Ordinary Portland Cement Mixes Research Articles

Alkali-Activated Binders as Sustainable Alternatives to Portland Cement and Their Resistance to Saline Water.

Alkali-activated binders have emerged as promising alternatives to Ordinary Portland Cement (OPC) due to their sustainability features and potential advantages. This study evaluates the durability properties of heat-cured fly ash (FA) and ground granulated blast-furnace slag (GGBFS) geopolymer mortars activated with sodium hydroxide, which were subjected to wet-dry cycling in saline environments. Three series of FA, a FA/GGBFS blend, and GGBFS mortars previously optimized on a compressive strength basis were investigated and compared against two control OPC mixes. Performance indicators such as the water absorption, porosity, flexural strength, and compressive strength were analyzed. The results demonstrate that geopolymer mortars have significantly reduced water absorption and porosity with increasing wet-dry cycles. The compressive strength of the FA/GGBFS mortars also increased from 66.5 MPa (untreated) to 87.9 MPa over 45 cycles. The flexural strength remained stable or improved slightly across all geopolymer mortars. The control OPC specimens experienced significant deterioration, with compressive strength in CEM I 42.5R dropping from 51.8 to 17.1 MPa. These findings highlight the superior durability of geopolymer mortars under harsh saline conditions, demonstrating their potential as a resilient alternative for coastal and marine structures.

Influence of recycled coarse aggregate on properties of fly ash and slag-based geopolymer concrete cured under oven and ambient temperature

Purpose The purpose of this paper is to investigate the effect of the replacement of natural coarse aggregate (NCA) with different percentages of recycled coarse aggregate (RCA) on properties of low calcium fly ash (FA)-based geopolymer concrete (GPC) cured at oven temperature. Further, this paper aims to study the effect of partial replacement of FA by ground granulated blast slag (GGBS) in GPC made with both NCA and RCA cured under ambient temperature curing. Design/methodology/approach M25 grade of ordinary Portland cement (OPC) concrete was designed according to IS: 10262-2019 with 100% NCA as control concrete. Since no standard guidelines are available in the literature for GPC, the same mix proportion was adopted for the GPC by replacing the OPC with 100% FA and W/C ratio by alkalinity/binder ratio. All FA-based GPC mixes were prepared with 12 M of sodium hydroxide (NaOH) and an alkalinity ratio, i.e. sodium hydroxide to sodium silicate (NaOH:Na2SiO3) of 1:1.5, subjected to 90°C temperature for 48 h of curing. The NCA were replaced with 50% and 100% RCA in both OPC and GPC mixes. Further, FA was partially replaced with 15% GGBS in GPC made with the above percentages of NCA and RCA, and they were given ambient temperature curing with the same molarity of NaOH and alkalinity ratio. Findings The workability, compressive strength, split tensile strength, flexural strength, water absorption, density, volume of voids and rebound hammer value of all the mixes were studied. Further, the relationship between compressive strength and other mechanical properties of GPC mixes were established and compared with the well-established relationships available for conventional concrete. From the experimental results, it is found that the compressive strength of GPC under ambient curing condition at 28 days with 100% NCA, 50% RCA and 100% RCA were, respectively, 14.8%, 12.85% and 17.76% higher than those of OPC concrete. Further, it is found that 85% FA and 15% GGBS-based GPC with RCA under ambient curing shown superior performance than OPC concrete and FA-based GPC cured under oven curing. Research limitations/implications The scope of the present paper is limited to replace the FA by 15% GGBS. Further, only 50% and 100% RCA are used in place of natural aggregate. However, in future study, the replacement of FA by different amounts of GGBS (20%, 25%, 30% and 35%) may be tried to decide the optimum utilisation of GGBS so that the applications of GPC can be widely used in cast in situ applications, i.e. under ambient curing condition. Further, in the present study, the natural aggregate is replaced with only 50% and 100% RCA in GPC. However, further investigations may be carried out by considering different percentages between 50 and 100 with the optimum compositions of FA and GGBS to enhance the use of RCA in GPC applications. The present study is further limited to only the mechanical properties and a few other properties of GPC. For wider use of GPC under ambient curing conditions, the structural performance of GPC needs to be understood. Therefore, the structural performance of GPC subjected to different loadings under ambient curing with RCA to be investigated in future study. Originality/value The replacement percentage of natural aggregate by RCA may be further enhanced to 50% in GPC under ambient curing condition without compromising on the mechanical properties of concrete. This may be a good alternative for OPC and natural aggregate to reduce pollution and leads sustainability in the construction.

