Effect of silica fume and expanded perlite addition on the technical properties of the fly ash–lime–gypsum mixture

The main objective of this research was to investigate the effect of different type of pozzolan additions to cement free lightweight block made from fly ash–lime–gypsum mixture and observe the changes in physical, mechanical, thermal properties and microstructure. Thermal conductivity of the fly ash–lime–gypsum mixture was improved by the addition of the expanded perlite. Optimal strength-thermal conductivity combination was obtained by the usage of silica fume and expanded perlite together. Improved strength properties were obtained by using hydrothermal curing conditions and superplasticizer addition.     

A three-stage full-range stress–strain inversion for stainless steel alloys as an explicit function of temperature

Presented in this paper is a new explicit full-range stress–strain inversion for stainless steel alloys which expresses the stress as an explicit function of strain and temperature. The relation utilizes an approximation of the closed form inversion of a highly accurate three-stage stress–strain relation recently obtained from a modified version of the Ramberg–Osgood equation. The inversion which is obtained by making a generalized rational function assumption on the fractional deviation of the actual stress–strain curve from an idealized linear elastic behavior is applicable both to tensile and compressive stresses. The temperature dependence is then accounted for by using modified mechanical properties which are functions of temperature. The paper also presents a new direct temperature dependent stress–strain relation based on material properties at normal temperature. While previous studies use temperature dependent material properties to account for the effect of temperature on the stress–strain relation, this paper proposes explicit formulation based on the material properties at normal temperatures. The explicit temperature dependence is introduced by modifying the form of the stress–strain relation which includes a factor with an appropriate temperature dependent function. The validity of the temperature-dependent expression is tested over a wide range of material parameters and a wide range of temperatures. It is demonstrated that the proposed expression is both qualitatively and quantitatively in excellent agreement with the fully iterated numerical solution of the full-range temperature-dependent stress–strain relation at moderate and high temperatures.     

Properties of polymer-modified mortars using epoxy and acrylic emulsions

Water based polymer systems are often used for improvement in the properties of plain cement mortar or concrete. Presently, latexes of a single or combinations of polymers like polyvinyl acetate, copolymers of vinyl acetate–ethylene, styrene–butadiene, styrene–acrylic, and acrylic and styrene butadiene rubber emulsions are generally used. One of the limitations of these polymer systems is that they may re-emulsify in humid alkaline conditions. To overcome this problem, an epoxy emulsion based polymer system has been developed. In this paper the properties of the cement mortar modified with this newly developed epoxy emulsion are compared with those of the acrylic-modified mortar. The results showed that the mortars with the newly developed system have superior strength properties and better resistance to the penetration of chloride ions and carbon dioxide.     

Carbon nanotube–cement composites: A retrospect

Although ordinary Portland cement (OPC) is widely used in the construction industry, its weak tensile strength, to some extent, limits its application. A carbon nanotube (CNT), on the other hand, has outstanding mechanical properties with a tensile strength of 63 GPa and Young's modulus of 1 TPa, making it a candidate as nano-scale reinforcements in OPC. Past research studies have reported improved mechanical and electrical properties of carbonnanotube–ordinary Portland cement (CNT–OPC) composites, which show future promise in practical civilengineering applications. In this study, recent research studies in developing CNT–OPC composites are comprehensively reviewed. Highlighted herein are the considerable efforts been made in the study of fabrication, hydration, porosity and transport properties of the CNT–OPC composites. There are, however, future investigations needed to provide a better understanding in the areas of uniform dispersion of CNTs within the OPC paste, durability, impact, fatigue properties and the theoretical modelling of CNT–OPC interaction.     

Dependence of ceramics physical–mechanical properties on chemical and mineralogical composition

To determine the dependence of physical–mechanical properties of ceramics on chemical and mineralogical composition, the appropriate raw materials have been tested and five batches of ceramic specimens have been formed. The aforementioned specimens have been made of the following components: fusible clay, quartz sand, chamotte, sawdust and crushed window glass. The specimens differed by the amount of the components (differences in burning regime were insignificant). After having formed and burned the specimens, their X-ray phase analysis has been carried out, elemental chemical composition has been defined and the composition of chemical oxides has been calculated. Moreover, the following physical–mechanical properties have been determined: density, general contraction and compressive strength. The test results showed that the physical–mechanical properties of ceramics mostly depend on the amount carbon, silicon and aluminum. The mineralogical structure of specimens under testing was practically unchanged.     

