Porosity Of Concrete Research Articles

Study on Concrete Deterioration and Chloride Ion Diffusion Mechanism by Different Aqueous NaCl-MgSO4 Concentrations

Chemical erosion of reinforced concrete by Cl−, SO42− and Mg2+ in saline soil is the main factor of steel corrosion and concrete damage. In this study, the effects of different molar ratios of aqueous NaCl-MgSO4 on concrete macroscopic properties (appearance, weight change, compressive strength, and dynamic elastic modulus), ion content, microstructure, and porosity of concrete were investigated. The effects of different molar ratios on the macroscopic characteristics and erosion depth of concrete were revealed through concrete appearance, weight, mechanical properties, and SO42− and Cl− content. Analysis of the microstructural evolution process and complex mineral composition of concrete using various microscopic testing methods. The results showed that with increased salt concentration and erosion time, the weight change rate, compressive strength change rate, and relative dynamic elastic modulus of concrete samples had a trend of first increasing and then decreasing. The evolutionary process of transition from large pores to medium and small pores and then to large pores. In the early erosion stage, with increased MgSO4, corrosion products were deposited in pores and cracks, which refined the concrete pore structure and reduced ion diffusion speeds of Cl−, SO42−, and Mg2+. In the later erosion stage, corrosion products caused matrix damage and produced intersecting cracks, which promoted ion diffusion rates and induced deterioration of concrete macroscopic properties. During experiments, the binding ability of SO42− and Mg2+ ions to hydration products was found to be higher than that of Cl−.

Application of Artificial Neural Network to Predict the Properties of Permeable Concrete

The structure of permeable concrete has been the primary reason for its use in construction. Permeable concrete is composed of water, cement, aggregate, and little- to no-fines resulting in the presence of a significant number of voids. This makes permeable concrete an ideal solution to water accumulation issues as it acts as a drainage system. This study employs a feedforward backpropagation artificial neural network model that combines experimental laboratory data from previous studies with appropriate network architectures and training techniques. The purpose of the analysis is to develop a reliable functional relationship, based on water-cement ratio, aggregate-cement ratio, and density parameters, with which to estimate the compressive strength, porosity, and water permeability of permeable concrete. Multiple linear regression correlations are also established to predict and correlate these inputs and outputs. The two derived methods are then compared and discussed. The results reveal that ANN is better to anticipate the permeable concrete properties than regression analysis.

Experimental study on the physico-mechanical properties and microstructure of foam concrete mixed with coal gangue

Coal seam fires are a significant disaster in coal mine production. In order to prevent spontaneous coal combustion, it is necessary to build airtight walls in areas such as mined-out areas or working face roadways. Coal gangue (CG) is a solid waste produced in coal mine production, causing ecological damage and resource waste. So in this paper, a coal gangue lightweight foam concrete is developed for confined filling in coal mines. The effect of water-binder ratio(w/b), CG content, fly ash(FA) content, and foam content on the compressive strength, dry density, water absorption, and porosity of coal gangue foam concrete was analyzed in the single-factor and orthogonal experiment. It was found that the w/b and foam content were the two factors with a more significant effect on the mechanical properties of the specimens. For the porosity of the specimens, the amount of CG content is the critical factor that affects them. A scanning electron microscope (SEM) analyzed the specimen's microstructure and observed its pore structure. It was found that the amount of CG content would significantly affect the specimen's microstructure. When the CG content was 30%, the specimen had the best performance index of pores and poor connectivity between pores. This study shows that the foam concrete mixed with CG can have good mechanical properties and pore structure, making a valuable reference for the coal gangue foam concrete for the confinement filling treatment in mined-out areas or working face roadways mines.

