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The expansive soil has serious impact due to its unstable volumetric behaviour when it undergoes seasonal variations. In order to utilise the problematic expansive soil for any kind of work it needs to alter the behaviour of soil by stabilisation using addition of admixtures. From the economical point of view using industrial waste materials is the cost-effective technique. In this work the selection of industrial waste materials which comes from tile manufacturing such as Tile Waste Powder (TWP) and Foundry Sand (FS) outcome of metal casting industries as an admixture. The Tiles Waste Powder has the nature to improve the compaction behaviour of expansive soil because of its high lime content and Foundry sand are used to develop the strength behaviour of problematic soil due to the presence rich silica content. In this paper, untreated soil got treated using the different proportions such as 5,10, 15,20 and 25% of Tile waste powder and their corresponding the compaction and strength characteristics of the soil sample were determined under different curing periods. Also the tests have been conducted for optimum percentage of tile waste mixed along with varying percentage of Foundry Sand (4, 6, 8, 10 and 12%) in soil sample. The results was obtained from the standard proctor test, UCC and CBR test and it further analysis shows that the increasing the proportion of TWP rises the peak strength of the treated soil up to 20% for the maximum 28 days curing. Also, from the result analysis for the combination of FS and TWP by optimum percentage of Tiles Waste Powder (20%) with 12% of Foundry sand shows the increment in the strength characteristics of soil. The TWP and Foundry Sand can be effectively used in stabilization works in order to utilise the waste by effective minimization of disposal problems.

This laboratory analysis was done to scrutinize the compressive strength of nominal mix concrete (NMC) and fiber reinforced concrete (FRC) for M30 grade of concrete. In this study, cubes of NMC prepared by adding fly ash 20% and 30% of the weight of cement. Apart from this, the FRC mix prepared by adding steel and glass fiber in the NMC mixture. The experimental study consists of the construction of 84 cubes, out of which 36 cubes of SFRC and 36 cubes of GFRC cast for different percentages of fiber. Out of 36 cubes of SFRC, 18 cubes cast with 20% fly ash and 18 cubes cast with 30% fly ash and the same as for GFRC and 12 cubes of NMC, 6 cubes cast with 20% fly ash and 6 cubes cast with 30% fly ash. The compressive strength calculated by averaging the strength of three cubes cast for each fiber ratio. These mixes tested for its hardened property like compressive strength in this comparative study. The compressive strength tested on UTM after 7 and 28 days curing, where results show improvement in individual fibers.

The life span of a structure depends on the strength and durability of concrete. The use of mineral admixtures in concrete plays a major role in achieving higher strength and durability characteristics. At present nanotechnology is being used in the concrete to decrease the permeability of concrete and also to extend the life service. Nanomaterials are extremely small in size which when used in concrete, improves the strength and reduces porosity. This study gives the characteristics of concrete when Nanosilica (NS) and Multi-Walled Carbon Nanotubes (CNT) were added to it. Manufactured sand was used as a fine aggregate in replacement of natural river sand. For conventional and nano-concrete, the durability characteristics were assessed by conducting water absorption, sorptivity, accelerated corrosion, and carbonation tests after 28 days and 90 days of curing. The formation of hydration products was studied through microstructural analysis by SEM and XRD. Closely packed concrete was achieved with the addition of NS and CNT. The permeability and porosity were reduced for nano-concrete because of the filler effect of nanomaterials.

Large quantity of water is required during the conventional curing methods. This becomes challenging in the areas facing water scarcity and for concreting work in high rise structures. In this work, we present a solution for the need of concrete which does not require extra water for curing. In the proposed solution, calcium lignosulfonate in different percentage was introduced as a self-curing agent in fresh concrete. The hardened concrete with calcium lignosulfonate was cured at ambient condition whereas the hardened concrete without calcium lignosulfonate was submerged in water for curing. The properties of fresh and hardened concrete with and without calcium lignosulfonate are compared. The results show a continuous increase in slump with the increase in calcium lignosulfonate, however, 0.3% calcium lignosulfonate is identified as an optimum percentage for desired mechanical property. The durability under saline environment is studied in term of loss in strength. Further, the change in strength is correlated with the mineralogical changes studied using X-ray diffraction results.

Micro-cracks are inherently present in concrete, leads to debilitation of structures. Methods used for managing micro-cracks have a certain degree of toxicity and also possesses certain drawbacks that made them not completely efficient. Bacterial technique when used in fresh concretes results in calcite precipitation in voids and consequently improves the strength and lowers permeability of concrete. Bio- cement is the combination of Bacillus pasteurii 5% and nutrients Urea, Calcium Lactate 95%. In this study by adding 0.5, 1, 1.5 and 2% Bio- cement by weight of cement and observed compressive strength, flexural strength values after 7 and 28 days of curing for M25 grade of concrete.

The construction industry is always in need of new technologies and products that improve technological characteristics. Alkali-activated materials appear as an alternative to reduce energy costs, improve technological properties and still present themselves as materials with the potential for incorporating industrial waste. The objective of this research was the development of roof tiles through the process of alkaline activation using ash from the kilns of burning of a red ceramic industry. After the process of processing the materials and their characterizations, prismatic specimens (115 × 30 × 20 mm) were made with the replacement of 0, 6.25, 12.5, 25 and 50% ash by metakaolin and subsequently separated into two groups, (i) subjected to curing at room temperature and (ii) subjected to curing at a temperature of 80 °C, in both cases with a curing time of 7, 14 and 28 days. After each curing period and group, the specimens were subjected to technological evaluation of water absorption, porosity, flexural strength and scanning electron microscopy. The results obtained demonstrate that the use of ash from ceramic waste, mainly replacing 12.5% of the metakaolin, promotes a reduction in water absorption and porosity, and an increase in flexural strength. The results obtained at 28 days in thermal curing are 44.05 MPa for 12.5% ash, much higher than the reference composition (16.02 MPa). The increase in strength happens due to the formation of tobermorite, due to the calcium present in the ash, and due to the formation of phases rich in potassium from the ash, such as kalsilite. Thus, it is concluded that the use of ash from ceramic waste is possible in the alkaline activation of roof tiles due to the occurrence of additional mechanisms of alkaline activation.

This study aims to develop the alkali activated slag-fly ash concrete (AASFC) using precious slag (PS) ball as the fine aggregate. The slag-fly ash proportion, sodium silicate/sodium hydroxide (SS/SH) ratio and sodium hydroxide concentration are the prime variables. The fresh concrete properties like workability, setting time and the hardened concrete properties of AASFC developed under ambient curing were analyzed and similar way by replacing with fly ash (FA). The sodium hydroxide concentration of 8 M, 10 M and 12 M, SS/SH ratio of 1.0, 1.5 and 2.0, alkaline liquid to binder ratio of 0.35 and variation in slag-fly ash proportion as major inputs for mix design. The test results showed that, the fresh state of AASFC blend has a shorter setting time of 12–16 min, because of calcium mineral from the FA, the workability and setting time of AASFC mix was enhanced by the addition of the tri-sodium phosphate as a retarder. At the higher SS/SH extent, the workability and setting time exaggerated, whereas the increased FA content and sodium hydroxide concentration had a greater influence on the fresh state of concrete. Also, the sodium hydroxide concentration, SS/SH ratio and slag-fly ash proportion are the most inducing parameters on the workability, setting time and strength parameters of AASFC.

