JOURNAL OF MATERIALS & CONSTRUCTION

IMPACTS OF NON-SIEVED WASTE CONSTRUCTION SAND UNDER VARIOUS MOISTURE STATES ON ENGINEERING PROPERTIES OF CEMENT-BASED MORTAR

2024-09-25T09:08:03+00:00

The construction industry generates a significant amount of waste, with leftover sand from masonry construction being a notable concern. This paper investigated the utilization of non-sieved waste construction sand (CS) under various moisture states to assess its impact on engineering properties of cement-based mortar. Along with the primary objective was to compare the effects of non-sieved and sieved waste CS on engineering properties of mortar. Various engineering properties of mortar were tested, including consistency of fresh mortar, bulk density, and the compressive and flexural strengths of hardened mortar specimens. Three moisture states for the waste CS were proposed, including oven-dry (OD), natural (NA), and saturated surface-dry (SSD) states. Compared to sieved waste CS, the consistency of fresh mortar with non-sieved CS increased by 14.3–66.7%. In addition, using CS in the SSD state improved the consistency by 60.0–133.3% and 23.3–27.2% compared to that in OD and NA states, respectively. Moreover, the difference in the bulk density of mortar specimens was insignificant, regardless of the moisture states of the waste CS. In terms of mechanical properties of mortar at 28 days, the results showed a reduction in compressive strength (27.0–32.3%) and flexural strength (32.2–36.4%) of mortar specimens using non-sieved waste CS compared to those using sieved waste CS, regardless of the moisture states of the CS. Furthermore, using waste CS in the SSD state improved the mortar strengths when compared to that in other moisture states (OD or NA state). Additionally, a linear correlation was observed between compressive and flexural strengths of the mortar, regardless of types and moisture states of the waste CS. In conclusion, the use of non-sieved waste CS led to a reduction in mechanical strengths of hardened mortar while increasing the consistency of fresh mortar, regardless of the moisture states of the waste CS. Utilizing the waste CS in the SSD state proved to be an effective method for enhancing the consistency of fresh mortar, and mechanical strengths of cement-based mortar compared to that in other moisture states.

An investigation of seepage flow through homogenous embankment dams using an iteration technique for determining the free surfaces

2024-11-30T06:21:40+00:00

This paper presents the application of the finite element method into solving the balance equation of seepage flows within the porous media. More specifically, these seepage flows occur within homogenous embankment dams. With the specific boundary conditions of water levels in the upstream and downstream sides, the seepage mechanism takes place, generating the unsaturated zones and the saturated ones as well. The demarcation surfaces between the un-saturated and saturated zones are called the free surfaces. For determining these free surfaces, an algorithm of loop is employed, and the convergence is required to locate the free surfaces. This paper combines the relevant ideas into a sub-routine using the programming language Python. Next, a case is shown using the current sub-routine considering the convergence of the solution and comparing it to the outcome of a popular software of seepage analysis SEEP/W. The results show that the algorithm used for locating the free surface is acceptable when dealing with this type of seepage mechanism.

Additive manufacturing technology in construction projects

2024-08-08T01:35:35+00:00

Additive manufacturing, widely known as 3D printing technology, has taken the world by storm, capturing the attention of researchers, engineers, architects, and investors alike. With the ability to transform a mere drawing into a physical object, 3D printing can change the game in various industries. However, the challenge lies in implementing this technology effectively with limited resources. That's where this study comes in - it sheds light on the breakthrough projects produced by a 3D concrete printer. From the iconic university structure to stunning furniture for interior and exterior spaces and even a small-scale village. This study showcases the possibilities of 3D concrete printing technology. By delving into practical techniques such as design, software manuals, slicing model methods, and visual appearance, this study provides valuable insights for anyone interested in this groundbreaking technology. The practical techniques in the printing process related to design, software manuals, slicing model methods, and the visual appearance of a specific model will be discussed.