A theoretical model of sulfuration depth of concrete based on SO2 reaction and mass balance

Industrial production emits a large amount of SO2, and the alkaline environment of pore solution of concrete is destroyed by the reaction of SO2 and Ca(OH)2. This process, called sulfuration of concrete, decreases the pore-solution pH and causes the damage of concrete cover and corrosion of rebar. In this paper, the sulfuration reaction process of concrete is presented, and the mass balance equations of SO2 and sulfurable substances are established. Some important parameters are discussed in the mathematical model. The formation rates, content and sulfuration rates of sulfurable substances, the consumption rate of SO2, as well as the porosity and pore saturation of concrete are analysed. A calculation method of SO2 diffusion coefficient is proposed. The initial conditions and boundary conditions of the model are determined, and the prediction model of sulfuration depth of concrete is obtained by using the dimensionless method. The accuracy of the model of concrete sulfuration depth is verified by comparing the calculated results and experimental results obtained from previous studies.

Influences of short-term heavy rainfall on interlayer properties and microstructure of concrete dam

Rainwater adversely affects the interlayer bonding quality of layered concrete. This study tested the influences of different treatment measures (i.e., discharging the rainwater accumulated on the layer and covering the insulation quilt) on the interlayer mechanical properties of concrete under the condition of short-term heavy rainfall, including compressive strength (CS), splitting tensile strength (STS), and shear strength (SS). Meanwhile, the influence of short-term heavy rainfall on the interlayer microstructure of concrete was analyzed using a scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). In addition, the ultrasonic non-destructive testing method was employed to quantify the deterioration degree of the concrete layer under the condition of short-term heavy rainfall. The results show that short-term heavy rainfall can reduce the CS, STS, and SS of concrete by 50%, 70%, and 37%, respectively. Meanwhile, the porosity and damage degree near the concrete interlayer were also increased by short-term heavy rainfall. This is mainly because rainfall increases the water-binder ratio (w/b) of concrete, resulting in the deterioration of concrete microstructure. The increase of w/b is not conducive to the development of concrete mechanical properties. Concrete with a large w/b will retain more water after hydration. The water not involved in hydration leaves more pores after evaporation, increasing the total porosity of concrete. Moreover, there is a linear relationship between the concrete damage degree and the interlayer STS and SS loss rate, as well as the correlation coefficients are 0.959 and 0.983, respectively. The porosity of concrete is linearly correlated with the interlayer STS and SS, and the correlation coefficients are 0.973 and 0.909, respectively. Draining the rainwater accumulated on the layer and covering the insulation quilt can improve the interlayer CS, STS, and SS of concrete. This is mainly because the above measures reduce the influence of rainwater on the interlayer.

Mechanical Performance of Date-Palm-Fiber-Reinforced Concrete Containing Silica Fume

The use of date palm fiber (DPF) as natural fiber in concrete and mortar continues to gain acceptability due to its low-cost and availability. However, the main disadvantage of DPF in cement-based composites is that it reduces compressive strength and increases the porosity of the composite. Hence, for DPF to be efficiently used in concrete, its negative effects must be counteracted. Therefore, in this study, silica fume was employed as supplementary cementitious material to alleviate the negative effects of DPF on the strength and porosity of concrete. The DPF was added in different dosages of 0%, 1%, 2%, and 3% by weight of binder materials. Silica fume was used as a cement replacement material at dosages of 0% to 15% (intervals of 5%) by volume of cement. The unit weights, mechanical strengths, water absorption, and microstructural morphology were all evaluated. The concrete’s fresh and hardened densities were reduced with the increment in DPF and silica fume. The compressive strength declined at all ages with the increment in DPF addition, while the flexural and splitting tensile strengths improved with addition of up to 2% DPF. Furthermore, the concrete’s water absorption escalated with an increase in DPF content. Silica fume significantly enhanced the mechanical strength of the concrete. The dissipation in compressive strength with the addition of up to 2% DPF was mitigated by replacing up to 10% cement with silica fume, where it densified the microstructure and refined the interfacial transition zone between the fibers and cement matrix, hence significantly decreasing the porosity and enhancing durability.