ABSTACT Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disulfide, hydrophobic, electrostatic, hydrogen, and calcium bridges) was monitored for 60 min after curd cutting. Hydrophobic inter-protein interactions originally present in casein micelles in milk were substituted by electrostatic, hydrogen, and calcium bonds throughout the curd curing period. Disulfide bonds were not disturbed by the experimental conditions employed in the study, remaining at a constant level in all studied treatments. Acidification of curds increased the availability of soluble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interactions established among proteins in curd, temperature modified the rate at which such bonds were formed.

This study explores the influence of partial replacement of high reactivity Attapulgite (HRA) with cement by weight and evaluate the effect of curing temperatures on the compressive strength of modified cement paste (MCP). Recently, the Iraqi clay(Attapulgite) has been processed to pozzolanic material HRA, after extracting it from the quarry the clays crushed and grind to filler then specific the suitable calcinations temperature to make this clays as a pozolznic material. The possibility of replacing the Iraqi clays with cement can be reduce the cost and the impact of cement manufacturing on environment. In this study, three percentages of high reactivity Attapulgite used as a replacement 0, 10 and 20 % by weight of cement. The samples cured in four temperatures 20, 40, 60 and 80 °C. The samples with dimension 50x50x50 mm3 were casted and tested at ages 7, and 28 days. The test result shows that the compressive strength at early ages without HRA and cured at 20 °C were higher than samples with HRA. The maximum percentage of HRA as a replacement with cement has a reduced the compressive strength of the concrete. The result at 28 days for the samples with 10% of HRA at curing temperature 40 °C shows increased in compressive strength up to 60 °C, while when the samples were cured at curing temperature 80 °C shows decreased the compressive strength.

Nano modified concretes have become the attractive research area now-a-days. It was anticipated that the inclusion of appropriate nano-sized particles would enhance the mechanical properties of the concrete. Though the capability of nano-TiO2 particles in improving the mechanical strength of the base material was documented in the earlier studies, their influence on the concrete was not yet dealt properly. The current study is attempting to enhance the mechanical properties of the concrete using small mass fraction of nano-TiO2 particles as cement substitute and nanoclay as the fine aggregate substitute. The initial tests were accompanied on the concrete, only with different fraction of nano-TiO2 particles to identify the best nano-TiO2 proportions for different curing periods (7 days, 28 days and 60 days). Then, the secondary tests were piloted with varying mass fractions of nanoclay with the identified best proportion of the nanoconcrete. The results revealed that 2.0% nano-TiO2 particles and 3.0% nanoclay were the optical fractions in the nanoconcrete to obtain maximum values of split tensile, compressive, and flexure strengths. The improvement in the mechanical properties of the concrete was attained about 30% with the help of nano-TiO2 particles and nanoclay.

This research work is carried out to find the self-healing time and mechanical properties of concrete by using Bacillus Subtilis and Escherichia Coli. These bacterias has the capability of healing the cracks by itself. M20 concrete designed as per IS 10262–2009 is taken as reference sample. Different mixes were casted varying the percentage of bacteria. The above-mentioned bacteria were mixed in percentages of 2%, 3%, 4% and 6% by weight of cement separately and combination of both bacteria at 50% each to make total 2% and 3% of mixed bacteria by weight of cement. Calcium Lactate (a calcium-based nutrient for the bacteria) is mixed at a constant 5% for all mix variations. All the mixing, casting, curing and testing is done as per standard practice. Slump cone test gave an increased workability of 45% with bacteria Bacillus Subtilis. Standard size cubes of 150 mm were casted (nine for each mix), cured and tested at the age of 7, 14, 28 days. Some samples were tested in Compression testing machine till cracks were evident and measurable. The bacteria gets activated when water comes in contact with it, starts to feed on calcium lactate and grow resulting in self-healing of cracks in concrete. It is observed that the cracks were healed within 48 hrs for 2% Bacillus Subtilis, 32 hrs for 3% Bacillus Subtilis, and 72 hrs for 4% Bacillus Subtilis, even after 72 hrs no evident healing was observed for 6% Bacillus Subtilis all percentages of Escherichia Coli and mix bacteria. Hence the optimum dosage for self-healing of concrete is 3% Bacillus Subtilis. Both Compressive strength and Split Tensile strength, tests are done as per IS 516-2002 (reaffirmed 2018) and results gave an increase of 60%, strength for samples with 3% Escherichia Coli bacteria.

This investigation exhibits a study on the effect of silica fume, Rice husk ash and Ground granulated blast furnace slag on mechanical property of Performance based concrete. The Performance based concrete with various proportion of different mineral admixtures were tested including compressive strength at 7,14 & 28 days of curing. The ordinary Portland cement by weight was partially replaced with Rice Husk Ash (10%, 15%, 20%), Silica Fume (10%, 15%, 20%) and Ground granulated blast furnace slag (10%, 20%,40%). Estimations were completed subsequent to restoring at 20 °C and 65% relative humidity. Total 90 cubes were casted for different mixes for compressive strength of concrete. The test results reported that optimum % of Rice Husk Ash is for the Mix(C90RHA10) and the compressive strength increases by 6.62% compare to control mix at 28 days. Also, the optimum % of Silica Fume is for the Mix (C80SF20) and the compressive strength increases by 13.4%. Similarly, the optimum % of GGBFS is for the Mix (C60GGBFS40) and the compressive strength increases by 6.81%.

Permeability is one of the principal factors related to durability of concrete. The responsible factor for volume change is permeability. This paper attempt to mechanical and durability study of Supplementary Cementitious Concrete where cement has been replaced by fly ash & GGBS in combination of (30%, 0%), (20%,10%), (10%, 20%) and (0%, 30%).16 such concrete samples has been cast in which water binder ratio introduced as 0.35, 0.40, 0.45 & 50 for each 4 set .cubical and cylindrical concrete 16 samples has been prepared for curing period of 7 and 28 days with replacement of manufactured sand and coarse aggregates. Compressive strength, ultra sonic pulse velocity test (UPV) and Rapid chloride permeability test has been done value at the end of each curing period. The results of this research show that both UPV and compression strength have augmented with supplementary Cementitious materials (SCM) Incorporations. Various empirical models were proposed for pulse velocity and compressive strength. Models for the compressive strength and ultrasonic pulse velocity was developed at individual percentage levels (fly ash or GGBS) and then for each replacement stage four different models (FA percent + GGBS percent) were developed. Similarly after curing for 28 days, Chloride permeability test as per ASTM C1202 has been done. Diverse parameters mathematical models were developed to acknowledge the effect of various factors like SCM incorporations, water binder ratio, replacement of manufactured sand etc., and Models has been tested in full range by data and has strong precision, correlation with experimental data.

