Papers by Keyword: Water-Cement Ratio

Abstract: An overview of literary sources related to the formation and development of the technology of aerated concrete is given. It is shown and systematized in which directions scientific research aimed at improving their functional properties was conducted. It is noted that almost all researchers associate the dependence of the properties of porous concrete with the character of their porosity. The conducted analysis allowed the authors to hypothesize that the properties of aerated concrete are exclusively determined by the nature of the distribution of the solid phase, that is, by the nature of its structure. Determination of the influence of the solid phase and its nature on the properties of aerated concrete is devoted to experimental studies. They were conducted in two stages. At the first, when applying physical modeling, the effect of the total porosity and water consumption of the dry mixture on the change in the nature of the solid phase of the model was studied. Internal interfaces between structural elements are taken as characteristics of the solid phase - their total length and width. It is shown that the water consumption of the mixture has different effects on materials with a dense and porous structure. At the next stage of experimental research, the influence of the water consumption of the mortar mixture on its strength (strength of the matrix material) and the strength of foam concrete was studied. The initial rheological conditions of the formation of the structure were changed by changing the size and amount of filler, changing the amount of liquid and plasticizing additives. The results of the experiments confirmed that the initial rheological conditions have different effects on the materials of dense and porous structure. Under certain conditions, in materials with a porous structure (in foam concrete), an increase in the water-solid ratio leads to an increase in the strength of concrete. Which indicates that with such water consumption, more favorable conditions are created for the formation of a porous structure, which is reproduced on the character of the solid phase. The given results confirm the given hypothesis and can be used in the synthesis of new building materials, including with the use of artificial intelligence.

Abstract: The object of study is a cement composite material with powdered utilized optical discs. The objective is to establish the dependences of the main strength characteristics – com-pressive strength, bending strength, and density – on the amount of waste added into the mix-ture and the water-cement ratio.The compositions of the mixtures for the production of the cement composite material samples consisted of the following components: cement, sand, powdered waste in the form of utilized optical discs and water.Based on the results of testing the samples, mathematical models have been developed which describe the dependences of the physical and mechanical properties of the cement com-posite material samples on the fraction of waste and water-cement ratio. It was found that with an increase in the amount of powdered waste added into the mixture, it reduces the compressive strength, bending strength, and density of the samples under study, however, the optimization of the water-cement ratio makes it possible to obtain equal strength compositions with a differ-ent fraction of waste.Component compositions of cement composite material mixtures with the addition of powdered utilized optical discs in the amount of 10 to 25 % of the total filler mass, which can provide construction products with a compressive strength class B20, are presented.

Abstract: The results of concrete testing on sulphate-resistant slag Portland cement for rigid coating of agricultural roads and aerodromes are presented in the paper. The results of experimental investigations of samples in the form of cubes on compressive strength and samples in the form of prisms on bending strength under different hardening conditions and at different water-cement ratios are presented. Selection of hardening conditions of concrete on sulphate-resistant slag Portland cement was made based on achievement of quality indicators no worse than in concrete on Portland cement. The expediency of introducing into the concrete organic surface-active additives - lignosulfonates in order to achieve the required strength is grounded. It is proved experimentally that the proposed concrete has sufficient frost resistance.

Abstract: In this study, crumb rubber was used to partially replaced fine aggregate in mortar mixture by 5, 10, 15 and 20 volume percentage (vol%) with untreated and NaOH-treated crumb rubber. There were three (3) different water-cement ratio used which are 0.45, 0.50 and 0.55. Thus, the total number of mixtures was 27. The mortars were tested for flowability, compressive strength, flexural strength and density. Based on the results, higher water cement ratio and percentage of crumb rubber replacement increased the flowability but lowered the density, compressive strength and flexural strength of the rubberized mortar. It was also discovered that the significant effect of water-cement ratio on the fresh and hardened properties of the rubberized mortar was due to the water content in the mixture. Meanwhile, the use of NaOH as treatment to crumb rubber improved the flowability, compressive strength and flexural strength of the rubberized mortar.