Relationship between electrical Conductivity, Half cell Potential, Linear polarization resistance and Macrocell current of cementitious repair materials

Corrosion degradation of RC could lead to instability and eventually the collapse of structures if not detected early. Electrochemical methods like Half Cell Potential (HCP), Linear Polarization Resistance (LPR), Macrocell Current and Electrical Conductivity were used in this research to evaluate the relationship between these four non-destructive methods. These four Non-Destructive Test (NDT) methods were used to assess the resistance against chloride attack on three different types of cement-based materials and Ordinary Portland Cement mix (control). Experimental research conducted in this study reveals that there is a linear relationship between electrical conductivity and corrosion current. There is also a fairly good relationship between corrosion current and half cell potential when measuring the degree of corrosion potential and corrosion current for all three repair materials and the control, showing a R2 = 0.72. However, there is an insignificant relationship between corrosion current and macrocell current showing a value of R2 = 0.66.

Experimental investigations on hybrid fibre reinforced alkali activated concrete mixes

The present study attempts a detailed evaluation of the strength performance of Fiber reinforced Alkali Activated Concrete mixes containing fly ash and ground granulated blast furnace slag (GGBS) as a sole binder. Fly ash and GGBS, a by-product obtained from industries, is incorporated in the AASC mixes as a full replacement to ordinary Portland cement (OPC). Initially OPC and AASC mixes are designed to obtain M30 grade. This experiment investigates the effect of the addition of hooked end steel fiber and polypropylene fiber on the physical and mechanical properties of high ductile Alkali Activated Concrete. Geo-polymer is called one of the best substitutes for ordinary Portland cement (OPC) because of its benefits over OPC. Hooked end steel fiber of length 35 mm and diameter 0.5 mm with aspect ratio of 70, polypropylene fiber of 12 mm length is used in hybrid manner, with five different fiber volume fractions of 0.25 & 1.25%, 0.50 & 1%, 0.75 & 0.75%, 1 & 0.50% and 1.25 & 0.25% respectively. All mixes of fiber reinforced Alkali Activated Concrete includes 50% of GGBS and 50% of fly ash from total binder content. Alkali activators used are, sodium hydroxide pellets and sodium silicate liquid. The experimental result indicated that, the addition of fibers affects the workability by 20–30% down. In the mechanical property wise, fibers variation doesn’t affect the compressive strength much. Flexure and tensile strength increase by about 20–40%, compared to other mixes without any fiber’s addition. This increment of strength is due to addition of both the fibers in hybrid way. Using Alkali Activated Concrete helps to reduce emission of carbon dioxide, which happens from manufacturing of cement. Geo polymer concrete make the environment very much sustainable by maintaining global warming in a limit.

