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Investigation of the effects of colemanite and colemanite concentrator wastes on the rheological and hardened properties of self-compacting concrete

Şeker Oğuz, Durgun Muhammed Yasin

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 1

art. no. e50, 2023

In this study, the use of colemanite (C) and colemanite concentrator wastes (CW) in self-compacting concrete (SCC) mixtures was investigated. It is known that additives containing boron minerals have a retarding effect on cement hydration. From this viewpoint, boron minerals containing various concentrations of C and CW were used and their effects on fresh concrete properties were investigated. In this context, single point tests and rheometer tests were applied. In addition, the setting times and unit weights of the samples were measured, and the compressive strengths at 7, 28 and 90 days were determined. The hydration developments of the samples were investigated by TGA and SEM investigations. The use of C and CW generally negatively affected the compressive strength, while the use of 1% C provided a slightly higher strength than the reference at the end of 90 days. The degree of hydration data obtained using TGA and the microstructural investigations via SEM supported these results. As a result of fresh state tests, it has been observed that the use of C improves and maintains the fresh properties and rheological parameters of self-compacting concrete, while the use of CW generally had the opposite effect. It is thought that this is due to the negative effect of the clay minerals in CW's composition and the fact that the B2O3amount in its content is less when compared to the C.

Curing Properties of Furotec 132 Resin- Bonded Foundry Sand

Mashingaidze M. M.

Archives of Foundry Engineering

2019

iss. 4

117--123

The study evaluated the curing properties of natural silica sand moulded with 1% by weight Furotec 132 resin binder catalysed by Furocure CH Fast acid and Furocure CH Slow acid. Physical properties of this sand included an AFS number of 47.35, 4.40 % clay, 0 % magnetic components, 0.13 % moisture, and 64.5 % of the size distribution spread over three consecutive sieves (150 – 600 μm). The sand was washed repeatedly to remove all the clay and oven dried. 2 kg washed sand samples were mulled with pre-determined weights of either catalyst to give 30 %, 50 % and 70 % by weight of 20 g Furotec 132 resin which was added last. Furotec 132 resin + Furocure CH Slow acid catalyst system gives longer bench lives and strip times but the maximum compressive strength in excess of 5000 N/cm2 is attained after more than 8.5 hours curing time irrespective of the weight % of catalyst added relative to the resin. On that basis, exceeding 30 weight % Furocure CH Slow acid catalyst when sand moulding with Furotec 132 resin has neither technical nor economic justification. In comparison, the Furotec 132 resin + Furocure CH Fast acid catalyst system was only capable of producing mould specimens with maximum compressive strength above 5000 N/cm2 at 30 weight % catalyst addition rate. At 50 and 70 weight % catalyst addition rates, the mulled sand rapidly turned dark green then bluish with a significant spike in temperature to about 40 oC, far exceeding the optimum curing temperature of Furotec 132. This high temperature accelerates the curing rate but with a very low degree of resin curing which explains the low compressive strength. In fact the sand grains fail to bond and have a dry, crumbly texture implying dehydration. Thus, not more than 30 weight % Furocure CH Fast acid catalyst should be used in sand moulding.