Pore development and mechanical properties of iced concrete during hydration

High geothermal temperature is a key problem that restricts the mining of mineral resources. In order to maintain the normal production of deep mines, we must seek a new stope cooling method that is more green, economic and efficient. Based on this, this paper proposes a iced concrete technology applied to the cooling of deep mine mining, and focused on the mechanical strength, pore structure, heat transfer evolution law, hydration reaction process and other change characteristics of concrete with different initial ice content (0 %, 10 %, 20 %, 30 %, 40 %, 50 %, 60 %). Finally, the pore structure and mechanical properties of iced concrete in the hydration process were analyzed and studied. The results demonstrate that (1) for concrete specimens cured for 1 d, the mechanical strength of iced concrete decreases slightly with an increase in initial ice content. After 28 d of curing, the mechanical strength is positively correlated with the initial ice content; (2) the porosity of macropores and mesopores of iced concrete is negatively correlated with the compressive strength, whereas the microporous porosity of iced concrete is positively correlated with the compressive strength because macropores and mesopores primarily undertake compression fracture penetration during dissipation, and micropores can be conducive to elastic strain energy accumulation; (3) the temperature change trend of iced concrete rises first and then decreases with the inflection point at 24 h. With an increase in the ice content in iced concrete, the initial temperature drops and the heating time is delayed. Therefore, in the initial hydration reaction stage, owing to the cooling effect of ice particles, an increase in the initial ice content decreases the content of hydration reaction products of concrete, increases the content of harmful pores such as macropores and mesopores, and relatively reduces the content of micropores; at 28 d, because the ice particles enhance the water-storage capacity of the concrete, an increase in the initial ice content leads to a more intense hydration reaction at the later stage and better pore structure distribution, which improves the final mechanical strength of the concrete.

Martian and lunar sulfur concrete mechanical and chemical properties considering regolith ingredients and sublimation

• Sulfur sublimation rate at vacuum is 8000 times lower at −60 °C than at 20 °C. • Sulfur concrete permeability decreases strongly with higher sulfur content. • Sulfur concrete porosity does not change much with varying sulfur content. • The presence of alumina in sulphur concrete results in higher porosity. • Alumina and iron oxide together in sulphur concrete leads to lower porosity. Space constructions require unique materials suitable for the harsh conditions in space. Sulfur concrete (SC) is one of the most promising materials for such applications. However, the behavior of sulfur concrete in a vacuum, microgravity, and different temperature conditions and its chemical changes has not been well established yet. This study investigated the effect of vacuum, sulfur content, and compaction (trowel effect) on mechanical and hydro-mechanical properties. Moreover, this study assesses the impact of chemical reactions of aluminum and iron oxides with molten sulfur on the sulfur concrete’s mechanical properties via X-ray diffraction analysis (XRD), scanning electron microscopy (SEM-EDS), and Fourier-transform infrared spectroscopy (FTIR). The predictions from this research show that the sublimation rate under vacuum conditions at very low temperature (−60 °C) can be reduced nearly 8000 times compared with that at 20 °C according to the vapor pressure-sublimation rate relationship. In addition, mechanical experimental tests show that a slight increase in sulfur content dramatically reduces the permeability of sulfur concrete. On the other hand, the porosity is not much affected by the sulfur content. Moreover, sample compaction leads to a significant reduction and increment of the hydro-mechanical and mechanical strength, respectively, indicating the trowel's positive effect. Chemically, sulfur dioxide reacts with alumina and iron oxide via chemical adsorption, and then reaction with molecular oxygen produces S O 4 2 - confirmed by SEM-EDS, XRD, and FTIR results. The presence of alumina increases the sample porosity, although, together with iron oxide, another mineral, namely A l 2 F e 2 S O 4 6 ( H 2 O ) 12 . 6 H 2 O (Aluminocoquimbite), is formed resulting in a lower porosity. To conclude, we have shed light on sulfur concrete properties and preparation processes in unconventional environments and we have shown how different unknown parameters affect the mechanical and chemical properties of the sulfur binder.

