Durability Factor Research Articles

Enhancing alkaline resistance of concrete using alccofine and metakaolin in mineral admixtures of sustainable development

Addressing the need for sustainable construction materials that minimize environmental impact and reduce CO2 emissions, particularly in OPC compositions. Assessing alccofine and metakaolin in OPC compositions to determine their impact on concrete strength, durability, and microstructure in alkaline environments for sustainable material development. Experimental investigation involved incorporating alccofine and metakaolin into OPC concrete mixes, creating binary and ternary blended systems. Modified concrete specimens were subjected to various alkaline attacks using diluted solutions of magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and sodium chloride (NaCl) both individually (5%) and in combination (2.5%), resulting in significant improvements in concrete strength and durability. The modified concrete exhibits enhanced resistance to alkaline attacks, reduced weight and compression strength loss, and superior performance in Base Durability Factor (BDF) and Base Attack Factor (BAF) compared to conventional specimens. Scanning electron microscopy (SEM) study of the altered concrete’s microstructure shows that it has a densely packed microstructure, which increases its load-bearing capability. Mineral admixtures aid pore clogging, leading to denser, more alkali-resistant concrete due to finer particles. Notably, Alccofine and metakaolin offer effective solutions for sustainable construction materials, aiding in the decrease of CO2 releases during cement production and addressing critical gaps in sustainable material development.

Pore fractal characteristics and ANN model of polyacrylonitrile fiber reinforced concrete under the synergistic effects of freeze-thaw and erosion

The degradation of the concrete pore structure is a major concern among scholars due to its negative impact on durability. This study conducted a salt freezing test on polyacrylonitrile fiber concrete (PANFRC) using a composite freeze-thaw medium consisting of Na2SO4, MgSO4, and NaCl (5 % + 5% + 3.5 %). The pore volume fractal dimension was determined by analyzing the T2 spectrum obtained through nuclear magnetic resonance technology. The study explored the influence of different types of pores on frost resistance and developed an artificial neural network-based machine learning model to predict macroscopic frost resistance using the pore volume fractal dimension. The experimental findings indicate that plain concrete exhibits a density loss of 4.67 % upon failure, whereas the density loss in PANFRC is reduced to less than 3 %. The frost resistance durability index is observed to improve as the fiber mass fraction increases within specific ranges. Notably, when the fiber content surpasses 1.2 kg/m³, the durability factor (DF) can be effectively doubled. Drawing from the concept of freeze-thaw cycles, a novel frost-thaw erosion damage model was developed, which incorporates the influence of fiber content under the combined action of freeze-thaw cycles and erosion. The analysis of pore dimensions reveals that the fractal characteristics become more pronounced with the increase in pore size, although this does not extend to the micro-pore range (i.e., those smaller than 0.1 μm). In comparison to other machine learning algorithms, the ANN demonstrates its superiority by establishing a meso-macro transfer prediction model with enhanced generalization capabilities.

Determine attenuation coefficients of saturated sand from standard penetration test, applied to Nhon Hoi economic zone

Vietnam is located in a strong earthquake zone with many areas having a ground acceleration (a<sub>g</sub>) of greater than 0.08 g (TCVN 9386:2012). According to Vietnamese standard TCVN 9386:2012, the calculation and design of construction grade III or higher in areas where have ground acceleration a<sub>g</sub> ≥ 0.08 g must include seismic design. In calculations of earthquake-resistant pile foundation, the bearing capacity of the pile including the tip resistance strength (q<sub>b</sub>) and endurance strength (f<sub>i</sub>) need to be multiplied by attenuation coefficients (g<sub>eq1</sub> and g<sub>eq2</sub>). They are the most important parameters and depend on the soil types, saturation conditions, and earthquake intensity. The article introduces a method to determine the attenuation coefficients according to the standard TCVN 10304:2014. In addition, analyzing the theoretical basis to give the expression to determine attenuation coefficients based on the durability factor (I<sub>red</sub>) and pore water pressure ratio (R<sub>u</sub>) of saturated sand under the earthquakes. Furthermore, the paper presents a method to determine R<sub>u</sub> from the results of standard penetration test (SPT) by combining the method of Seed and Alba (1986) with the method of Marcuson and Hynes (1990). In which, Seed and Alba's method was used to determine factor of safety against liquefaction (F<sub>SL</sub>), and then Marcuson and Hynes' method was used to determine R<sub>u</sub> from F<sub>SL</sub>. The application in Nhon Hoi Economic Zone shows that: The silty fine grained sand, which is medium dense and saturated, has a attenuation coefficient of tip resistance g<sub>eq1</sub> = 0.74÷0.76 and attenuation coefficient of friction g<sub>eq2</sub> = 0.90; The fine grained sand, which is dense and saturated, has g<sub>eq1</sub> = 0.79÷0.82 and g<sub>eq2</sub> = 0.94. 

