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The Cu-MOF has outstanding catalytic activity because of its capacity to buffer oxygen. As a result, when added to diesel fuel, this additive reduces nitrogen dioxide emissions while also oxidising hydrocarbon emissions. The current study examines the impact of Cu-MOF nanoparticles on diesel engine efficiency and emissions. The SEM, and XRD methods were utilised to characterise the nanoparticles of Cu-MOF, which were generated by chemical approach. In a two-step method, Cu-MOF was combined with diesel using a conventional ultrasonic shaker in order to get a stable suspension, Extensive experiments using ASTM-standard testing procedures have also examined the impact of nanoparticles on several physicochemical parameters of diesel fuel. For the purpose of examining the impact of nanoparticles on engine efficiency and emissions, a diesel engine load test was conducted. Also included are side-by-side comparisons of fuel qualities with and without additives.

This paper presents the use of crude oil ash in asphalt flexible pavement and concrete rigid pavement. Conventional micro-size fly ash produced from burning crude oil in Jizan electrical power plant in Saudi Arabia was used in this study. The size of conventional crude oil ash waste reduced from micro-scale to nano-scale using ball-milling techniques. The first series of testing investigate the development of flexible pavement using asphalt bituminous AC60/70 incorporated conventional and nano-crude oil fly ash waste. The percentage of conventional and nano-ash used in asphalt mixes was varied from 0 to 15% of asphalt binder. The use of nano-fly ash increases the rutting factor by 0%, 33%, 61% and 38% at 0%, 5%, 10% and 15% nano-fly ash content, respectively. The nano-fly ash improves the rutting factors and bearing load capacity of flexible pavement mixes more than the control mix and mixes containing conventional micro-fly ash. The second series of testing investigates the use of nano-fly ash in rigid pavement asphalt concrete. Conventional and nano-fly ash replaced cement content in concrete material at 0%, 5%, 10%, and 15%. Concrete material incorporated nano-fly ash shows higher compressive strength and lower absorption compared to concrete control sample and concrete containing conventional micro-fly ash. The strength of concrete incorporated nano-fly ash increases by 14.8%, while absorption of concrete improves by 20.1% at 10% nano-fly ash content. The optimum nano-fly ash content was 10% to achieve the highest performance of both pavement materials. The use of nano-crude oil fly ash improves the performance of both pavement materials and helps in reducing the cost of repair in road and highway construction. Moreover, the use of nano-fly ash in paving materials can help in the recycling of this toxic waste to produce sustainable and environmentally friendly road construction materials.

Incorporating pigments into polymers can be done for various purposes, including the introduction of color, interfacial effects, or aesthetics. If these pigments are to disperse properly, then the process of extrusion must be optimized. During polymer compounding extrusion, three effective processing factors were investigated: feed rate (FR), speed (Sp.) and temperature (temp.) for a colored compounded polycarbonate (PC) grade (30/70%). The processing design techniques were obtained by applying design experiments in a response surface methodology (RSM) to blend two polycarbonates with pigments and optimize the processing temperatures at center points. The first study decided to utilize the response surface approach of Box–Behnken design (BBD) to design an experiment to optimize the process parameters. Statistical significance was demonstrated by the model passing all diagnostic tests. Furthermore, the three processing factors strongly impacted the characteristics of the tri-stimulus color, according to the results from a variance analysis. The second study identified process variables for the same PC grade at the center level, 25 kg/h FR, 750 rpm speed, and (255 °C) temp. The characterization and scanning morphology were examined using MicroCtscanner image analysis, SEM, DOM, rheology, FT-IR, and color-pigmented values were measured using a color spectrometer. The output response was significantly impacted when excellent color dispersion was observed with few agglomerates and less differences in colors at the center point. By characterizing these results and having good insight into color difference output and processing condition relationships, which have an adverse effect on color variation characteristics and minimize recycling compounds of different grades, results in cleaner environments benefits.