The effects of using lime and styrene–butadiene–styrene on moisture sensitivity resistance of hot mix asphalt

This study focuses on determining the effects of styrene–butadiene–styrene (SBS) and using mineral filler with lime on various properties of hot mix asphalt especially moisture damage resistance. The asphalt cement was modified with 2%, 4% and 6% SBS. The lime treated mixtures containing 2% lime by weight of the total aggregate as filler. The physical and mechanical properties of polymer modified binder and binder–aggregate mixes were evaluated through their fundamental engineering properties such as dynamic shear rheometer (DSR), rotational viscosimeter (RV) for binders, Marshall stability, stiffness modulus, indirect tensile strength and moisture susceptibility for mixes. The retained Marshall stability (RMS) and tensile strength ratio (TSR) values were calculated to determine the resistance of mixtures to moisture damage. To investigate clearly the effective of SBS and lime seven freeze–thaw cycle was applied to specimens at TSR test. The results indicate that application of SBS modified binders and lime as mineral filler one by one improves the stability, stiffness and strength characteristic of hot mix asphalt. According to retained Marshall stability it is concluded that addition of only 2% lime have approximately same effect with addition of 6% SBS. Using lime together within the SBS modified mixes exhibit high accordance and exacerbates the improvement of properties. Specimens containing both 2% lime and 6% SBS, have the highest stiffness modulus which is 2.3 times higher than those of the control mixture and showed the least reduction in tensile strength ratio while maintaining 0.70 tensile strength ratio after seven freeze–thaw cycle.     

Influences of mixture composition on properties and freeze–thaw resistance of RCC

The paper reports a series of lab investigations carried out on roller compacted concrete (RCC) mixtures containing a wide range of cement contents (100 and 450 kg/m³). The key objectives were to appreciate the effects of variations in the cement content and air entrainment on basic physical, mechanical properties and freeze–thaw (F–T) resistances of RCC mixtures. The Vebe consistency, moisture–density relations, water absorption, permeable voids, compressive strength, and F–T resistances of comparable mixes were evaluated. Physical and mechanical properties indicated a significant deviation from the behavior shown by conventional concrete. Air entrainment was found to be affecting the strength and F/T durability of the mixes. Further analysis shows wide range applications of RCC in various pavement applications.     

Modelling of the performance of asphalt pavement using response surface methodology

Response surface methodology (RSM) is a practical and useful statistical procedure to develop empirical models for predicting asphalt pavement properties. In this work three empirical models were developed to predict the load and the flow resistance increment (ΔL and ΔF, respectively) according to ASTM D 5581 [Annual Book of ASTM Standards, Section 4, Construction, vol. 04.03, Roads and Paving Material; Vehicle-pavement Systems] and the “volatilised material” (VM) according to ASTM D 1188 [Annual Book of ASTM Standards, Section 4, Construction, vol. 04.03, Roads and Paving Material; Vehicle-pavement Systems] via RSM using the obtained properties of the specimens placed in a conventional oven for laboratory aging. In addition a mechanistic–empirical (M–E) model was proposed to describe the increment and decrement in surface course properties due to aging (A). The adequacy of the predicted properties by the models was demonstrated with the cores properties extracted from a pilot road.     

Prediction of elastic and acoustic behaviors of calcarenite used for construction of historical monuments of Rabat,Morocco

Natural materials (e.g. rocks and soils) are porous media, whose microstructures present a wide diversity. They generally consist of a heterogeneous solid phase and a porous phase which may be fully or partially saturated with one or more fluids. The prediction of elastic and acoustic properties of porous materials is very important in many fields, such as physics of rocks, reservoir geophysics, civil engineering, construction field and study of the behavior of historical monuments. The aim of this work is to predict the elastic and acoustic behaviors of isotropic porous materials of a solid matrix containing dry, saturated and partially saturated spherical pores. For this, a homogenization technique based on the Mori–Tanaka model is presented to connect the elastic and acoustic properties to porosity and degree of water saturation. Non-destructive ultrasonic technique is used to determine the elastic properties from measurements of P-wave velocities. The results obtained show the influence of porosity and degree of water saturation on the effective properties. The various predictions of Mori–Tanaka model are then compared with experimental results for the elastic and acoustic properties of calcarenite.     