Effects of water-to-cement ratio on the performance of concrete and embedded GFRP reinforcement

Lowering water-to-cement (w/c) ratio is a conventional method for reducing the diffusion rate of chlorides in concrete and hence reducing the corrosion risk of internal steel reinforcements. However, the potential effect of w/c ratio on the mechanical performance of glass fiber reinforcement polymer (GFRP) is unknown. In this study, concrete mix design was first carried out with different w/c ratios of 0.3, 0.4 and 0.5. Experimental results showed that a lower w/c ratio effectively reduced the concrete porosity and increased the concrete compressive strength and GFRP-concrete interfacial bonding strength. Then mortar-wrapped GFRP reinforcements were exposed to 40 °C water for up to 12 months. Tensile test results demonstrated that the tensile strength of GFRP decreased with exposure durations, but the varying w/c ratio (0.3 ∼ 0.5) had no significant effect on the tensile strength retention (63.3 % ∼ 69.3 %) of GFRP reinforcements from the life-span perspective. Furthermore, flexural strength and inter-laminar shear strength of GFRP reinforcements basically remained intact after water exposure and were hardly affected by the w/c ratio. To explain the various observations, the glass transition temperature, surface morphology and hydrolysis reaction of GFRP reinforcements were examined to reveal the degradation process at the microscopic level. The findings of this study on the effect of w/c ratio provide engineers with a more comprehensive database to incorporate engineering and durability properties of concrete and GFRP reinforcement into project considerations.

Development of a Simplified Method of Designing Pervious Concrete Mixes using chip aggregate

Pervious concrete can be referred to a sustainable paving material which reduces urban runoff, heat-island effect and improves the ground water quality. Due to the lack of awareness and the unavailability of a simplified design method, the applications are limited in the local context. In this research study, a new method of preparing pervious concrete mixes using commercially available chip aggregate together with coarse aggregate was developed. Five volume based binary combinations were prepared with varying coarse aggregate and chip aggregate proportions. A simple mix design method which is based on the porosity of the pervious concrete was used to determine the required cement paste content. For each aggregate combination, cement paste contents were calculated for four different design porosities. Overall, twenty pervious concrete mixes were prepared and test specimens for compressive strength, bending strength and permeability tests were conducted. Based on the test results, relationships between aggregate combination, compressive strength, permeability, and cement paste content were identified and a simplified graphical method of designing pervious concrete mixes to achieve required strength and permeability characteristics was introduced. Further, the addition of chip aggregate enhanced the strength characteristics while retaining adequate permeability. KEYWORDS: Chip aggregate, Coarse aggregate, Pervious concrete, Cement paste, Mix design.

Effect of Aggregate Size and Water/Cement on Compressive Strength and Physiological Performance of Planting Concrete

Planting concrete, an eco-friendly concrete in which plants can grow directly, has been widely used in roof greening and the slopes of rivers. Porosity and compressive strength are important indicators for evaluating the properties of planting concrete. By preparing planting concrete with different aggregate gradations (10–30 mm, 20–40 mm) and water–cement ratios (0.25, 0.27, 0.29, 0.31, 0.33), the effect of aggregate gradation and water–cement ratio on the porosity and compressive strength of the planting concrete was analyzed, the intrinsic relationship between aggregate gradation and plane pore parameters was studied, the strength growth pattern and microscopic strengthening mechanism were studied, the relationship between porosity and compressive strength of the planting concrete were explored, and a tall fescue planting experiment was carried out to evaluate the plantation performance of the planting concrete. The results show that under the same conditions of water–cement ratio, the smaller the particle size of the aggregate, the smaller the porosity of the plane, and the denser the structure. The average diameter of the planting concrete shows an exponential relationship with the porosity of plane. The early growth of the compressive strength of the planting concrete is rapid; the compressive strength has a linear relationship at the ages of 7 days and 28 days. Compared to polynomial and logarithmic functions, the exponential function gives a better insight into the relationship between the porosity and compressive strength of the planting concrete. Tall fescue seeds germinate and grow well; height, cover, and leaf rootstock and element content of plants can be used as indicators to assess the performance of vegetated concrete planting.