Seashell is a very hard and protective outer layer produced by an animal that lives in the sea. Empty seashells are mostly found in the shore and collected as waste by beachcombers. This marine by-product can be used as partial replacement of coarse aggregate and cement in concrete. This paper describes the potential use of seashell powder and seashell waste as cement and aggregate replacement in concrete, to produce a greener concrete. This study also focused on the effect of seashell powder and aggregate in concrete with respect to compressive, split tensile and flexural strength after 7, 28, 56 and 90 days of curing the concrete specimen. The three different replacements of cement by seashell powder (5%, 10% and 15%) and replacement of coarse aggregate by seashell aggregate (10%, 20% and 30%) was used in mix proportion with w/c ratio of 0.5. The mechanical properties of seashell concrete were compared with control mix specimen of M25 grade of concrete. It was found that replacement of cement and coarse aggregate by seashell products enhances the compressive strength by 30 %, at the later age (after 90 days of curing) and thus enable proper utilisation of these seashell waste as sustainable material for the concrete. The 5% seashell powder and 10 % seashell aggregate replacement mix is the optimum percentage of replacement in the concrete. Therefore, this study recommends replacing cement with 5% seashell cement and 10% seashell aggregate.

Steel filings are primarily composed of steel. These steel filings are produced by grinding, shaving and cutting the various steel in the mechanical workshop or factories. The steel wastes are disposed into the landfills, rivers and oceans thereby increasing pollution. To reduce these wastes reaching the landfill sites, one solution is to reuse them in construction. There have been some studies on the strength of concrete made with steel filings, however, no study has been reported on the durability. The purpose of this research was to evaluate the durability of concrete made with steel fillings as a replacement of fine aggregate. In the current study, different replacement levels of steel fillings such as 0%, 10%, 20%, 30% and 40% have been used in the making of concrete. Cube samples were tested for durability after normal curing for 28 days. It was found that the cube looses its workability and slump, when the percentage of steel filing were increased beyond 40% as replacement of fine aggregate. The water absorption increased with increasing percentage of steel filing and the sorptivity tests showed that the weight of capillary rise of water increased with the increasing percentage of steel filing due to the increased porosity of the concrete. This type of concrete may be used for the pavement and parking lots, where there is a problem of water logging, as it would allow the water to pass through it and may help in recharge of the ground water.

Cellular lightweight concrete (CLC) or sometimes referred to as foamed concrete is widely used in construction for many decades. The foamed concrete properties include low density, as well as good thermal conductivity, high workability and self-compaction and these characteristics enable foamed concrete in many applications. This research deals with the properties of cellular lightweight concrete (foamed concrete) using wastes of palm oil industries namely, palm oil fuel ash (POFA) of 10% as cement replacement and palm oil clinker (POC) at 50% and 100% as sand replacement to develop 1200 kg/m3 foamed concrete. Six different mixes of foam concrete were prepared and various tests on fresh density, flow table, ultrasonic pulse velocity (UPV), compressive strength, and splitting tensile conducted. The results show that the use of 10% of POFA as cement replacement and 50% of POC sand produced requisite strength for structural grade. For the mix with POC100POFA10, under air curing method, 10.3 MPa was the highest compressive strength was achieved; while, for the mix, POC50 under water curing method, the highest strength of 9 MPa obtained. In a nutshell, the byproduct palm oil industrial waste has a good contributing to the sustainable development of the construction industry as well as the agricultural sector in Malaysia and other oil palm growing countries of the world.

Future human space exploration and habitation on the lunar and Martian surfaces necessitates in-situ resource utilization (ISRU) for the development of construction materials tailored for infrastructure and environmental protection. Here we explore the use of lunar and Martian regoliths to create construction materials with properties suitable for such structures as landing pads. Alkali activation of a spectrum of lunar and Martian regolith simulants generates geopolymer binders under ambient and vacuum curing conditions as well as exposure to extreme high and low temperatures (600 and -80 °C). Compressive strength is reduced for binders prepared from each simulant after curing under vacuum and exposure to sub-zero temperatures. In lunar simulant binders, the compressive strength is increased after heating to 600 °C, but the opposite effect is observed in the Martian simulant binder. Amorphous aluminosilicate content and percentage of small particles in the simulants are hypothesized to have a positive impact on compressive strength under ambient curing. Iron and magnesium content may be responsible for decreased compressive strength of the Martian binder after heating. This study offers a robust framework for comparing performance of different simulants under the same curing protocols and environmental exposures, as well as offering insight as to the effects of vacuum curing, and exposure to high and low temperature environments on cured binder samples. Developing a landing pad by transporting activator to the lunar surface is shown to be conceptually feasible within current payload constraints.

Innovative approaches are under research to study the resistance of chloride ion penetration in concrete containing chloride ions, to minimize the impact of chloride ion penetration test errors in coastal reinforced concrete (RC), which is helpful to the design of coastal RC structures. In this study, the diffusion depth, free ion concentration and diffusion coefficient of chloride, iodide ions with different curing ages and GGBFS content were measured by the Rapid Chloride Migration Test (RCM) and Rapid Iodide Migration tests (RIM). The SEM-EDS and MIP were used to analyze the microstructures, pore size distribution and the hydrated products. The results show that the performance of GGBFS concrete against the diffusion of corrosive ions is affected by the curing age and the content of GGBFS. With the increase of GGBFS content, especially concrete with 60% GGBFS, the influence of chloride, iodide ion penetrating into concrete gradually becomes smaller. The long-age curing system is more conducive to the concrete resistance to the migration and diffusion of chloride, iodine ions. Compared with the ordinary concrete, the total porosity of concrete mixed with GGBFS is lower, the internal microstructures have fewer cracks and defects, the density is better, and the diffusion coefficient of chloride and iodide ions is also lower. In addition, using the concept of corrosive ion adjustment coefficient (conversion coefficient of diffusion between chloride ion and iodide ion) and applying the data regression analysis (DRA), it is found that there is a good quadratic parabolic function relationship between the GGBFS content and the ions adjustment coefficient.

