Published: 2024-05-04

Utilizing coal combustion bottom ash as a sustainable alternative to natural aggregate in eco-friendly building bricks

Trong-Phuoc Huynh, Si-Huy Ngo, Van-Dung Nguyen
Abstract | PDF
As a substitute for fried clay and stone powder-cement bricks, this study developed novel green bricks based on coal-combustion bottom ash (CCBA) obtained from a thermal power plant in Vietnam. By using varied replacement amounts of stone powder at 0, 10, 20, 30, and 40% in weight, ten brick compositions with water-to-binder (w/b) ratios of 0.35 and 0.40 were developed. Testing was done on the bricks' characteristics, such as compressive strength, ultrasonic pulse velocity, water absorption, water permeability, electrical resistance, and thermal conductivity. The findings showed that increasing CCBA content or w/b ratio has a negative impact on the characteristics of unburnt bricks. However, all the brick samples made for this investigation performed exceptionally well when compared to the requirements of the national Vietnamese standard. The brick samples produced in this study are recommended to apply in real practice.

Properties of unfired solid bricks produced primarily from thermal power plant fly ash and bottom ash

Trong-Phuoc Huynh, Van-Dung Nguyen, Vu-Linh Nguyen, Thi-Thuong Le
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In this study, a large amount of fly ash (FA) and bottom ash (BA) from the Nghi Son coal-fired thermal power plant in Thanh Hoa, Vietnam is used in producing unfired solid bricks. FA was utilized to substitute up to 85% (by weight) of the cement amount, while BA was used as a fine aggregate. Test results showed that all bricks produced in this study had a unit weight of 1.51 – 1.68 T/m3 and were classified as Grade M3.5 to M15. As FA replacement level increased, the unit weight, compressive strength, and thermal conductivity of bricks reduced, meanwhile water absorption and water permeability increased. The quality and amount of FA used had a strong effect on the brick’s properties. When the amount of FA used was too much, a part of them did not participate in the chemical reaction but played a role as a fine aggregate.

Erosion in the coastal areas of the Vietnamese Mekong Delta: Current challenges and solutions

Le Anh Tuan
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Coastal erosion is one of the types of geological disasters that is occurring quite commonly and seriously in the Mekong Delta. The problem of landslides and erosions is one of the major concerns for coastal stability. Currently, along 9 coastal provinces, there are over 115 serious erosion and landslide points; each year, a total of 300 –500 hectares of coastal land can be lost. Erosion and landslides narrow the area of mangrove forests, residential land, and aquaculture land of local people. The Mekong Delta has to spend billions of VND yearly to build breakwaters and sea dikes and restore mangrove forests. Many structural and non-structural measures have been implemented to reduce the risk of erosion over the past two decades. However, there is not much assessment of the sustainability of landslide prevention projects. The research question is what are the challenges and difficulties in the ongoing fight against erosion in the coastal plain. Through a practical approach from surveying works in coastal areas, the results show that choosing an effective solution depends mainly on the cost factor and the terrain of the ground. Water resource management policy on the Mekong River system is difficult to find a satisfactory answer.

Assessing reinforced pavement performance: Influence of geogrid position, axial stiffness, and applied stress

Tan Hung Nguyen, Kyra Kamille A. Toledo, Trong-Phuoc Huynh
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This study examined the performance of pavement, considering geogrid’s position within the pavement layers, geogrid’s axial stiffness, and applied stress through the Plaxis 2D program. Results showed that the position of the geogrid has a significant effect on the pavement performance. Using geogrid at the top of the base layer produced a deformation of 2.357 mm, and one at the top of the subbase had a deformation of 2.433 mm. Thus, the use of geogrid on the top of the base layer could provide the highest effectiveness on the pavement performance. Additionally, the geogrid’s axial stiffness had a slight impact on the performance of reinforced pavement. When the axial stiffness increased 2.5 times, the deformation of the pavement decreased only about 0.061 mm. The response of the stress-strain of the reinforced pavement was found to be nonlinear for the static applied stress and to be linear for the dynamic applied stress. The results obtained in this study were theoretically extracted using finite element analysis and the discussions were based on those. Therefore, further studies for the pavement reinforced with geogrid by experiments in the laboratory and on-site should be carried out to understand the impact of geogrid on pavement performance.