Determination of carbonation resistance of concrete through a combination of cement content and tortuosity

The underlying motivation of the study is to understand the effect of CO2 buffering capacity and pore structure characteristics on the rate of carbonation of concrete. An investigation on the influence of different parameters of concrete on the rate of carbonation of 11 concrete mixes made using PC (Portland cement) and six different SCMs (Supplementary cementitious materials) is presented in this work. Compressive strength and various transport properties (oxygen permeability, porosity, resistivity and sorptivity) of concrete are measured after 28 days of curing. Concrete samples are subjected to accelerated carbonation conditions (2.5% CO2, 60% R.H. and 20 °C temperature) for 60 days after the end of the curing and preconditioning period. No notable correlation is observed between the rate of carbonation and measured parameters of concrete. A pragmatic approach to measure the carbonation resistance of concrete is proposed by means of a carbonation resistance factor derived using the tortuosity and cement content of concrete. The carbonation resistance factor could be effectively used to compare concrete mixes containing different SCMs for their carbonation resistance providing an alternative to tedious and time-consuming carbonation tests.

Utilization of molybdenum tailings as fine aggregate in recycled aggregate concrete

The increasing emissions of construction waste and industrial by-products have caused a serious burden on the environment. The shortage of natural coarse aggregate (NCA) and river sand provides the impetus for the reuse of solid waste. This research provides a cleaner option for the production of recycled aggregate concrete (RAC) from industrial by-product molybdenum tailings (MTs). MTs are used as alternative material to river sand (10%, 30%, 50%, 70% and 100%). Three types of concrete natural aggregate concrete (NAC), RAC, and MTs recycled aggregate concrete (MTs-RAC) were prepared. Firstly, the mechanical properties of the specimens were tested, including compressive strength (fcu) and splitting tensile strength (fst), and the digital image correlation (DIC) system was used to evaluate the strain field distribution. Then, the freeze-thaw (F-T) cycle corrosion resistance of concrete was evaluated. Subsequently, the pore structure was visualized and quantitatively analyzed based on industrial CT technology. The evolution of corrosion resistance of MTs-RAC was confirmed by microstructure. Finally, the economic efficiency factor (EEF) and environmental impact (EI) were evaluated. The experimental results showed that the appropriate amount of MTs significantly improved the pore structure and mechanical properties of RAC, and the fcu of RAC with a 50% MTs replacement rate increased by a maximum of 14.4%, which could achieve the same mechanical properties as NAC. However, the combination of excess MTs and recycled coarse aggregate (RCA) increases the porosity of concrete. The F-T cycle resistance of RAC decreased with the increase of MTs replacement rate. The increase in the proportion of large pores (>10 mm3) is the main factor leading to the destruction of F-T cycles. On balance, the replacement rate of MTs for use in RAC should not exceed 50% in salt lakes and cold regions. The results are helpful to understand the influence mechanism of MTs on RAC performance and provide the theoretical basis for the application of MTs in RAC.

Study on SO42-/Cl- Erosion Resistance and Mechanism of Recycled Concrete Containing Municipal Solid Waste Incineration (MSWI) Powder.

In this paper, the strength characteristics and erosion resistance of solid waste incineration (MSWI) powder were studied. Firstly, the optimum process for the preparation of regenerated powder from MSWI bottom slag by ball milling was determined as follows: rotational speed 350 r/min, time 45 min. The strength activity index of regenerated powder reached the maximum when the substitute content of powder was 30%. Secondly, the semi-erosion method was used to study the strength variation rule of mortar with different content of MSWI powder in semi-immersion of salt solution. It was found that the higher the content of MSWI powder, the greater the anti-erosion coefficient of mortar specimen. Finally, the capillary rise test, crystallization test and capillary pore water absorption test were used to study the total porosity, coarse capillary-pore porosity and fine-capillary pore porosity of concrete containing MSWI powder. The results showed that, with the increase in MSWI powder content, the above pore structure properties were improved. The results revealed the transport and crystallization process of salt solution in concrete mixed with MSWI powder and the mechanism of corrosion resistance.

