Properties of cement mortar incorporated high volume fraction of GGBFS and CKD from 1 day to 550 days

This study aims to investigate the effect of cement replacement with high volume fraction of ground granulated blast furnace slag (GGBFS) and cement kiln dust (CKD) on mechanical, durability and microstructural properties of cement mortar from 1day to 550 days. Compressive strength and ultrasonic pulse velocity (UPV) were used to evaluate the mortars' performance. Besides, statistical analyses were conducted to predict mortars' mechanical and durability performance as well as investigate the influence of mortars’ properties (mixture and curing time) on their performance. The results indicated that replacing the cement with up to 60% GGBFS and CKD showed a comparable behavior to the cement after 28 days of curing onward. The statistical analysis revealed that the developed models achieved high level of agreement between the predicted and observed results with a coefficient of determination (R2) of more than 0.97. The findings in this study announced on the development of promising binder that can be used in different construction sectors with the benefits of reducing the CO2 emissions

A novel industrial technique for recycling ethylene-propylene-diene waste rubber

This paper was accepted for publication in the journal Polymer Degradation and Stability and the definitive published version is available at http://dx.doi.org/10.1016/j.polymdegradstab.2014.11.003© 2014 Elsevier Ltd. All rights reserved.Recycling waste rubber has gained importance in recent years. Ethylene-propylene-diene rubber (EPDM) is used to manufacture various automotive parts. Reclaiming EPDM rubber waste is a major problem. Waste powder from discarded EPDM automotive parts was devulcanized using an industrial autoclave which provided both heating and high pressure steam. To aid the devulcanization process, 2-mercaptobenzothiazoledisulfide (MBTS) and tetramethylthiuram disulfide (TMTD) devulcanizing agents, and aromatic and aliphatic oils were also used. A portion of the virgin EPDM rubber in a common formulation for the automotive rubber strips was replaced with the devulcanized product to produce blends, which were revulcanized using a semi-efficient (SEV) vulcanization system. The viscosity, cure and mechanical properties of the blends were subsequently determined. This study showed that the oils had different effects on the devulcanization of the waste powder and MBTS was more efficient than TMTD. Replacing 60 wt% of the virgin rubber in the automotive rubber strips with the devulcanized powder had no adverse effect on the scorch and optimum cure times, crosslink density, rate of cure, and viscosity. Also, when 20 wt% of the virgin rubber was replaced, the hardness, compression set, and modulus at 20% elongation were unaffected. It was concluded that the reclaimed rubber could be used in low percentage in order not to extremely deteriorate the mechanical properties of the virgin rubber. This provided a new effective recycling route for the waste EPDM powder in the automotive rubber strips

Durability performance of concrete containing laterite aggregates

© 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. In Malaysia, concerns about the depletion of granite aggregates in the future and the availability of laterite aggregates locally have incentivized researchers to integrate laterite aggregate into the production of concrete. Studies found that the use of 20 to 30% of laterite aggregates, as partial replacement for coarse aggregates, results in concrete with the targeted strength. However, the effect of laterite aggregate content on the durability performance of this concrete is unknown. As such, the acid resistance and water absorption of concrete consisting of various percentages of laterite aggregates, integrated as partial replacement of coarse aggregates, are presented and discussed. Mixes consisting of varying amounts (0–50%) of laterite aggregates were prepared in the form of cubes (150 × 150 × 150 mm). After water curing for 28 days, the specimens were tested for the determination of compressive strength and durability against acid attack and water absorption. It was found that concrete with low water absorption can be produced through the integration of 50% of laterite aggregates. Similarly, the integration of laterite aggregates of up to 20% produces concrete that exhibits good durability against acid attack, chloride ion penetration, and water absorption