Soil nailing as a ground reinforcement method of a storey building constructed on weathered siltstone: Analytical and numerical evaluation

Vietnam is located in a strong earthquake zone with many areas having a ground acceleration (a<sub>g</sub>) of greater than 0.08 g (TCVN 9386:2012). According to Vietnamese standard TCVN 9386:2012, the calculation and design of construction grade III or higher in areas where have ground acceleration a<sub>g</sub> ≥ 0.08 g must include seismic design. In calculations of earthquake-resistant pile foundation, the bearing capacity of the pile including the tip resistance strength (q<sub>b</sub>) and endurance strength (f<sub>i</sub>) need to be multiplied by attenuation coefficients (g<sub>eq1</sub> and g<sub>eq2</sub>). They are the most important parameters and depend on the soil types, saturation conditions, and earthquake intensity. The article introduces a method to determine the attenuation coefficients according to the standard TCVN 10304:2014. In addition, analyzing the theoretical basis to give the expression to determine attenuation coefficients based on the durability factor (I<sub>red</sub>) and pore water pressure ratio (R<sub>u</sub>) of saturated sand under the earthquakes. Furthermore, the paper presents a method to determine R<sub>u</sub> from the results of standard penetration test (SPT) by combining the method of Seed and Alba (1986) with the method of Marcuson and Hynes (1990). In which, Seed and Alba's method was used to determine factor of safety against liquefaction (F<sub>SL</sub>), and then Marcuson and Hynes' method was used to determine R<sub>u</sub> from F<sub>SL</sub>. The application in Nhon Hoi Economic Zone shows that: The silty fine grained sand, which is medium dense and saturated, has a attenuation coefficient of tip resistance g<sub>eq1</sub> = 0.74÷0.76 and attenuation coefficient of friction g<sub>eq2</sub> = 0.90; The fine grained sand, which is dense and saturated, has g<sub>eq1</sub> = 0.79÷0.82 and g<sub>eq2</sub> = 0.94. 

Post-evaluation of frost resistance of cement concrete entities based on pore spacing factors of hardened concrete

In this paper, the effects of water-cement ratio, air-entraining agent type, and air content on the pore characteristic parameters of hardened concrete were investigated through an extensive series of experimental studies. First of all, according to different water-cement ratios, air-entraining agent types, and air contents, the correlation between the concrete pore spacing factor and the frost resistance durability factor was revealed by using the automatic analysis and testing instrument for the pore system of hardened concrete. Then, the decision tree method was utilized to propose specific pore spacing factors for different concrete scenarios, including the non-air-entrained concrete, air-entrained concrete, concrete with unqualified frost resistance, and concrete with qualified frost resistance. In cases where the pore spacing factor measurement fell within an ambiguous range, the classification was further refined according to the water-cement ratio. On that basis, the comprehensive range of pore spacing factors for the concrete with a qualified frost resistance was determined. Finally, the post-evaluation method and standard procedure for assessing the frost resistance of concrete entities based on pore spacing factor and water-cement ratio were proposed to verify whether the frost resistance of concrete buildings meets the life expectancy requirements. This method facilitates the evaluation of the frost resistance quality of newly-built concrete projects, as well as the investigation and monitoring of frost resistance in existing structures during service.