ARTIFICIAL INTELLIGENCE AND APPLICATIONS IN THE CONSTRUCTION INDUSTRY IN VIETNAM

2024-11-15T09:18:44+00:00

The construction industry plays a crucial role in the socio-economic development of the country, providing essential infrastructure and facilitating the growth of manufacture, business, commerce, and service activities. In the context of digital transformation bringing numerous benefits to enterprises in Vietnam, digital transformation in the construction industry is essential, serving as a positive catalyst, helping construction enterprises enhance labor productivity and develop construction products in the context of global integration. Artificial Intelligence (AI) aids managers in easily identifying errors that are difficult for humans to detect, thereby minimizing potential risks in construction activities such as design, construction supervision, and urban management. This paper outlines the benefits of applying AI to certain tasks in construction projects, discussing the limitations, and proposing measures to further the development of AI technology applications in the construction industry in Vietnam.

Shear wall thickness affects high-rise building internal force and horizontal displacement according to TCVN 2737:2023

2024-11-05T03:40:49+00:00

Shear walls increase the horizontal stiffness of multi-story buildings in wind and earthquake conditions. According to TCVN 2737:2023, Etabs software must be used to study how shear wall thickness affects internal stresses and horizontal displacements in multi-story buildings. This study examines the impact of varying initial shear wall thicknesses, starting with b_w=200mm and subsequently increasing to b_w=250mm (25%), b_w=300mm (50%), b_w=350mm (75%), and b_w=400mm (100%). The focus is on type I high-rise buildings (under 16 floors) and type II high-rise buildings (from 17 to 25 floors), specifically analyzing how these changes affect internal forces and horizontal displacements at the building's top. The survey results of the 9-storey building indicate a 6% reduction in bending moment, a 13% increase in shear force, and a 7% increase in axial force when the shear wall thickness is increased by 100% compared to the original thickness. For the 21-storey building, increasing the shear wall thickness by 100% leads to a 31% reduction in the bending moment, a 47% reduction in the shear force, and a 12% reduction in the axial force compared to the original thickness. As the height of the building rises from 9 to 21 floors, the horizontal displacement increases by a ratio of 6.4 times in both directions

Effect of the moisture states of artifical fly ash aggregate as a partial river sand replacement on bulk density and mechanical strengths of hardened concrete

2024-09-25T08:57:05+00:00

In this study, artificial fly ash aggregate (FAA) under oven-dry (OD) and natural (N) states was employed for partially replacing natural river sand (RS) to investigate effect of moisture states of FAA on slump of fresh concrete, bulk density and mechanical strengths (i.e., flexural strength and compressive strength) of hardened concrete. The FAA with particle sizes ranging from 1.25 to 5 mm was made from 85% Class-F fly ash, 15% Porland cement, a water-to-binder ratio of 0.21, and cured for 1 day in air and 13 days in water condition. Compared with RS, density and bulk density of FAA were lower by 22.4 and 32.5%, respectively, while water absorption was significantly higher. Based on the particle size distribution results of fine aggregate mixtures (including FAA and RS), replacing RS with FAA at volume ratios of 20 and 40% were selected for producing concrete. The slump of fresh concrete with 20 and 40% replacements of FAA under the N state was higher than that with corresponding replacement of FAA in the OD state and the fresh control concrete without FAA had the highest slump. The use of FAA changed insignificantly bulk density at 28 days of hardened concrete, regardless of FAA moisture states. In contrast, the flexural strength at 28 days of hardened concrete declined when FAA content increased, and the difference in flexural strength of hardened concretes using FAA under different moisture states was in a range from 9.3 to 13.6%. Meanwhile, the compressive strength at 3, 7, and 28 days of hardened concrete tended to increase when using FAA in the OD state and decreased when using FAA in the N state. Consequently, 40% replacement of RS with FAA in OD state can be suggested for the concrete production to limit the exploitation of RS and utilize the most fly ash released from coal-fired power plants, towards sustainable development for the concrete industry.