Concrete Paver blocks are ideal materials for footpaths, parking areas for easy placing, aesthetic look and finish. It was found that rapid failure occurred on pavers and blocks became unusable within few years of its utility. The application of paver blocks has extended to the traffic areas and due to movement of vehicles, the formation of cracks on the paver blocks. An attempt is made by partially replacing cement with Rice Straw Ash (RSA) in paver blocks. Rice Straw ash is one of the agriculture waste materials that create most of the environmental conflicts. These conflicts are on the rise over the world, posing a serious threat to human health. The aim of this research is utilization of RSA as cement replacement material in concrete for making paver blocks. RSA increases the compressive strength, flexural strength, decrease water permeability and workability of the concrete. Partial replacement of cement in different percentage as like 0%, 5%, 10%, 15% and 20% has been done. The strength properties have been determined at the end of 7 and 28 days of curing. The durability properties such as sulphate resistance, acid resistance, salt resistance tests have been conducted at 90 days immersion in the solutions.

This research defines the result of studies on a Sugar cane bagasse ash (SCBA) material through laboratory experiment. The material prepared with mix ratio (0.2 % to 1.0 %), Blast furnace slag as mix ratio proportion (10%), glass fibre as reinforcing materials, cement (10%,15% and 20%) and water (50%,60%) for mix in to homogeneous slurry were added to material. The consequence of mix ratio percentages on density, compressive strength are studied. It was observed that the density of materials with inclusion of glass fibre ranging between 1101 kg/m3 to 1326 kg/m3. The compressive strength of material increases as percentages of cement increase from 10 to 20%. The compressive strength of materials influenced considerably by mix ratio 0.2 % to 1.0 %. The stress–strain outline was observed to be nonlinear for every mix ratio percentage and curing duration.

Environmental sources are diminishing every day and hence, usage of available sources become even more important. The novelty of this research reports the experimental examination of applying Recycled Plastic (RP), Treated Wastewater (TW) and GGBS in concrete. Four groups of mixes were developed (Groups NW, TW, NWG, and TWG) with each group consisting of four mixes, providing a total of 16 mixes. Group NW: 100% Natural Water (NW) with different percent ratio of RP contents Group TW: 100% Treated wastewater (TW) with different percent ratio of RP contents Group NWG: 100% Natural Water (NW) and 50% GGBS (replacement with Portland cement [PC]) with different percent ratio of RP contents Group TWG: 100% TW and 50% GGBS (replacement with PC) with different percent ratio of RP contents. Scientific contribution to the knowledge is using recycled plastic material, treated waste water and 50% GGBS simultaneously in the concrete mix. The experiments performed to compare Fresh (Compaction Factor and Slump tests), Hardened (compressive – cube & cylinder, flexural-beam strengths) and thermal properties (density & thermal conductivity). Results indicate as the plastic ratio increases, the workability of the concrete, decreases (reduction range 5 to 50% in all groups). In addition, the compressive strength values decrease as the amount of recycled plastic increases. Specifically when 50% RP content is used, mixed were affected more in all groups where the mean strength is between 10 to 30 MPa. On the other hand, 50% RP content decreases the density and it was also determined that 100% treated waste water content affected the concrete properties less than RP content in the mix. However, 50% GGBS content did not show a positive effect on the results obtained which may due to a limitation of observing up to 28-day curing age. Finally, it can be recommended to use waste materials with lower thermal conductivity because it supplies thermal comfort for the occupants.

The main components of concrete are cement and river sand (R-sand). Due to excessive production of cement, CO2 emission also increases which causes air pollution. On using R-Sand, large scale depletion of natural sources creates environmental problems. In view of the increasing national and global consensus on the environmental protection, the governments have put restrictions on mining of R-Sand from the river beds. To overcome these problems, there is a need of cost effective alternatives materials so as to make the construction sustainable without compromising its quality. In the production of Self Compacting Concrete (SCC), fly ash (FA) is utilized as an additional cementitious ingredient, which improves its performance. It solves the problem of FA disposal and environmental pollution too. The manufactured sand (M-sand) is also an alternative material which may solve the problem of shortage of R-Sand, if found suitable. In this study, M-Sand and FA were incorporated in the preparation of a sustainable SCC. After optimisation of FA and M-sand doses in the final mix, two types of SCC mixtures were developed: M-1, which consisted of 100% OPC + 100% R-Sand, and M-2, which consisted of 80% OPC + 20% FA + 50% R-Sand + 50% M-sand. Fresh properties of all SCCs were determined as per EFNARC/BIS recommendations. For destructive testing standard size specimens were cast to determine desired strengths after curing in tap water for 90 days. Rebound Hammer (RH) and Ultrasonic Pulse Velocity (UPV) were utilised in Non-Destructive Testing (NDT) to determine the strength, homogeneity, and integrity of both SCCs. Further, the water absorption of the specimen was measured up to 90 days. XRD analysis was also performed.

The indicated paper investigates about concrete’s mechanical properties casted besides partial replacement of reprocessed aggregate as coarse aggregate and sorptivity of small concrete specimens cured in MgSO4 solution. Recycled aggregate has been replaced at 10%, 20%, 30%, 40% and 50% by weight of coarse aggregate by adding the super plasticizer CERA HYPER PLAST XR W 40 and reducing 20% water by weight of the normal water content calculated for M30 mix concrete. The comparison has been made between recycled aggregate concrete and normal concrete cured in normal water and MgSO4 solution by testing cube specimens for 7, 28, 90 days respectively. As per final results concrete prototype’s strength decreases by increasing reused aggregate’s percentage by weight of natural coarse aggregate (NCA). The strength value is higher at 10% replacement of recycled aggregate. In the comparison between normal water curing and MgSO4 solution curing, it has been seen that the prototype’s strength value cured in normal water is more than that of cured in MgSO4 solution. The sorptivity of specimens cured in MgSO4 solution is greater than that cured in normal water.

In this study, the Geopolymer mortar had been examined under flowability and compressive strength using metakaolin. The binder content of 50% fly ash and 30% Ground Granulated Blast Furnace Slag (GGBFS) has been kept constant. The remaining 20% of binder is partially replaced by metakaolin to fly ash such as 5%, 10% 15% and 20%. The sodium silicate (Na2SiO3) solution molarity has been varied from 1.5 M to 2 M. The test results indicate that, the fine particles of metakaolin (up to 15%) improves the flowability and also act as a filler material and another hand, increase in molarity of the solution leads to decrease in flowability but increase in compressive strength had observed. The compressive strength of the Geopolymer mortar had been increased with increase in metakaolin content. The optimum proportion of 15% metakaolin with 1.5 M Na2SiO3 solution is suggested in terms of workability and compressive strength of Geopolymer mortar under ambient curing.