Performance evaluation of alkali activated slag based recycled aggregate pervious concrete

The present study attempts, a detailed evaluation of the strength performance of Alkali Activated Slag based Pervious Concrete (AASPC) mixes, containing fly ash and ground granulated blast furnace slag (GGBS) as binders. Fly ash and GGBS, by-product obtained from thermal power plants and steel industries respectively, is incorporated in the AASPC mixes as a full replacement to ordinary Portland cement (OPC). Initially OPC and AASPC mixes are designed to obtain M30 grade. OPC based pervious concrete is considered as control concrete. Pervious concrete is a type of concrete that has a high-water permeability and a higher void content than regular concrete.Experiments investigates the effect of the addition of Recycled Coarse Aggregate (RCA) on the physical and mechanical properties of alkali activated pervious concrete. Certain physical test has been conducted on recycled coarse aggregate to check the quality of aggregates, RCA varying percentage in 0, 25, 50, 75 and 100%, in the mixes. All mixes of alkali activated pervious concrete includes 50% of GGBS and 50% of fly ash from total binder content. Alkali activators used are, sodium hydroxide pellets and sodium silicate liquid. Workability of the alkali activated pervious concrete has a low slump value compare to the control concrete, but the workability of pervious concrete with cement is equal to alkali activated pervious concrete and workability will decreases with increase in RCA percentage because has a high capacity of water absorption. Compressive strength of alkali activated pervious concrete has increased by 23% compared to the OPC based pervious concrete and then there will be a decrease in compressive strength with increase in RCA percentage. The flexural strength and split tensile strength results for both the alkali activated pervious concrete and OPC based concrete shows almost similar values. Permeability and void ratio results shown increase with increase in RCA percentage in AASPC.

Effect of sodium sulfate activation on the early-age matrix strength and steel fiber bond in high volume fly ash (HVFA) cement mortar

Retarded hydration and delayed microstructure development could reduce the early-age mechanical performance of fiber reinforced, High Volume Fly Ash (HVFA) cement composites. In this study, the effects of the pH-neutral Sodium Sulfate (SS), as a chemical activator on the early-age matrix mechanical strength development and bond performance of a steel macrofiber in HVFA cement mortar mixtures were examined. Mortar mixtures containing 0–10% Silica Fume (SF), 30–40% Ordinary Portland Cement (OPC) and 4–6 wt% SS were tested. Specifically, changes in matrix compositional structure, mechanical strength, bond strength and absorbed energy of two End-deformed (ED) steel macrofiber were evaluated. The microstructure of the fiber–matrix Interfacial Transition Zone (ITZ) was also studied through Scanning Electron Microscopy-Backscattered Electron (SEM-BSE) imaging. Results showed that the SS accelerated pozzolanic reaction in HVFA mixtures, causing a rapid depletion of portlandite and a moderate enhancement of the 7th day mechanical strength properties. The positive influence of the SS increased considerably with respect to the pullout test whereby bond strength and pullout energy higher than those of the fiber embedded in 100% OPC (Mix 1) mortar were measured. SEM-BSE imaging showed that a denser fiber–matrix ITZ, a more efficient fine aggregate-fiber interlocking, and enhanced stress transfer from the cement paste to the solid inclusions in the matrix were responsible for the superior pullout performance of steel macrofiber embedded in SS-activated HVFA mortar mixtures. Based on these results, applications such as rigid pavements and repair overlays where accelerated deployment is an important consideration can be constructed using steel macrofiber reinforced HVFA cement mixtures.

The influence of alkali activators on the properties of ternary blended cement incorporated with ferronickel slag

In this study, the influence of alkali activators on the properties of blended cement containing pulverized fly ash (PFA) or/and ferronickel slag (FNS) powder was investigated. As a binder, ordinary Portland cement (OPC), PFA, and FNS were used to produce alkali-activated blended mixes; OPC and ternary mix, including two different types of admixtures, respectively. Setting time, adiabatic temperature rise, and development of compressive strength was evaluated for physical performance. Hydration characteristics of the blended pastes with hydroxide activators were analyzed by x-ray diffraction, thermogravimetric analysis, and scanning electron microscope. It was found that blended cement containing FNS as the binder can prolong the setting time and hydration heat which was substantially mitigated due to a latent hydration characteristic. In terms of geopolymerization, the formation of hydration products was enhanced in ternary blended cement, which showed the highest compressive strength in the long-term curing.

