Physical and mechanical properties of mortars containing PET and PC waste aggregates

Non-biodegradable plastic aggregates made of polycarbonate (PC) and polyethylene terephthalate (PET) waste are used as partial replacement of natural aggregates in mortar. Various volume fractions of sand 3%, 10%, 20% and 50% are replaced by the same volume of plastic. This paper investigates the physical and mechanical properties of the obtained composites. The main results of this study show the feasibility of the reuse of PC and PET waste aggregates materials as partial volume substitutes for natural aggregates in cementitious materials. Despite of some drawbacks like a decrease in compressive strength, the use of PC and PET waste aggregates presents various advantages. A reduction of the specific weight of the cementitious materials and a significant improvement of their post-peak flexural behaviour are observed. The calculated flexural toughness factors increase significantly with increasing volume fraction of PET and PC-aggregates. Thus, addition of PC and PET plastic aggregates in cementitious materials seems to give good energy absorbing materials which is very interesting for several civil engineering applications like structures subjected to dynamic or impact efforts. The present study has shown quite encouraging results and opened new way for the recycling of PC waste aggregate in cement and concrete composites.     

Recycled sand in lime-based mortars

The increasing awareness of the society about safe guarding heritage buildings and at the same time protecting the environment promotes strategies of combining principles of restoration with environmentally friendly materials and techniques. Along these lines, an experimental program was carried out in order to investigate the possibility of producing repair, lime-based mortars used in historic buildings incorporating secondary materials. The alternative material tested was recycled fine aggregates originating from mixed construction and demolition waste. Extensive tests on the raw materials have been performed and mortar mixtures were produced using different binding systems with natural, standard and recycled sand in order to compare their mechanical, physical and microstructure properties. The study reveals the improved behavior of lime mortars, even at early ages, due to the reaction of lime with the Al and Si constituents of the fine recycled sand. The role of the recycled sand was more beneficial in lime mortars rather than the lime–pozzolan or lime–pozzolan–cement mortars as a decrease in their performance was recorded in the latter cases due to the mortars’ structure.     

Mechanical and thermo-physical characterization of mortars made with uncontaminated marine sediments

Journal of Material Cycles and Waste Management - In a context of sustainable development, civil engineering must increasingly use recyclable materials to preserve natural resources. Sediments...     

Use of rubble from building demolition in mortars

Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from building demolition. If suitably selected, ground, cleaned and sieved in appropriate industrial crushing plants, these materials can be profitably used in concrete. Nevertheless, the presence of masonry instead of concrete rubble is particularly detrimental to the mechanical performance and durability of recycled-aggregate concrete and the same negative effect is detectable when natural sand is replaced by fine recycled aggregate fraction. An alternative use of both masonry rubble and fine recycled material fraction could be in mortars. These could contain either recycled instead of natural sand or powder obtained by bricks crushing as partial cement substitution. In particular, attention is focused on the modification that takes place when either polypropylene or stainless steel fibers are added to these mortars. Polypropylene fibers are added in order to reduce shrinkage of mortars, stainless steel fibers for improving their flexural strength. The combined use of polypropylene fibers and fine recycled material from building demolition could allow the preparation of mortars showing good performance, in particular when coupled with bricks. Furthermore, the combined use of stainless steel fibers and mortars containing brick powder seems to be an effective way to guarantee a high flexural strength.     

Reuse of ground waste glass as aggregate for mortars

This work was aimed at studying the possibility of reusing waste glass from crushed containers and building demolition as aggregate for preparing mortars and concrete. At present, this kind of reuse is still not common due to the risk of alkali-silica reaction between the alkalis of cement and silica of the waste glass. This expansive reaction can cause great problems of cracking and, consequently, it can be extremely deleterious for the durability of mortar and concrete. However, data reported in the literature show that if the waste glass is finely ground, under 75mum, this effect does not occur and mortar durability is guaranteed. Therefore, in this work the possible reactivity of waste glass with the cement paste in mortars was verified, by varying the particle size of the finely ground waste glass. No reaction has been detected with particle size up to 100mum thus indicating the feasibility of the waste glass reuse as fine aggregate in mortars and concrete. In addition, waste glass seems to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance.     

Chemically treated plastic aggregates for eco-friendly cement mortars

Journal of Material Cycles and Waste Management - The use of waste plastic as aggregate in cement composites can solve the problem of the disposal of waste plastics in a sustainable way, and it...     