Properties of steel fiber reinforced fly ash concrete

This paper reports on a comprehensive study on the properties of concrete containing fly ash and steel fibers. Properties studied include unit weight and workability of fresh concrete, and compressive strength, flexural tensile strength, splitting tensile strength, elasticity modulus, sorptivity coefficient, drying shrinkage and freeze–thaw resistance of hardened concrete. Fly ash content used was 0%, 15% and 30% in mass basis, and fiber volume fraction was 0%, 0.25%, 0.5%, 1.0% and 1.5% in volume basis. The laboratory results showed that steel fiber addition, either into Portland cement concrete or fly ash concrete, improve the tensile strength properties, drying shrinkage and freeze–thaw resistance. However, it reduced workability and increase sorptivity coefficient. Although fly ash replacement reduce strength properties, it improves workability, reduces drying shrinkage and increases freeze–thaw resistance of steel fiber reinforced concrete. The performed experiments show that the behaviour of fly ash concrete is similar to that of Portland cement concrete when fly ash is added.     

Effect of a polypropylene fibre on the behaviour of aerial lime-based mortars

A polypropylene fibre was added to lime-based mortars in order to check whether they were improved by this admixture. Different properties of lime-based mortars were evaluated: fresh state behaviour through water retention, air content and setting time; hardened state properties such as density, shrinkage, water absorption through capillarity, water vapour permeability, long-term flexural and compressive strengths, pore structure through mercury intrusion porosimetry, and durability assessed by means of freezing–thawing cycles. An improvement in some properties of aerial lime-based mortars – such as permeability, mechanical strengths, reduction in macroscopic cracks or durability in the face of freezing–thawing cycles – was achieved when fibre was added at a low dosage. When a larger amount of additive was used, only the reduction in cracks and the durability of the material were improved.     

The use of brick–lime plasters and their relevance to climatic conditions of historic bath buildings

Brick–lime mortars and plasters have been widely used as water-proof materials in aqueducts, bridges and cisterns since early Hellenistic time. In this study, the characteristics of brick–lime plasters used in some Ottoman bath buildings were investigated in order to understand their relevance as plasters in hot and humid environmental conditions of the baths. For this purpose, basic physical properties, raw material compositions, mineralogical, microstructural and hydraulic properties of brick–lime plasters of some historic bath buildings in ?zmir (Turkey) were determined by XRD, SEM-EDX, AFM and chemical analyses. The results indicated that their survival without loosing their strength and adhesion in hot and humid conditions of the baths was explained by their hydraulic characters due to the consciously use of porous and pozzolanic crushed bricks as aggregate in the manufacturing of plasters.     

The study of welded semi‐rigid connections in fire

Considering the deterioration of steel properties by temperature increase and the importance of the influence of connection behavior on the behavior of steel structures, we find that the exact understanding of the behavior of a specific steel connection in fire as well as the information about the effect of fire on the principal constitutive characteristics of the connection is necessary for safe design against fire. Thus, in this paper, the behavior of welded angle connections is studied at elevated temperatures using the abaqus finite element software. Steel members and connection components are considered to behave nonlinearly; the degradation of steel properties with increasing temperature is considered according to EC3, BS5950 recommendations. The results of finite element and experimental tests conducted on welded angle connections are compared, and the obtained failure modes and moment–rotation–temperature characteristics are in good agreement with those associated with the experimental tests. In the following, since the knowledge about moment–temperature–rotation behavior of a specific connection is needed for a fire‐resistant design, these properties are accurately determined, and finally, the effect of some parameters such as the moment applied on beam, change of column axial force and change of beam shear force on the stiffness of these connections at elevated temperatures is determined. Copyright © 2011 John Wiley & Sons, Ltd.     

Utilization of Mn–Fe solid wastes from electrolytic MnO2 production in the manufacture of ceramic building products

The aim of this work is to evaluate the utilization of Mn–Fe solid wastes, originating from electrolytic manganese oxide production plants, as raw materials in the manufacturing process and on the properties of traditional ceramic building products such as bricks, roof or floor tiles. The Mn–Fe solid wastes are chemically and morphologically characterized. Subsequently, ceramic test specimens incorporating 2.5, 5, 7.5 and 10 wt.% solid wastes are made. Two different shaping technologies are used, namely compaction and extrusion. The green specimens are finally fired to different peak temperatures ranging from 950 to 1100 °C. The final products are characterized concerning important properties such as modulus of rupture, water absorption, weight loss and color. It appears that Mn–Fe solid wastes when used up to a percentage of 7.5 wt.% improve the basic properties of traditional building ceramic products. The results of this study are demonstrated by the successful pilot production of real size ceramic products.     

Leverage and Elderly Homeowners’ Decisions to Downsize

We study the effect of financial leverage, measured using the loan-to-value (LTV) ratios, on elderly homeowners’ decisions to downsize. Using a 1999–2011 sample of elderly homeowners from the Panel Study of Income Dynamics, we find that a higher LTV ratio increases the propensity to downsize. Elderly homeowners with higher LTV ratios are more likely to move into properties with fewer rooms, to move from single-family properties into multifamily properties, and to move into less expensive homes. Our point estimates suggest that on average, a 10 per cent increase in the LTV ratio is associated with a 7.7–9.7 per cent increase in the probability to downsize.     