Electromagnetic waves in the X-band (8.2–12.4 GHz frequency) are used for radar, satellite communication, and, in some countries, for wireless computer networks. Shielding allows to protect humans and electronic devices from harmful effects of these waves. Cement-based composites containing conductive material can be used for this purpose, and pyrolysed carbonaceous residues (biochars) are promising in this respect. Two different biochars originated from wood (CB) and sewage sludge (SSB) pyrolysis were used as fillers in cement-based composites. The electromagnetic shielding properties of these composites are analysed vs the type and amount of biochar added. The influence of water content arising from different curing and ageing in ambient conditions is investigated for one set of samples. Results show that CB and SSB contain 74% and 30% of graphitic carbon, respectively. In the composites, SSB particles are bulky and scarcely dispersed, while CB particles are elongated and homogenously distributed. Values of Shielding Effectiveness (SE) > 20 decibel at normal incidence are achieved for the composites containing 18% of CB biochar. The influence of ageing was also investigated for a sample with 18% of wood commercial biochar: increasing wet curing increases the shielding effectiveness, while increasing ageing in air decreases the shielding effectiveness values: after 10 weeks, the measured value is about 5 dB less. The evidence suggests that the amount of physically adsorbed water is responsible for this behaviour, and it should be taken into account when dealing with cement based composites used for electromagnetic shielding.

The construction of a lunar base and habitation on the moon has always been of great significance to utilizing lunar resources and deep space exploration. In this paper, a new type of lunar regolith simulant denoted as BH-2 of similar compositions and particle size distribution with real one was developed and used for geopolymer synthesis under simulated lunar surface temperature and vacuum conditions. The geopolymer products were characterized by compressive strength test, Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscope coupled, and 29Si magic angle spinning-nuclear magnetic resonance (29Si MAS-NMR). The results showed that BH-2 lunar regolith simulant could be used to synthesize geopolymer. And the 72-h compressive strength of the geopolymer cured at the temperature of group C, corresponding to the 324–384 h of one lunar day, could reach 38.2 MPa, which was advantageous in the early stages of lunar construction because no additional curing equipment is required. The pores originated from lunar regolith simulant and caused by incomplete geopolymerization resulted in decreased compressive strength of the resulting geopolymer. Vacuum conditions on the moon favored the preparation of lunar geopolymers due to the lack of carbon dioxide weakening the efflorescence effect. This study benefits to lunar base construction with in-situ resource.

Annually, the thermal coal industries produce billion tons of fly-ash (FA) as a waste by-product. Which has been proficiently used for the manufacture of FA based geopolymer concrete (FGC). To accelerate the usage of FA in building industry, an innovative machine learning techniques namely gene expression programming (GEP) and multi expression programming (MEP) are employed for forecasting the compressive strength of FGC. The comprehensive database is constructed comprising of 311 compressive strength results. The obtained equations relate the compressive strength of FGC with eight most effective parameters i.e., curing regime (T), time for curing (t) in hours, age of samples (A) in days, percentage of total aggregate by volume (% Ag), molarity of sodium hydroxide (NaOH) solution (M), silica (SiO2) solids percentage in sodium silicate (Na2SiO3) solution (%S), superplasticizer (%P) and extra water (%EW) as percent FA. The accurateness and predictive capacity of both GEP and MEP model is assessed via statistical checks, external validation criteria suggested by different researcher and then compared with linear regression (LR) and non-linear regression (NLR) models. In comparison with MEP equation, the GEP equation has lesser statistical error and higher correlation coefficient. Also, the GEP equation is short and it would be easy to use in the field. So, the GEP model is further utilized for sensitivity and parametric study. This research will increase the re-usage of hazardous FA in the development of green concrete that would leads to environmental safety and monetarist reliefs.

Recently, the capture of carbon dioxide (CO2) using alkaline waste and byproducts has garnered considerable interest. Construction sludge may be categorized as alkaline waste, as it often exhibits high alkalinity during its generation or intermediate treatment. Hence, researchers have attempted to accelerate pH neutralization and recycle alkaline construction sludge by curing it under a high CO2 concentration. By exposing concentrated CO2 gas to an alkaline sludge, cement hydrates such as calcium hydroxide and calcium–silicate–hydrate gels form calcium carbonate (CaCO3). Subsequently, the generation of CaCO3 is expected to reduce the pH of the sludge. However, the amount of CO2 captured in sludge has not been investigated extensively, unlike those of other alkaline wastes. Therefore, the amount of CO2 captured in alkaline sludge that is associated with pH neutralization is evaluated in this study. It is demonstrated that accelerated carbonation tests using a CO2 incubator and carbonate content evaluation tests based on the gas pressure method successfully reveal the amount of CO2 captured in the alkaline sludge that is associated with pH neutralization. Additionally, the test results show that the amount of mCO2 (i.e., the amount of CO2 captured per 1 g of dry mass of alkaline sludge) increases with ΔpH (ΔpH is the difference between the initial pH and the pH after the alkaline sludge is neutralized). A maximum of 0.021 g of CO2 is captured per 1 g of dry mass of alkaline sludge when the addition ratio of quicklime AQL = 3% and 0.040 g when AQL = 6%. The CO2 capture ratio mCO2/mCO2max, which represents the ratio of CO2 captured in the sludge to the maximum capturing capacity, increases with ΔpH. CO2 capture ratios of up to 90.0% and 84.9% are recorded when AQL = 3% and AQL = 6%, respectively. It is discovered that a higher AQL results in a higher mCO2. Moreover, the test results indicate that a higher AQL causes a more significant change in the CO2 capture ratio, even when the pH decreases slightly.

Microfibers-weaved ceramic filters are in increasing demand due to their high filtration efficiency, stable structure and remarkable ceramic properties in water and gas treatment. To date, it remains a challenge to find an effective way to weave ceramic microfibers. This work demonstrates a novel strategy that combines gel-casting and in situ cross-flow microfluidic molding to fabricate highly flexible and shape-retentive green microfibers and then weaves them before sintering. By tailoring the curing temperature and flow rate, the diameter and surface morphology of the microfiber is accordingly tuned. Besides mesh structure, the microfibers can also be weaved into more complex three-dimensional structures such as dragonfly knot, Chinese knot, etc. Benefitting from the widely used solution system and microfluidic method, this system can serve as a general and stable platform for preparing microfibers-weaved ceramic filters made from different materials, thus holds great potential in a wide range of working conditions.

In this study, the mechanical properties of hybrid basalt fiber (BF) and polypropylene fiber (PF)-reinforced concretes (HBPRCs) having different matrix strengths were systematically studied, the action mechanism of the BFs and PFs was analyzed, and a prediction model of the mechanical properties of the HBPRCs was established. The results indicated that the BFs and PFs had a significant influence on the workability, compressive strength, flexural strength, and splitting tensile strengths of the concrete; however, they had little effect on elastic modulus. In general, the mechanical properties of the concrete were improved by adding only BFs and hybrid BFs and PFs when the fiber content was 0.1%. Although 0.2% hybrid BFs and PFs can reduce the compressive strength of the concrete, this composition can improve its flexural and splitting tensile strengths. With the increase in the matrix strength, the influence of the fibers on the mechanical properties of the concrete was weakened. BFs improved the strength of concrete more remarkably than PFs. Both BFs and PFs were beneficial for reducing the shrinkage cracking of the concrete. The synergistic effect of the BFs and PFs was advantageous for inhibiting the expansion of cracks in the concrete under loading and enhancing the integrity and mechanical properties of the concrete, particularly the flexural and splitting properties. Considering the factors of curing age, matrix strength, and BF and PF content, a prediction model of the mechanical properties of the HBPRCs was established, and its effectiveness was verified.