ANALISIS FAKTOR-FAKTOR YANG MEMPENGARUHI KEPUASAN KONSUMEN PRODUK SUSU MURNI KPUB SAPI JAYA MENGGUNAKAN METODE REGRESI LINEAR BERGANDA

Customer satisfaction became one major priority for business agent to attract customer buying interest. Customer satisfaction is the feeling of happiness or sadness which appear after buying and comparing the product with other brands. The process of getting good Multiple Linear Regression analysis result in this research, then it has to be examined in these following steps: (1) Testing the validity and reliability of questionnaire measuring instruments. (2) Describing variables of the research. (3) Testing the classical assumptions such as heterokedasticity, multicollinearity, collinearity and normality test. (4) Analyzing Multiple Linear Regression, which includes the F_test (joint test), t_test (partial test), and the coefiicient of detemination (R-squared) test. Identification values of the factors that affect customer satisfaction towards KPUB Sapi Jaya pure milk products obtained from the result of the linear regression equation, where the value of the influence constituent is 2,117 units, the value of the influence of X1. of 0.367 units, the value of influence X3. Product features of 0.671 units, the value of influence X4. The product beauty is 0.259, the value of influence X5. The perceived quality is 0.814 units and the value of influence X6. Service is 0.211 units. Furthermore, the results of the significance test, which significantly affects customer satisfaction of KPUB Sapi Jaya pure milk products, it is concluded that there are 2 factors, the first is product durability factor (X1) and the second is perceived quality factor (X5). Meanwhile 4 other factors are not significant, such as product suitability factor (X2); product features (X3); beauty products (X4) and services (X6).

A Locally Available Natural Pozzolan as a Supplementary Cementitious Material in Portland Cement Concrete

For several decades, class F fly ash has been an attractive supplementary cementitious material, at least in part, due to its ability to reduce Portland cement consumption and mitigate alkali-silica reactions in concrete. However, fly ash availability is becoming uncertain as the energy industry decommissions coal burning power plants as it transitions to renewable energy production. This situation creates a need to identify viable and sustainable alternative supplementary cementitious materials. There are several types of supplementary cementitious materials, such as natural pozzolans, metakaolin, or ground granulated blast-furnace slag, which appear to be potential alternatives to fly ash in concrete. In this research, a locally available natural pozzolan (pumicite) was selected to replace fly ash in concrete. After conducting alkali-silica reaction tests on mortar mixtures, rheological and strength properties, shrinkage, resistance to freezing and thawing, and chloride ion permeability of concrete mixtures containing different amounts of fly ash and natural pozzolan were evaluated. The results showed that pumicite was more effective than fly ash at mitigating the alkali-silica reaction, and a pumicite content of 20% was necessary to mitigate the alkali-silica reaction. Ternary mixtures containing both pumicite and fly ash were the most effective cementitious materials combinations for mitigating the alkali-silica reaction expansion. Additionally, pumicite provided acceptable compressive strength and modulus of rupture values (greater than 4.0 MPa) that exceeded the flexural strengths provided by established mixtures containing only fly ash. Shrinkage and durability factor values for all mixtures were less than 710 μstrain and greater than 75, which are generally considered acceptable. Additionally, all mixtures with acceptable alkali-silica reaction expansions had very low chloride permeability. These results indicate that pumicite can be a reliable alternative for fly ash.

Utilizing halloysite nanotube to enhance the properties of cement mortar subjected to freeze-thaw cycles

This study investigates the impact of the long-term pozzolanic properties of halloysite nanotube (HNT) on the physical and mechanical properties, permeability, durability, and microstructural characteristics of cement mortar subjected to repeated freeze-thaw cycles. For this purpose, the two-year cured samples were exposed to 300 freeze-thaw cycles. Deterioration of the cement mortar surface was visually assessed and regularly quantified by mass loss and length change. Furthermore, helium porosity, electrical resistivity, and ultrasonic pulse velocity (UPV) were performed on cement mortar mixtures to elucidate the effect of repeated freeze-thaw cycles on permeability. In terms of mechanical properties, compressive and flexural strength tests were conducted; static elastic modulus and flexural toughness were also calculated. The frost durability of samples was analyzed using the relative dynamic modulus of elasticity and durability factor as the indexes to assess mortar's freeze-thaw resistance. Moreover, the microstructures of specimens before and after 300 freeze-thaw cycles were analyzed by scanning electron microscopy. Visual comparisons and experimental results demonstrated that the HNT introduction in cement mortars markedly enhances the frost resistance of plain mortar. It leads to the refinement of the cement paste pore structure and a reduction in its porosity due to the nucleating, filling, and long-term pozzolanic effects of HNT. It was found that the contribution of HNT's pozzolanic activity is the most important of these mechanisms. Therefore, less water penetration into the hardened cement composites occurs, which results in higher frost durability. The samples containing 2 wt.% HNT (by weight of cement) exhibited the lowest mass loss, expansion, porosity, and UPV loss due to repeated freeze-thaw cycles. The highest electrical resistivity and residual mechanical strengths also pertained to samples with 2 wt.% HNT. Hence, the HNT replacement dosage of 2 wt.% can be regarded as an optimal content for the cement mortars studied in this work. Finally, the two-way ANOVA revealed that HNT percentage is the factor with the greatest impact on mass loss, electrical resistivity, and compressive strength. In terms of length change, porosity, and flexural strength, the freeze-thaw cycle was the most statistically important factor.

