Materials Science Forum Vol. 1161

Abstract: The feasibility of molten polyethylene terephthalate (PET) and laterite as composite for the production of masonry units was investigated. This aligns with the United Nations sustainable development goals of a cleaner environment, sustainable and affordable mass housing through innovative materials with low CO₂ emissions. Using standard testing procedures, cubes of molten PET and laterite composite of 150 mm by 150 mm were used to assess the compressive strength of both the treatment and control groups. The treatment groups were formulated in mix ratios of 1:1, 1:1.5 and 1:2 of PET to laterite while the control group was made of 100% PET. The results recorded were 1.53N/mm² for the control group, 4.7 N/mm², 9.9 N/mm² and 9.17 N/mm² in ratios 1:1, 1:1.5 and 1:2. Furthermore, there was an upward trend in the density of the test cubes recorded as 15.30kg/m³, 16.6 kg/m³ and 17.4 kg/m³ for ratios 1:1, 1:1.5 and 1:2 respectively. However, despite the increase in density in ratio 1:2, there was a reduction in strength. This could be due to a trade-off in the bonding quality between PET and laterite at that ratio. Nevertheless, given the values of compressive strength recorded and the remarkable difference between the control group and the treatment group, there is are prospects of the suitability of the composite for sustainable building construction.

Abstract: This study relates to the development of geopolymer concrete (GPC) and empirical models which can be used to predict strength and durability under different curing temperatures. The binders and alkaline activators used for the GPC production were characterized to determine their physical and chemical properties. The partial and pure geopolymer concrete samples were produced. The partial replacement of Geopolymer concrete (GPC) samples was done with cement at varying percentages of 0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20% to determine the optimum cement stabilization. Fourier transform infrared spectroscopy (FTIR) results show key absorbance level at the zone between 950.1 and 3250.12 cm⁻¹. It means that enhancement of the laboratory-produced (bespoke) superplasticizer enhanced the performance of GPC by reducing the viscosity and enriching the flow behaviour of the concrete. The optimal geopolymer product showed substantial strength and durability enhancements at 70°C followed by declining values at temperatures above 70°C, indicating material deterioration. A positive correlation between hot-state temperature, strength and durability properties was also established. Furthermore, scrutiny of the model shows that overall dataset points for training and test sets are clustered close to the diagonal line, signifying that the model provides precise estimation of the strength and durability features. .

Abstract: This paper investigates the influence of two proprietary redispersible polymers, i.e. Ethylene Vinyl Acetate (EVA) and Styrene Acrylate (SA) - at varying contents of 10%, 15% and 20% by mass of cement - on cracking and crack-determining material properties in non-structural concrete patch repair mortars. Five mortar mixes, one control mix and four polymer-modified mixes, were designed, developed and tested under a controlled laboratory environment. The effects of polymer type and content on macroporosity, the age at cracking and crack widths in restrained shrinkage specimens, compressive strength, direct tensile strength, elastic modulus, drying shrinkage and tensile relaxation were investigated. From the test results, it was observed that polymer type and content influence cracking and crack-determining material properties significantly. An increase in polymer content resulted in a significant reduction in elastic modulus, crack widths, compressive and direct tensile strength. An increase in polymer content also resulted in a significant increase in drying shrinkage, tensile relaxation and the age at cracking. The performance of EVA polymers, with respect to the susceptibility to cracking, was better than that of SA polymers at constant polymer content. Overall, the addition of polymers improved the cracking performance of the non-structural concrete patch repair mortars under investigation significantly, highlighting their potential for use in practice to improve the durability of non-structural concrete patch repairs.

Abstract: This study looked into the economic production of self-compacting concrete (SCC) using affordable and locally available materials such as fly ash (FA), laterites (LA), and polyethylene terephthalate (PET) fibres. To achieve optimal properties of SCC, Response Surface Methodology (RSM) - Central Composite Design (CCD) was employed. Thus, twenty different SCC mixes were designed with varying input factor combinations (FA: 0–40%, LA: 0-50%, and PET fibre: 0–2%) and tested for six responses (rheological properties, namely slump flow, V-funnel time, and L-Box; and mechanical properties, namely compressive, split-tensile, and flexural strengths test). Mathematical models were created in response to the experimental results and assessed using analysis of variance (ANOVA) test. L-Box, V-funnel, and Slump flow test results showed that while fly ash may improve the flowability of SCC, inclusion of high volume of PET-fibres (above 1%) and laterite (above 25%), has high negative impact on SCC flowability. The results further revealed that inclusion of PET-fibres in SCC largely improves the flexural strength (FS) and split tensile strength (STS) by about 20%. However, high volume of laterite contributes negatively to the strength values. Although SCC’s compressive strength decreased with addition of each or a combination of the three different materials, a combination of 20% fly ash, 25% laterite and 1% PET-fibres can result in strength values that are comparative to that of the control mix. The RSM models developed showed relatively good predictive capabilities especially for the compressive strength, L-box and V-funnel models with adjusted R² values ranging between 0.8 – 0.9. Among all the combinations, it is recommended that 20% FA, 25% LA, and 1% PET fibres be adopted in production of sustainable and cost-effective self-compacting concrete, as it gave relatively stable characteristics compared to the control mix in terms of the strength and rheological properties.