Water Binder Research Articles

Study on Static Mechanical Properties and Numerical Simulation of Coral Aggregate Seawater Shotcrete with Reasonable Mix Proportion

This study aims to explore the static mechanical characteristics of coral aggregate seawater shotcrete (CASS) using an appropriate mix proportion. The orthogonal experiments consisting of four-factor and three-level were conducted to explore an optimal mix proportion of CASS. On a macro-scale, quasi-static compression and splitting tests of CASS with optimal mix proportion at various curing ages employed a combination of acoustic emission (AE) and digital image correlation (DIC) techniques were carried out using an electro-hydraulic servo-controlled test machine. A comparative analysis of static mechanical properties at different curing ages was conducted between the CASS and ordinary aggregate seawater shotcrete (OASS). On a micro-scale, the numerical specimens based on particle flow code (PFC) were subjected to multi-level microcracks division for quantitive analysis of the failure mechanism of specimens. The results show that the optimal mix proportion of CASS consists of 700 kg/m3 of cementitious materials content, a water–binder ratio of 0.45, a sand ratio of 60%, and a dosage of 8% for the accelerator amount. The tensile failure is the primary failure mechanism under uniaxial compression and Brazilian splitting, and the specimens will be closer to the brittle material with increased curing age. The Brazilian splitting failure caused by the arc-shaped main crack initiates from the loading points and propagates along the loading line to the center. Compared with OASS, the CASS has an approximately equal early and low later strength mainly because of the minerals’ filling or unfilling effect on coral pores. The rate of increase in CASS is swifter during the initial strength phase and decelerates during the subsequent stages of strength development. The failure in CASS is experienced primarily within the cement mortar and bonding surface between the cement mortar and aggregate.

Optimizing compressive strength of quaternary-blended cement concrete through ensemble-instance-based machine learning

Optimizing the composition of concrete, particularly when incorporating ordinary Portland cement (OPC) along with supplementary materials such as ground granulated blast furnace slag (BF), fly ash (FA), and silica fume (SF), poses challenges due to the intricate nonlinearity inherent in concrete properties. Addressing this challenge has urged growing interest in employing Machine Learning (ML) techniques for precise property assessment. In this investigation, various predictive models, encompassing eXtra Gradient Boosting (XGB), random forests (RF), and K-Nearest Neighbor (KNN) algorithms were formulated to predict the compressive strength (CS) of ternary-blended concrete incorporating OPC, BF, FA, and SF. Through comprehensive analysis of an extensive dataset comprising 810 distinct records, the study identifies optimal concrete blends, providing invaluable insights for practical applications. Evaluation of ML models underscores the superior performance of XGB, with a coefficient of multiple determination (R2) values of 0.923 and 0.997 for training and testing datasets, respectively, indicative of exceptional predictive accuracy. Additionally, SHAP values underscore the importance of input age, water–binder ratio, and OPC content. This research enhances understanding of ternary-blended concrete characteristics, offering practical implications for construction practices and laying a foundation for future research endeavors to refine ML models, explore attribute interactions, and optimize concrete constituent proportions for broader civil engineering applications.

Predicting corrosion behaviour of steel reinforcement in eco-friendly coral aggregate concrete based on hybrid machine learning methods

ABSTRACT This study proposes a machine learning-assisted method for assessing steel reinforcement corrosion, utilising data on chloride ion concentration (CIC) and chloride ion concentration threshold (CCT) from eco-friendly coral aggregate concrete (EFCAC). A total of 2185 data points were collected to establish the EFCAC-CIC database. A multi-objective slime mould optimised support vector regression (MOSMA-SVR) model for EFCAC-CIC was developed. The significance of each feature to EFCAC-CIC was analysed. Subsequently, a graphical user interface (GUI) was developed based on the MOSMA-SVR model. Finally, the GUI and EFCAC-CCT were used to assess the corrosion behaviour of reinforcement. Results indicate that the MOSMA-SVR model provides predictions that are closer to the actual values, with smaller mean errors and standard deviations. The performance indicators, including coefficient of determination, mean absolute error, mean absolute percentage error, mean square error, root mean square error, and a20-index, of the MOSMA-SVR model are 0.987, 0.0124, 0.0332, 2.91e − 4, 0.0171 and 0.9991, respectively, and they are superior to those of the other tested models. The water type and the water–binder ratio are identified as the two most critical factors. Furthermore, by integrating the GUI and feature importance analysis results, chloride salt-resistant EFCAC can be designed. When this is combined with the GUI and EFCAC-CCT, the corrosion of rebar in EFCAC can be assessed in real time.