Strength, durability and shrinkage behaviours of steel fiber reinforced rubberized concrete

Many studies have recently been conducted to reduce the environmental influences of construction in industrial sectors. Recycling rubber as aggregate in concrete helps to reduce the environmental effects of waste automobile tires, and enhances the deformability of the concrete in structural applications such as slabs on grade and concrete pavements. This study aims at examining the reinforcement of rubberized concrete by a hybrid system of fibers comprising industrial steel fibers and steel fibers from waste tires. Six concrete mixtures with/without steel fibers were investigated, using 0, 20% and 40% by volume of waste tire rubber (WTR) particles as a substitute for natural aggregates. The fresh properties of these concrete mixes were evaluated using concrete slump and air content tests, as well as unit weight. Compressive and splitting tensile strengths at 7 and 28 days and flexural strength at 28 days were used to evaluate the hardened concrete properties. Concrete porosity and rapid chloride permeability tests were conducted to evaluate the concrete’s permeability, and its volume stability was assessed by examining free-drying shrinkage and restrained shrinkage. The results showed that, although the mechanical properties of the concrete were negatively impacted when a portion of the crushed rock and sand aggregates were replaced by rubber particles, it was possible to produce rubberized concrete with comparable mechanical properties and durability to conventional concrete when 40 kg/m3 of steel fibers was used in conjunction with 20% rubber. The flexural strain capacity and post-peak properties of the rubberized concrete containing 20% rubber and 40 kg/m3 steel fibers were substantially better than conventional concrete. In addition, the free drying shrinkage strain after 56 days for all mixes was low, below 457 micro-strain or 0.046%, and the presence of high quantities of rubber particles and/or steel fibers in the concrete ring specimens subjected to restrained shrinkage testing prevented the initiation and propagation of cracks. The outcome of this study highlights the potential of these combinations for use in concrete pavement and slab on grade applications.

A Comparative Study of the Thermal Conductivities of CBA Porous Concretes.

Porous concrete has recently gained increasing attention in the construction industry. To improve the properties of porous concrete, coal bottom ash (CBA) was used as the aggregate in the concrete mixtures studied herein. Hybrid CBA aggregates, including a 20% proportion of particles with sizes of 1.2~2.5 mm and an 80% proportion of particles with sizes of 2.5~5.0 mm, were used in the mixtures. Various water/cement ratios ranging from 0.25 to 0.35 were used in the mixtures. The effects of compaction at 0.5, 1.5, and 3.0 MPa on the properties of the porous concrete were also examined. The increase in the water/cement ratio reduced the unit weight and thermal conductivity while increasing the porosity of the porous concrete. Although the compaction had a significant impact on the other properties of the porous concrete, the thermal property was not significantly influenced. By using CBA in porous concrete, the mechanical and thermal properties of the concrete were significantly improved. Finally, the relationships between the thermal conductivity and other properties of the porous concrete were investigated.

Effects of graphene oxide on resistance to chloride ion penetration of concrete

The effects of graphene oxide (GO) on the microstructure and resistance to chloride ion (Cl−) penetration of matrix containing 0-0.05% GO were investigated through isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, mercury intrusion porosimetry and the rapid chloride penetration test method. A proper dosage of GO promoted the hydration process of cement, increased the calcium hydroxide (Ca(OH)2) content, refined the size of calcium hydroxide, promoted the formation of high-density calcium silicate hydrate and improved the pore size distribution of cement matrix. Compared to the group without GO, the porosity of concrete containing 0.03% GO decreased by 8.56%, the largest pore diameter decreased by 29.05% and pores larger than 50 nm were reduced by 36.93%. In addition, the incorporation of GO improved the resistance to chloride ion penetration of concrete. The charge passed through the concrete first decreased and then increased with the increasing GO dosage. When the dosage of GO was 0.03%, the charge passed through the concrete was 27.71% lower than that of the control group. There was a significant correlation between the permeability of chloride ions and pore structure, especially the proportion of pores larger than 50 nm of concrete.

