Unconfined Mechanical Properties of Nanoclay Cement Compound Modified Calcareous Sand of the South China Sea

Calcareous sand is characterized by low strength, multiporosity, and high-pressure shrinkage. This often leads to poor engineering properties. Therefore, it is often necessary to reinforce the calcareous sand in order to meet the actual engineering demand for bearing capacity. To study the modification effect of calcareous sand of nanoclay by cement, mechanical tests and microscopic tests of the cement calcareous sand (CCS) modified by different nanoclay content and cement content were conducted. Through the unconfined compressive test, the mechanical properties of nanoclay and cement compound modified calcareous sand (NCCS) were studied. The micromechanism of nanoclay and cement composite modified calcareous sand was analyzed by SEM. Representative curves of data groups of stress and strain data were obtained by the fusion algorithm, which effectively circumvented the discrete distribution of determined data. Test results showed that the following: (1) The compressive property of CCS could be improved by the admixture of nanoclay, and the optimum admixture ratio was 8%. (2) The admixture of nanoclay could enhance the deformation modulus of CCS and improve the resistance of CCS against external load deformation capacity. (3) Nanoclay could increase the density of the internal structure of CCS and improve its mechanical properties.

Advanced Vitreous Wasteforms for Radioactive Salt Cake Waste Immobilisation

Salt cake radioactive waste is a remnant solid salt concentrate after deep evaporation of radioactive evaporator concentrate at WWER NPP’s. The traditional cementing of borate-containing liquid radioactive waste, to which the salt cake belongs, leads to a significant increase in the volume of the final product. This work describes borosilicate vitreous wasteforms developed to immobilize radioactive salt cake waste and comprises data on both glass synthesis and characterization. The composition of glass selected for the purpose of immobilisation of the salt cake radioactive waste allows to include up to 40 wt. % of the oxides contained in the salt cake and to reduce the volume of the final product by more than 2 times compared with the cement compound. The batches were melted in a cold crucible melter at 1200 °C. The normalized cesium leaching rate of the vitrified wasteform product was within range 3.0·10-5 – 3.7·10-6 g/(cm2·day).

Bond Behaviour of Steel and Concrete with Pull-Out Test

This experimental investigation presents the influence of rebar’s which has protecting coating, rested rebar and fresh rebar and there bond strength development between the steel and concrete. Pull-out experiment was conducted Universal Testing Machine (UTM) which has a capacity of 400 KN as per IS code procedure. The tested rebar includes rusty rebar, acid preserved rebar and cement chemical compound anticorrosive coated rebar. The Concrete mix design for M25 grade of concrete were used and therefore 18 concrete cube specimens with external projection of steel rod were tested. The various load slip behaviour was studied at the free end finish and loaded end victimization dial gauges. The last word bond stress just like the lowest load worth of 0.025 mm metal slip and 0.25 mm slip was thought of as a result of the usable bond strength of steel rebar’s and concrete. The check results blatant correlation exists between Load at 0.025 mm free finish slip and 0.25 mm loaded finish slip. It had been found that presence of rust and cement compound anticorrosive coating among the steel concrete interface appreciably can increase the bond strength of the order of 20 % and 27 % severally for 16mm diameter bars as compared to rust free rebar. For 20mm dia. Bars has totally different bond strength for rusty rebar’s and therefore the increase in bond strength for coated bars are compared with 2 differing kinds of uncoated bars and rusted rebar’s were determined. It’s over that presence of rust influences in reduction / increase in bond strength hoping on the character of rust at the interface among the initial ages. Application of cement compound coating has been improves the bond strength of the order of 31% – 37 % to satisfies the necessities of Burse Indian Standards code (IS)

Study Pembuatan Durable Cement dengan Penambahan Pozzolan Silica Fume

Selama ini silica fume dikenal sebagai bahan campuran pembuatan beton karena dapat meningkatkan kuat tekan beton, menurunkan permeabilitas beton dan memiliki ketahanan sulfat yang tinggi. Dalam penelitian ini mencoba mengaplikasikan silica fume pada pembuatan durable cement. Silica fume dijadikan sebagai bahan pozzolan karena didalamnya mengandung silica tinggi yang bersifat reaktif agar dapat meningkatkan ketahanan terhadap sulfat. Bahan pozzolan ini dapat bereaksi dengan Ca(OH)2 pada suhu biasa untuk membentuk senyawa bersifat semen. Pada penelitian ini silica fume divariasikan mulai dari 0; 7,5; 15; 22,5; 30; 37,5%. Durable cement ini akan diuji ketahanan sulfatnya dengan menggunakan metode pengujian kuat tekan. Hasil percobaan menunjukkan terjadinya penururan nilai kuat tekan sampel pada umur 7 dan 28 hari jika dibandingkan dengan blanko. Hal ini disebabkan lambatnya reaksi pozzolan (silica fume). Namun proses peningkatan kuat tekannya akan terus berlanjut hingga setelah umur 360 hari. Jika dibandingkan dengan Standar Nasional Indonesia (15-0302-2004) semen PPC tipe IP-K, hasil sampel durable cement masih memenuhi standar untuk variabel dengan penambahan silica fume antara 7,5% sampai 22,5%. Silica fume is known as a mixture of concrete manufacturing since it can increase the compressive strength of concrete, decrease the permeability of concrete and have a high resistance to sulfates. In this research, try applying silica fume to make durable cement. Silica fume is converted to pozzolan because it contains highly reactive silica to increase sulfate resistance. This pozzolan material can react with Ca (OH)2 at a room temperature to form a cement compound. In this study, silica fume was varied from 0; 7.5; 15; 22.5; 30; 37.5%. The durable cement will be tested for its resistance to sulfates by using a compression resistance test method. The results showed that the compressive strength of the sample was decreased at 7 and 28 days compared to the blanks. This is due to the slow reaction of pozzolan (silica fume). But the process of increasing the resistance to compression will continue until after 360 days. Compared with Indonesia cement national standard (15-0302-2004) of PPC type IP-K, the durable cement sample still meets the standard for variables with the addition of silica fume between 7.5% and 22.5%.