Showing papers by "Payam Shafigh published in 2020"

Thermal properties of cement mortar with different mix proportions

Abstract: The energy required for the heating and cooling of buildings is strongly dependant on the thermal properties of the construction material. Cement mortar is a common construction material that is widely used in buildings. The main aim of this study is to assess the thermal properties of cement mortar in terms of its ther­mal conductivity, heat capacity and thermal diffusivity in a wide range of grades (cement: sand ratio between 1:2 and 1:8). As there is insufficient information to predict the thermal conductivity and diffusivity of a cement mortar from its physical and mechanical properties, the relationships between thermal conductivity and diffu­sivity and density, compressive strength, water absorption and porosity are also discussed. Our results indicate that, for a cement mortar with a 28-day compressive strength in the range of 6–60 MPa, thermal conductivity, specific heat and thermal diffusivity are in the range of 1.5–2.7 W/(m.K), 0.87–1.04 kJ/kg.K and 0.89–1.26 (x10-6 m2/s), respectively. The scanning electron microscope (SEM) images showed that pore size varied from 18 μm to 946 μm for samples with different cement-to-sand ratios. The porosity of cement mortar has a signifi­cant effect on its thermal and physical properties. For this reason, thermal conductivity and thermal diffusivity was greater in cement mortar samples with a higher density and compressive strength.

Optimum moisture content in roller-compacted concrete pavement

Abstract: Roller-compacted concrete pavement (RCCP), named from a construction method, is a drier mix-stiff enough to be compacted by a vibratory roller. RCCP's fresh and hardened properties are considerably...

Appropriate drying shrinkage prediction models for lightweight concrete containing coarse agro-waste aggregate

Abstract: Oil palm shell (OPS) agro-waste aggregate was successfully employed to produce lightweight aggregate concretes. However, the high rate of drying shrinkage for this type of concrete can impair the intended functionality of the structures or reduce service life. In this study, drying shrinkage strain behaviour of normal-weight and lightweight aggregate concretes was compared with prediction models. Twelve different mix proportions were designed by using of crushed granite (NWA) and OPS aggregates as replacement of the NWA at increasing intervals of 20%. Actual drying shrinkage at early and long-term ages (275 days) was compared against theoretical results from drying shrinkage prediction models such as ACI209R, EN1992, GL2000, B3 and SAK. Comparison between the test results and predicted results indicated that the EN1992 was the most precise model at early-ages as well as GL2000 at long-term ages. In contrast, B3 was found the least precise model at both early and long-term ages.

Experimental Study on the Flexural Behavior of over Reinforced Concrete Beams Bolted with Compression Steel Plate: Part I

Abstract: The purpose of this paper is to investigate the flexural behavior of over-reinforced concrete beam enhancement by bolted-compression steel plate (BCSP) with normal reinforced concrete beams under laboratory experimental condition. Three beams developed with steel plates were tested until they failed in compression compared with one beam without a steel plate. The thicknesses of the steel plates used were 6 mm, 10 mm, and 15 mm. The beams were simply supported and loaded monotonically with two-point loads. Load-deflection behaviors of the beams were observed, analyzed, and evaluated in terms of spall-off concrete loading, peak loading, displacement at mid-span, flexural stiffness (service and post-peak), and energy dissipation. The outcome of the experiment shows that the use of a steel plate can improve the failure modes of the beams and also increases the peak load and flexural stiffness. The steel development beams dissipated much higher energies with an increase in plate thicknesses than the conventional beam.

The effect of superplasticizer admixture on the engineering characteristics of roller-compacted concrete pavement

Abstract: This study investigates the effect of using different amounts of superplasticizer (SP) (0.25% and 0.50%) on fresh and hardened properties, durability, ultrasonic pulse velocity (UPV) and thermal co...

Energy Performance of a High-Rise Residential Building Using Fibre-Reinforced Structural Lightweight Aggregate Concrete

Abstract: The increasing need for eco-friendly green building and creative passive design technology in response to climatic change and global warming issues will continue However, the need to preserve and sustain the natural environment is also crucial A building envelope plays a pivotal role in areas where the greatest heat and energy loss often occur Investment for the passive design aspect of building envelopes is essential to address CO 2 emission This research aims to explore the suitability of using integral-monolithic structural insulation fibre-reinforced lightweight aggregate concrete (LWAC) without additional insulation as a building envelope material in a high-rise residential building in the different climatic zones of the world Polypropylene and steel fibres in different dosages were used in a structural grade expanded clay lightweight aggregate concrete Physical and thermal properties of fibre reinforced structural LWAC, normal weight concrete (NWC) and bricks were measured in the lab The Autodesk@Revit-GBS simulation program was implemented to simulate the energy consumption of a 29-storey residential building with shear wall structural system using the proposed fibre-reinforced LWAC materials Results showed that energy savings between 32% and 148% were incurred in buildings using the fibre-reinforced LWAC across various climatic regions as compared with traditional NWC and sand-cement brick and clay brick walls In conclusion, fibre-reinforced LWAC in hot-humid tropical and temperate Mediterranean climates meet the certified Green Building Index (GBI) requirements of less than 150 kW∙h∙m−2 However, in extreme climatic conditions of sub-arctic and hot semi-arid desert climates, a thicker wall or additional insulation is required to meet the certified green building requirements Hence, the energy-saving measure is influenced largely by the use of fibre-reinforced LWAC as a building envelope material rather than because of building orientation

Durability Property of Oil-Palm-Boiler Clinker Lightweight Concrete Based on Water Absorption Test

Abstract: Utilizing waste material in the construction industry is an effective way to protect the environment and minimize construction cost. Oil-palm-boiler clinker (OPBC) is a waste material obtained by the burning off solid wastes of the palm oil industry during the process of palm oil extraction. This study presents an investigation on the use of OPBC as coarse aggregate in a grade 40 conventional concrete when normal coarse aggregate was fully substituted (by volume) with this porous and lightweight aggregate. Workability of concrete was assessed based on slump test. The development of compressive strength up to 56 days as well as initial and final water absorption were measured. Test results showed that full substitution of normal coarse aggregate with OPBC reduced workability, compressive strength and density of the concrete. However, OPBC concrete has still good workability for casting and also practical favorable 28-day compressive strength. Water absorption test results revealed that OPBC concrete could be considered as good quality concrete in term of durability property.

The effect of cement content on drying shrinkage of roller compacted concrete pavement

Abstract: Roller compacted concrete pavement (RCCP) became a proper alternative to conventional concrete pavement due to its cost-effectiveness and easier production. RCCP is a zero slump concrete with appropriate mechanical properties which make it to be a durable rigid pavement. It has lower drying shrinkage due to its lower water demand and less cement content compared to normal vibrated concrete. In this research, the drying shrinkage behavior of two type of RCCPs with two different cement dosages of 12% and 15% (of dry materials) was investigated. The experimental test results were also compared with ACI 209.2R-08 drying shrinkage strain prediction model. The test results show that increasing cement content from 12% to 15% has not significant increasing on drying shrinkage strain of the RCCPs at early ages, while, the mix with 15% cement content showed 6% higher drying shrinkage strain in long-term.