Properties of compressed lateritic soil stabilized with a burnt clay–lime binder: Effect of mixture components

In this study, a pozzolanic binder containing lime and a common thermally activated kaolinitic clay, at 750 °C, was formulated. The chemical, mineralogical and pozzolanic properties of raw materials were determined. The percentage of lime in the binder varies between 20% and 30%. The binder was used as a stabilizer in compressed lateritic soil in which water–solid (laterite and binder) and laterite–binder ratios vary, respectively, from 0.12 to 0.20 and 4 to 9. Sodium hydroxide (NaOH) was added as a chemical activator in the mixture. The NaOH–binder ratio varies from 0.02 to 0.04. The average effect of each component of the mixture on compressive strength, water absorption and apparent density of compressed laterite after 7 or 28 days of conservation at 40 ± 1 °C in an atmosphere saturated with water vapour was evaluated in a screening design of the “design in graeco – latin squares” type. It was observed that water–solid and laterite–binder ratios are the factors that influence more the properties of the products. Compressive strength increases up to a water–solid ratio of 0.16 then decreases for higher ratios. Compressive strength decreases with the increase of laterite–binder ratio. Water absorption decreases with the increase of water–solid ratio up to 0.16 then sharply increases for higher ratios. However, water absorption decreases slightly with the increase in the lime content of the binder and sodium hydroxide–binder ratio. The maximum apparent density is observed at water–solid ratio of 0.16. It increases when sodium hydroxide–binder and laterite–binder ratios increase.     

Influence of parent concrete on the properties of recycled aggregate concrete

This paper discusses first the properties of recycled aggregates derived from parent concrete (PC) of three strengths, each of them made with three maximum sizes of aggregates. The relative physical and mechanical properties of fresh granite aggregate are discussed. Using these nine recycled aggregates, three strengths of recycled aggregate concrete (RAC) were made and studied. Typical relationship between water–cement ratio, compressive strength, aggregate-cement ratio and cement content have been formulated for RAC and compared with those of PC. RAC requires relatively lower water–cement ratio as compared to PC to achieve a particular compressive strength. The difference in strength between PC and RAC increases with strength of concrete. The relative evaluation of tensile and flexural strengths and modulus of elasticity has also been made.     

Geotechnical characteristics of soils susceptible to severe gullying in eastern Nigeria

The geotechnical characteristics of soils that are susceptible to severe gullying in the rain forest zone of Nigeria were studied. The soils are predominantly sands whose fines (silt/clay) contents are very negligible. The sands are loose (dry density 1.42–1.73 g/cm³) and highly permeable (permeability 9.43×10³?3.4×10²cm/s) with permeability increasing with depth. Porosities and void ratios are also high (41.6–50.3% and 0.71–1.01 respectively), while cohesion is small to zero (0–85 kN/m²). It is thought that although these conditions favour less runoff and high infiltration, they lead to high internal flow velocities and seepage pressures, and ultimately high internal erosion. It is concluded that once a gully is initiated, the soil properties become responsible for rapid propagation. Non response of the gullies studied to afforestation control measures is thought to result from these soil properties.     

Seismic performance of an immersed tunnel considering random soil properties and wave passage effects

This paper presents the results of the dynamic finite element analysis of the Hong Kong–Zhuhai–Macau immersed tunnel, conducted to study the effects of the random soil properties and the wave passage effect. According to the results of the free-field analysis, it was found that the wave passage effect could decrease peak ground acceleration (PGA) and causes a time lag in wave arrivals. Conversely, the random soil properties enlarge PGA sharply. The ‘low-frequency amplification, high-frequency filter’ phenomenon also occurs. The results of the structural dynamic analysis indicate that the soil properties and the wave passage effect have a significant influence on dynamic responses of the immersed tunnel. Although random soil properties only alter bending moments slightly, it can enlarge axial forces by up to 230% and the deformations of Gina gaskets. The wave passage can increase bending moments, Gina gaskets deformations and especially axial forces. The inertial force is the main cause for the sharp increases in axial forces. The combined effects of the random soil properties and the wave passage effect are remarkable. In some cases, Gina gasket deformations will exceed their upper and lower limits of compression, raising the possibility of joint failure and leakage. Thus, it is necessary to consider the influences of the random soil properties and the wave passage effect when conducting a practical seismic design.