Durability of concrete mixtures containing Iranian electric arc furnace slag (EAFS) aggregates and lightweight expanded clay aggregates (LECA)

This article reports the results of an experimental investigation on novel concrete mixtures containing electric arc furnace slag aggregates (EAFS) and lightweight expanded clay aggregates (LECA), focusing on the durability properties. Six concrete mixtures consist of EAFS-natural-LECA (M-Group) and five mixtures of EAFS-LECA (N-Group) compared with 100% EAFS as reference. Workability and density of the mixtures were studied as fresh properties and compressive strength, as well as durability indexes including the electrical resistivity (RCPT and four-point Wenner test), salt-scaling under freeze and thaw cycles, abrasion resistance (abrasive groove length and wear depth), durability under wet and dry cycles, and durability factor under freeze/thaw cycles. Results showed that application of both LECA and natural aggregates, by maintaining the structural-level strength, leads to density adjustment while increasing the freeze/thaw durability factor, improving dimensional stability and controlling the level of cyclic wet/dry-stains. An average increase of durability factor of M-Group and N-Group comparing to the reference were observed up to about 124% and 63% respectively. The results indicated the positive effects of using natural aggregate and LECA on modifications of reference mixture. Measured abrasive groove length ranged between 20 and 23 mm and the depth of wear ranging from 0.1 to 0.3 mm confirming the improving effects of physical structure of EAFS aggregates. The studied mixtures, namely M6 and N5 with 0.744 kg/m2 and 1.204 kg/m2 exhibited the lowest salt-scaling mass-loss with 31% and 112% increase compared with the reference.

Mechanical and durability performance of concrete with recycled tire steel fibers

The increasing waste tire disposal and the related environmental pollution have led to the further exploration of utilizing recycled-tire steel fiber (RTSF) to replace industrial steel fiber (ISF) for better cost-effective concrete production. This study compares the workability, mechanical properties, and durability of RTSF-reinforced concrete (RSC) to those of commercial ISF-reinforced concrete (ISC). Plain concrete samples, ISC samples named IS05 and IS05R (with 0.5% of ISF by volume), and RSC samples named RS05, RS10, and RS15 with three-volume percentages of RTSF (0.5%, 1.0%, and 1.5%) were prepared accordingly. The results show that RSC has better flowability than ISC when adding the same volume percentage of fibers. In terms of mechanical properties, the addition of RTSF slightly increases the 28-day compressive strength. The splitting tensile strength is also increased by up to 15.4% with the added RTSF, which is very close to the ISF (16.9%). Regarding flexural performance, RS15 samples show a very close enhancing effect to IS05 samples with enlarged residual strength and fracture energy. The ultrasonic pulse velocity test results also indicate that both RTSF and ISF slightly increase the concrete modulus. In terms of durability, RS10 samples reduce drying shrinkage by up to 9.2%, which is better than IS05 samples (6.3%). RTSF also improves the freeze–thaw resistance by reducing the change percentage of relative dynamic modulus and increasing the durability factor by up to 4.6%. Overall, the RTSFs in concrete have a slightly lower mechanical reinforcement and better workability by comparing with one type of thin ISFs. These findings can facilitate the usage of RTSF in concrete mixes as mechanical reinforcements and provide another market for waste tire fiber recycling.