Strength and Leaching Behavior of Contaminated Mining Sludge at High Water Content Stabilized with Lime Activated GGBS.

Sludge management is one of the major challenges in mining activities. The direct disposal of contaminated mining sludge can bring severe damages to the environment and community. Solidification/stabilization (S/S) is a very efficient technology for the treatment of contaminated mining sludge because it improves the stability of sludge dumping sites and reduces the leachability of contaminants. Very few studies investigate the S/S of mining sludge, especially with high water content. This paper investigated the effectiveness of S/S for the treatment of mining sludge at high water content by using quick lime (CaO) activated ground granulated blast furnace slag (GGBS) in comparison to ordinary Portland cement (OPC). To evaluate the mechanical, leaching, and microstructural behavior of CMS at high water content stabilized by lime-activated GGBS and OPC, a series of laboratory experimental tests were performed. Experimental results indicated that increasing the dosage of binder led to increased strength and decreased leachability of the heavy metal. In contrast, an increase in the water content of the mixture resulted in a decrease in compressive strength and an increase in the leachability of heavy metals. On the other hand, lime-activated GGBS mixes had substantially better performance than OPC mixes in the aspect of strength development of treated mining sludge and showed comparable capability of heavy metal stabilization compared to OPC. The microstructural tests revealed the formation of different hydration products such as calcium silicate hydrate, calcium aluminum silicate hydrate, ettringite, hydrotalcite, and heavy metal complexes in CG and OPC mixes.

RETRACTED: Abrasion and skid resistance of concrete containing waste polypropylene fibers and palm oil fuel ash as pavement material

During the entire service life of pavement, the exposed surface must have an adequate level of roughness, so as to expedite the friction amongst vehicle wheels and the surface of the pavement. Therefore, the abrasion and skid resistance should be considered when measuring the wear, sliding, and skidding levels of a pavement surface. It is well-known that the lower the skid resistance value, the higher the percentage of traffic accidents (particularly under wet conditions). Therefore, this study aimed to enhance the abrasion and skid resistance of concrete as a pavement material by reinforcement with polypropylene (PP) fibers. The influences of waste PP fibers and palm oil fuel ash (POFA) on the tensile and compressive strengths, modulus of elasticity, abrasion resistance (tested using a Bohme surface abrasion machine), and skid resistance (tested using a British pendulum skid resistance tester) of the concrete were investigated. Overall, 12 mixes were cast, including six concrete mixtures comprising 0%, 0.25%, 0.5%, 0.75%, 1%, and 1.25% PP fibers with 100% ordinary Portland cement (OPC). Another six concrete mixtures were prepared with the same fiber dosages, but with 20% POFA as a cement replacement. The experimental results revealed that using PP fibers at concentrations up to 1.25% reduced the compressive strength of concrete mixtures by approximately 17%. However, the addition of PP fibers significantly enhanced the tensile strength (by 30%), along with the abrasion and skid resistance of all of the fiber-reinforced concrete mixtures. It was found that the 1.25% PP fiber mix had the highest abrasion and skid resistance, i.e., approximately 25% higher than that of a control mix. In addition, the POFA mixes performed better than the OPC mixes, owing to the high pozzolanic activity and the formation of additional hydration products.

Compressive Strength, Splitting Tensile Strength, and Chloride Penetration Resistance of Concrete with Supplementary Cementitious Materials