A simple chemical co-precipitation approach was used to produce in situ nanocomposites based on Mn-BIM, and the results were promising. It is possible to increase the photocatalytic degradation efficiency. The morphology of the nanocomposites is investigated using X-ray diffraction data and the structural features of the nanocomposites are investigated using electron microscopy. Mn-BIM is a nanoparticle with an average size of 50 nm. In order to determine their photo-catalytic activity, researchers investigated nanocomposites produced from industrial waste dyes rhodamine-B. Following 90 minutes in direct sunshine, the photo-degradation of these dyes occurs, with a photo-degradation rate of more than 90 percent. To evaluate whether nanocomposite materials have the ability to photodegrade dyes, tests have been carried out. The rate-limiting stepwise de-ethylation process for the degradation of rhodamine-B dye has been proposed as the mechanism of degradation.

The Co-MoF was identified as better catalyst for colorimetric sensing for effective detection of Hg2+ ions. The mimicking activities and oxidise the TMB in the existence of hydrogen peroxide (H2O2) to create a blue-colored sample. The oxidation of TMB was greatly delayed or reduced in the existence of bio-molecule Glutathione since of its stronger cations to repair capability. GSH substrates are oxidised when Hg2+ is introduced because of the higher interaction of mercury ions for GSH's thiol groups. Hg2+ concentrations ranged from 1 to 50 nM, and it exhibits a LOD of 0.28 nM reached in this study. To our surprise, the proposed sensor technology for detecting mercury contamination from industrial wastewater shows great potential.

The photo-catalytic degradation of Congo red (CR) was examined in presence of visible light at various operating condition, pH and amount of catalyst and time. The CR dye degradation rate was 97% about 80 minute of exposure, respectively, indicating that pH 7 was the optimal pH for degradation. The photo degradation processes of dyes were considered to be connected to a kinetic models, which was later shown incorrect. The effective degradation process might be used to explain the degradation of congo red dye.

Concrete is one of the most common construction materials used in rigid pavement, bridges, roads, highways, and buildings. Compressive strength is one of the most important properties of concrete, which determines its quality. This study aims to present the use of a new surface dielectric method to estimate concrete compressive strength. Six concrete mixtures were produced with compressive strengths ranging from 30 to 60 MPa. Compressive strength and strength development were determined during 28 days of curing. All concrete mixes were tested using the ASTM standard. The dielectric properties, ultrasound velocity, and rebound number of all concrete mixes were also measured at each day of curing. The results obtained from the proposed dielectric method in predicting the compressive strength of concrete were compared with the rebound hammer and ultrasonic velocity that are frequently used to evaluate the compressive strength of concrete. The dielectric method shows a higher square correlation coefficient than the other two methods. The results also indicate that combined more than one method of nondestructive techniques will lead to higher prediction and could help to reduce some errors associated with using a certain method alone. The result indicate that the finding of this study could lead to help in reducing the time of evaluating concrete during construction and could also provide tools for practicing engineer to take decision faster with more confidence level on quality of concrete. Doi: 10.28991/cej-2021-03091645 Full Text: PDF

The high rate of heat transfer through the residential roof assembly aggravates the condition of indoor thermal discomfort. Bulk insulation can be installed in the assembly to improve thermal performance. However, although it can efficiently reduce diurnal heat transfer from the outdoor environment into the indoor space through the roof assembly, it can also suppress nocturnal heat transfer in the opposite direction. Alternatively, high-albedo roof tiles employ cool colors to reflect heat at the roof surface, whereas bulk insulation hinders the conduction of heat through the roof assembly. In light of the potential of high-albedo roof tiles and bulk insulation in reducing heat transfer, thermal-energy performance of an urban pitched residential roof assembly, which adopted varying configurations of high-albedo roof tiles and bulk insulation under a hot, humid climate, was evaluated. Energy savings were generated, which were 15.13% when the change from a conventional to a high-albedo roof surface was performed, and 17.00% when the installation of bulk insulation was performed on the high-albedo roof assembly.