RACBase: A cloud-based database of recycled aggregate concrete durability

This paper presents the first universal cloud-based database of recycled aggregate concrete (RAC) durability, named RACBase. The database collects experimental data on the durability of RAC from published literature all over the globe. Each set of data consists of the literature source, materials information, and the unified test result. The resistance to chloride ion attack, carbonation, sulfate attack, and freeze-thaw for RAC is quantified by the passed electric charge, carbonation depth, compressive strength loss, and durability factor, respectively. Based on the web interface, RACBase provides the functions of searching, adding, acquiring, and storing data, and gives the statistical distribution of data for each durability test. Users can freely access RACBase at https://www.racbase.com and browse and upload their data after online registration. One illustration of building a machine learning model for predicting the chloride resistance of RAC is presented to show the potential application of the database. The extreme gradient boosting model shows superiority to the artificial neural network and random forest models with the R2 of 0.975, RMSE of 246.719, and MAPE of 0.081. RACBase enriches the way for users to conduct in-depth research on the durability of RAC and construct performance prediction models.

Effect of curing conditions on the strength and durability of air entrained concrete with and without fly ash

In cold regions, air entrained concrete has been widely used against freeze–thaw deterioration. This paper studied the influence of curing conditions on the strength and durability of air entrained ordinary portland cement (OPC) and fly ash (FA) concrete. Four different curing conditions including standard curing (SC), air curing (AC), mild temperature curing (MC), and elevated temperature curing (EC) were utilized to cure the cast specimens. The compressive strength at 3, 7, 14, and 28 days was measured respectively. Also, the water absorption, sorptivity, air void system, as well as freeze–thaw durability after 28 days of curing were investigated. Test results suggested that AC condition impeded the strength gain of both concrete, but it affected FA concrete more than OPC concrete. EC condition improved the early-age strength while compromised the later-age strength of OPC concrete, whereas EC condition improved the compressive strength of FA concrete at both early ages and later ages. AC condition has more adverse effects on water absorption as well as sorptivity of FA concrete than those of OPC concrete. EC condition increased the water absorption and sorptivity of OPC concrete, whereas reduced the water absorption and sorptivity of FA concrete. Although the air content in fresh OPC and FA concrete were comparable, FA concrete had less proportion of microvoids (air voids smaller than 300 μm), larger spacing factor but smaller specific surface, regardless of curing conditions. EC condition caused the reduction in air content, the increase of spacing factor, and decrease of specific surface. For both OPC concrete and FA concrete, the four curing conditions produced different freeze–thaw durability factor (DF), but all the specimens passed the failure limit of 60 %. The freeze–thaw test results based on specimens under SC condition may overestimate the DF.

Study on strength and durability characteristics of nano-silica based blended concrete

The present paper highlights on the strength and durability characteristics of blended concrete mixes in different strengths of concrete. A lot of research is being carried out all over the world on various supplementary cementitious materials (SCMs) using various combinations which could be best suitable to achieve strength and durability aspects. Very few emphasized on the usage of Nano-silica as one of the SCMs along with other materials in producing blended concrete mixes. Three SCMs were used in the present study namely fly ash, ground granulated blast furnace slag and Nano-silica as a partial replacement material of cement in various proportions to assess the performance of nano-silica in the development of blended concrete mixes. The great advantages in terms of environmental and economic aspects is the utilization of these three materials (since two of these materials are industrial by-products) point of view. The inclusion of Nano-silica as a SCM up to certain extent can enhance mechanical and durability properties of concrete. Concrete compressive strength increases as the content of Nano-silica increases. Nano-silica has a very high pozzolanic activity. Filling effect of Nano-silica notably influences the refinement of pore structure. The durability properties of blended cement concrete mix were examined by immersing the specimens to HCl and H2SO4 at 5% concentration. Acid Mass Loss Factor (AMLF) and Acid Strength Loss Factor (ASLF) and acid durability factor (ADF) were determined and the results were compared with control mix. Rapid Chloride penetration test (RCPT) on control mix and blended cement concrete were performed to assess the short term chloride ions penetration. From the results, it was shows that the practice of these mineral admixtures is having a beneficiary role on the strength as well as the durability properties. The results indicated that the utilization of these materials as a partial replacement of cement have significantly improved the compressive strength of blended concrete mix in by 36.91%, 27.82% and 19.35% in 29.58 ​MPa, 51.40 ​MPa and 72.33 ​MPa. The results indicated that there is a significant improvement in the mechanical properties, shown better resistance in acid environment and chloride ion penetration.