Ureolytic bacteria strains of Bacillus show its ability of calcium carbonate precipitation through metabolic activity. Different studies related to self-healing concrete material were reported associated with the generated calcium carbonate of Bacillus subtilis HU58 metabolism in recent communications. In this paper, recent findings of soil cementing with a combination of such precipitated products were presented. The experiments relied on the lab-scale studies with the use of sand-clay mixture as the controlled soil specimens. Bacillus bacteria and nutrients were mixed to introduce in the sand matrix and then curing in high moisture condition. The composition and morphology of soil specimens were characterized after solidifying by FTIR, XRD, and SEM. Water percolation and mechanical stability for the physicomechanical properties were also tested with the unconventional method. Discussing the relevant results can help to figure out the next experiments in the field of geotechnical engineering. From the perspective of this study, the sustainability factor should be considered to apply this promising technique for soil stabilization and improvement and/or for the formulation of bio-brick as an alternative to sintered clay-based brick. From the perspective of this study, this technique for soil stabilization and improvement and/or for the formulation of bio-brick can be considered a promising sustainable alternative to sintered clay-based brick.

Noncorrosive reinforcement materials facilitate producing structural concrete with seawater and sea sand. This study investigated the properties of seawater and sea sand concrete (SSC), considering the curing age (3, 7, 14, 21, 28, 60, and 150 d) and strength grade (C30, C40, and C60). The compressive behavior of SSC was obtained by compressive tests and digital image correction (DIC) technique. Scanning electron microscope (SEM) and X-ray powder diffraction (XRD) methods were applied to understand the microstructure and hydration products of cement in SSC. Results revealed a 30% decrease in compressive strength for C30 and C40 SSC from 60 to 150 d, and a less than 5% decrease for C60 from 28 to 150 d. DIC results revealed significant cracking and crushing from 80% to 100% of compressive strength. SEM images showed a more compact microstructure in higher strength SSC. XRD patterns identified Friedel’s salt phase due to the chlorides brought by seawater and sea sand. The findings in this study can provide more insights into the microstructure of SSC along with its short- and long-term compressive behavior.

Agricultural solid waste is used in several sectors due to its low cost, lightweight, and enhanced environmental friendliness. The present work aims to study the impact of date seed waste (DSW) on physic-mechanical properties and the firing resistivity of cement pastes (CPs). The Portland cement (PC) is individually added with 2.5, 5, 10, and 15 wt% of DSW. The chemical composition of raw materials was investigated by using FTIR analyses. SEM techniques studied the microstructure of raw materials and hardened CPs. An experimental Taguchi method and an analysis of variance (ANOVA) were employed in this study to evaluate the most optimal and significant conditions of the process. The CPs-mix, which contains 2.5 wt% of DSW (MDS-2.5/A), showed the highest compressive strength values at all ages of hydration compared with other mixes and M0-mix. According to the results of this investigation, DSW showed a negative effect on the water consistency values of CPs at all ages of hydration. It was also observed that hardened DSW-CPs increased significantly with a rising in DWS content up to 15wt% at all curing ages. Particularly in the case of MDS-2.5/A-mixes, the DSW increased the firing resistance of the CPs. Finally, the Taguchi analysis revealed that the best parameters are 2.5 wt% DSW and 28 days of curing time. When it comes to the optimal fire resistance values, it becomes 2.5 wt% of DSW at 250 °C. This study revealed that DSW affects both compressive strength and fire resistance from the technical and economic points of view.

Fly ash-based geopolymer is a crucial application for tackling climate change, limiting the production of greenhouse emissions. The main aim of this study was to determine the effect of the fundamental parameters on compressive strength to ensure a feasible and effective solidification of mine tailings. Three sodium hydroxide (NaOH) molarities (5, 8, and 10 M) and sodium silicate (Na2SiO3) were combined to form the alkaline solution. Four fly ash (FA) proportions (28%, 44%, 54, and 61%) of the dry mix and mine tailings (MT) were utilized as raw materials. This study demonstrated that both 25 °C and 65 °C have a considerable effect on the mechanical properties of geopolymers. The UCS value increased with an increase in NaOH molarity. In addition, the highest Unconfined Compressive Strength (UCS) value was achieved (36.04 MPa) at 10 M. Furthermore, the results also showed that UCS values kept decreasing with the increase of SiO2/Al2O3 and Na2O/SiO2 ratios. The optimal UCS values found were in the range of 0.28–0.38 liquid/solid ratio. It has been concluded that the previously mentioned parameters have a strong influence on the mechanical strength of fly ash-based geopolymer with the new proposed FA proportion.

Excessive accumulation of waste materials has presented a serious environmental problem on a global scale. This has prompted many researchers to utilise agricultural, industrial, and by-product waste materials as the replacement of aggregate in the concrete matrix. In this present study, the prediction and optimisation of coconut shell (CA) content as the replacement of fine aggregate were evaluated based on the mechanical properties of the concrete (M30). Based on the suggested design array from the response surface methodology (RSM) model, experimental tests were carried out to achieve the goal of this study. The collected data was used to develop mathematical predictive equations using both GEP and RSM models. Analysis of variance (ANOVA) was also taken into account to appraise and verify the performance of the proposed models. Based on the results, the optimum content of replacing CA was 50%. In particular, the compressive, tensile, and flexural strength obtained after 28 days of curing were 46.2, 3.74, and 8.06 MPa, respectively, from the RSM model and 46.18, 3.85, and 7.99 MPa, respectively, from the GEP model. The obtained values were superior to those of the control concrete sample (43.12, 3.51 and 7.14 MPa, respectively). Beyond the optimum content, a loss in strength was observed. It was also found that both the GEP and RSM models exhibited high prediction accuracy with strong correlations (R2 = 0.97 and 0.95, respectively). In addition, minimum prediction error (RMSE

This research focuses on studying the effect of different supplementary cementitious materials (SCMs) such as waste ceramic powder (WCP), lime powder (LP), and ground granulated blast furnace slag (GGBS) in combination on strength characteristics and microstructure of quaternary blended high-strength concrete. To achieve the aims of the study, necessary physical and chemical composition tests were done for the raw materials. Then, mixes were designed into control mix with 100% Ordinary Portland Cement (OPC) and experimental mixes containing 30%, 40%, 50%, and 60% of GGBS, WCP, and LP in combination. Tests were conducted during casting and at curing ages of 7 and 28 days. Accordingly, the control mix which is concrete grade 50 (C-50) as per American Concrete Institute (ACI) mix design is used as a reference for comparison of test results with those specimens produced by partial replacement of SCMs. The characterizations of high-strength concrete are done using consistency, setting time, workability, compressive strength, flexural strength, and morphological tests. The optimum percentage replacement is 50% OPC replacement by 30% GGBS + 10% WCP + 10% LP. Based on the experimental investigations, the workability increases as the replacement level of SCMs increases from 30% to 60% by weight. Compressive strength and flexural strength results increase up to 11.41% and 20% when the percentage replacement increases from 30% to 50% of SCMs replacement at 28 days of curing time, respectively. There are also improvement in the microstructure and significant cost saving due to replacing OPC partially with SCMs with proportions mentioned above. Therefore, the practice of utilizing increased percentage of SCMs in quaternary blend in concrete can be beneficial for the construction industry and sustainability without compromising the quality of the concrete product.