Mechanical Performance Optimization and Microstructural Mechanism Study of Alkali-Activated Steel Slag–Slag Cementitious Materials

The optimal proportion of alkali-activated steel slag–slag cementitious materials is investigated by considering the combined effects of steel slag content, alkali content, water glass modulus, and water–binder ratio using the Box–Behnken design in response surface methodology. Qualitative and semi-quantitative analyses of X-ray diffraction (XRD) patterns and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) images are conducted. The microstructural mechanism is elucidated based on the chemical composition, surface morphology, and microscale pore (crack) structures of the samples. A microreaction model for the alkali-activated steel slag and slag is proposed. The optimal composition for alkali-activated steel slag–slag cementitious materials is as follows: steel slag content, 38.60%; alkali content, 6.35%; water glass modulus, 1.23; and water–binder ratio, 0.48. The strength values predicted by the response surface model are p1d = 32.66 MPa, p7d = 50.46 MPa, and p28d = 56.87 MPa. XRD analysis confirms that the compressive strength of the sample is not only influenced by the amount of gel formed, but also, to a certain extent, by the CaCO3 crystals present in the steel slag, which act as nucleation sites. The SEM-EDS results confirm that the gel phase within the system comprises a hydrated calcium silicate gel formed through the reaction of volcanic ash and geopolymer gel formed through geo-polymerization. Analysis of the pore (crack) structure reveals that the compressive strength of the specimens is primarily influenced by porosity, with a secondary influence of the pore fractal dimension.

Preparation and performance influencing factors of sludge-based non-sintering ceramsite foam concrete block

In this study, the preparation of ceramsite foam block using Sludge-based Non-sintering Ceramsite (SNSC) was investigated through orthogonal test and performance optimization test to investigate the effects of different coal fly ash addition, volume ratio of SNSC, water binder ratio and sodium silicate concentration on the performance of the concrete block, and the optimal material mixing ratios were obtained as follows: cement was 400 kg/m3, coal fly ash was 100 kg/m3, SNSC was 371 kg/m3, water binder ratio was 0.43, CaCl2 was 10 kg/m3, and Na2SO4 was 5 kg/m3. The performance of Sludge-based Non-sintering Ceramsite Foam Concrete Block under these conditions meets the specification requirements of GB/T 36534–2018 "Ceramsite Foam Concrete Block". Its compressive strength was 7.76 MPa, dry bulk density was 948.7 kg/m3, the water absorption was 20.75 %, and the softening coefficient was 0.861. XRD and SEM analyses revealed that the internal physical phase of the concrete blocks under the optimal conditions was tightly bonded, with fewer and uniformly distributed pores, and that the hydration generated C-S-H, C-A-H gel-like substances, calcium alumina (AFt), and hydrated calcium chloroaluminate generated by hydration could significantly improve the physical and mechanical properties of concrete blocks.

Compressive performance and analytical modeling of early strength seawater sea sand engineered cementitious composites

Early strength seawater and sea sand engineered cementitious composites (ESSECC) are novel fiber-reinforced cementitious composites that exhibit strain-hardening behavior and a high early strength. The compressive properties of ESSECC with different polyvinyl alcohol (PVA) fiber content, carbon nanotubes (CNTs) content, and water–binder ratios were investigated at different curing ages in this study. Experimental evaluations were conducted to assess compressive strength, elastic modulus, Poisson's ratio, peak strain, energy dissipation capacity, toughness index, and stress-strain curves. The experimental results showed that early strength of ESSECC reached 58.0 %, 81.6 %, and 86.7 % of its 28-day compressive strength after 2 h, 3 days, and 7 days of curing, respectively. An increase in the PVA fiber volume fraction from 0 to 2 % resulted in a 32.8 % increase in average peak strain. Incorporating 0.15 % CNTs into ESSECC led to an average enhancement of compressive strength by 7.2 %. Based on these experimental results, an analytical model considering the effects of curing age and the addition of PVA fibers and CNTs was developed to describe the compressive stress–strain behavior of ESSECC. This model showed strong consistency with the experimental results.