This paper presents a new method of dielectric capacitance cell as a proposed device for measuring the impedance of pure sand artificially contaminated with four heavy metals. Dielectric constant and loss factor of clean and contaminated sand at various levels were calculated from the measured sand impedances. The advantages and benefits of using the proposed dielectric capacitance cell were its low cost, simple calculation, calibration procedures, portable and lightweight, and easy to modify the electrodes to suit testing in the field. Pure sand was saturated with water artificially polluted in the lab with Pb, Cd, Fe, and Zn at heavy metal contents 0, 7.5, 15, 22.5, and 30 mg/kg of sand. The dielectric properties of polluted sand were evaluated at a frequency range from 100 kHz to 1000 kHz. The polluted sand exhibit different dielectric constants and loss factors from the unpolluted sand. The results also indicate that the dielectric constant decreases with increasing pollution level for all heavy metals. This may attribute to the polarization mechanism change with existing heavy metal. The loss factor of sand increases with the increasing pollution level. This may be explained by the increase of ionic conductivity of pore water with heavy metal in the sand. Sand polluted with heavy metal with higher resistivity and density possess a higher dielectric constant and lower loss factor than other polluted metals. Evaluation of the dielectric characteristics of polluted sand could have the potential to monitor heavy metal pollution. Even with promising results obtained with the proposed dielectric device, it is necessary to explore several other factors affecting the measurements such as sand water content, soil texture, and type of soil. Also, testing polluted soil near industrial pollution is needed.

In this study, a method for determining the setting time and the porosity of fly ash-based geopolymer binders (FAGPBs) has been established. This method permits a real-time monitoring of the geopolymerisation and hardening progressions. A parallel plate capacitor cell technique was used to determine the dielectric constant e r ' and dielectric loss factor e r ' ' of fresh and hardened mixes. Equivalent model-circuits of the measurement system were developed, and the accuracy of the system was verified. The dielectric properties were monitored at different ages until 56 days over a frequency range of 0.1–60 MHz. The alkaline solution to fly ash ratio, sodium silicate to alkaline solution ratio, and sodium hydroxide solution molarity were varied to study their effects on the dielectric properties. It was found that dielectric properties can provide valuable information when measured in the frequency range of 10–25 MHz. In this range, the dielectric values responded well to the variations with age and with mix properties. The relationships between the dielectric properties and the different physical states and constituent materials of FAGPBs could be used for quality control applications. The e r ' and e r ' ' time plots were effectively utilized to determine the setting time and the rate of geopolymerisation of FAGPBs. Measurements showed a strong correlation between e r ' and porosity; the e r ' values decreased 2.3-fold over a porosity range of 3–15%. The proposed regression models can be further used in determining the porosity of FAGPBs at a high accuracy level.

In this study, different types of plasticizers were used to investigate their effects on the fresh and hardened properties of high calcium fly ash geopolymers (HCFA). Modified polycarboxylate polymers (G3) and lignin-based polymers (G1) were used as plasticizing admixtures and the results were compared to the effect of tap water addition. The results showed that all the admixtures used are effective in increasing the workability of the HCFA geopolymers mixtures and the workability increased by 25-48% compared to the control mixtures. However, the use of G3 has adversely affected the strength by a reduction of 20%. While the use of G1 reduced the final setting time by 7% which is critical in the case of HCFA geopolymers where the final setting time occurs within 70 minutes. Water can be considered as the best admixture in terms of cost, setting time, and effect on compressive strength and it can be used where medium workability enhancement is required.

In this study, the possibility of producing new geopolymer concrete from olive oil waste in Jordan is presented. Olive oil residues in Jordan and many Mediterranean countries constitute a major environmental and health problem. So far, the waste is disposed of by means of sanitary landfill, and this poses an environmental risk and pollutes the groundwater, the main source of water in Jordan. The ash remaining from burning olive oil residues was used to produce geopolymer concrete by adding sodium hydroxide and without using any Portland cement. Mixtures were prepared using the central composite design. The focus was on the two most important factors affecting the properties of geopolymer concrete, which is the amount of ash and the amount of alkaline solution. After curing the concrete and passing 28 days, the compressive strength, slump, absorption, and porosity were measured. The Results of compressive strength, absorption and porosity was excellent in comparison with the results obtained from conventional concrete. Despite the promising results the slump of the proposed concrete is low, and the slump loss was very fast. Further studies are needed to improve the workability of geopolymer concrete from olive oil waste. This concrete allows to recycle a large amount of olive waste in Jordan and many other countries which reduce the impact on health and environment.

