Effect of nano-silica slurry on engineering, X-ray, and γ-ray attenuation characteristics of steel slag high-strength heavyweight concrete

High molar mass materials (nano-silica slurry [NSS] and aggregate of steel furnace slag [ASFS]) can improve concrete shielding properties. However, only a few studies have been reported in this regard. Hence, this paper aims to determine the effect of NSS and ASFS on the properties of the resulting steel slag heavyweight concrete (SSHWC). The use of NSS in this study is a novel contribution. Furthermore, the maximum percentage of NSS to be introduced into the concrete for maximum effect was also optimized. This study also implemented an investigation program with six concrete mixtures prepared using ASFS as the primary by-product aggregate. The engineering, X-ray, and γ-ray attenuation characteristics of the SSHWC were evaluated. The results showed that the addition of NSS in SSHWC at the optimal content of 3% by weight of cement improved the X-ray shielding by 6.4%. Besides, all the concrete’s engineering and γ-rays’ properties were enhanced correspondingly.

Influence of Parent Concrete Properties on Compressive Strength and Chloride Diffusion Coefficient of Concrete with Strengthened Recycled Aggregates

Parent concrete coming from a wide range of sources can result in considerable differences in the properties of recycled coarse aggregate (RCA). In this study, the RCAs were obtained by crushing the parent concrete with water-to-cement ratios (W/Cparent) of 0.4, 0.5 and 0.6, respectively, and were strengthened by carbonation and nano-silica slurry wrapping methods. It was found that when W/Cparen was 0.3, 0.4 and 0.5, respectively, compared with the mortar in the untreated RCA, the capillary porosity of the mortar in the carbonated RCA decreased by 19%, 16% and 30%, respectively; the compressive strength of concrete containing the carbonated RCA increased by 13%, 11% and 13%, respectively; the chloride diffusion coefficient of RAC (DRAC) containing the nano-SiO2 slurry-treated RCA decreased by 17%, 16% and 11%; and that of RAC containing the carbonated RCA decreased by 21%, 25% and 26%, respectively. Regardless of being strengthened or not, both DRAC and porosity of old mortar in RCAs increased with increasing W/Cparent. For different types of RCAs, DRAC increased obviously with increasing water absorption of RCA. Finally, a theoretical model of DRAC considering the water absorption of RCA was established and verified by experiments, which can be used to predict the DRAC under the influence of different factors, especially the water absorption of RCA.

Preparation and Performance of a Waterborne UV/Al Low Infrared Emissivity Coating

An Al powder filler, nano silica slurry and KH560 were mixed with a prepared waterborne UV-curable coating, and the coating was optimized by an orthogonal experiment. Influences of the Al powder concentration on the gloss, infrared emissivity, brightness, mechanical properties, corrosion resistance and other related properties of the coating were further discussed. The results show that the influence of the Al powder concentration on the gloss was more significant, followed by the UV curing time and nano silica slurry concentration. After studying the key role of the concentration of the Al powder, we found that as the concentration of the Al powder is augmented from 10.0% to 25.0%, the gloss lessened from 19.1% to 8.5%. As the concentration of the Al powder was augmented from 10.0% to 40.0%, the infrared emissivity lessened from 0.649 to 0.083 and the brightness L’ value of the coating was step-by-step augmented and inclined to be stable; in addition, the coating’s mechanical properties reached an excellent level. The coating containing 25.0% Al powder had the best corrosion resistance, surface morphology and comprehensive properties, which can potentially be used for infrared stealth technology.

The Properties of an Aluminum/UV-Curable, Infrared, Low-Emissivity Coating Modified by Nano-Silica Slurry

To improve the performances of UV-curable coatings, the effects of nano-silica slurry, aluminum and UV-curing time on the glossiness and infrared emissivity of UV-curable coatings were investigated by orthogonal experiments. The results showed that UV-curing time is a key factor affecting the performance of the coating. When the UV-curing time was increased from 30 to 360 s, the glossiness of the UV-curable coating slowly decreased from 11.1% to 9.0%. The L’ value decreased from 78.6 to 75.0. The infrared emissivity of the coating with UV-curing time of 180 s was 0.106, which was the lowest. The coating hardness with different curing time was 6H. The coating roughness was high when the UV-curing time was 30–120 s. When the UV-curing time was greater than 300 s, the coating adhesion was 0 and the coating had the best impact resistance of 500 N/cm. The overall performance of the aluminum/UV-curable coating was optimal when the UV-curing time was 180 s. This research is able to promote the industrial development of UV-curable, infrared, low-emissivity coatings.

Preparation and Characterization of Low Infrared Emissive Aluminum/Waterborne Acrylic Coatings

An aluminum/waterborne acrylic coating was developed by orthogonal experiments, and the gloss, emissivity, chromatic distortion, hardness, adhesion, impact resistance, and corrosion resistance of the coatings were examined. The results showed that the effect of drying time on the infrared emissivity of coatings was more significant than that of the Al powder concentration and nano-silica slurry. When the drying time was prolonged from 0.5 to 6.0 min, the gloss of the coating decreased slowly and the gloss remained low. The infrared emissivity first decreased and then increased. The infrared emissivity of coatings dried for 2.0 min was better. The L’ value gradually decreased and showed a small change of range. With the increasing of the drying time, the hardness of the coating gradually decreased and was the highest at 0.5–2.0 min. The drying time had no effect on the adhesion level. The impact resistance of the coating was better during the drying period of 1.0–3.0 min. The corrosion resistance of the coating was better at 2.0 min. When the drying time was 2.0 min, the waterborne coating showed the better comprehensive performance. This study provides new prospects in using low infrared emissive coatings for infrared stealth and compatibility with visible light.