Abstract: The total volume of cellular porosity, which comprises pores, interpore partitions, and air-entrained pores, depends on the spatial packing of pores, size distribution, maximum and average size, their shape, and the thickness of interpore partitions. Interpore partitions contain gel and capillary pores, which have a significant impact on the total porosity, thus affecting the operating properties of aerated concrete. This paper presents the calculations of gel, capillary, air, and total porosity in non-autoclaved aerated concrete of average-density grades D100...D1200 for different cement hydration degrees (0.6; 0.8, and 1) and water-cement ratios (0.5; 0.6, and 0.7); calculations use the author-developed methodology. Cement consumption depends on the average-density grade as well as on cement hydration degree. Reducing the latter from 1 to 0.6 in D500 concrete raises cement consumption by 7.4 %; other grades have similar patterns. This is why aerated concrete should be conditioned to maximize the utilization of the binder by enabling its complete hydration. The amount of water in the mixture is what determines the cement consumption and the water-cement ratio, whereby the density of cement dough will not depend on the average-density grade provided that the hydration degree and the WC ratio are constant. The finding is that the ability of cement to form its own pore structure is crucial to D500 and D400 aerated concrete if the mixture has high initial water content.

Abstract: This paper is devoted to research of directional regulation possibility of the properties of a composite based on the Portland cement by using limestone waste. It is shown that the introduction of limestone waste contributes to changing the nature of crystallization and structure formation of cement stone. With the introduction of limestone waste, in the amount of 15 % by weight of cement, it is possible to obtain the compositions of the class not less than B25-B35.

Abstract: The article is devoted to the use of waste power plants. The basic physical and mechanical properties are investigated and the optimal compositions of fine concrete are developed. The optimal granulometric composition of ash and slag waste was selected for use as aggregates for concrete

Abstract: An unconventional approach to the design of cement mixtures with the addition of cement bonded particle board (CBPB) production waste is presented, which is characterized by high water consumption. For various compositions of fine-grained concrete prepared in accordance with the simplex-lattice design of the experiment, compressive strength and bending, as well as density of the samples, depending on the mixture factors, were researched. The fractions of CBPB wastes, water and sand at constant cement consumption were chosen as the influencing factors. For practical purposes, related to the design of cement composite compositions with the addition of CBPB wastes and with the determination of optimal values of the selected factors, mathematical models have been constructed on the basis of laboratory experiment data and with their help, the optimal ratios of components in the mixture have been determined. It was found that the content of water for the mixture mixing in the mixture has a significant effect on the strength characteristics of composites: increase of the strength of materials with a decrease in the water-cement ratio is a characteristic for compositions with the minimum amount of CBPB waste; increasing the content of the CBPB waste in the mixture the increase of the water-cement ratio leads to gain in strength. Optimal ratios of the mixture components providing maximum utilization of CBPB waste without loss of strength of composites are given.

Abstract: This article deals with the ways of mixing method for concrete with extremely low water-cement ratio (w/c) typical for ultra-high performance concretes. For this purpose, the mixture with w/c ratio of 0.2 and amount 6% superplasticizers of cement weight was used. In total 6 various mixing methods was tested, which differed in application of superplasticizers, mixing order or mixing length. Workability, electricity consumption during mixing and compressive and flexural strength after 28 days were examined. The performed experiments showed that workability can be increased by, for example, separate doses of superplasticizers and water or other mixing methods. Strength of concrete was identical for all produced mixtures, even though the total mixing time was shortened in two cases.

Abstract: Water-cement (w/c) ratio is an important parameter in concrete mix ratio design, which also plays an important influence on concrete sulfate corrosion rate. In this paper, concrete cubic specimens with w/c of ratio as 0.4, 0.5 and 0.6 were fabricated, respectively, and put into 10% Na₂SO₄ solution and tap water for 240 days. During the submerging process, superficial corrosion phenomena were observed and concrete cubic strengths were measured periodically. The results showed that the lower the w/c ratio, the stronger the concrete sulfate corrosion resistance is. At the same time, concrete with lower w/c ratio always correspond smaller corrosion layer thickness. Based on the degradation of cubic compressive strength of corroded concrete specimens, the development models of corrosion thickness of each w/c ratio concrete are established as sulfate corrosion goes on