This paper presents a new dielectric sensor which could be used for assessment and evaluation of soil pollution in the field. The new device determines the dielectric properties of soil from the measured soil impedances. The dielectric properties used as indirect method to estimate type and pollution content in soil. The new device was calibrated and validated for accurate measurement of soil dielectric properties in the frequency range of 1 kHz to 30 MHz. The new proposed dielectric sensor was used to measure the dielectric properties of clean and contaminated soil. The measured dielectric properties of soil using the proposed sensor could be used to estimate soil moisture content, hydrocarbon diesel and salinity in sand soil. The results also show that the dielectric properties of clay soil were higher than the dielectric properties of san due to existing bound water in clay minerals. Further testing is necessary to evaluate the effects of other parameters such as temperature and various type of soil prior to adopt the sensor for field testing.

In this paper, the near- and far-field microwave methods used in this study indicate that the microwave reflections and dielectric properties are useful parameters for the detection of chloride in concrete material. Furthermore, the amount of chloride present in concrete at the time of mixing can also be determined. The reflection coefficients, dielectric constant and loss factor in the X-band microwave frequencies increase with increasing chloride content in concrete materials and can be used to monitor the hydration process. A linear relationship between the microwave properties of concrete and chloride content were established.

Most available methods for determination of water quality in water bodies such as rivers, lakes, and reservoirs are based on the collection of water samples from water bodies and subsequent laboratory analysis. While these methods are standard and could provide accurate measurements and evaluation of water quality, they are costing and time consuming and do not provide the continuous monitoring and assessing of water quality. In this paper, low frequency dielectric cell is developed for determination the water quality. The proposed method was used to measure the dielectric properties of water. The method was calibrated and validated by measuring dielectric properties of standard materials such as Teflon. The measured dielectric properties of water were used to determine several water quality parameters such as salinity, temperature, turbidity. The proposed method has advantages in compare with the available techniques for water quality including simple, low cost, safe, possible to be continuous and online method, and can be used for in-situ as in the lab. Dielectric constant and loss factor of water decrease with increasing frequency. The rise of water temperature caused an increase in loss factor and a decrease in dielectric constant. The dielectric constant increases with increasing water salinity while it decreases with increasing the turbidity of water. Further investigation is needed to determine the effect of other water quality indices on the dielectric properties of water prior to use the proposed system in practical application.

Geopolymers are novel binding materials produced by the alkaline activation of rich aluminosilicate materials. Geopolymer binders are considered as green building materials that have increasing potential to replace the ordinary Portland cement in the concrete industry. This study investigated the alkali solution effects on the physical and mechanical properties of the high calcium fly ash based geopolymers. The parameters involved in this study were the NaOH solution molarity and the Na 2 SiO 3 /NaOH ratio. Three NaOH concentrations (8, 10, and 12 molars) were investigated. The Na 2 SiO 3 /NaOH ratio was varied between 1 and 2.5. The results showed that the studied parameters significantly affected the properties of the produced geopolymer mortars. The workability and setting time were found to decrease by increasing the NaOH concentration or by increasing the Na 2 SiO 3 /NaOH ratio. The influence of the NaOH concentration was higher on the workability and setting time while the Na 2 SiO 3 /NaOH ratio highly affected the compressive strength. The initial setting time was in the range of 45-105 minutes while the final setting occurred quickly after that within 70-115 minutes. Oven curing method resulted in high strength at early ages where all of the mixes were able to achieve more than 75% of the 28 days strength within the first 3 days. The 28-days compressive strength ranged between 60-85 MPa, which promotes the use of the high calcium fly ash for the production of early high strength geopolymer concrete.

Eight large-scale reinforced self-compacted engineered cementitious composite (R-SC-ECC) beams with different steel reinforcement ratios have been designed, prepared, cast, cured, and tested to failure at the age of 28 days. The experimental results have been compared with theoretical values predicted using EC2, RILEM, and VecTor2 models. Results show that failure modes in flexure and shear of R-SC-ECC beams are comparable to that of normal reinforced concrete beam. Nevertheless, contrary to VecTor2, models of EC2 and RILEM are not suitable for predicting reasonable ultimate moments for the beams, while results using VecTor2 model have successfully predicted the failure modes and load-deflection curves for all R-SC-ECC beams. It has been concluded that R-SC-ECC fall in the category of ductility class medium to high which gives advantages of using R-SC-ECC beams in regions susceptible to seismic activities.