Capillary water absorption and free shrinkage characterization for seawater sea-sand concrete

The durability of seawater sea-sand concrete (SSC) and/or sea-sand concrete (SC) structures exposed to harsh marine environments is crucial to their service life. In this study, we investigated the capillary water absorption of SSC, SC, and ordinary concrete (OC) with different water–binder ratios (i.e., 0.38 and 0.28) in deionized water and composite saline solutions. The results showed that the cumulative water absorption of OC, SC, and SSC in the composite saline solution were lower than that in deionized water. In deionized water, the cumulative water absorption of OC is the largest, followed by those of SC and SSC. However, in composite saline solution, the cumulative water absorption of the three types of concrete with a low water–binder ratio at less than 6 h was similar; after that, SSC exhibited the highest absorption, followed by SC and OC. Moreover, the initial water absorption rate in deionized water was approximately four times higher than that in the composite saline solution. In contrast, for concrete with a low water–binder ratio, the secondary water absorption rate (after 6 h) was approximately two times lower in deionized water than in the composite saline solution. The free shrinkage of the three concrete types have been measured up to the age of 210 d. The results showed that under the same curing age, the shrinkage strain of OC was the largest, followed by those of SC and SSC. Based on the GL2000 model, a new prediction model for the shrinkage of SSC and/or SC was established by introducing an expansion effect coefficient. The proposed model could accurately predict the development of the shrinkage strain in OC, SC and SSC.

Microstructure and chloride transport of aeolian sand concrete under long-term natural immersion

Abstract River sand was consumed in large quantities, and alternatives to river sand were urgently needed. There are a large number of natural resources of aeolian sand in western China. Aeolian sand was prepared into aeolian sand concrete (ASC). It can greatly reduce the consumption of river sand and inhibit the process of desertification to protect the environment. ASC is a new type of concrete material prepared by using aeolian sand as fine aggregate. To clarify the chloride ion transport behaviour in the ASC under long-term natural immersion, the aeolian sand was 100% substituted for the river sand to prepare the full ASC with three water–binder ratios. The ASC was naturally immersed in 3 and 6% NaCl solutions for a long time, and nuclear magnetic resonance and microscopic scanning electron microscopy techniques were used. The change rule of chloride ion content at different depths of the ASC was studied, and its microstructure characteristics under different erosion times were analysed. The results showed that the free chloride ion concentration at different depths of the ASC increased with increasing water–binder ratio, immersion time, and chloride concentration. After soaking in the salt solution, the hydration products in the ASC reacted with chloride ions to form Friedel salt, which filled the internal pores and microcracks of the ASC, improved its interface transition zone structure, and increased the compactness of the test piece. The porosity of the three groups of ASC with different water–binder ratios decreased by 0.95, 1.03, and 1.15% after soaking in 6% salt solution for 12 m. To study the diffusion law of chloride ions in ASC, combined with influencing factors such as temperature, humidity, D value, deterioration effect and chloride ion combination, Fick’s second law was modified, and a chloride ion diffusion model of ASC with high accuracy was established, with a fitting correlation number above 0.93, which provided a reference for the research and application of ASC in saline areas.