Review article: Atmospheric Pressure, Water with Air, Porosity and Strength of Concrete (In memory of Professor László A Gömze)

The review shows that the gas content in tablets and solutions of medicines can significantly change their physical and chemical properties, qualitative and quantitative characteristics of the mechanism of action of medicines when applied topically, and even allows you to turn “old” and known medicines into “new” medicines with completely new and previously unknown mechanisms of action. Therefore, artificial changes in the gas content in solid and liquid dosage forms were recommended as an original method of developing new drugs. It has been shown that this method is particularly promising for the development of new antiseptic, cosmetic and hygiene products. The fact is that the additional forced introduction of gas into a liquid or into solid through excessive pressure increases their volume, reduces their specific gravity and strength. Moreover, it allows you to “blow up” them by cold boiling. Conversely, the removal of gas from them due to vacuum reduces the volume, increases the specific gravity and strength. By analogy with the change in the physical and chemical properties of liquid and solid medicines, achieved by removing gases from them, it is proposed to reduce the porosity and volume of concrete and increase its specific weight and strength by degassing the water used for wetting cement in the concrete manufacturing process. Due to the fact that under normal conditions, the gas content in the water used for the manufacture of concrete directly depends on the atmospheric pressure, it is concluded that the production of concrete at different atmospheric pressure changes its quality. In particular, low atmospheric pressure can reduce the porosity and volume of concrete, as well as increase the specific gravity and strength of concrete. On the other hand, high air and/or gas pressure can increase the porosity and volume of concrete and reduce the concrete’s specific gravity and strength. Therefore, the amount of atmospheric pressure and/or air and/or gas pressure on concrete during its production should be included in the list of controlled indicators of concrete manufacturing technology.

Numerical Determination of Moisture Diffusivity in Concrete

Accurate modelling of moisture diffusion is essential, as it dominates the drying process in concrete and governs the development of shrinkage strains that affect the short- and long-term deformation and cracking behaviour of structural elements. Key models available in the literature use porosity as the main parameter to predict the diffusivity of the material. Although physically sound, this approach is difficult to apply in practice, as the in-situ determination of concrete porosity is challenging. To address this, the present study uses readily available quantities (namely w/c ratio and concrete maturity) as primary material modelling parameters and investigates the effects of pore relative humidity and ambient temperature on the diffusivity properties of concrete using inverse numerical analysis and available experimental data. As a result, a diffusion modelling approach that can be readily used in practical applications is proposed and verified through finite element analyses. The results show that numerical predictions are in good agreement with experimental data. Specifically, the model is capable of capturing the effects of w/c ratio, concrete maturity and thermal conditions on the evolution of the moisture profile within drying concrete elements. The model can be used to determine drying shrinkage strains with a high degree of accuracy, thereby allowing for a more realistic assessment of crack evolution in drying concrete elements and its effects on overall structural performance.

Performance Evaluation of Rice-husk Ash Based Bacterial Concrete

The performance evaluation of bacterial concrete made with Rice Husk Ash (RHA) is presented in this paper. Concrete is the most widely used construction material on the planet, and because of its longer service life than other building materials, it is sometimes viewed as indestructible. Continuous exposure to harsh weathering, on the other hand, causes an increase in concrete porosity and, as a result, a reduction in mechanical properties. The effect of concrete permeability on porosity and porosity connection. Microbial concrete, which uses microorganisms to increase the durability and life of the concrete, has been presented. These bacteria are employed to precipitate calcium carbonate in concrete, which is extremely desired because the calcite precipitation caused by microbial activity is pollution-free and natural. Rice husk is used to substitute fine aggregate in concrete mixes of 0, 5, 10 and 15.