This article presents the outcomes of a study that examined the durability and mechanical characteristics of self-consolidating concrete (SCC) mix in which a percentage of the required ordinary Portland cement (OPC) was substituted with either fly ash or ground granulated blast furnace slag (GGBS). The first part of the study evaluates the chloride penetration resistance and compressive strength of SCC mixes in which OPC in a designed control mix was partially replaced in a series of mixes by fly ash in percentages ranging from 10% to 40%. It noted that replacing OPC with fly ash at each of the four percentages studies improved chloride resistance of concrete compared to the control mix made of 100% OPC as binder. The 40% fly ash mix was the best performer in terms of resistance to chloride migration in contrast with the 100% OPC mix. Samples prepared using the 40% fly ash mix SCC mixes had the lowest compressive strength after 7 days of moist curing. However, the 28-day compressive strength of 40% fly ash mix was a healthy 55.75 MPa, only slightly lower than the 100% OPC mix. Tests also showed that adding 2% or fewer basalt fibres to the SCC mix in which 40% of OPC improves concrete resistance to chloride migration in contrast with the 40% fly ash mix that didn’t contain basalt fibres. This paper also reports the relationship between splitting tensile strength and compressive strength of SCC mixes in which up to 80% of OPC was substituted with GGBS. A total of eight mixes were produced by varying the amounts of GGBS used to replace the OPC content of the control mix. The fresh properties were assessed through the flow test, visual stability index (VSI), and the T50. An empirical relationship was developed to predict the splitting tensile strength based on 28-day compressive strength, and its accuracy was evaluated in comparison to formulas in various design codes.

Green concrete composites production comprising metalized plastic waste fibers and palm oil fuel ash

Amongst the potential solutions to a cleaner environment is to minimize the consumption of non-biodegradable materials and to reduce wastes. The generation and disposal of waste plastics cause severe impacts on the environment. The utilization of solid waste in the sustainable constructions has concerned much attention due to the lower cost of wastes along with saving a necessary place of landfills. In this paper, the feasibility of metalized plastic waste (MPW) fibers and palm oil fuel ash (POFA) in the production of concrete composites was investigated by assessing the mechanical properties and ultrasonic pulse velocity. Six concrete mixes containing MPW fibers varying from 0 to 1.25% with a length of 20 mm were made of ordinary Portland cement (OPC). A different six concrete mixtures with the same fiber content were made, where 20% POFA substituted OPC. The results show that MPW fibers, together with POFA reduced the workability of concretes. It has also been found that by adding MPW fibers to the concrete mixtures, the compressive strength decreased for both OPC and POFA mixes at the early ages. Though at the curing period of 91 days, the mixes contain POFA attained compressive strength higher than those of OPC mixes. The mixture of MPW fibers and POFA subsequently enhanced the tensile and flexural strengths, thereby increasing the ductility. The study revealed that the MPW fibers are potential to be used in sustainable concrete by improving the mechanical properties.

Sensitivity analysis for binders in concrete mix to the corrosion risk of steel embedment in chloride-bearing environments

The sensitivity to corrosion-free life in concrete structures exposed to chlorides was evaluated with respect to different binder in mix. As binders, ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBS), pulverised fuel ash (PFA) and silica fume (SF) were selected. Prior to the sensitivity analysis, experimental works were performed to achieve control values for the apparent diffusion coefficient, surface chloride concentration and critical chloride threshold level for corrosion. The cover depth was set 100 mm in the sensitivity analysis. The margin for the variation in parametric values was set −50 to +100% to the control. As a result, OPC had the highest sensitivity for the chloride threshold level and surface chloride concentration to corrosion-free life, whilst these sensitivities in other mixes were lower in a similar range between them. Either a double of the chloride threshold level or half of the surface chloride in OPC mix could produce the corrosion-free life in an equated range for 65% GGBS mix at an equivalent condition. As for cover depth and apparent diffusion coefficient, their sensitivity to corrosion-free life was independent to binder type, which nevertheless affects the corrosiveness.