Mechanical Properties and Durability of Sustainable UHPC Using Industrial Waste Residues and Sea/Manufactured Sand

Abstract Considering the continuous development of sustainable development, energy saving, and emission reduction concepts, it is very important to reduce concrete’s cement content in order to improve its environmental impact. Using a reactive admixture to replace part of the cement in ultra-high-performance concrete (UHPC) can effectively improve the overall performance of the concrete and reduce carbon dioxide emissions, which is an important aspect of environmental protection. Here, industrial waste residue (fly ash and slag), sea sand (SS), and manufactured sand (MS) were used to produce UHPC under standard curing conditions to reduce the material cost and make it more environmentally friendly and sustainable. The effects of water–binder ratio, contents of cementitious materials, types of sands, and content of steel fibers on the mechanical performance of UHPC under standard curing were investigated experimentally. In addition, evaluations of the impermeability, chloride, and freeze-thaw resistance of various UHPCs produced were conducted by investigating the effects of various factors on the depth under hydraulic pressure and electric flux of UHPC, as well as the mass loss, relative dynamic modulus of elasticity, flexural strength, and compressive strength of UHPC specimens after freeze-thaw cycles. The obtained experimental results show that the SS-UHPC and MS-UHPC prepared by standard curing exhibit high strength, excellent impermeability, and chloride resistance. The frost-resistant grade of all groups of UHPCs prepared by standard curing was greater than F500 and had excellent freeze–thaw resistance, including those produced with local tap water or artificial seawater. The investigation presented in this paper could contribute to the production of new low-cost and environmentally friendly UHPCs and accelerate the application of UHPC in engineering structures.

Defect Detection in Grouting Sleeve Grouting Material by Piezoelectric Wave Method

The construction defects in grouting sleeves can jeopardize the safety of precast reinforced concrete structures. Thus, efficient and accurate defect detection is critical in engineering construction. In this paper, a defect detection method based on piezoelectric wave theory was proposed. Two piezoelectric ceramics were arranged within the grouting sleeve. One piezoelectric ceramic was affixed on the top of the steel bar, while the other was embedded in the grouting material, serving as the driver and sensor, respectively. The compactness defects, air cavity defects, steel anchoring defects, and water–binder ratio defects were set in the grouting sleeves, and the trends in time domain signals and signal evaluation indicators based on the wavelet packet total energy value (WPTEV) of different specimens were investigated. Based on the WPTEV, the evaluation index (EI) was proposed. In addition, the effect of the grouting material’s age on the piezoelectric wave signal was verified. Furthermore, the influence of grouting material defects on signals was simulated in ABAQUS, and the time domain signals and wavelet packet energy of sensor signals for specimens with varying defect dimensions were evaluated. The results showed that: (1) The defects in the grouting materials reduced the stress waves propagated through the grouting materials, resulting in a decrease in attenuation and an increasing trend in the signal; (2) The peak-to-peak values of piezoelectric ceramic sensors and the WPTEV of the signal increased with the degree of defects, and the WPTEV was more pronounced. For specimen M68, the WPTEV was 3.3 times that of the healthy specimen, however, the peak-to-peak value was only 2.3 times that of the healthy specimen; (3) The degree of defects was accurately determined by the defect evaluation index (EI) based on the WPTEV; (4) The signal was significantly attenuated with the increase in the age of the grouting material, especially in the first three days, and finally the signal achieved a stable value; (5) The numerical simulation indicated that the defects in the length and thickness of the air cavity in the grouting material were efficiently detected by the proposed piezoelectric arrangement in this study.

Mixing approach for 3D printable concrete: method of optimisation of superplasticiser dosage

This study is a systematic investigation of superplasticiser (SP) addition methods and optimum SP dosage with various water-to-binder ratios (w/b) for mixing three-dimensional printable concrete. In this study, five distinct strategies were adopted to arrive at the optimum method of addition. In the first strategy, a random mixing approach was applied to identify, through visual observation, methods for adding SP with varying time patterns. Secondly, a constant time pattern was adopted from the random approach for mixing and the optimal SP dosage was determined. In the third strategy, different methods of adding the optimum SP dosage were examined. In the fourth strategy, the batching effect of the material with the optimum SP dosage was assessed. Finally, the printable regions with different values of w/b and SP dosages were correlated. It was observed that the optimum SP dosage, in the range of 0.10–0.21% of binder, with w/b = 0.21–0.25 achieved adequate printability parameters by full addition of SP following a constant wet mixing time as the optimal application. However, after applying the optimum SP dosage, a supplemental SP dosage is required at appropriate intervals to retain the workability for higher batches.

