Upcycling of Waste Polyethylene and Cement Kiln Dust to Produce Polymeric Composite Sheets Using Gamma Irradiation

Cement kiln dust (CKD) is a residue produced during the manufacture of cement that contains hazardous solid waste of high toxicity that affects the environment and public health. In this study, the possibility of using cement waste as a filler in the plastic and rubber industry was studied. Different concentrations of (CKD) and gamma irradiation on the mechanical, thermal stability of the prepared composites sheets were investigated. Different concentrations of (CKD) 10, 15, 20, 30, 35, and 40 wt % were prepared with double screw extrusion by mixing waste polyethylene (WPE), de-vulcanized rubber (DWR), and EPDM rubber. These prepared composites were irradiated with doses 25, 50, 75, 100, and 150 kGy to study the effect of radiation on the physical, mechanical properties, and thermal stability of the prepared composite sheets. The prepared composite sheets were characterized and verified by FTIR and soluble fractions. The morphology of the composite sheets was investigated by SEM. Mechanical and thermal properties were investigated to evaluate the possibility of its application in the plastic and rubber industry.

Evaluation of Different Binder Combinations of Cement, Slag and CKD for S/S Treatment of TBT Contaminated Sediments

The seabed in the ports needs to be regularly cleaned from the marine sediments for safe navigation. Sediments contaminated by tributyltin (TBT) are environmentally harmful and require treatment before recycling. Treatment methods include leaching, stabilisation and solidification to remove toxic chemicals from the sediments and improve their strength for reuse in the construction works. This study evaluated the effects of adding three different binder components (cement, cement kiln dust (CKD) and slag) to treat sediment samples collected in the port of Gothenburg. The goal of this study is to assess the leaching of TBT from the dredged marine sediments contaminated by TBT. The various methods employed for the treatment of sediments include the application of varied ratios of binders. The project has been performed by the Swedish Geotechnical Institute (SGI) on behalf of the Cementa (HeidelbergCement Group) and Cowi Consulting Group, within the framework of the Arendal project. An experiment has been designed to evaluate the effects of adding CKD while reducing cement and slag for sediment treatment. Methods that have been adopted include laboratory processing of samples for leaching using different binder combinations, followed by statistical data processing and graphical plotting. The results of the experiment on leaching of TBT for all samples are tested with a varied ratio of cement, slag, CKD and water. Specimens with added binders ‘cement/CKD’ have demonstrated higher leaching compared to the ratio ‘cement/slag/CKD’ and ‘cement/slag’. The ‘CKD/slag’ ratio has presented the best results followed by the ‘cement/slag/CKD’, and can be used as an effective method of s/s treatment of the sediments. The results have shown that the replacement of cement and slag by CKD is effective at TBT leaching for the treatment of toxic marine sediments contaminated by TBT.

Evaluating the Durability of Green Cement Mortar Using Ultrasonic Pulse Velocity

Various experimental studies have highlighted the negative consequences of Portland cement on health and the environment, such as toxic emissions and alkaline sewage. The development of environmentally acceptable substitutes for cement is thus one of the objectives of current investigations. The proposed environmental alternatives to cement, nevertheless, might have detrimental impacts on the concrete’s characteristics. This investigation intends to study the suitability as alternatives to cement in cement mortar, using industrial wastes like silica fume and cement kiln dust. As a replacement for cement, the cement mortars developed in this research continue from 0% to 60% silica fume and cement kiln dust. Ultrasonic pulse velocity tests at 1 to 4 weeks of age were conducted on hardened specimens. The findings showed that a low reduction in the pulse velocity resulted from high proportions of silica fume and cement kiln dust replacements, whereas an improvement in the characteristics of the mortars with low replacement ratios. Using low kiln dust and silica fume of 20 to 40%, the durability of mortars may increase.

Use of Cement Kiln Dust and Silica Fume as partial replacement for cement in concrete

Cement is amongst the most polluting materials utilized in the building sector, contributing to a variety of hazardous pollutants, including greenhouse gas emissions. This raises health impacts related to the manufacture of cement. As a result, a substitute substance for conventional cement with low environmental effects and better building characteristics is required. The purpose of the study would be to look at the consequences of using supplementary cementitious materials (SCMS) to substitute cement in a concrete mix partially. This study employed silica fume (SF) and cement kiln dust (CKD) as supplementary cementitious materials. Several concrete mixtures were created by substituting cement by a combination of SF and CKD in three proportions which that 25%, 35%, and 45% within curing periods of (one week and four weeks); the concrete mixtures were tested. The ultrasonic pulse velocity (UPV) test has been used to investigate the concrete mixture’s strength in this study. The findings show that the optimal proportion of SF replacement cement and CKD involvement ranged from 25% to 35%. The pulse velocity of specimens improves when the proportion of CKD and SF increases to the optimal percentage, while the larger amounts of these by-products begin to lower the pulse velocity of specimens.

Microstructure of CEM II/B-S Pastes Modified with Set Accelerating Admixtures

The presented paper aims to describe the influence of accelerating admixtures on the properties and microstructure of cement pastes and mortars. Blended slag cement CEM II/B-S containing two different clinkers (differing amounts of siliceous and aluminous phases) and four types of accelerators (calcium nitrate, sodium hydroxide, cement kiln dust, and crystal seeds) were used in research. Compressive strength tests (after 12, 24, 48 h of curing), Scanning Electron Microscope (SEM) observations together with an Energy Dispersive Spectroscopy (EDS) analysis, Mercury Intrusion Porosimetry (MIP) tests, and X-ray diffraction (XRD) analysis were conducted. Results have shown that SEM and EDS examination of the microstructure of cement pastes modified with accelerating admixtures at the observed points did not reveal differences that would be sufficient to explain the changes in compressive strength. Still, the increase in amorphous phase content indicates a faster hydration reaction rate for all pastes modified with accelerating admixture. It is backed up also by lower non-hydrated compounds content. All admixtures accelerate the hydration reaction of calcium silicate phases of cement, but only NaOH and cement kiln dust (CKD) influence the aluminate phase reaction rate. The pore volume is independent of the clinker type, while the pore size distribution is not.