Generally the methods were used to characterize soil contamination include collecting samples of soil then analyzing them to recognize contaminates in the laboratory. Commonly, this method of characterizing the contamination of a soil system is the only one agreeable to regulatory societies. However, sample analysis in the lab faces important problems such as soils sampling is really time consuming and costly, sampling is not constant with time and the samples be able to contaminate through sampling and carrying to the lab. Thus several geophysical techniques have been developed which used the dissimilarity in the soil physical properties after soil contamination. Dielectric technique shows high conceivable for characterization diesel contaminated soil. Further use of this technique; rely upon the availability of information about the dielectric properties of the contaminated soil. In this study, the effects of induced by a diesel presence in an unsaturated soil, on the complex dielectric properties were sought. It has been shown experimentally that the diesel presence in an unsaturated soil is traduced by an increase of both dielectric constant and loss factor. A comparison with the existing results in this study and in the literature for saturated soils shows an opposite effect on the complex dielectric properties. The importance of the influence induced by the diesel on the dielectric properties of an unsaturated soil was noticed and compared to a saturated soil. On the basis of the theoretical dielectric mixture models, a justification to these opposite behaviors and their importance has been presented and various models for the two cases have been developed.

Introducing steel fiber to concrete materials enhances the performance of concrete structures in terms of their flexural strength, impact load resistance and limited crack propagation. The fiber concrete performance depends on the fiber content, dispersion and orientation. No standard method is currently available to evaluate these three parameters, especially in situ. This paper describes the feasibility of using a surface electromagnetic sensor as nondestructive radio wave test system to determine the concentration, dispersion and orientation of steel fibers in the concrete. The system needs to contact the concrete material and requires only one face of the concrete material for testing. The surface electromagnetic sensor can slide on the fiber concrete surface and measure the dielectric properties at various locations to assess the fiber distribution. In addition, the sensor can rotate to polarize the electric field to various angles and evaluate the fiber orientation. The mean and standard deviation of the measured dielectric properties increase with increasing fiber content and fiber dispersion. The results indicate that the dielectric properties are maximal when the fiber is oriented in the direction of the electric field and minimal when perpendicular. A simple linear model was established to determine the fiber content and flexural strength from the measured electromagnetic properties.

Soil contamination with petroleum hydrocarbons has become one of the most serious problems due to its negative repercussion on ecosystems. For this reason, different analytical techniques have been developed to evaluate the quantity and the quality of organic pollutants using electrochemical techniques, and a geophysical methods have been developed which utilizes the contrast caused by the contaminant on physical properties of the soil dielectric methods shows high potential for characterization kerosene contaminated soil and determination of the level of contaminant. The potential of dielectric measuring techniques for soil characterization has not been fully explored. For this purpose, dielectric measurements, in the frequency range from 100 kHz to1000 kHz, were carried out in sandy soil samples, contaminated with solutions of kerosene, at different concentrations. The differences of the dielectric behavior with contaminant content suggest that the monitoring of complex dielectric constant has the potential to quantify contaminants.

The paper deals with dielectric properties of concrete and the effect of frequency, curing time and water to cement (w/c) ratio, concrete compression strength, steel fibre concrete and moisture content on the dielectric properties. The concrete dielectric properties such as transmission coefficients, reflection coefficients, dielectric constants and loss factors; were investigated using microwave nondestructive testing (MNDT) tech- nique. The MNDT system consists of transmit and receive horn lens antennas, a vector network analyzer, mode transitions, and a printer. The horn lens antennas are used for minimizing diffraction effects due to the edges of the sample. Electromagnetic waves at micro- wave frequency range 7.0-13.0 GHz using free-space microwave method was used for measuring dielectric properties of concrete. Concrete specimens were prepared using different w/c ratios and different com- pressive strengths. Concrete dielectric properties were measured and correlated with compressive strength and w/c ratio of concrete, curing time. The experimental results indicate that microwave non-destructive tech- nique has correlated well with to determine the compressive strength and w/c ratios of concrete. The results also show the potential to be used to determine the percentage of fiber. This technique is easy to adapt for in situ measurements.