Characterization of different types of silica-based materials

Waste glasses based on silicon dioxide (silica) belong to one of the most demanded secondary raw materials. Besides the glass industry, with strict requirements for source materials, silica-based granular materials from waste glasses are considered suitable for use as fillers in alkali-activated cement-based composites. However, due to variations of ground waste glass powder composition and properties a comprehensive characterization is often needed. This study investigated commercially available silica-based powders by scanning electron microscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and Fourier transform infrared Raman spectroscopy, zeta-potential and pH measurements, etc. The differences found in the non-silica impurities composition and structure of SiO2 particles (amorphous vs crystalline) were considered as determinative factors that will affect particles’ interaction with water and cement binder. The observed results provide a fundamental background and will contribute to a better understanding and explanation of the silica-based secondary raw materials interaction reactions in concrete or mortar.

Early mechanical properties and strength calculation method of slag-based alkali activated concrete

The use of slag-based alkali-activated concrete (AAC) could effectively address the issues of resource extraction and carbon emissions caused by traditional Portland cement. In this study, the effects of the fly ash content, water–binder ratio, and alkali activation modulus on the early mechanical properties of AAC were investigated. A total of 105 cube specimens (35 sets) were designed and subjected to compressive strength tests, scanning electron microscope tests, and x-ray diffraction composition analysis. The results indicated that excellent early strength was observed in AAC, with a compressive strength reaching ∼90% of the 28th day strength before 14 days. An increase in the fly ash content and a decrease in the water–binder ratio significantly improved the compressive strength within the same age period. The impact of a lower alkaline activation modulus on strength was found to be insignificant. Based on the experimental results, a calculation method and a constitutive model for early strength were proposed, and the theoretical values exhibited a high level of agreement with the measured values.

Strength development and self-desiccation of saline cemented paste backfill.

Given that many mines around the world are located in areas where fresh water is scarce, and companies are being held to increasingly stringent sustainability and environmental responsibility standards, many mines are looking to use locally available saline groundwater or seawater as mixing water in cemented paste backfill (CPB). However, the impacts of this decision on key engineering properties of CPB (e.g. strength and self-desiccation) that affect its mechanical stability need to be better understood to allow confident selection of this practical and more sustainable solution. Thus, the effect of mixing water salinity and binder type on the strength (unconfined compressive strength, UCS) development and self-desiccation (measured by suction and volumetric water content) of CPB is explored in this research. NaCl concentrations from 0 to 300g/L were used in CPB made with silica tailings and Portland cement type I (PC). Concentrations of 10 and 35g/L were found to moderately increase UCS, while a concentration of 100g/L had comparable UCS to non-saline CPB and a concentration of 300g/L was found to significantly decrease UCS over all curing times. The overall trend is 10g/L > 35g/L > 0g/L > 100g/L > 300g/L. The UCS of the 60-day-old CPB with a NaCl of 300g/L is significantly lower, registering a 26% decrease compared to the UCS of the 60-day-old CPB without salt. In contrast, the UCS of the 60-day-old CPBs containing 10g/L and 35g/L of salt exhibits a notable improvement, being 15% and 10% higher, respectively, than the UCS of the 60-day-old CPB without salt. Water content and suction monitoring were conducted up to 28days of curing time, and it was found that suction only slightly contributed to UCS gain of the saline CPB, and high salt contents (100 and 300g/L) significantly inhibited the self-desiccation ability of CPB due to inhibition of cement hydration by the excessive amount of salt. The increase in strength of both saline and non-saline samples was attributed primarily to the increase in cement hydration products, while the increased strength of the samples with salinities of 10 and 35g/L was mainly attributed to the enhancement of the binder hydration due to the low amount of salt and the presence of Friedel's salt in the pores. The effect of PC replacement by 25 to 75% with slag on CPB with 35g/L mixing water salinity was also studied. Slag replacement of 50% and higher resulted in significantly higher UCS over most curing times. Suction likely moderately contributed to UCS of the saline CPB with slag, in addition to the presence of Friedel's salt in the pores and the acceleration of cement and slag hydration by the presence of NaCl.