Enhancing riverbank stability: A case study on soil improvement through Jet grouting along Can Tho riverbank

Pham Huu Ha Giang, Le Hai Tri, Phan Thanh Ngoc Phuong, Nguyen Truong Phat, Tran Hoang Nam, Nguyen Manh Cuong, Hoang Vi Minh
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Soil cement mixing (SCM) using a high-pressure grouting method (Jet grouting), considered an improvement solution for soft soil has been popular in countries, especially in Japan and other countries in Northern Europe. However, the implementation of Jet grouting is still quite modest in the Mekong Delta. In this study, the depth effect on the compressive strength of soil-cement mixing is conducted at the Can Tho River embankment project. The results show that the uniformity of SCM depends on the cement content. The higher cement content gives a better distribution of compressive strength from the bottom to the top of SCM. In this study, the cement content of 400 kg/m3, considered the suitable content for the Jet-grouting method in Can Tho, is much higher than in (TCVN 9906:2014).

Optimization of non-thermal plasma process to remove methyl blue towards application in wastewater treatment

Quoc-Phong Ho, Hoang-Nam Truong, Phuc-Thong Lam, Bich-Thuyen Nguyen Thi, Van-Dung Nguyen, Pham Huu Ha-Giang, Lien-Huong Huynh
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This study was carried out to optimize the treatment process of methyl blue (MB) in aqueous solution using dielectric barrier discharge (DBD) plasma and experiments were designed by using response surface methodology and central composite design (RSM-CCD). Four independent factors such as plasma power, liquid flow rate, air flow rate, and exposure time were investigated. According to the analyzed results of RSM, the experimental data is best fitted with a model of the quadratic polynomial with regression coefficient values of more than 0.9 for all responses. At optimal degradation conditions, the plasma power, liquid flow rate, air flow rate, and exposure time were 100 W, 1.5 lpm, 6 lpm, and 108.8 minutes respectively and the concentration of methyl blue was reduced to 95.8% with a concentration of 1.06 ppm. The degradation of methyl blue followed kinetic reaction rate was r = 1.6 10-3[MB]2.2.

An investigation of timber frame housing in Vietnamese Mekong River Delta

Pham Phi Phuong, Pham Duy Quan, Le Hoang Thien Long, Le Thi Binh Phuong
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Timber frame housing is one of the most common structures in many countries in the world. In Vietnam, timber frame buildings are well-known for having special whittling techniques that should be considered a lesson for modern methods. In the Vietnamese Mekong River Delta, the housing in rural areas was built mostly with timber frames, and some housing was built with bamboo frames and used natural materials such as nipa-leave, and coconut-leave. Therefore, the study aims to investigate the characteristics of timber frame housing in the Mekong River Delta. To achieve this, firstly, an on-site investigation of ten local housings in the Vietnamese Mekong River Delta is carried out. Secondly, the architectural characteristics of local housing are introduced, and finally, we analyze the details of timber frames. The result shows that the timber frame housing in the Vietnamese Mekong River Delta has the following features: simple structure, light framing, and a flexible connection to other local materials. These characteristics should be considered in detail as a lesson for housing design in the region.

Effect of fiber type on performance of fiber reinforced concrete applied for hydraulic construction

Vu-An Tran, Bui Le Anh Tuan, Duc-Cuong Nguyen, Hoang-Anh Nguyen
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This study aims at evaluating effect of fiber types on comprehensive property of a practical fiber reinforced concrete (FRC) applied for hydraulic construction. Three fiber types including polypropylene, glass, and steel fiber were used to replace concrete volume at 0.3 vol.%. Experimental results illustrated that when compared with the reference concrete, the fiber reinforced concretes with steel or glass fiber had comparable or slight changes on the fresh properties. But, addition of polypropylene fiber induced the fresh FRC with decreased slump flow and significantly increased air entrained volume. Although using various types of fibers led to unbeneficial effect on the compressive strengths of the FRCs, presence of fiber induced the FRCs with significant enhancements on the flexural strength, drying shrinkage, and water absorption and slightly increased UPV at 28 days. In this study, steel fiber was considered as the best choice for improving the mechanical properties of the hardened concrete while, as the volume stability and durability performance of the concrete were primarily considered, polypropylene seemed to be a preferable selection. According to standardized requirements, all concrete proportions were in classification of M40(28)-M45(28), being assigned to concretes suitably applied for widespread on-site hydraulic constructions.