Hydration characteristics of coconut fibre-reinforced mortars containing CSA and Portland cement

Journal of Material Cycles and Waste Management - This study aims at investigation of the effects of incorporating natural fibres and two types of cement [ordinary Portland cement and calcium...     

Mechanical properties and microstructure of cement mortars incorporating Cd-zeolitized fly ash

Journal of Material Cycles and Waste Management - A solid enriched with NaA zeolite was synthesized from a coal fly ash, and the so-obtained zeolitized material was used as ion exchanger for...     

Investigation of physical and mechanical properties of mortars produced with recycled asphalt waste under the influence of high temperature

Journal of Material Cycles and Waste Management - In recent years, the use of waste products in cement-based building materials has been increasing. In this study, it is aimed to examine the...     

Characterization of the leaching behaviour of concrete mortars and of cement-stabilized wastes with different waste loading for long term environmental assessment

The leaching behaviour of cement-based products-both construction products and cement-stabilized wastes--have been shown to be similar after assessing the leaching characteristics by means of a pH dependence leaching test. This procedure is particularly suited to identifying the chemical speciation of materials. Geochemical modelling has shown a number of solubility controlling phases in this largely inorganic matrix, that can very well explain the observed leaching patterns as a function of pH. Understanding these relationships allows the prediction of leaching behaviour under other exposure conditions and to improve the ultimate quality of products, if so desired. The role of ettringite-type phases for the binding of oxyanions in the pH range above pH 12 has been identified before and confirmed in this work. The order of incorporation follows from the ratio between the maximum leachability at mildly alkaline pH and at high pH. Increased levels of sulfate negatively influence the binding of oxyanions in cement-stabilized waste through site competition.     

Influence of recycled fine aggregates on the resistance of mortars to magnesium sulfate attack

The influence of recycled fine aggregates, which had been reclaimed from field-demolished concretes, on the resistance of mortar specimens to magnesium sulfate attack was investigated. Mortar specimens were prepared with recycled fine aggregates at different replacement levels (0%, 25%, 50%, 75% and 100% of natural fine aggregate by mass). The mortar specimens were exposed to 4.24% magnesium sulfate solution for about 1 year at ambient temperature, and regularly monitored for visual appearance, compressive strength loss and expansion. Additionally, in order to identify products of magnesium sulfate attack, mortar samples incorporating 0%, 25% and 100% replacement levels of the recycled fine aggregates were examined by X-ray diffraction (XRD) technique.Experimental results confirmed that the use of recycled fine aggregates up to a maximum 50% replacement level is effective under severe magnesium sulfate environment, irrespective of type of recycled fine aggregates. However, the worse performance was observed in mortar specimens incorporating 100% replacement level. It was found that the water absorption of recycled fine aggregates affected deterioration of mortar specimens, especially at a higher replacement level. XRD results indicated that the main cause of deterioration of the mortar specimens was primarily due to the formation of gypsum and thaumasite by magnesium sulfate attack. In addition, it appeared that the conversion of C–S–H into M–S–H by the attack probably influenced mechanical deterioration of mortar specimens with recycled fine aggregates.     

Alkaline hydrolysis of PVC-coated PET fibers for simultaneous recycling of PET and PVC

Journal of Material Cycles and Waste Management - Polyvinyl chloride (PVC)-coated poly(ethylene terephthalate) (PET) woven fibers are one of the hardest-to-recycle polymeric materials. Herein we...     

Thermal Stabilization of Recycled PET Through Chain Extension and Blending with PBT

This study investigates the effect of using a multifunctional epoxide chain extender (Joncryl^® ADR 4468) on the thermal stabilization and rheological properties of recycled polyethylene terephthalate (R-PET) and its blends with polybutylene terephthalate (PBT). The R-PET samples were prepared without and with chain extender (CE) contents of 0.4 wt% and 0.8 wt%. R-PET/PBT blends with weight ratios of 75w/25w, 50w/50w and 25w/75w were also prepared without and with a given CE content of 0.2 wt%. The thermal stability of the melt blended samples was analyzed through small amplitude oscillatory shear (SAOS) rheological experiments. The structure of the samples was evaluated using a Fourier transform infrared (FTIR) spectrometer. While the dynamic rheological properties of R-PET were improved with the addition of Joncryl and by blending with PBT, during the SAOS rheological experiments, the complex viscosity of R-PET further increased due to the concurrent polycondensation of R-PET and the resumption of Joncryl reaction with R-PET molecules. These reactions during the rheological experiments were further expedited with increasing the testing temperature. On the other hand, in R-PET/PBT blends, the reactivity of Joncryl was more noticeable in blends with higher R-PET contents due to the higher available internal reactive sites of much shorter R-PET molecules. It was observed that the addition of only 0.2 wt% Joncryl to the blends of R-PET/PBT (75w/25w) dramatically improves the thermal stability and dynamic rheological properties of R-PET and most likely its processability.