Performance evaluation of marble powder and fly ash concrete for non-structural applications

This research was carried out to produce non-structural concrete by utilizing the maximum quantity of marble powder without compromising the strength and durability. Low-strength concrete is often regarded as non-structural for its various non-load bearing applications. This type of concrete has a huge volume of consumption in construction. However, it needs to be addressed in mainstream research. Concrete production consumes a large amount of non-renewable material and can be reduced by utilizing industrial by-products, namely marble powder and fly ash. The objective of the study is to explore the maximum potential utilization of marble powder to produce non-structural low-strength green concrete. Generally, low-strength concrete is prepared with a higher water binder (w/b) ratio, which has the potential for utilization of high-volume powder material. Therefore, marble powder concrete mixes without and with 15 % fly ash are prepared with a w/b ratio of 0.5, 0.7, 0.85, 1.0, and 1.15. Different quantities of marble powder were added into the mixes to maintain powder content of 350 kg/m3, 550 kg/m3, 750 kg/m3, and 950 kg/m3 in all w/b ratios. This study evaluates the effect of marble powder on mechanical and permeability properties and economic and natural resource saving. In higher w/b ratios, the conventional permeability (DIN 1048) test method is not helpful as water completely percolates the samples. Therefore, a new test method was used to assess water permeation. The result reveals that marble powder utilization improves cohesivity, making it easier to control workability. It reduced the permeability, so the time of water penetration was delayed. The cost of the concrete is reduced by 10 % due to marble powder, saving about 40 % of aggregates. A higher quantity of marble powder utilization up to 794 kg/m3 is possible at the higher water-cement ratio, making the mix producible and feasible for non-structural concrete applications.

Compressive and flexural strength of cement mortar blended with cassava peel ash and high-range water-reducing (superplasticizing) admixtures

This paper presents the outcome of an experiment carried out by using cassava peel ash (CPA) of varying quantities to partially replace cement in mortar mix and the influence of adding superplasticizer in the mortar mix is further investigated. The experiment was carried out by partially replacing CPA in the range of 0 to 25 percent by weight of cement at 5% intervals. A water binder ratio (w/b) of 0.5 and superplasticizer dosage of 1.5l/100kg were used to produce the blended mortar of mix 1:3. The samples were cured and tested for compression and flexure at 7, 28, and 90 days after demolding. The results of the first experiment confirmed the suitability of the cassava peel ash (CPA) at not more than 15% replacement with cement for mortar and concrete works. In the second experiment, the superplasticizer has a linear relationship with the conventional mortar while the blended cement-cassava peel ash (CCPA) mortar retarded in strength at an early stage. However, 5% CPA mortar with superplasticizer gained 52 percent strength from 7 days to 28 days of the test. In addition, at the 90-day test, 5% CPA mortar with superplasticizer has almost an equivalent strength (96%) of the conventional mortar with superplasticizer. The flexural strength for blended CCPA mortar of 5-15% showed an acceptable value with that of mortar with a superplasticizer. Generally, the addition of admixture to the blended CCPA mortar showed a different trend compared to the conventional mortar.

Research on the development of green foaming fluid and the improvement in the performance of foamed cement

The promotion of green foamed cement in engineering aligns with the double carbon strategy and sustainable development goals. The impacts of different foaming materials, their concentrations, the water–binder ratio, the foam–grout ratio, and the mineral powder on the slurry performance of foamed cement were investigated. Orthogonal and comprehensive tests were conducted to examine these factors. The results demonstrated that surface active agent molecules formed an interfacial film with mechanical strength, significantly enhancing the strength and uniformity of green foam. Although the density of green foamed cement was similar to that of commercial foamed cement, its compressive strength at 28 d was three times higher, reaching 8.07 MPa. Scanning electron microscopy observations revealed that the green foamed cement mainly featured 0–0.2-mm-diameter pores with independent pore spaces and thick pore walls, which could be improved by using surface active agents. Moreover, the production price per cubic meter of green foamed cement was 79.56 RMB lower than that of ordinary cement. In brief, the research indicated that the application prospects for green foamed cement are promising due to its performance and economic benefits.