Determination of optimum ordinary Portland cement content in solidifying/stabilizing mineral sludge

Binder plays important role in Solidification/Stabilisation (S/S) technique for sludge treatment. However, mineral sludge namely water treatment sludge (WTS) and ceramic sludge (CS) are rarely treated using S/S technique. Therefore, this study was conducted to obtain optimum percentage of Ordinary Portland Cement (OPC) content as a binder in S/S technique to treat the mineral sludge. Twenty (20) OPC mix proportions at 10% to 100% OPC with 10% increment were prepared to treat both 200 g WTS and 200 g CS. Binder-to-sludge (B/Sd) ratio of one (1) was used. Air curing was applied for all mixes. Compressive strength was conducted at 28 curing days. The compressive strength of treated mineral sludge was then compared to the requirement stipulated in Waste Acceptance Criteria in Landfill at 0.34 MPa. It was found that the optimum percentage of OPC to treat 200g WTS and 200g CS were 50% and 60% respectively.

RETRACTED: Waste metalized film food packaging as low cost and ecofriendly fibrous materials in the production of sustainable and green concrete composites

Abstract Among the potential solutions to a cleaner environment is to decrease the consumption of non-biodegradable materials and to reduce wastes. The generation and disposal of waste plastics cause severe impacts on the environment. The utilization of solid waste in the sustainable constructions has concerned much attention due to the lower cost of wastes along with saving a necessary place of landfills. The current paper investigates the feasibility of utilizing waste metalized plastic (WMP) fibers used for food packaging and palm oil fuel ash (POFA) in concrete in terms of mechanical and transport properties. Six fiber dosages of 0–1.25% were used for ordinary Portland cement (OPC) mixtures. In addition, the same dosages of fibers were used in mixes with 20% POFA. The results show that WMP fibers, together with POFA, reduced the workability of concretes. It has also been found that by adding WMP fibers to the concrete mixtures, the compressive strength decreased for both OPC and POFA mixes at an early age. Though at the longer curing time, say 91 days, the mixes contain POFA attained compressive strength higher than those of OPC mixes. The mixture of WMP fibers and POFA subsequently enhanced the tensile and flexural strengths, thereby increasing the ductility as well as the higher post-failure compressive strength of concrete. Besides, water absorption, sorptivity, and chloride penetration depth were reduced for concrete mixes incorporating WMP fibers up to 0.75% and 20% POFA. The study revealed that the WMP fibers are potential to be used in sustainable concrete by developing transport and mechanical properties.

Effect of Incorporating Pottery and Bottom Ash as Partial Replacement of Cement

This study addressed the environmental constraints in cement produc­tion. Ordinary Portland cement (OPC) was replaced with pottery powder (PP, produced by grinding locally available pottery) and bottom ash (BA) at 10%, 20% and 30% of cement mass. Moreover, 4% calcium chloride solution (CaCl2.2H2O) was used as mixing water. Material properties, such as standard consistency, setting time and compressive strength, were measured with different percentages of OPC replacement with PP and BA. Results indicated that the replacement with PP and BA increased the water demand to achieve the standard consistency. These results revealed that the strength evolution of 30% PP and BA is lower than that of the corresponding OPC mix, whereas the 10% and 20% replacements have a similar compressive strength to the control mix at 28 and 90 days, respectively. Slightly higher compressive strength was observed with the addition of 4% CaCl2 than the OPC mix.

Performance of Date Palm Ash as a Cementitious Material by Evaluating Strength, Durability, and Characterization

Cement manufacturing is indeed a major contributor to global warming that involves energy-intensive production processes along with emitting huge greenhouse gasses into the atmosphere. To adopt sustainable construction practices, agro-industrial waste materials as supplementary cementitious materials (SCMs) have been used by numerous researchers to partially replace conventional ordinary Portland cement (OPC) with SCMs by evaluating its optimum replacement dosage. This study aims to: (1) highlight the background of the date palm tree and the application of date palm waste as a construction material; (2) optimizing the dosage of date palm ash (DPA) as a cementitious material, at the replacement level of 10%, 20%, and 30%; and (3) understand the reaction kinetics by way of characterization techniques. DPA-based binary mixes were compared with each other and with the control (100% OPC mix) through fresh, mechanical, durability, and microstructural properties. The mechanism of reaction at early- and long-term period of curing was studied by characterization tests on paste, including nitrogen adsorption test (BET), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR). The outcome revealed 10% DPA as a strong and durable substitute to OPC, by formation of more Calcium Silicate Hydrate (C-S-H) and Calcium Aluminosilicate Hydrate (C-A-S-H) gel, whereas up to 30% DPA replacement can further maximize clinker replacement with reasonable performance, together with enhanced sustainability and reduced construction cost.