Data-Based Statistical Analysis of Laboratory Experiments on Concrete Frost Damage and Its Implications on Service Life Prediction.

To meet the requirements of durability design for concrete suffering frost damage, several test standards have been launched. Among the various damage indexes such as deteriorated compressive strength, relative dynamic elastic modulus (RDEM), residual deformation, etc., the concept of a “Durability Factor” (DF) is proposed by many standards to define the frost resistivity of concrete against frost action based on the experimental results from standard tests. Through a review of the literature, a clear tendency of strength/RDEM decay and residual deformation increase is captured with increasing cycles of freezing and thawing. However, tests following different standards finally derive huge scattering quantitative responses of frost resistance. Based on the large database of available laboratory experiments, this study presents a statistical analysis to propose a predictable model to calculate the DF with respect to other material factors. The statistical model is believed to be more convenient for engineering applications since the time-consuming experiment is no longer needed, and it is more precise compared with that developed according to only single experimental results to cover the uncertainties and unavoidable errors in specific tests. Moreover, the formula to calculate the DF is revised into a more general form so as to be applicable for all the laboratory experiments even for those cases without fully following the standards to derive a DF value.

Performance of Treated Soft Clay with Nano-Modified Cementitious Binders at Reference and Cold Temperatures

Lime is considered the preferred choice for the treatment of the high plasticity clayey soils; however, for environmental concerns (quality of water and vegetation), it is prohibited in many regions, including Manitoba, Canada. Hence, it is imperative to find a suitable treatment alternative that provides an optimal solution for such a problematic soil type during different periods of the construction season. Hence, improvement of problematic/weak soils such as soft clay by nano-modified cementitious additives was tested under normal and cold conditions. This approach may significantly impact the construction of roads/pavements in cold regions. This current study focused on investigating the effects of single, binary, and ternary cementitious systems, comprising General Use cement (0–15%) with/without slag (0–15%), and nano-silica (0–3%), on the properties of soft clay (Type A7/CH) under reference (22 ± 2 °C) and cold temperatures (+ 5 °C). The mechanical performance of the control and treated mixtures were tested in terms of California Bearing Ratio (CBR) as well as unconfined compressive strength at 7, 28, 56, and 91 days of curing, while the durability properties were assessed based on the resistance to freezing–thawing cycles [durability factor (DFF/T)]. Moreover, thermogravimetry and scanning electron microscope analyses were conducted to corroborate the trends of the aforementioned tests. In comparison to the untreated clay, increasing the binders’ content significantly enhanced the mechanical/durability properties of the soil treated herein. The ternary mixtures comprising cement, slag and nano-silica showed the highest mechanical and durability properties at both reference and cold temperatures. Its CBR, 7-day compressive strength, 28-day compressive strength, and DFF/T were 46.3 and 31.6%, 700 and 562 kPa, 1349 and 891 kPa, and 94 and 71%, respectively. Such mixtures may present a viable option for soft clay stabilization at low temperatures, thus contributing to extending construction activities during fall and spring periods in cold regions.

The Study on Blast Furnace Slag on Different Conditions as Curing Condition and Blaine Value Ratio Influence Improving Strength Performance

The sustainable building aims to minimize environmental impact by reducing carbon dioxide pollution by using by-products. Concrete materials are well-known for being the most extensively used construction material. Carbon dioxide emissions are the permissible greenhouse gas emissions that would have an impact on the long sustainability. Blast furnace slag reduces carbon dioxide emissions as an environmentally responsible building material, and sustainable steelmaking aims to minimize waste. Steel corrosion and chloride damage are several of the most apparent problems for concrete structure durability. Incorporating BFS into the cement is beneficial for concrete durability as the Structures' serviceability increased. This study aimed to explore the material properties and compressive strength of BFS mortar while considering the replacement ratio, Blaine fineness of the BFS, and curing conditions. This study mainly discovered that substituting BES for cement in the mortar increased the compressive strength and durability factor, indicating that the material's properties depend on the BFS, based on the experimental results, which cover the materials properties and salt preventive property. The low water-to-binder ratio (W/B) of the BFS-blended cement mixture is the reason for this. The study reported that the investigation of salt preventive by adding BFS with a low Blaine fineness and average substitution ratios (45%) could improve the compressive strength of BFS mortar samples. These mortar samples were even more resistant to carbonation, which could also be attributed to the hydration products of BFS.

