Modelling and Optimization of the Compressive Strength of High Volume Fly Ash ECC with Low Modulus PVA Fiber Using Response Surface Methodology (RSM)

Engineered cementitious composite (ECC) also known as bendable concrete is popular for its high ductility behavior under tensile load. However, to achieve this amazing characteristic, the compressive strength is usually compromised due to the high volume fly ash (HVFA) effect of reducing the composite’s toughness. This research is aimed at developing a response surface model and optimization of the two major ingredients (fly ash and PVA fiber) with the view to developing a composite with the desirable compressive strength for structural application. Results indicated that although the FA affects the compressive strength development negatively, the presence of PVA fiber especially at 1 to 1.5% volume fraction enhances the compressive strength. A quadratic response surface model was developed and was analyzed using analysis of variance (ANOVA) and found to have a R2 value of 96.82%. The model validation showed a very good agreement between the predicted and the experimental results with less tha 5% error margin

MAT-736: DEVELOPMENT OF HIGH STRENGTH NANO-SILICA MODIFIED RUBBERCRETE

Several research works have been carried out to study properties of concrete containing crumb rubber (rubbercrete) as a partial replacement to fine aggregate. Rubbercrete exhibits numerous benefits compared to conventional concrete such as lower in density, increased ductility, enhanced plastic capacity, higher toughness, higher impact resistance, better chloride penetration, lower thermal conductivity, higher noise reduction factor and better electrical resistivity. It has also been known to have better energy dissipation, durability and damping ratio. However, the main drawbacks of rubbercrete are decreasing in strengths and Young\u27s modulus. Therefore, to improve strengths of the rubbercrete, the crumb rubber has been pre-coated with nano-silica. Results have revealed that nano-silica modified rubbercrete can be produced with high strengths due to the densification of the interfacial transition zone (ITZ) and refining pore system of the rubbercrete

Effect of GGBS Slag on Setting Time and Compressive Strength of One-Part Geopolymer Binders

This paper investigated the influence of ground granulated blast furnace slag (GGBS) on the setting time and compressive strength of one-part geopolymer binders (OPGB). Powdered sodium metasilicate activator was utilized in the range of 8 – 16% by weight of the total binder. Central composite design method was used in designing the mixtures. Experimental investigation revealed that both the initial and final setting time of the OPGB decreased drastically with the increase in the GGBS and the activator content. The inclusion of GGBS in the binder influences the setting time of the binders thereby resulting in quick setting time. The variance analysis of the established models demonstrated that the setting and compressive strength models could be predicted using quadratic models with high R2 coefficient. Optimizations results revealed that the optimum mixture can be obtained by substituting 95.8 % fly ash with GGBS and 13.4 % solid activator

Methods of curing geopolymer concrete: a review

Geopolymer concrete is a new approach of concrete production by exclusion of ordinary Portland cement entirely with pozzolanic material. Beside water, concrete is the largest consumed substances, which demand huge portion of Portland cement. During Portland cement manufacturing process, high emission of carbon dioxide (CO2) is produced which results in polluting the surrounding environment. Moreover, a lot of energy is expended during cement production. Based on manufacturing situations, geopolymer concrete displays different behaviors and attributes. This paper succinctly discusses the different methods of curing of geopolymer concrete and figures out the best method of curing. Experimental findings revealed that condition of curing has a good influence on the mechanical properties of geopolymer concrete. Conventionally, ambience temperature curing of geopolymer concrete result in low strength development at an early age, while higher temperature curing results in significant strength improvement. Similarly, extended curing time enhanced the geopolymerisation mechanism and achieved greater strength. However, longer duration of curing at an elevated temperature result in failure of the sample

Tropical sapric peat–rubber agglomerates as adsorbent for wastewater treatment

Tropical sapric peat soil with severe leaching problems and poor hydraulic conductivities was converted into a functional filter media via heat treatment at 500 °C for 3 hours and agglomerated with natural rubber latex. The optimum weight ratio of peat material to rubber latex was 10:1. The peat-rubber agglomerates (PRA) had improved hydraulic conductivities, neutral pH and low organic leaching. PRA was found to be effective in the removal of chemical oxygen demand (COD) from molasses wastes and domestic wastewater. Adsorption isotherms analysis showed that the uptake of COD by PRA followed both the Langmuir and Freundlich models. Both adsorption and biological processes occurred in the removal of COD. The presence of rubber had improved the rate of bacteria growth on PRA. Sustainable removal of about 80% COD from molasses solution was achieved upon its recycled applications. This self-regenerating characteristics was proven to be due to the growth of bacteria on the surface of the adsorbent