Ground improvement by permeation grouting is widely utilized for improving engineering properties of soil. The accurate evaluation of a region improved by grouting is a critical issue to ensure the performance of grouting; nevertheless, current methods to evaluate the area of grouted bulbs under the ground are not well-documented. This study aims to use cross-hole electrical resistivity tomography (CHERT) to evaluate a grouted bulb region by considering the effect of electrode configuration at laboratory scale using a cylindrical container filled with saturated sand. Curing time monitoring was also conducted on grouted bulbs with various recovered Carbon Black (rCB) concentrations. Based on the inverted result, the predicted area of the grouted bulb was addressed, and then the error value between the actual and predicted areas was examined. The results of this study show that CHERT can be employed to assess the location and area of a grouted bulb. Also, it was observed that electrode spacing, damping factor, and curing time had significant influences on the image resolution and error value. Unlike the above-mentioned factors, change of rCB concentration ratio had only a slight effect on the image resolution. Thus, the use of a small amount of rCB as an additive material to enhance the grout strength can also provide a distinct contrast of measured resistivity between the grouted bulb and surrounding soil. In this study, a grouted bulb containing 3% of rCB is recommended based on the test results on strength characteristics. In addition, CHERT measuring can be conducted even in early stages of curing, during which it exhibits a better electrical resistivity contrast between the objective area and the surrounding soil.

Limestone calcined clay cement (LC3) is a new type of low-carbon cement that can reduce energy consumption and carbon dioxide emissions while meeting the performance requirements of ordinary cement. In this study, polypropylene (PP) fibers were mixed into limestone calcined clay cement-based materials to make new low-carbon ECCs. In this study, a total of 24 sets of specimens were designed for 4 groups of curing ages and 6 types of mix ratios. The compressive load–displacement data were measured the compressive curve characteristics were analyzed then, a compressive constitutive model of the composites was deduced and obtained. Through XRD, SEM-EDS and MIP experiments, the reasons and laws of the compressive strength ranges of adding PP fibers and LC3 to engineered cementitious composites (LC3-PP-ECCs) are further explained from the perspective of the pore size, microstructures and hydration products. The results show that, after 28 days, the compressive strength values of LC3-PP-ECCs generally decreases with increasing PP fiber content and the combined effect of PP fibers and hydration products causes the compressive strength of LC3-ECCs with 0.5% PP fibers to drop sharply. In addition, the specimens showed better properties in terms of toughness, ductility and energy absorption. However, in the microstructures, the addition of PP fibers will cause more internal defects and flaws. This results of this study can provide some theoretical experience and technical support for the engineering application of LC3-ECCs.

This paper presents a study on evaluating the effect of two key factors, namely, the hybridization of straight and hooked steel fibers and curing methods, on the mechanical properties of ultra-high-performance concrete (UHPC). The UHPC specimens using the same proportions of the water, binder, and filler were prepared considering five different combinations of straight and hooked steel fibers. The UHPC specimens were subjected to normal water curing and steam curing. The mechanical properties studied included the compressive strength, flexural strength, modulus of elasticity, flexural toughness, and steel-UHPC bond characteristics considering steel bars of two different strength grades (G60 and G230). The experimental data were used to discuss the effects of both the hybridization of steel fibers and curing methods on the mechanical properties of UHPC as well as to conduct an analysis of variance (ANOVA) and to obtain the empirical models correlating the variables with the mechanical properties. The test results exhibited a significant effect of the hybridization of the fibers on the studied properties of UHPC. The UHPC containing a higher amount of hooked fibers significantly enhanced the modulus of elasticity, flexural tensile strength, and flexural toughness. The performance of UHPC cured using steam was found better than that cured using water in all aspects.

To achieve sustainability in the field of civil engineering, there has become a great interest in developing reactive powder concrete RPC through the use of environmentally friendly materials to reduce the release of CO2 gas produced from cement factories as well as contribute to the recycling of industrial wastes that have a great impact on environmental pollution. In this study, reactive powder concrete was prepared using total binder content of 800 kg/m3, water to binder ratio (0.275), and micro steel fibers 1% by volume of concrete. The experimental program included replacing fly ash with (8, 12, 16) % by cement weight to find the optimal ratio, which achieved the best mechanical properties of (RPC) at 7, 28, and 90 days with standard curing. Some mechanical properties of reactive powder concrete (flow, compressive strength, tensile strength, and density) were verified. The results at 28 days showed that the compressive strength (96.5) Mpa, tensile strength (9.38) Mpa, and density (2395 kg/m3). The results showed that the percentage of replacement of 8% of fly ash with cement is the optimal percentage, which achieved the highest resistance compared to the others. The results also indicated that it is possible to develop RPC using fly ash with a high withstand stress, tensile strength, and density.

This research aimed to present the improvement of the cementitious material in high-volume fly ash using only one alkali activator. Fly ash was used as a partial replacement for Portland cement type I, varying from 0 to 60% by weight of the binder. Concentrations of NaOH varying from 0.00 to 1.25 molar were used as alkali activator. Paste properties and mortar compressive strength at the ages of 3, 7, 14, 28, 60, and 90 days of water curing were investigated. The results reveal that fly ash paste with an alkali activator provides shorter initial setting time when compared to control paste without alkali activator. The use of 0.50 molar NaOH concentration in mortar containing fly ash not exceeding 50% by weight of binder provides the highest compressive strength at any age of curing. At that concentration, there is a significant increase in the 28-day compressive strength of up to 45% over that of the control mortar. In addition, higher NaOH concentration (not exceeding 1.00 molar) has a significant positive effect on the compressive strength of mortar with higher fly ash content, especially over longer curing periods.

