Advanced Materials Research Vols. 168-170

Abstract: To study damage evolution of high-strength concrete under the frozen environment, based on the background of YunCheng auxiliary shaft engineering, this paper studies the damage pattern of C100 concrete under loading by applying the method of industry CT scanning. It aims at showing the evolution process of concrete damage by contrasting of the damage factor on standard curing and negative temperature curing condition, which analyzes the trend of damage modulus of elasticity of C100 high-strength concrete uniaxial compression conditioned from the micro level, combining change of fractal dimension of concrete. The results showed that the change of fractal dimension can reflect the evolution trend of inner damage of concrete, fractal dimension is related with the size of concrete when it damaged. Negative temperature frozen brings about the increase of inner hole of high-strength concrete and decrease of modulus of elasticity, and the ratio of damage energy release rate and strain energy release rate decrease, the energy needed by concrete damage is very low. Moreover, the nonlinear positive correlation between fractal dimension and damage factor of high-strength concrete has been gained.

Abstract: The present study aims to investigate the opportunity to largely substitute low heat Portland cement of mass concrete with supplementary cementitious materials. The pozzolanic reaction of two types of supplementary cementitious materials, phosphorous slag powder and fly ash , were determined by X-ray diffraction, differential thermal analysis–thermogravimetry and scanning electron microscopy from 28 to 90 days. The properties of mortar and mass concrete containing 30% of supplementary cementitious materials were also investigated. Results showed that supplementary cementitious materials could decrease the amount of calcium hydroxide, fill the capillary pores, thus making the mortar and mass concrete more compact and durable. Long-term strength of mass concrete containing 30% of supplementary cementitious materials were comparable (or even better) than the control concrete (without supplementary cementitious materials) at constant workability, while the Young’s modulus was lower than the control concrete.

Abstract: An experimental program has been conducted to investigate the influence of limestone powder (LP) on fluidity, strength, and hydration of cement mortar. Four laboratory grinds were prepared using a ball mill. The relationship between roundness of the LP and water requirement of paste, fluidity and strength of mortar was studied. The influence of LP on hydration of cement was investigated. Hydration products were determined by X-ray diffraction (XRD) analysis. Test results show that the roundness of LP significantly affected the water requirement of paste, fluidity and strength of mortar. In addition, the sites for the nucleation and growth of hydration products, provided by LP, accelerate the hydration of cement at early ages. While the enhancement of cement hydration at later ages mainly due to the formation of calcium aluminate monocarbonate.

Abstract: Fourier Transform Infrared Spectroscopy (FT-IR), thermal analysis and X-Ray Diffraction (XRD) are commonly performed to study the hydration products in cement pastes. The three methods were compared in this frame to detect products of cement hydration at different ages, especially at early ages (before 24h ages). The results indicate from the present experiment that CH (Calcium hydroxide) can be detected by three methods at all ages; C-S-H can be distinguished by FT-IR at all ages; ettringite may be detected by FT-IR before 24h ages and by XRD at all ages; and monosulphate can be detected by FT-IR before 24h ages. The process of cement hydration, characterized by formation and development of some hydration products, can be clearly observed by three methods. FT-IR is suggested for detecting the major hydration products before 24h ages, FT-IR and XRD are suggested for detecting the major hydration products after 24h ages, and thermal analysis is suggested for analyzing the degree of hydration quantitatively.

Abstract: The dynamic shear rheometer (DSR) was used to measure viscoelastic properties of asphalt mastic. Mechanical volume filling effects and additional interacting mechanisms within mastic systems are discussed on the basis of micromechanical-rheology model to predict the complex shear modulus of asphalt mastic from the measured mastic data. The Einstein coefficient is 3.761, and the maximum volumetric packing fraction is 0.562 for the measured asphalt mastic. The predicted G* of asphalt mastics is very close to the actual value, and the relative error is not exceeding 10%. The micromechanical-rheology model can predict the complex shear modulus of the asphalt mastic from the viscoelastic property of neat asphalt, the volumetric filler effect and an interactive effect between the filler and the asphalt.

Abstract: Brick masonry is a traditional building material widely used loading-bearing or partition walls in various building structures. The detailed distinctive modelling of brick and mortar of a realistic masonry structure or a structure with masonry infilled walls are usually not possible due to the computational cost. In this paper, a homogenized dynamic material model which including the damage of brick and mortar and strain rate effect is developed based on dynamic test results of brick and mortar. The proposed homogenized material model was used in analysis of blast response of brick masonry wall.

Abstract: In order to study the influences of initial curing conditions on fly ash (FA) cement concrete durability, fly ash cement samples with 30% replacement ratio were fabricated and cured in water at 10°C, 20°C, 30°Cand 40°C for 3d, 7d, 14d and 28d respectively. Hydration degrees of fly ash at early age were measured using the selective dissolve method. Correspondingly the pore structure and morphology of FA-cement mortar and compared cement mortar were studied by using MIP and SEM methods. Then early age compressive strengths of FA-cement concrete and compared normal cement concrete were tested. Experimental results show that initial curing temperatures and ages are important factors to fly ash early age hydration degree, FA-cement system microstructure, morphology and early age compressive strength etc. High curing temperatures and longer curing time can lead higher fly ash hydration degree, and then higher compressive strength of FA-cement concrete, and make the micro-structures of fly ash-cement system denser.

Abstract: The influence of fly ash content, water-cement ratio, sand ratio and polycarboxylic acid type water-reducer dosage on the early-strength and performance of C50 concrete is investigated combined with engineering application. The concrete mixture ratio is optimized by the orthogonal experimental design. Concrete strength, slump and slump loss are verified by experiments. Application results show the designed concrete mixture ratio reaches the expected requirements

Abstract: In this paper, the cement water reduction agent from modified lignosulfonate was synthesizd using a new process consisting of pre-oxidation, hydroxymethylation and sulfonation. The optimum synthesis conditions were identified: the oxidizing agent dosage is 15%, reaction temperature is 80-90oC, the dosage of formaldehyde is 30%, reaction temperature is about 95oC, pH is about 9.5. Fluidity of cement paste can be measured under the conditions of the addition of 0.25%, and the water-cement ratio is 0.4%. The results showed the modified lignosulfonate prepared under the above conditions had the better slushing performance. The fluidity of cement paste can reach 178 mm that is close to the high efficiency water reduction agent requirements.

Abstract: The ubiquitous terrace house is undeniably the most popular and affordable housing type in Malaysia. It has long been considered as one of the densest forms of property development and has become the common typology of accommodating the masses for this country. However, in Malaysia (like other third world countries), the design of a house has never grow from novelistic idea of style and revivalism. As stated by Tajuddin Rasdi (2003), housing in Malaysia has been plague with various issues for decades. We are currently living separate and individual lives in the sea of congested modern housing and we will be forever plagued by the mercy of crime, climate, cultural tensions and threats from accidents. For the last 50 years it has never grown to create the idea of community and fulfill the true need of a family with its culture and context called ‘Malaysia’. Based on our paper N. Utaberta (2009), we have identified the ability of traditional Malay house to grow and transform based on the need and interest of one family. This paper tries to study and evaluate the flexibility of a low rise house in Malaysia. It will explore some design and construction framework based on the flexibility of our traditional (timber) Malay house of growing and transformable house.