Papers by Keyword: Strength

Abstract: Nowadays, there is a great demand for the accelerated hardening construction mixtures. That causes the necessity to the methods development for testing the effectiveness of accelerators, well as the analysis of kinetics of cement systems hydration in the early stages of hardening. This paper presents the results of an experimental research of interrelation between the growth kinetics of cement-based binder system strength and the heat release for pure cement hydration. How it was found, two compositions of construction mix, which are identical in mineral composition and differ in the presence of mono-functional accelerator, a comparison of strength growth dynamics can be carried out indirectly via the integral curve of heat release, obtained using the method of isothermal calorimetry.

Abstract: Chicken feather have many excellent properties, unfortunately, the dark color affects its wide applications. In this study, the three stage bleaching process was used to bleach the dark chicken feather. The effects of the key chemicals on bleaching properties were discussed, and the change of the fine hair whiteness and strength before and after bleaching were investigated. It provides a sound theoretical basis for people understanding and studying the bleaching properties of chicken feather.

Abstract: These are many factors that can influence the properties of alkali-activated slag cementitious material, such as the modulus and content of water glass, water-cement ratio, curing conditions, and so forth. The rules that how these factors affect setting time and strength of the material are systematically discussed in the paper. It is found that the setting time of the material depends on the concentration of alkaline ions in solution; The material will have the best strength when the modulus and content of water glass are 1.4 and 8%, respectively. The curing temperature increase will be helpful to compressive strength increase.

Abstract: This paper studies the influence on compressive strength, freezing resistance and microstructure of cement mortar with different content of mica in stone powder, in the tests, manufactured sand with high content of mica and natural river sand were mixed with different proportion, and the content of stone powder was the same in mixed sand. Experiment results indicate that, with the increasing of mica content in stone powder, 28d and 60d compressive strength of cement mortar decreases obvious, mass loss rate and strength loss rate with 50 freeze-thaw cycles increase a little. Microstructure of cement mortar with higher content of mica is not compactly by SEM, the internal defects of cement hardened pastes could be increased because of the flake mica which surface is smooth, and it will cause the spread of micro crack.

Abstract: This study deals mainly deals with the rheological and strength properties of self-compacting concrete (SCC) incorporating high volume replacements of slag. Plastic viscosity and yield stress were evaluated using ICAR rheometer. The effect of high range water reducing admixture (HRWR) dosage, the time to reach 500 mm diameter (T50), the final slump flow, V-funnel flow times and L-box blocking ratio were also investigated and studied in this research program. The results show that the plastic viscosity decreases with the increase of the percentage of slag and the yield stress was nearly zero for all the replacements studied. The compressive strengths determined for the SCCs demonstrate that high strength SCC of more than 100 MPa can be realized by using slag appropriately.

Abstract: Abstract: The same amount of mixture ratio of cement, replacing a part of fly ash with a certain amount of mud to research about the workability of fresh concrete and the effect of the mechanical and shrinkage properties of hardened concrete. Test's results show: The different kinds of mud lead that the fluidity of the fresh concrete and the strength of hardened concrete are different. The influence of sand mud is lighter than planting mud on the fluidity and strength of concrete. The compressive strength of concrete decreases and the early shrinkage increase with an increase of mud replaced the fly ash.

Abstract: This paper presents an original research on the influence of defects in recycled aggregate (RA) on mechanical properties of recycled aggregate concrete (RAC), including compressive strength, splitting tensile strength, fracture energy and elastic modulus. Six types of concretes, with the water to binder ratios (W/B) of 0.26 and 0.60, were prepared using nature aggregate (NA), RA and recycled aggregate treated by 3 mol/L (RA-H). Mechanical properties of RAC was inferior to that of NAC, and treated RA by sulfuric acid solution could improve the mechanical properties. Attached mortar in RA was the main factor resulting in the decrease of mechanical properties of RAC with 0.26 W/B, and for the RAC with 0.60 W/B, the effect of aggregate damage was more significant than that of attached mortar.

Abstract: Ultra-high performance concrete (UHPC) incorporating coarse aggregate was prepared with common raw materials. Fresh concrete had excellent good workability with slump of 265 mm and slump spread of 673 mm. Compressive strength of UHPC at 56 d reached 150 MPa. However, UHPC exhibited high brittleness in terms of spalling failure which occurred during compression loading.The ratio of splitting tensile strength to compressive strength of about 1/18 and the ratio of flexural strength to compressive strength of about 1/14 at 56 d were also associated with the brittleness of UHPC in this research. Mineral admixtures and fluidity of fresh concrete influenced compressive strength of UHPC significantly. Moreover, UHPC had excellent permeation-related durability but considerable shrinkage. Autogenous shrinkage of UHPC was less than half of free shrinkage, for which the reason is unknown and needs further research.

Abstract: The coarse aggregate volume fraction in conventional plastic concrete is controlled relatively low to ensure a required workability, but its low aggregate content play negative roll on the service properties of the concrete. In this paper, we revealed the mechanism of a coarse aggregate interlocking concrete prepared by Scattering-Filling Stone Concrete (SFSC), it can keep the fresh concrete its workability but increase its service performance by scattering coarse aggregate during the concrete casting, the experimental and engineering application of SFSC indicated that: the strength of concrete prepared with this method increases obviously whereas the shrinkage decreases significantly when 20% cement dosage is saved. The SFS process was utilized in a highway pavement, the core of the concrete is very dense and no obvious defect could be found when 8% pavement concrete was replaced by coarse aggregate. The SFSC is a type of low carbon concrete.

Abstract: With the increasing attention towards energy-efficient and zero emission buildings, improvement to concrete properties is becoming more and more significant in construction and building sectors. One such area is to enhance the thermal properties, while maintaining maximum strength of the material. Here, attempts were made to address this challenge by formulating mortar composites with low thermal conductivity while targeting a minimum compressive strength of 20 MPa at 28 days. For this purpose, aerogel was utilized in an ultrahigh performance concrete (UHPC) formulation to create new aerogel-incorporated mortar (AIM). It was found that AIMs possessing 50 vol% aerogel registered a compressive strength of 20 MPa, while displaying a thermal conductivity of ~ 0.55 W/(mK). By adding more aerogel to reach 70 vol%, while the thermal conductivity of the concrete decreased by ~ 20 %, a sharp decrease in strength to 5.8 MPa was observed. This represents only 1/30 of the original strength of the UHPC mortar. Further addition of aerogel till 80 vol% showed negligible compressive strength, attributing to the imbalance of the particle-matrix ratio in the mortar system, causing a decrease in adhesion of the binder-aggregates.