Vietnam is one of the leading rice exporters in the world. Popularly, as other rice producing countries, rice husks from rice processing in this nation are used widely not only in electricity generation and silicon making but also one kind of raw material for various building materials production. This article presents a reusing waste method of Rice Husk Ash (RHA) in Vietnam to improve the behavior of hydrotechnical concrete (HTC), one of the most significant building materials. In this study, RHA plays a role as a highly active fine mineral additives, containing 88.42% amorphous SiO₂ oxide in component. The combination of RHA and superplasticizer ACE 388 as mineral additives is able to modify the concrete structure. Not only the compressive strength of hydrotechnical concrete at the age of 28 days increase 7.39% (from 11.71 to 19.1%), but also its water resistance rises up to 50% (from the point of 25%) due to compaction of the structure. The experimental results of permeability of chloride-ion according to standard ASTM C1202-97 (American) show that the HTC patterns containing 10% and 20% RHA by mass of the binder have the average value of electrical energy, respectively 351.18 C and 297 C. While other control samples without RHA have the average value of electrical energy of 1013.22 C. In comparison to the American Concrete Association classification table, these chlorine-ion permeability values of samples HTC-10 and HTC-20 are, precisely, at low level. Therefore, hydraulic concrete, using modified structure from mineral additives of superplasticizer ACE 388 and RHA, is appropriate building material for construction of irrigation works and hydroelectric projects in Vietnam.

Light-weight aerated concrete (LAC) is produced by making LAC involves the addition of a gas-forming admixture like aluminium powder (AP) to a wet mortar mixture. In concrete during curing, AP will react with the calcium hydroxide in the mixture to form hydrogen. The amount of gas-forming is dependent on the mechanical properties requirements. The aim of the current work was to investigate the properties of aerated concrete (AC) containing 30% fly ash and various AP content, including dry density, porosity and modulus of elasticity, as well as strengths of test specimens. The results of this study showed that when AP content increased, the density of AC decreased, but its porosity increased. Whereas an increase in the amount of AP caused a decrease in both the compressive strength, tensile strength and the modulus of elasticity of ACspecimens. The investigation of newly modified AC through combination of local by-product in Vietnam would decrease the content of Portland cement was used and as well as reduce the amounts of ash and slag TPP as well as industrial waste thrown at a landfill. Therefore, assisting the thermoelectric power plants to be more environmentally friendly in the future.

The usage of industrial and agricultural wastes for building materials production plays an important role to improve the environment and economy by preserving nature materials and land resources, reducing land, water and air pollution as well as organizing and storing waste costs. This study mainly focuses on mathematical modeling dependence of the compressive strength of high performance concrete (HPC) at the ages of 3, 7 and 28 days on the amount of rice husk ash (RHA) and fly ash (FA), which are added to the concrete mixtures by using the Central composite rotatable design. The result of this study provides the second-order regression equation of objective function, the images of the surface expression and the corresponding contours of the objective function of the regression equation, as the optimal points of HPC compressive strength. These objective functions, which are the compressive strength values of HPC at the ages of 3, 7 and 28 days, depend on two input variables as: x₁(amount of RHA) and x₂(amount of FA). The Maple 13 program, solving the second-order regression equation, determines the optimum composition of the concrete mixture for obtaining high performance concrete and calculates the maximum value of the HPC compressive strength at the ages of 28 days. The results containMaxR²⁸_HPC= 76.716 MPa when RHA = 0.1251 and FA = 0.3119 by mass of Portland cement.

The dense development of high-rise construction in urban areas requires a creation of new concretes with essential properties and innovative technologies for preparing concrete mixtures. Besides, it is necessary to develop new ways of presenting concrete mixture and keeping their mobility. This research uses the mathematical method of two-factors rotatable central compositional planning to imitate the effect of amount of rice husk (RHA) and fly ash of thermal power plants (FA) on the workability of high-mobility concrete mixtures. The results of this study displays regression equation of the second order dependence of the objective functions - slump cone and loss of concrete mixture mobility due to the input factors - the amounts RHA (x1) and FA (x2), as well as the surface expression image of these regression equations. An analysis of the regression equations also shows that the amount of RHA and FA had a significant influence on the concrete mixtures mobility. In fact, the particles of RHA and FA will play the role as peculiar "sliding bearings" between the grains of cement leading to the dispersion of cement in the concrete mixture. Therefore, it is possible to regulate the concrete mixture mobility when transporting fresh concrete to the formwork during the high-rise buildings construction in the hot and humid climate of Vietnam. Although the average value of slump test of freshly mixed concrete, measured 60 minutes later after the mixing completion, decreased from 18.2 to 10.52 cm, this value still remained within the allowable range to maintain the mixing and and the delivery of concrete mixture by pumping.

In recent years, the reuse of industrial waste has become increasingly important for sustainable development. Therefore, this study investigated the application of granulated blast furnace slag (GBFS) as a cementitious replacement material in fly-ash-based geopolymer mortar containing silica fume (GMS). The performance changes in the GMS samples manufactured with different GBFS ratios (0–50 wt%) and alkaline activators were evaluated. The results indicated that GBFS replacement from 0 wt% to 50 wt% significantly affects GMS performance, including improving the bulk density from 2235 kg/m³ to 2324 kg/m³, flexural-compressive strength from 5.83 MPa to 7.29 MPa and 63.5 MPa to 80.2 MPa, respectively; a decrease in water absorption and chloride penetration, and an improvement in the corrosion resistance of GMS samples. The GMS mixture containing 50 wt% GBFS demonstrated the best performances with notable results regarding strength and durability. Owing to the increased production of C-S-H gel, the microstructure of the GMS sample containing more GBFS was denser, as obtained via the scanning electron micrograph analysis results. Incorporating the three industrial by-products into geopolymer mortars was verified when all samples were determined to be in accordance with the relevant Vietnamese standards. The results demonstrate a promising method to manufacture geopolymer mortars that aid sustainable development.