Effect of gypsum content on some properties of blast furnace slag cement

2024-06-05T09:40:15+00:00

The objective of the study is to evaluate the influence of gypsum content on certain properties of blast furnace slag cement (with 40% blast furnace slag) at gypsum levels ranging from 2% to 5%. The properties of the cement investigated include water of consistency, initial and final setting times, compressive strength at ages of 1, 3, 7, and 28 days, and heat of hydration of the cement paste within the first 24 hours. Experimental results indicate that increasing the gypsum content has minimal impact on the water of consistency but prolongs the setting time, while still meeting the technical requirements according to TCVN 6260:2020. The optimal gypsum content, in terms of strength, for blast furnace slag cement is 4%, providing compressive strength comparable to the control sample of ordinary Portland cement at 3 and 28 days of age.

Research and development of high performance fine- grained concrete for floating pontoons

2024-11-20T09:26:45+00:00

The paper presents the results of research and development of high-performance fine-grained concrete (HPFGC) for floating pontoons. Concrete Pontons have thin-walled structures and often work in water and seawater environments. The developed HPFGC has high flowability and can self-compact into the formwork, suitable for the construction of thin-walled structures such as floating pontoons. The amount of Silicafume used is from 0 - 15%, the amount of fly ash used is from 0 - 30% replacing the amount of cement used in HPFGC. The experimental research results show that it is possible to manufacture HPFGC using fly ash/silicafume with a compressive strength of 60 - 80 MPa. This HPFGC has high water impermeability and chloride ion resistance, suitable for floating pontoons working in water environments, including seawater environments.

A REVIEW OF STUDIES ON CONSTRUCTION INVESTMENT PROJECT RISK MANAGEMENT USING SEM MODEL

2024-11-15T09:08:00+00:00

Construction investment activities involve numerous risks, both during construction and operation phases. Some risks recur frequently across multiple projects, while others have a lower probability of occurrence. SEM is one of the optimal methods for assessing a project's performance under risk conditions. Globally, there are numerous studies on construction investment project risk management using SEM. In Vietnam, while SEM has been applied in fields such as biology, sociology, psychology, medicine, business, and education, its application in the construction sector remains limited. This paper reviews scientific studies on construction investment project risk management using SEM both domestically and internationally, identifies limitations in the application of this model in Vietnam, and aims to provide managers with a comprehensive overview of this modern multivariate analysis technique.

ANALYSIS OF FOUR POINT BENDING CHARACTERISTIC OF COMPOSITE ASSEMBLED HOLLOW SLAB USING PROFILED STEEL WIRE MESH

2024-11-11T04:23:10+00:00

Optimizing the performance of reinforced concrete structures by reducing mass, reducing component height, increasing ductility and flexibility, durability, fast construction, and environmental protection has always been the goal of countless studies related to reinforced concrete structures. In this study, 03 hollow slab plates, each slab has one different assembly combination, without beams, using profiled fiber wire mesh, assembled by assembling 12 small slab panels with dimensions of 2800x2000x300, 3000x1950x300 (mm), 2800x1950x300 (mm), respectively were put into 4-point bending for sagging behavior analysis, deformation, crack formation, analysis of slab plasticity. Using profiled steel wire mesh with a grid cell size of 12x12x1 (mm) and steel fiber diameter of 1mm can not only completely replace the reinforcement but also improve the slab's flexibility, flexibility, and toughness. In addition, the way the complex assembles small panels according to the working method also contributes to improving the behavior efficiency of the slab. The plasticity of slab specimens shows that arranging multiple layers of mesh involved in tensile resistance will increase the structure's load-bearing capacity, but the ductility of the structure decreases. The main reason is the use of cold-drawn steel fiber mesh to make reinforcement to bear the load because cold-drawn steel has high brittleness, so at a large load, pulling off steel layers occurs in a fast branch chain effect, thereby reducing the ductility of the structure. The results can be applied to the design of prefab concrete slabs and structures.