In this paper, copper foams cured MIL-101(CFCM)/isobutane double-bed adsorption cooling system (ACS) were designed and constructed by using the CFCM unit tube adsorbers. Adsorption cooling characteristic curves of CFCM/isobutane double-bed ACS were studied. Influence of cycle parameters and mass recovery process on the cooling capacity, specific cooling power (SCP) and coefficient of performance (COP) of the CFCM/isobutane double-bed ACS was investigated. Results show that under the conditions of cycle time of 600 s, pre-cooling/pre-heating time of 120 s, condensation temperature of 15°C and hot water temperature of 85°C with the flow rate of 20 L h−1, and cooling water temperature of 14-16°C with the flow rate of 50 L h−1, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS is 65.20 kJ kg−1, 108.67 W kg−1 and 0.2260, respectively. Compared with basic cycle, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS increases by about 26%, 24% and 22% under mass recovery time of 10 s. The cooling performance of CFCM/isobutane double-bed ACS remains stable after 100 sets consecutive basic cycles and 20 sets mass recovery cycles.

Mine tailings-based geopolymer was proved to be successfully created with enhanced strength for potentially construction and building materials applications. Through geopolymerization, the mining wastes can be reused and the storage, economic, and environmental issues can be mitigated. However, the geopolymerization effect was relatively limited comparing to the ordinary Portland concrete. Therefore, the additions of amorphous supplementary fly ash were considered in the paper. In this study, class F fly ash was utilized as an amorphous additive and the additional aluminum source to adjust the Si: Al ratio for better geopolymerization effects. To better understand the mechanical and fracture behavior of the geopolymer after adding fly ash, the Brazilian indirect tensile tests were then conducted to evaluate the influence of different fly ash additions, 5%, 10%, 15%, and 20%, on the tensile strength of the geopolymer. Meanwhile, besides the load-displacement relationships, the digital image correlation was used to investigate the crack initiation and propagation in the geopolymer disks with respect to different fly ash additions. The crack evolution was evaluated from the full-field strain field from digital image correlation. Crack opening displacements, failure patterns, and strain evolutions for the geopolymer disks with different fly ash additions were examined. Results showed that, under the presented sample curing condition, the geopolymer with 15% fly ash addition had the largest tensile strength. Geopolymer disks without and with lower fly ash additions had plastic deformation prior to the peak load that can obviously be classified into three different stages. The geopolymer made without and with lower fly ash additions had both tensile and shear crack modes.

Natural-fiber-reinforced geopolymer composites are environmentally friendly materials that have garnered considerable attention. In practice, the drying shrinkage and uneven dispersion of fibers in geopolymers result in low flexural strength, which limits the use of large-scale composites. In this study, high-flexural strength geopolymer composites with self-assembled nanofiber networks were hybridized using in situ polymerization. Composites with different fiber contents were evaluated via morphology and mechanical strength assessments. A mixed nanofiber and geopolymer solution was created to achieve uniform dispersion, and then the geopolymers were optimized at the nanoscale level using a bottom-up approach to achieve self-assembled nanofiber networks with good interfacial bonding. Due to the water retention properties of the nanofibers and subsequent gel material, the networks facilitated internal curing of the geopolymers, thus preventing drying shrinkage. This ultimately reduced the weight loss and increased the density of the composites. In addition, high flexural strength properties were observed in composites with a fiber content of 0.5%, due to the combination of fiber reinforcement and porosity. Thus, this work introduces new considerations for geopolymer applications.

As cement manufacturing is associated with CO2 emissions that contribute to environmental problems, cement usage must be reduced and alternative aggregates must be developed. Thus, we developed and evaluated a mortar that uses feldspar as a fine aggregate, which does not require additional mineral admixtures. Feldspar and conventional plastering sand-based specimens were prepared with a fine aggregate proportion of 75%, 80%, or 85%. The compressive strength test results confirmed that the strength of the feldspar-based mortar was 1.1–4.5 times higher than conventional plastering sand-based mortar. Microstructure analysis after 3 and 7 d of curing revealed the existence of capillary micropores and gel pores, which improved water tightness. C-S-H and C-S-H gel hydration was also observed at the early stage, and the amount of C-S-H also increased. Further, an additional reaction may have occurred between feldspar compounds, SiO2 and Al2O3, and Ca(OH)2 that accelerated C-S-H production and contributed to the higher compressive strength. The relatively high-strength feldspar-based mortar is expected to reduce cement dependency, which can be achieved using a fine-aggregate feldspar mixing ratio according to project requirements. Thus, the proposed fine aggregate alternative can help alleviate the environmental problems associated with cement usage. It also has potential as an eco-friendly building material.

One of the sustainable alternatives to Portland cement is geopolymer concrete consisting of industrial waste. Practical application of geopolymer concrete is restricted as it requires the use of high temperature to develop compressive strength. This study aims to develop a mixture design for geopolymer prestressed concrete specifically designed to take prestressing force using ambient curing technique and compare its performance with the same grade of Portland cement concrete mix. As ambient curing technique is used for geopolymer concrete hence a combination of blast furnace slag and fly ash is taken as source materials and due to ease of availability and economy, sodium hydroxide and silicate are chosen as activators. After several trial mixtures, M 40 grade of geopolymer concrete is developed using an equal proportion of fly ash and ground granulated blast furnace slag (GGBFS) as source material. GGBFS provides early strength at ambient curing in geopolymer concrete and hence was incorporated with fly ash. 3 ply of 3 mm diameter bars were used as pre-tensioning wire. Load v/s deflection graph for non-prestressed geopolymer concrete beams and beams with same grade Portland cement concrete show that the load-carrying capacity of both beams was at par. It was also observed that prestressed geopolymer concrete beams which were cured under ambient curing developed sufficient strength and were equally capable of carrying the load as compared to Portland cement concrete beams. Load carrying capacity increased in prestressed Portland cement concrete beams increased by 78% while in prestressed geopolymer concrete beams the increase was 83% and also the deflection of both prestressed beams was more compared to non-prestressed beams. This indicates that sustainable material can be effectively utilized in prestressing work without comprising on strength.

Magnesium oxychloride cement (MOC) is a promising binder with many advantageous properties over traditional binders. Its main downfall, restricting large-scale use, is its inherent susceptibility to moisture. However, in recent years, niche applications have developed where MOC has been deployed successfully. These include lightweight wall panels, floor tiles, and decorative panels. This paper investigates the effect of molar ratios (MgO/MgCl2 and H2O/MgCl2) and curing conditions on MOC. Findings illustrate that the use of appropriate molar ratios and the implementation of a suitable curing regime can significantly improve the moisture resistance of MOC. After 28 days of immersion in water, the MOC samples lost between 40% and 90% of their strength depending on the molar ratio, demonstrating the importance of correct proportioning. It was also found that curing MOC at temperatures between 20°C and 50°C provides the most stable MOC in humid conditions. These findings add to the current knowledge available on MOC. They will help end users to improve the performance of MOC in its current applications and work toward broadening the range of applications where MOC can be used successfully.

The present study deals with the severity of delay before carrying out the curing of concrete in hot weather. The effect of delay before curing on the strength and durability of ordinary po...