Asbestos cement materials: impacts on the use and waste generation in Brazil

This article updates data on consumption of chrysotile (white asbestos), in the global and national context, and presents an estimate of the amount of MCA in use in the country; discusses situations of risk to health and the environment, due to the release of chrysotile fibers, and proposes warnings for their use; questions waste disposal routes at the end of life. For the global update, the evolution of the market and ban were researched, by collecting data on domestic consumption of chrysotile, from 1998 (period of permission to use) to 2017 (year of ban), the generation of asbestos-cement waste (RCA) (2012 to 2017), as well as the percentage of fibers per composite and durability factor. There was a significant difference between the average annual production of MCA (1.38 million t) and the generation of RCA (17 thousand t), evidencing a large amount in use and that the installed capacity of class I landfills in the country is below the projected RCA demand. Considering aspects of reuse, maintenance, pollution, and climatic actions, in addition to situations associated with the construction characteristics of low-income housing with asbestos-cement tiles (TCA), hazards were identified for residents due to the possibility of inhaling asbestos fibers. These situations require adequate management of the MCA and RCA, with routes for treatment and recovery, mapping of areas of use, monitoring and preventive actions, such as measuring the concentrations of fibers/cm³ in the environment, and creating technical instructions for training the hands of work for safe removal and disposal with a view to reducing risk to the health of the exposed population.

Effect of nano silica on frost resistance of pervious concrete

The performance of Portland cement pervious concrete (PCPC) was evaluated in the lab, focusing on freeze–thaw(F/T) durability. The effects of nano-silica (NS) and superplasticizer (SP) on the performance of PCPC were investigated in various mixes. Two water to binder(w/b) ratios of 0.34 and 0.30 were investigated to address the varied behaviors of PCPC generated in the lab. Four concrete mixes with and without NS were prepared in this study, with 3 percent nano-silica by weight of cement is included in the mix. The freeze–thaw test was conducted as per ASTM C 666/C 666M – 03 standards on the samples. Various parameters like Compressive strength, percentage weight reduction, the density of specimens, and ultrasonic pulse velocity (UPV) for cubes were measured. The modulus of elasticity using the UPV and the relative modulus, durability factor was also calculated. The results observed showed that previous specimens with nano-silica performed better resistance against F/T cycles than those of the control mix specimens. The durability factors observed are greater than 70% for nano silica added pervious mixes.

Experimental investigations on durability properties nano-silica based concrete

With increasing amount of research being diverted to nanotechnology has gained major attention with its potential uses of particles. Nano silica is a fine convergent material. The present study aims to investigate the acid resistance of M40.M50, M60 grades of concrete and the influence of nano silica in it.The replacement of cement by nano silica should considerably reduce the CO2 foot print of concrete.The casts of concrete cubes with the sizes of 100mm×100 mm×100 mm and with individual grades of M40.M50, M60 were prepared and cured for 28 days. After this stipulated period of 28 days of water curing, samples of definite number were immersed in the chemical solutions of 5% sulphuric acid, hydrochloric acid, sodium sulphate separately and was exposed for a specific time of 28, 90 and180 days respectively. This paper is aimed to investigate the influence of Acid, Chloride, Alkali attack resistance on M40, M50, M60 grades of concrete and to compare their performance with conventional concrete in terms of weight loss and compressive strength. It is noticed that the weight loss and percentage loss in compressive strength in the situation of Nano silica concrete cubes with the grades M40. M50, M60 is less when compared to ordinary concrete. when submerged in 5% of H2So4, Na2So4, HCl for 28, 90 and180 days respectively. There was an increase of durability factor for a period of 28 days, 90 days,180 days for all grades of Nano silica concrete. The principal outcome of a present research stated that nano silica has enhanced strength and durability properties.

Durability and Self-Sealing Examination of Concretes Modified with Crystalline Waterproofing Admixtures.

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete’s overall freeze–thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze–thaw cycles, concrete mixes containing CWA—even non-air-entrained ones—showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix—due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate.