolution process of EPS foam wastes is an easily environmental friendly technique that allows afterward using the resultant resin for producing an added value, low cost, promising market competitive, and multipurpose light weight cement composite. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

WITHDRAWN: The suitability of utilising flax by-product materials for lightweight cement composites

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Influence of granule properties and concentration on cork-cement compatibility

Cork granules are produced as by-products and waste by the cork processing industries that make ‘bottle stoppers’ as a main product. These granules are of low density and could be used as lightweight aggregates for making concrete. This paper describes an investigation carried out to assess the compatibility of cork granules with cement for the manufacture of lightweight cementitious composites. Five different grades of cork granules varying in terms of size and density were investigated. The effects of extractives, particle size and density of the cork granules were studied. The results indicate that these parameters affect cement hydration in a complex way. At lower concentrations of cork (10%), only the extractives have an influence on hydration behaviour. At higher cork concentrations (20% and 30%), however, particle size and density also affect the compatibility. Nevertheless, cork granules are found to be compatible with cement.

Effects of processing and materials variations on mechanical properties of lightweight cement composites

Low-density/low-cost cement composites were fabricated. Carbon and alkali-resistant glass fibers were used to reinforce the matrix of industrial by-products; fly ash with silica fume, Portland cement, and calcium silicates were mixed in different proportions. The additional low density was obtained by adding perlite and foaming agents followed by hot water curing. The composites also were prepared by autoclave curing for comparison. The mechanical properties were improved by increasing the amount of silica fume, fly ash, and fibers. Both carbon fibers and alkali-resistant glass fibers were effective in reinforcing the matrices, but carbon fibers were superior to glass fibers. Fabrication techniques for producing lightweight cement composites that can substitute for autoclaved lightweight concrete was developed.

Flexural and tensile strength developments of various shape carbon fiber-reinforced lightweight cementitious composites

Effects of three types of carbon fiber shapes (C, round, and hollow shape) on tensile and flexural strength developments of randomly oriented carbon-fiber-reinforced lightweight cement composites (CFRLC) were investigated. C-shape CFRLC (C-CFRLC) showed higher tensile and flexural strength development than any other shape. C-CFRLC loading V f = 3% in particular increased about 40% in tensile and flexural strength, compared to round shape CFRLC (R-CFRLC). Hollow-shape CFRLC (H-CFRLC) showed slightly higher tensile and flexural strength than R-CFRLC. C-CFRLC presented stronger fiber-matrix interfacial adhesive force, due to mechanical anchorage into the matrix, than any other fibers. Silica fume significantly influences the increase of tensile and flexural strength for the CFRLC.

Surface treatmet of sillimanite-based microspheres for strength enhancement of high-temperature lightweight cement composites

The compressive strength of high-temperature lightweight cementing materials containing sillimanite-based hollow microspheres as a filler can be improved by treating the surfaces of the microspheres with a calcium hydroxide-saturated solution at temperatures up to 200° C. The precipitation of an epitaxial layer formed by an interaction between the hot calcium hydroxide solution end the surface of the sphere played an essential role in developing favourable bonding characteristics at the interfaces and in promoting the hydration of the cement matrix. Bonding is associated with the formation of an intermediate layer of aluminium-rich calcium silicate hydrate, produced by an interfacial reaction of the cement paste with the epitaxy under the hydrothermal environment at 300° C. A dense intermediate layer consisting of a rim structure of 4μm thickness acts in cross-linking and coupling functions that serve to connect the cement matrix and spheres, thereby improving the interfacial bond strength. The presence of the epitaxial layer on the treated sphere surfaces leads to the formation of a well-crystallized tobermorite matrix phase, which is responsible for the development of strength in autoclaved lightweight cements.