• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.117-126
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• 2001

In this research, evaluation of adhesion in tension property of SBR-modified concrete to ordinary portland cement concrete was conducted with uniaxial direct tensile bond test which was proposed by Kuhlmann. A test set-up was fabricated in order to minimize the eccentric force by introducing a joint which might fully rotate. The main experimental variables were cement-latex ratios, surface preparations and moisture levels. The results obtained were as follows: The LMC specimen at 15% latex-cement ratio increased the adhesion in tension by range of 37% compared to that of conventional cement concrete. This might be due to latex film formed between cement paste and aggregate. The effects of surface preparation on bond of latex modified concrete to conventional concrete were significant at the conditions by sand paper and wire brush. A better bond could be achieved by rough surface rather than smooth. The saturated and surface dry (SSD) condition were considered to be the most appropriate moisture level followed by wet, finally by dry. Thus, a proper surface preparation and moisture level are quite necessity in order to obtain better bonding at LMC overlay.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.99-104
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• 2009

For recycling of waste foundry sands, researchers recently try to recycle them rather than depend on reclamation, and are studying on how to combine waste foundry sands with cement and use them for various kinds of construction material as the effective recycling method of waste foundry sand. In this research, The ways to find the proper replacement rate of waste foundry sands and to make use of them were suggested through the experiments on the range to apply waste foundry sands with two levels of 1:3 mixture rate of W/C 43% and 50%. The research result showed that in terms of liquidity as the characteristic of unhardened mortar, as the replacement rate of waste foundry sands increased, its flow tended to decrease. The amount of air also displayed a similar tendency to that of liquidity in that the higher the replacement rate of waste foundry sands became, the lower it became. With regard to the solidity trait of hardened mortar, it increased when the waste foundry sands were replaced more, and the replacement of waste foundry sands caused increased initial solidity. As for the amount of water permeated and that of water absorbed as the water tight proofing properties, the amount of permeated water was proved to decrease because of the gap recharge effect by the fine powder of waste foundry sands, and the replacement of waste foundry sands in the structures requiring watertightness is concluded to be very effective.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.339-345
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• 2013

This study is to derive from the required performances and the optimum mix proportion of the roof concrete placed in the in-ground LNG storage tank with a capacity of 200000 $m^3$, and propose the actual data for site concrete work. The concrete placing work without sliding and segregation in the fresh concrete condition is very important because the slope of domed roof is varied in the large range by its curvature. Also the control of hydration heat and the strength development at test ages are classified with massive section about 1.4 m thick and considered to the pre-stressing work and removal of air support after concrete placing work. Considering above condition, slump range is selected $100{\pm}25$ mm under the slope $20^{\circ}$ and $150{\pm}25$ mm over the slope $20^{\circ}$ s until 60 minutes of elapsed time. Also, the roof concrete is satisfied with compressive strength range including design strength at 91 days (30 MPa), pre-stressing work at 7 days (10 MPa), air support removal work at 21 days (14 MPa). Replacement ratio of limestone powder is determined by confined water ratio test and main design factors include water-cement ratio (W/C), sand-aggregate ratio and dosage of admixture. As test results, the optimum mix proportion of the roof concrete used low heat cement is as followings. 1) Replacement ratio of limestone powder 25% by confined water ratio test 2) Water-cement ratio 57.8% 3) Sand-aggregate ratio 42.0%. Also, test results for the adiabatic temperature rising test is satisfied with its criteria and shown the lower value compared to preceding storage tank (TK-13, 14). These required performances and the optimum mix proportion is to apply the actual construction work.