Heavy metal content determination in locally available traditional medicines using Atomic Absorption Spectroscopy (AAS)

Traditional medicine (TM) is a system of health care that has ancient roots. It has been defined as practices designed to promote mental, physical and spiritual well-being of mankind. Usually (TM) are made from various types of medicinal plants. Sometimes they contain other ingredients such as animal parts and minerals however, the primary source of remedies is botanical. The use of traditional medicine has started beyond recorded history, but has increased tremendously in recent years. It is considered as alternative treatments which are widely used in developing countries. Recently became more popular in most developed countries as well. According to the world health Organization (WHO) reports that more than 70% of the population all over the world relies on non-conventional medicine. This high percentage indicates the positive attitudes towards herbal medicine in various places in the world, probably due to the people’s believe that such products are more likely to be safe ‘natural’ rather than ‘synthetic’ origin. In Malaysia, folk medicines are widely used .The huge demand of TM has been driven the total Malaysian market for TM to US $ 1.29 billion in 2005. The global popularity of(TM) has created great concern about the safety and efficacy of traditional medicines. Although WHO has developed guidelines for the quality control of herbal drugs, there is still a gap between available knowledge and implementation. Processors of herbal drugs are still not much aware of WHO’s guidelines yet they continue their work without proper quality control which results in products with lots of contaminants such as heavy metals, pesticides residues and microbes, therefore inappropriate consumption of herbal preparation can cause serious health complication even toxicity.. In our study we are focusing on identifying the presence of toxic heavy metals in locally available traditional medicines in the east coast region of Malaysia. Traditional medicine samples were collected from different sources such as shops, open market, night market and weekend market. Most of them are not registered with the Malaysian drug authority. All samples were digested using freshly prepared aqua regia (mixture of concentrated nitric acid and hydrochloric acid 1:3 ratio). 0.5 g of each sample was weighed and placed in 100 ml PTFE beaker, after which 9 ml of freshly prepared aqua regia was added. The mixture was then heated over water bath for 4-5 hours or until the sample had completely dissolved. The mixture was then allowed to cool and filtered; the residue was then washed with deionised water, and the extract was then made up to 50 ml with deionised water. The samples were then analysed by using atomic absorption spectroscopy (AAS). Out of twenty over traditional medicine samples most of them has shown the presence of lead (Pb), chromium (Cr), ferrum (Fe) and zinc (Zn). The results for nickel (Ni) and cadmium (Cd) were found below the detection limit using flame ionization technique and expected to be detected using graphite furnace AAS (GFAAS) method which will be the second part of this study. From the results we conclude that the traditional medicines available in local markets contain heavy metals which are considered toxic for human if consumed more than the permissible amount. Key word: Traditional medicine, heavy metal, Toxicity, Aqua regia, AAS

Structural Behavior of Reinforced Self-Compacted Engineered Cementitious Composite Beams

Eight large-scale reinforced self-compacted engineered cementitious composite (R-SC-ECC) beams with different steel reinforcement ratios have been designed, prepared, cast, cured, and tested to failure at the age of 28 days. The experimental results have been compared with theoretical values predicted using EC2, RILEM, and VecTor2 models. Results show that failure modes in flexure and shear of R-SC-ECC beams are comparable to that of normal reinforced concrete beam. Nevertheless, contrary to VecTor2, models of EC2 and RILEM are not suitable for predicting reasonable ultimate moments for the beams, while results using VecTor2 model have successfully predicted the failure modes and load-deflection curves for all R-SC-ECC beams. It has been concluded that R-SC-ECC fall in the category of ductility class medium to high which gives advantages of using R-SC-ECC beams in regions susceptible to seismic activities

EdTech in humanitarian contexts: whose evidence base?

This study reports on the design and development of a methodological toolbox prototype for evaluating EdTech deployed in the contexts of fragility and crisis. The project adopted a bottom-up approach: training EdTech users in participatory action research approaches was followed by a comprehensive mapping of problems in the Azraq refugee camp that might be addressed through the chosen EdTech installed in a local Makerspace. Students as researchers used a developmental evaluation approach to deepen their understanding of evaluation as a concept and as a process and proceeded to match the results of their Azraq camp problem-tree analysis with evaluation questions related to the EdTech tools available in the Makerspace. The study concludes with a proposed methodological toolbox prototype, a set of approaches and processes that include research capacity building in fragile contexts, and user-led evaluation that emphasizes the notion of evaluation as a learning process driven by those designed to benefit from EdTech in fragile contexts