     

Chemical Recycling of PET Waste with Multifunctional Pentaerythrytol in the Melt State

Chemical recycling of poly(ethylene terephthalate) PET waste in the melt state through alcoholysis with multifunctional alcohol—pentaerythrytol (PENTE)—was performed in a internal mixer Haake Rheomix 600, at 250 °C, 60 rpm, for 10 min, in presence of zinc acetate. The following PET:PENTE molar ratios 1:0; 1:0.16; 1:0.48 and 1:3.4 were studied. The chemical structure of the end-products was characterized by FT-IR. Thermal properties and X-ray diffractograms were also assessed. The esterification and alcoholysis reactions took place and were dependent on the molar ratio. The first one is dominant in compositions rich in PET leading to the formation of star-branching copolymer. The second one brings about the PET oligomerization and an oligoester named herein bis(tri-hydroxylneopentyl) terephthalate (BTHNPT) was obtained. The end-products have potential application as asphalt additive or adhesive.     

Properties of mortars made by uncalcined FGD gypsum-fly ash-ground granulated blast furnace slag composite binder

A series of novel mortars were developed from composite binder of uncalcined FGD gypsum, fly ash (FA) and ground granulated blast furnace slag (GGBFS) for the good utilization of flue gas desulphurization (FGD) gypsum. At a fixed ratio (20%) of GGBFS to the composite binder, keeping consistency of the mortar between 9.5 and 10.0 cm, the properties of the composite mortar were studied. The results show that higher water/binder (W/B) is required to keep the consistency when increasing the percentage of FGD gypsum. No obvious influences of the W/B and content of FGD gypsum on the bleeding of paste were observed which keeps lower than 2% under all experimental conditions tried. The highest compressive and flexural strengths (ratio is 20% FGD gypsum, 20% GGBFS and 60% FA) are 22.6 and 4.3 MPa at 28 days, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that massive ettringite crystals and C-S-H gels exist in the hydration products. At 90 days the mortars with FGD gypsum is dramatically smaller drying shrinkage (563-938 micro strain) than that without FGD gypsum (about 2250 micro strain). The release of the SO(4)(2-) from the mortar was analyzed, indicating that the dissolution of sulfate increases with FGD gypsum. The concentration of SO(4)(2-) releasing from the mortar with 10% FGD gypsum is almost equal to that obtained from the mortar without FGD gypsum. The release of SO(4)(2-) from the mortar with 20% FGD gypsum is 9200 mg·m(-2), which is lower than that from the mortar with 95% cement clinker and 5% FGD gypsum.     

Valorization of marine sediments in geopolymer mortars: physico-mechanical,microstructural and environmental investigations at laboratory scale

Journal of Material Cycles and Waste Management - The high consumption of natural sand and the accumulation of mineral wastes in landfills such as dredged sediments make it necessary to valorize...     

Fly ash from biomass combustion as replacement raw material and its influence on the mortars durability

Journal of Material Cycles and Waste Management - Several types of industrial solid waste have been used as byproducts in the construction and materials industries. Some of the applications seem to...     

Effects of sewage sludge ash produced at different calcining temperatures on pore structure and durability of cement mortars

Journal of Material Cycles and Waste Management - The effects of calcining temperatures (ranging from 500 to 900 ℃) on the characterization of sewage sludge ash (SSA) and the pore...     

Improvement of Waste Recycling in PET Fiber Production

Production of polyethylene teraphtalate (PET) fiber in the world is increasing every year and reached to an amount of about 20 million tons a year in 2001. The wastes occur in the production of PET fiber in the amount of about 3–5% of total production. The PET does not degrade for a long time in nature. Since PET is a derivative of petroleum, the wastes of PET are valuable and must be recycled. One of the recycling method of PET wastes is re-melting. Thus, various properties of the PET wastes were improved using the re-melting method by employing an extruder manufactured for the work. Degradation during re-melting decreases the properties of the final product. The results indicate that the properties of recycled PET wastes can be monitored by designing the parameters of the extruder. Also, the further degradation of the material can be prevented and the recycling costs are minimized.