Effects of Elevated Temperature on Splitting Tensile Strength of OPC and BLA Pozzolanic Concrete and Mortar

Concrete is one of the most common and widely applied construction materials in the world. It is good in compression but weak in tension. The weakness in tension is been catered for through the use of reinforcement but there is still need to ensure that its minimum tensile strength is retained during the course of production and usage to avoid cracks development at the reinforcement cover. Concrete mixes of 1:2:4 (cement: sand: granite) and mortar of 1:6 mix ratio of cement to sand were produced. The ordinary Portland cement (OPC) content was partially replaced with bamboo leaf ash (BLA) from 0% to 12% at 2% interval. They were tested under normal and elevated temperature to know the effect of elevated temperature on their splitting tensile strength. The results obtained showed OPC concrete mix to improve in splitting tensile strength (3.5 N/mm2 to 3.7 N/mm2 at 28 days curing) whereas there was a decrease in the splitting tensile strength obtained for BLA mixes (3.29 N/mm2 to 1.75 N/mm2 for 12% percentage replacement at 28 days curing). The same trend of results was obtained for mortar mix; OPC mix increases from 1.65 N/mm2 to 1.86 N/mm2 while BLA at 12 % percentage replacement decreases from 2.02 N/mm2 to 1.7 N/mm2. OPC concrete and mortar under high elevated temperature (100oC) will improve in splitting tensile strength while elevated temperature decreases the splitting tensile of BLA concrete and mortar mixes at 12%.

Influence of cementitious binder on chloride removal under electrochemical treatment in concrete

The present study concerns electrochemical treatment to extract chloride ions and to repassivate the corroded steel in chloride-contaminated concrete. As binder, ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBS) and pulverised fuel ash (PFA) were used to produce different concrete mixes: OPC, GGBS and ternary mix containing the three binders, respectively. After 56days of curing, a DC was supplied to the concrete specimens, ranging 250, 500 and 750mA/m2 for 4weeks. Then, the corrosion rate was measured by the anodic polarisation. In fact, an increase in the current density applied to the specimens resulted in a decrease in the corrosion rate, imposing a reduction of the corrosiveness of steel in concrete. For a change in the chloride profile, a removal of chlorides at the depth of the steel was more significant in GGBS and ternary mixes, presumably due to a release of adsorbed chlorides on the hydration surface into free, which was further removed under electric charge. However, all chlorides could not be removed by the immobility of chlorides chemically bound into chloroaluminate and chloroferrite hydrates; a mostly half of chlorides in cast were, in fact, present even after the treatment.

Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties.

Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

Recent Advances in Coal Bottom Ash Use as a New Common Portland Cement Constituent

New additions to cement will help to obtain sustainable and durable construction materials. One of these new Portland cement constituents could be coal bottom ash. Currently, it is dumped as waste, provoking an environmental problem. However, shows how this material can be used as the main constituent of Portland cement when it is mixed in an optimized proportion with fly ash. Therefore, this study may also be considered as a pre-standardization work to meet, partially, an environmental demand of society.The compressive strength and durable characteristics of standardized mortars made of coal combustion bottom and fly ash are to mortars made of CEM I 42,5 N according to the European standard EN 197-1:2011, which is used as reference. The mortars made up of bottom ash, fly ash and ordinary Portland cement mixes have similar proportions to the standardized ones for CEM II/A-V, CEM II/B-V and CEM IV/A (V) cements.It was concluded that the utilization of bottom ash mixed with fly ash does not modify the compressive strength or durable characteristics of the mortars studied in this research program.