Investigation on Tensile and Flexural Behaviour of Fibre Reinforced Concrete Using Artificial Neural Network

<p>The purpose of this study is to investigate the impact that using marble sludge powder as a partial replacement for cement in concrete can have. Experiments were conducted to investigate a variety of characteristics of fiber-reinforced concrete using both fresh concrete and concrete that had been allowed to solidify. In order to determine the split tensile and flexural property of FRC, two water binder ratios, such as 0.35 and 0.40, as well as percentage re-placements of 0%, 5%, 10%, 15%, 20%, and 25% of marble sludge powder and 0.5% of polypropylene 3S fibre were used. After curing for 7, 14, 28, and 56 days, the samples were put through a battery of mechanical tests to evaluate their qualities. The flexural strength and split tensile strength of the material were evaluated over the course of this investigation. In the end, an artificial neural network, also known as an ANN, was utilised in order to create a prediction model for split tensile and flexural strength. We displayed the experimentally obtained Split Tensile Strength and Flexural Strength against the regression analysis strength after 56 days for ANN. This was done so that we could compare the two. According to the findings of the experiments, using powder made from marble waste might lessen the damage that concrete causes to the environment while also providing economic benefits. In this study, dependable mechanical strength was developed by the use of a feed-forward back-propagation neural network, which consisted of eight input neurons, two hidden neurons, and one output neuron. According to the findings, it was discovered that the mechanical properties of concrete might be improved by using dry marble sludge powder as a substitute for up to 15% of the normal aggregate.</p>

Pengaruh Suhu dan Waktu Ekstraksi dalam Proses Pembuatan Pektin dari Kulit Buah Sukun dengan Pelarut Asam Sitrat

The breadfruit rinds has never been used, even though breadfruit rinds is known contain pectin which has a high economic value. Pectin is a biopolymer compound that functions as a water binder or liquid thickener obtained through the extraction process of fruits waste. The purpose of this research is to utilize the waste of breadfruit rinds into pectin to increase the economic value. This research used reflux extraction method with 7% citric acid as solvent, extraction time used was 170, 175,180, 185, and 190 minutes at 85, 90, and 95°C. The highest research results were obtained at a temperature of 95°C with a long extraction time of 195 minutes, namely yield of 40,762%, water content of 1,92%, methoxyl content of 8.06%, galacturonic content of 81%.

Measurement and modelling of the moisture distribution in early-age concrete in the joint of composite beam and hollow core slab

The building moisture in concrete can damage the surface material if applied too early before the excess moisture has dried out. The composite beam forms an abnormal structure at the joint of the hollow-core slab, in which the thickness of the structural concrete is almost the thickness of the entire slab. For this reason, the joint of the beam and hollow core slab must be taken into account when assessing the adequate drying of concrete structures. The considered composite beams are steel casing beams, which are casted full of concrete. To achieve a composite structure, there are holes in the sides of the casing, through which moisture from the concrete transfers to the surrounding structure. However, the drying of the concrete inside the beam is significantly limited. The level of relative humidity of the concrete inside the beam remains moderately high for a long time, depending on the quality of the concrete and, consequently, the self-desiccation of the concrete. When using concrete with a low water binder ratio, drying occurs at a level of about 85%RH as a result of self-desiccation. In the study, relative humidity in the joint was measured continuously and with instantaneous measurements. The relative humidity in the joint concrete was also monitored after the surface structure layers were installed. In addition, humidity was measured from below the surface material and continued until equilibrium was reached. The structure was simulated as a 3D model and studied using a concrete material model which takes into account the self-desiccation and the thermal dependence of the sorption. A good agreement was found to describe the effect of temperature changes on the relative humidity of concrete that can be observed in continuous measurement. In addition, a suitable prediction of relative humidity below the surface material can be achieved based on modelled relative humidity distribution before the installation of the surface structure.