Study on the stable behavior of the river embankment system considering climate change impacts and pressure wave

Le Hoang, Nguyen Trung Phuong, Do Hung Thoi, Le Thi Anh Hong, Do Ngoc Trieu, Le Nong, Ho Quang Vinh
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Understanding the behavior of working conditions of the embankment structural system on reinforced concrete pile foundations is very important in design, construction, operation exploitation, and use. This study assessed the adaptive performance of the Hau River landslide protection embankment in regard to climate change scenarios, specifically the impacts of more extraordinary groundwater table drawdown conditions including pressure waves. The study uses Plaxis 2D V.22 software to simulate and calculate the safety factor of the stability of landslide protection embankment on the right bank of Hau River in the area of Binh Duc Ward, Long Xuyen City, An Giang Province. Simulation. The research results on the effectiveness of shore protection works by the seawall system show that the impact of rising water levels as forecasted by climate change projections (+2.8m elevation) is still within the safe limits. Besides, the dangerous scenario of lowering water levels from the design elevation of -1.0 m (Msf = 1.114) down to the climate change water level of -1.5m elevation (Msf = 1.113)) affecting the protected shoreline also has a minor influence on the stability of the structure. Moreover, the impact of waves on the protection works, which is negligible, is also reduced by the shore protection seawall.

Applications of IoT technology for climate change adaptation in the Mekong Delta

Luong Vinh Quoc Danh
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The Mekong Delta, with an area of over 40,000 square kilometers, is the largest agricultural and fishery production center in Viet Nam. However, along with the Ganges River Delta and the Nile River Delta, the Mekong Delta is one of the three delta regions most severely impacted by climate change. In recent years, this region has faced drought, saltwater intrusion, environmental degradation, and land subsidence mainly caused by climate change. The Internet of Things (IoT) technology has been envisioned as a powerful tool for combating climate change. This paper presents some research projects that leverage the potential of IoT technology and applications to improve the effectiveness of rice cultivation and aquaculture; and support the development of riverbank landslide early warning systems for the region. Through these applications, IoT technology has provided practical answers to address climate change and save the environment.

Investigation on manhole sludge in Can Tho City

Pham Huu Ha Giang, Le Gia Linh, Tran Duc Khanh, Vo Kim Ngan, Phan Thanh Ngoc Phuong, Nguyen My Phuong, Dien Thanh Binh, Ho Quoc Phong
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During the rainy season, Can Tho city frequently faces severe flooding on its streets. In this study, the investigation is carried out on 30 streets and 10 canals nearby the streets in the center of Can Tho city. The results indicate that the surveyed manholes contain a lot of sludge with an average volume percent of 39.29%. In the food service areas, the average volume percent of sludge in manholes is found more than 70%. In the concentrated residential areas, the amount of sludge is less, but still at a relatively high rate (over 50%). In addition, the results show that the studied canals in the inner city are polluted due to waste directly from the drainage system. These issues have an effect on the drainage capacity of the roads. Some discussion on sand also shows that the sand shortage has reached an alarming level, which is the main factor leading to slow progress of some road projects. The sand reserves in the Mekong Delta region decrease sharply and the scarcity of sand causes sand prices to skyrocket, which is a difficult problem for this area. The development of mobile sludge treatment technology to produce a replacement material suitable for levelling and fertilizer purposes can be a potential topic for future research.

Shoreline evolution in adjacent to a coastal structure in Hiep Thanh commune, Duyen Hai district, Tra Vinh province

Dinh Van Duy, Tran Nhat Thanh, Pham Tan Dat, Lieu Do Nhut An, Tran Van Ty
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Coastal erosion is significant along the coastline in Hiep Thanh commune, Duyen Hai district, Tra Vinh province, Viet Nam. In order to address this severe coastal erosion, the local community has constructed a concrete embankment as an emergency solution to protect the coastline. However, this solution exacerbates the issue since the fundamental processes of coastal erosion remain inadequately explored and understood. Specifically, in beach sections without the concrete embankment, erosion still occurs. Therefore, this paper aims to investigate the shoreline changes adjacent to the embankment using an integrated approach with remote sensing and diffusion theory. The results show that beach erosion is occurring near the embankment at a rate of 44 meters per year, and the diffusion coefficient for longshore sand transport in the study area is 130 square meters per day. This study offers a practical approach to examining changes in the shoreline adjacent to a coastal structure, particularly valuable in situations where there is a scarcity of measured field data.