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In order to prepare a new type of fine-grained concrete without coarse aggregate instead of ordinary concrete usingdredged sand in channels, the physical and mechanical properties, such as mobility, compressive strength and abrasionresistance of fine-grained concrete filled with limestone powder and fly ash were compared and analyzed, and the influence ofdifferent mud contents (1.3%, 5.3%, 9.3%, 13.3%) of dredged sand on the performance of fine-grained concrete was explored.The results showed that the maximum bulk densities of dry mixed materials filled with fly ash and limestone powder were2 083.8 kg/m³ and 1 979.9 kg/m³, respectively. The ratio of filler to sand was 0.13 and 0.10, and the compressive strength at 28days was 39.8 MPa and 34.1 MPa, respectively; Compared to the 1.3% mud content, the compressive strength of fine-grainedconcrete with a mud content of 13.3% filled with fly ash at 3 days, 28 days, and 90 days decreased by 27.8%, 13.5%, and16.4%, respectively. Samples with lower mud content have higher apparent density, lower bleeding capacity, and better waterretention and workability. The prepared fine -grained concrete can replace ordinary concrete to prepare small prefabricatedblocks such as pavement bricks, interlocking blocks, fish groove bricks, and twisted king blocks, which can be applied nearbyin waterway regulation, roads, or municipal engineering. [ABSTRACT FROM AUTHOR]

The Pussur River, an important river in Bangladesh, requires approximately 6 × 106 m3 of sediment to be dredged per year. At present, this dredged material is mainly dumped on the nearby agricultural and fish-cultivation lands, causing a reduction in productive land and producing negative impacts on people's livelihoods. This study aimed to investigate the engineering and environmental properties of the dredged sand of the Pussur River and evaluate the viability of its potential uses in different sectors. Bed sediments from the Pussur River and dredged material from disposal sites were collected, and laboratory investigations were performed. The test results showed that the dredged material of the Pussur River mainly consisted of fine sand with a fineness modulus ranging from 0.58 to 0.72 and could be classified as poorly graded sand according to the Unified Soil Classification System. This sand was also found suitable for land development, with a fair to poor suitability rating. Given the low concentration of heavy metals (at uncontaminated/slightly contaminated levels), the dredged sand might be safely used for land reclamation, landfill cover, and horticultural purposes, or else for other geotechnical applications without further treatment. After washing/leaching, the dredged sand could also be used as a partial replacement for local sand in concrete works. Moreover, there is a possibility of exporting the dredged sand to Singapore and the Maldives as filling material. These findings will help policymakers design dredging projects with a proper spoil management plan accounting for the dredged material's beneficial use.

The ultra-fine dredged sand (DS) from the lower reaches of the Yangtze River is a large amount of solid waste with the potential to be recycled and applied as a replacement for fine aggregate. This article discussed the utilization of dredged sand by producing alkali activated materials (AAMs). The chemical and physical characteristics of the DS were analyzed. The effect of the DS on durability and mechanical characteristics of the alkali activated slag/fly materials were studied with different precursor systems. From the results, it was found that the addition of DS improved the 28 d strength and even 56 d strength. The 25% DS content increased the compressive strength of both slag rich and fly ash (FA) rich AAMs by about 5%, and the microstructure showed a denser matrix at this content. However, excessive DS can cause a decrease in flowability, early compressive strength and a decline in the compactness of the matrix. Adding an appropriate amount of DS can control the drying shrinkage. The 25% DS content has an inhibitory effect on the shrinkage development of slag rich mortar, while the similar effect on FA rich mortar appears at a content of over 50%. The adoption of DS addition to produce AAMs improves the ecological benefits of concrete engineering projects on the Yangtze River coast.

This paper is aimed at determining the texture, compaction, and cement stabilization properties of the dredged sand used in the Ogbia-Nembe road construction in Bayelsa State, Nigeria. Both field and laboratory studies were undertaken. Results from the laboratory tests revealed the various properties as follows: moisture content (41.3 – 58.2%), Liquid limit (45.5 – 50.5%), Plastic limit (26.2 – 33.7%), Plasticity Index (16.8 – 20.6%), Cu (2,15 – 3.16), Optimum moisture content (OMC) and Maximum dry densities (MDD) for the dredged sands are (9.2 – 9.4) and (1600 – 1620kN/m3 respectively. The OMC, MDD and California bearing ratio (CBR) of the sand-cement mixture are 10.2 – 12.6%, 1830 – 1880kN/m3, 177 -313% and 1140 -2905kN/m2 respectively. The dredged sands are classified as A-3 according to the AASHO classification system. However, the average MDD of the dredged sand is 1620kN/m3 which is below the Federal Ministry of Works (FMW) specification for pavement construction, therefore the need for stabilization. Stabilization of the sand with 6% – 10% cement increased the MDD, CBR, UCS to 1880kN/m3, 313% and 2905kN/m2, respectively. The results of this study revealed that the minimum percentage of cement required to stabilize the dredged sand used for the construction of the road is 6%. Also, particle size of cohesionless soil affects the density and sand-cement stabilization is more economical than paying for additional maintenance cost if the pavement fails. This study also revealed that increasing the percentage of cement of a sample does make the soil brittle as well as increases the strength of the material/soil.

Two kinds of dredged sand in the lower reaches of the Yangtze River were used as raw materials, including sand A with silt content of 25.8%, fineness modulus of 0.1 and sand B with silt content of 6.5% and fineness modulus of 0.3. The mortar was prepared by mixing mineral powder and fly ash instead of part of cement and the physical and mechanical properties of two kinds of dredged cement-based materials were compared. The test results show that, the 28 d compressive strength of mortar A and B reach 31.2 MPa and 38.3 MPa respectively, and the 28 d splitting tensile strength reaches 3.9 MPa and 4.3 MPa respectively. The water immersion strength of sand samples A and B are 24.2 MPa and 34.1MPa respectively, and the abrasion resistance of sand samples A and B are 9.5 h/(kg/m² )and 12.5 h/(kg/m² )respectively, which have good water erosion resistance and abrasion resistance, and can be used to replace C30 concrete for nearby waterway regulation projects. The study provides a reference for building materials and resource utilization of dredged sand with high silt content and small fineness modulus. [ABSTRACT FROM AUTHOR]

Port structures (quays and dykes) need an enormous consumption of materials, in particular concrete and its components, as well as sand, hence the need to develop alternative solutions using port dredging sand, estimated at thousands of tonnes through its use in the concrete that forms the blocks of the quay walls. After having demonstrated in a previous work the possibility of using the dredged sand from the port of Agadir in concrete formulations, the present work consists in showing the possibility of using the dredged sand from the port of Agadir in concrete formulations that can be used in the construction of concrete tetrapods from a concrete formulation based on dredged sand, more precisely 50% of the sand entering in the formulation is dredged sand extracted from the port of Agadir. The eventual use of dredged sand in the concrete of the tetrapods will lead to enormous gains in the quantities of sand and thus to a lower consumption of construction materials, and will also play a more important role in the preservation of the marine environment by avoiding the trapping of the dredged materials.