Advanced Materials Research Vols. 168-170

Abstract: Hwangtoh (loess) has pozzolanic properties that mean it can be used as a cement admixture when activated at high temperatures, and that it can be used in combination with building materials such as fly ash or blast furnace slag. This study aimed to analyze the relationship between the compressive strength and the brick bond strength of various mortars containing hwangtoh, and also to find the optimum mixing conditions for the use of hwangtoh. It was found that the mortars’ strength properties are significantly influenced by the water/cement ratio W/C and the activated hwangtoh substitution ratio. We recommend the following materials and mixing conditions: W/C 60%, a cement substitution ratio of activated hwangtoh of 20 ~ 25%, and the addition of 10% blast furnace slag to improve the compressive strength of such mortars.

Abstract: In order to evaluate the crack resistance of high strength fly ash concrete, concretes with different contents of silica fume and fly ash were compared with same strength grade by adjusting water to binder ratio. Compared with the concrete with 5% silica fume plus 35% fly ash，concrete with 40% fly ash has same mechanical properties and tensile strain as well as lower drying shrinkage. Complex crack resistance of high strength fly ash concretes were evaluated by Temperature Stress Testing Machine (TSTM). The results show that fly ash concretes have outstanding crack resistance because of higher allowable temperature differential and lower cracking temperature.

Abstract: Lateral buckling and local buckling are two important influential factors for bearing capacity of a steel-concrete composite beam. The existing codes of a steel-concrete composite beam generally use steel structure design methods to calculate stability of a composite beam, and the results do not agree with the fact. This paper analyses global lateral buckling forms of I shape steel concrete composite beam and a calculation model of I shape composite beam stability analysis is presented. The critical moment of lateral buckling of the composite beam compressive bottom flange in the hogging bending moment region is derived in accordance with computation module. The author also studies the mechanical property of the steel web under combined action of bending stress, axial compressive stress and shear stress in the hogging bending moment region. In the light of correlation equation under combined eccentric compression and shear force, an elastic buckling factor of the steel web in complicated stress state is obtained. Based on buckling analysis results, a height to thickness ratio of steel beam in the elastic strained stage without transverse stiffening rib is proposed. Compared with existing stability theory and calculation method of I shape composite beam, correction methods and advices of stability design for I shape composite beam in the hogging bending moment region are presented.

Abstract: Iron tailing is a kind of waste after extracting iron element. It caused a series of environmental problems. In this paper, it was used to make mineral polymer. After activation of it, the product compressive strength reached 70.46MPa when the dosage of iron tailing was 70%, sodium hydroxide 50% and the solid-liquid ratio was 0.4. This experimental study provides a good basis for the utilization of iron tailing.

Abstract: Metallurgical industry factory building is usually high. Under the action of wind load and horizontal crane force, large moment will be induced at the column base. That is to say, the moment acting on the foundation is large. The embedded depth is relatively deep and the size of factory building foundation is relatively big. In the case of foundations based on the natural rock, if the routine design code adopted, the high capacity of the rock can not be fully utilized. The use of bolt at the bottom surface of the foundation integrates the foundation and the natural rock, hence reduces the foundation size and embedded depth to save the investment.

Abstract: Recently, the cracks of concrete by drying shrinkage become one of the problems in the construction industry in Japan. The drying shrinkage decreases when the concrete is produced with limestone aggregate. However, it is not clear why the drying shrinkage is decreased. The purpose of this study is to clarify the relation between the drying shrinkage of concrete and the limestone aggregate. In this study, the experiments about the strength, elasticity and drying shrinkage of concrete and the physical properties and shrinkage of coarse aggregates were conducted. It is thought that the volume change of aggregates affects directly the drying shrinkage in concrete.

Abstract: It’s necessary to establish criterion of recycled fine aggregate for the application of recycled concrete and recycled mortar. Strength ratio and water demand ratio are important technical indexes of recycled aggregate. In this paper, a series experiments are hereby performed to determine testing and classification method for recycled fine aggregate. The experimental results indicate that fineness modulus of recycled sand influences inversely the strength ratio and water demand ratio. Furthermore strength ratio of various aggregates decreases with the increasing of water demand ratio in using identical cement type. The present paper also provides definition and testing method of water demand ratio and strength ratio. Consequently the quality classification criterion for recycled aggregate is proposed based on the double-control concept of water demand ratio and strength ratio and has been adopted by national code “Recycled fine aggregate for concrete and mortar”(Revision for Approval).

Abstract: The Discrete Element Method(DEM) has become a powerful numerical method for analysing discontinuous media. This paper provides a new ellipse particle modeling of fresh concrete by DEM. So far, research has been limited to experimental research and qualitative simulation. In this research, the parameters are defined from rheology. Then, a quantitative simulation is proposed. Slumping behaviors of fresh concrete are simulated.

Abstract: Aerated concrete is kind of normal silicate products, which is made by hydration of lime, cement, gypsum fly ash/sand, forming agent. And it has become the major wall material of frame structure caused by its characteristics of light weigh, high strength, and heat insulation. Petroleum coke is the by-product of delayed coking system in oil refinery. Oil refinery in coast area of east China mainly exploits high-sulfur crude oil from Middle East. The petroleum coke contains even 5-8% sulphur, and calcium injection desulphurization is usually employed to reduce the SO2 emission, and leads to that Ca/S of reaction is up to 2.0-2.5. Therefore, there remain many unhydrated Lime and desulfurized gypsum in petroleum coke. It presents drying powdery and a favorable cementing performance. In this paper, chemical and mineral compositions of petroleum coke desulfuration residue are analyzed by means of X-ray fluorescence spectrometer and X-ray diffracto-meter. And lime and gypsum are replaced by petroleum coke desulfuration residue to produce aerated concrete. The experimental results indicate that products made of high-sulfur petroleum coke desulfuration residue and fly ash has better performance than traditional lime aerated concrete products. The fly ash-desulfuration residue aerated concrete products possesses the dry density level of B06 [1] and strength of 4.5MPa. Consequently, it should have expansive application potential because of their prominent economic, social, and environmental benefits.

Abstract: Silane-base water repellent agents can significantly suppress the capillary water absorption of concrete and consequently improve the durability of the concrete and protects the internal steel reinforcement. This paper presents test result on chloride diffusion property of natural and recycled aggregate concrete externally and internally treated with silane-based water repellent agents based on the ASTM C1202 test method. The effects of concrete cracks on the chloride diffusion property were also investigated. After the tests, the impregnation depth of silane into the natural and recycled aggregate concrete, the total charges passing the testing samples and penetration depth of chloride during the testing period were determined. It was found that, for both cracked and uncracked concrete, externally treated natural and recycled aggregate concrete performed better than internally treated ones. The water repellent treatment method is more effective for recycled aggregate concrete than natural aggregate concrete because a deeper impregnation depth can be achieved in the former case.