The rapid development of electronic systems and telecommunications has resulted in a growing and intense interest in microwave electromagnetic absorber technology and microwave absorbing composite material. This research was conducted to develop microwave absorber composites called thermoplastic natural rubber barium ferrite (TPNR-BF). The composite was characterized by determination of its physical, mechanical, magnetic and microwave properties. TPNR-BF with the fine particles barium ferrite filler content of 0-20% by weight were prepared using melt blending method. The microwave electromagnetic properties were measured using free-space microwave non-destructive testing system (MNDTS) in the frequency range of 7-13 GHz. The mechanical and Magnetic properties of the thermoplastic natural rubber-barium ferrite were also measured using Magnetometer. The effects of the different percentage of filler content on the mechanical and microwave properties of the composites have been evaluated. Both microwave dielectric constant and the reflection coefficient of TPNR-BF increase with increasing frequency and filler content while transmission coefficient decreases with increasing filler content which indicates that the composite absorbs more microwave energy by the filler. Barium ferrite contents show an inverse relation with the mechanical properties such as tensile strength and stiffness. MNDTS shows excellent capability for advanced characterization of a microwave composite material.

Problem statement: For predicting workability and hardened properties of Self-Compacting Concrete (SCC) no well known explicit formulation. Approach: Statistical models were carried out to model the influence of key mixture parameter (cement, water to powder ratio, fly ash and super plasticizer) on hardened properties affecting the performance of SCC. Such responses included compressive strength at 3, 7 and 28 days and modulus of elasticity. Thirty one mixtures were prepared to derive the numerical models and evaluate the accuracy. The models were valid for a wide range of mixture proportioning. Results: The research presented derived numerical models that can be useful to reduce the test procedures and trials needed for the proportioning of self-compacting concrete. The qualities of these models were evaluated based on several factors such as level prediction, residual error, residual mean square and correlation coefficients. Conclusion: Full quadratic models in all the response (compressive strength at 3,7 and 28 days and modulus of elasticity) showed high correlation coefficient (R2), adjusted correlation coefficient, less level of significant and sum of square errors from the four predictions models (linear, interaction, full quadratic and pure quadratic) were developed.

The existence of moisture in concrete is a major cause of damage to the concrete structure, so there is an increasing need for nondestructive detection and monitoring of moisture content in concrete. Microwave nondestructive testing (MNDT) techniques have advantages over other NDT methods (such as radiography, ultrasonic, and eddy current) regarding low cost, good penetration in nonmetallic materials, good resolution and requirement of only one face of material for testing. In this paper, microwave open-ended rectangular waveguide was used to measure the electromagnetic properties of Portland cement concrete (PCC) over a frequency range of 7.0 to 13.0 GHz. PCC specimens of six different water cement ratio (w/c) were prepared. PCC dielectric properties were evaluated at different moisture content ranges from saturated to oven dry. The results show reflection coefficients, dielectric constants and loss factors increase with increasing moisture content of PCC. At the same values of moisture content, the reflection coefficients, dielectric constants and loss factors of PCC increase with decreasing w/c ratio. The measured values of reflection coefficients, dielectric constants and loss factors can be used to determine the moisture content of PCC.

Geopolymer binders offer a possible solution for several problems that facing the current cement industry. These binders exhibit similar or better engineering properties compared to cement and can utilize several types of waste materials. This paper presents the recent research progress regarding the structural behaviour of reinforced geopolymer concrete members including beams, columns and slabs. The reported results showed that the structural behaviour of the reinforced geopolymer concrete members is similar to the known behaviour of the ordinary reinforced concrete members. In addition, the currently available standards have been conservatively used for analysis and designing of reinforced geopolymer concrete structures. On the other hand, the main hurdles facing the spread of geopolymer concrete was the absence of standards and the concerns about the long-term properties. Other issues included the safety, cost and liability.

