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.
Typical low-calcium fly ash (LC-FA) and silica fume SF 90 (SF-90) was used as a binder in the mixture of high-strength concrete (HSC), replacing (20-40)% and (5-15)% of the weight of Portland cement, respectively. The slump of fresh HSC mixtures, compressive strength, density and water absorption of HSC samples were investigated. Applying the standard NT Build 356 combined with standard ASTM C1202-97 for assessment of the chloride resistance and the corrosion resistance reinforced of tested concrete produced using high-calcium fly ash and Silica fume was studied in this work. The results show that the compressive strength of examined concrete decreased with increasing LC-FA content and was lower than the concrete used mix control, while the compressive strength of concrete mixtures with SF-90 at 5%, 10% and 15% by mass cement was higher than the sample tested with mix control and significantly higher than the LC-FA concrete mixtures. LC-FA and SF-90 in HSC decreased the charge passed and tends to decrease, while the times of initial crack of the test specimens gain increased with increasing LC-FA and SF-90 contents. The chloride ion penetrability of HSC is very low.
This paper used the absolute volume method combined with the experiment to determine the compositions of high performance fine-grained concrete (HPFC) and presented the effect of limestone fine aggregate (LFA) and pozzolan (PU) on the HPFC properties. Test results showed that by increasing the LFA and PU, the workability of the concrete mixture decreased, the maximum slump loss after 90 minutes of mixing was 37.84%, whereas the mechanical properties of HPFC increased. The fine-grained concrete mixture containing 40% PU and LFA completely replaced material for natural sand, the compressive strength of concrete at 28-day increased about 23.87% in comparison to the control mixture. By using the standard NT Build 356, the destruction time of the four specimens tested was of 45, 63, 60 and 61 days, respectively. This result is due to the presence of PU increased the volume of the C-S-H, as well as the density of concrete structure and enhanced the strength of HPFC, thus increased destruction time of specimens used for the assessment of corrosion damage of reinforced in the concrete. The results of the current study support the use of the waste limestone from the quarries as a fine aggregate of green concrete in the future.
This study uses the mathematical method of two-factors rotatable central compositional planning to predict and simulate the effect of the ratio of water-cement (N/X) and sand - binder (C/CKD) as the input parameters on the objective functions of the spreading flow of concrete mixtures and the compressive strength of fine-grained high-performence concrete (FGHPC) at 28 days. Results of the study showed that, from the material source in Vietnam, it is possible to FGHPC with a flow of 18.5 cm in the mini cone, its compressive and flexural strengths at the age of 28 days are 68.5 MPa and 6.13 MPa, respectively. Furthermore, from the obtained objective functions, it has been shown that the both two-input parameters have a significant influence on the values of the experimental models. Particularly, using Matlab software is showed the expression surface, the contour line of the experimental models, and determined the maximum value of compressive strength of FGHPC at this age of 69.84 MPa at N/X=0.326 and C/CKD=1.315. The contribution of this study is to obtain regression functions to predict the mechanical-physical properties of FGHPC that will be used in the next in-depth studies.
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