This study aimed to present the current state of research about the terminology, chemical reactions, mechanisms, and microstructure modelling of geopolymer binders. Modelling the structure of the geopolymerization products is essential for controlling the product properties. The currently available models have shown some limitations in determining the rate of geopolymerization and setting time of the gel. There is a need for deeper knowledge regarding the physicochemical analysis of geopolymer binders. Most of the available models have used pure material like metakaolin; however, the less pure materials are expected to have different mechanisms. The FTIR and MAS-NMR analysis are considered as effective tools in providing information on the molecular deviations during geopolymerization. However, XRD analysis is not effective because most of the changes take place in amorphous phases. Also, the role of the iron oxides and some of the other impurities still not clear where none of the previous method of investigation can be used to detect the molecular changes of the iron compounds. This issue is very relevant hence the iron oxides are existed in substantial amounts in most of the waste materials that are suitable to be used as geopolymer source materials.

Design of concrete mixtures is the process of selecting the most economical and practical proportions of all the ingredients to produce quality concrete. Because of the nature of the mix design process and all the heuristic knowledge that is associated with it, concrete mix design lends itself well to a knowledge-based application. This paper describes a prototype knowledge-based system called HPCMIX that can be used to load the experimental data, develop several statistical models to determine the responses, evaluate the predicted models, and predict the 28 days strength and slump. It can also be used to design HPC mix proportions that are subjected to specified constraints (e.g. strength and slump). It is capable of selecting proportions of mixing water, cement, supplementary cementitious materials, aggregates and superplasticizer, with consideration being given to the effects of air content as well as water contributed by superplasticizer and moisture conditions of aggregates. As most of knowledge-based systems, this system has explanation facilities, can be incrementally expanded, and has an easy to understand knowledge base. The system was tested on a sample project. The system’s selection of the concrete proportions compared favourably with the expert’s selection. The system is very useful for civil engineering students as well as practicing engineers. KEWORDS: high performance concrete; mix design; statistical analysis; knowledgebased system; superplasticizer.

Methods available for measuring the water quality of rivers, lakes, reservoirs, etc. involve the collection of water samples for these water bodies and subsequent chemical laboratory analysis. These methods and technologies provide accurate measurements and evaluation of water quality for a point in time and space; they are time consuming, expensive and do not provide either the continuous, spatial or temporal view of water quality needed for monitoring, assessing, or managing water quality. In this paper, the measured complex reflection coefficients and complex permittivity (dielectric constant and loss factor) of water using a microwave open-ended rectangular waveguide system called microwave reflectometer system (MRS) is used to monitor the water quality. MRS uses the electromagnetic properties of water to indicate the quality parameters of waste. This system offers the potential of relatively inexpensive, frequent, continuous and synoptic measurements using sensors immersed in the water bodies (reservoirs, rivers, lakes, treatment plant). Dielectric properties of water of different salinity are measured and evaluated.

Microwave nondestructive testing methods are fast, contactless, accurate and continuous techniques for the evaluation of moisture content, slope-of-grain, density of knots and specific gravity of timber. Dielectric properties of timber are determined by these factors. We describe how the dielectric properties were deduced from reflection and transmission coefficient measurements of Malaysian timber specimens using a free-space measurement system in the frequency range 8-12.5 GHz. Dielectric properties were evaluated over different angles between the electric field and the direction of grain. Relationships between density, modulus of elasticity, strength, grain angle (angle between the direction of grain and electric field) and dielectric properties of Malaysian timber were established.

A fast and nondestructive method for measurement of compressive strength and water cement ratio (w/c), will be of great interest to the construction industry because compressive strength is one of the most important parameter in the structural design of concrete structures. Also, compressive strength is specified for building code compliance. In this paper, a study was conducted to apply a free-space microwave technique for determination of compressive strength and w/c ratio of concrete. This technique utilizes the reflection properties of concrete in the frequency range of 8-12.5 GHz. Concrete specimens were prepared using different concrete mix constituents, different w/c ratios and different compressive strengths. The reflection properties of concrete specimens were evaluated over a range of frequency and curing age. The results indicate that free-space microwave sensing has the ability to determine the compressive strength and w/c ratios of concrete. This technique is easy to adapt for in-situ measurements and can determine concrete constituent proportions.