Durability performance of ternary blend alkali activated mortars for concrete surface damage repair

The progressive deterioration of concrete surface structures being the major concern in construction engineering requires special protection and precise repairing. The adverse physical, chemical, thermal and biological processes that cause such rapid decay need to be overcome. The durability of concrete structure is found to be strongly influenced by inappropriate use of materials as well as their physical and chemical condition of the surroundings. The immediate consequence is the anticipated need of maintenance and execution of repairs. Lately, many alkalis activated mortars are synthesized by selectively combining some waste materials containing alumina and silica compounds which are further activated via strong alkaline solution. Despite the emergence of various alkalis activated as prospective material toward emergency repairs and coating, a functional alkali activated with efficient repairing attributes and endurance is far from being achieved. Generally, the alkaline solution prepared by mixing concentrated sodium silicate and sodium hydroxide restrict the broad array of repairing applications of alkalis activated mortar. Furthermore, they are not only expensive and hazardous to the workers but negatively impact the environment. The research attempted to produce environmental friendly alkali activated by blending different ratios of sodium hydroxide and sodium silicate at low concentration. Durability and mechanical strength of the synthesized ternary blend alkalis activated mortars were evaluated to inspect their repairing effectiveness towards concrete surface damage. Tests were performed for determining the porosity, shrinkage, compressive strength and slant bond shear strength. Microstructures and thermal properties were evaluated using XRD, SEM, TGA, DTG and FTIR measurements. The prepared ternary blend contained the ground blast furnace slag, fly ash and palm oil fuel ash or ceramic waste powder. The prepared fresh, hardened and durable mortars were activated with affable alkaline solution (at low concentration) of sodium hydroxide and sodium silicate. The ground blast furnace slag that acted as the main resource of Ca++ was used to replace the low amount of Na+ in the geopolymerization process. The amount of slag in the blend varied in the range of 20 - 70%. The addition of slag to the blend had improved the strength and durability properties as well the microstructure characteristics. This improvement is majorly attributed to the participation of calcium silicate hydrate and calcium aluminosilicate hydrate beside sodium aluminosilicate hydrate bonds in reaction products. The results revealed that all the prepared mixes developed appreciable strength under mild alkaline solution. Furthermore, the alkali activated specimens prepared with high slag content displayed good durability including abrasion, thawing-freezing and shrinkage. The research has established that the ternary blend alkalis activated mortars with friendly alkaline solution contributes towards the development of high strength and durable repairing materials for concrete structures

Effective microorganism solution and high volume of fly ash blended sustainable bio-concrete

Currently, the production of sustainable concrete with high strength, durability, and fewer environmental problems has become a priority of concrete industries worldwide. Based on this fact, the effective microorganism (EM) solution was included in the concrete mixtures to modify the engineering properties. Concrete specimens prepared with 50% fly ash (FA) as an ordinary Portland cement (OPC) replacement were considered as the control sample. The influence of EM solution inclusion (at various contents of 0, 5, 10, 15, 20, and 25% weight) in the cement matrix as water replacement was examined to determine the optimum ratio that can enhance the early and late strength of the proposed bio-concrete. The compressive strength, porosity, carbonation depth, resistance to sulphuric acid attack, and the environmental benefits of the prepared bio-concrete were evaluated. The results showed that the mechanical properties and durability performance of the bio-concrete were improved due to the addition of EM and FA. Furthermore, the inclusion of 10% EM could increase the compressive strength of the bio-concrete at 3 (early) and 28 days by 42.5% and 14.6%, respectively. The durability performance revealed a similar trend wherein the addition of 50% FA and 10% EM into the bio-concrete could improve its resistance against acid attack by 35.1% compared to the control specimen. The concrete mix designed with 10% EM was discerned to be optimum, with approximately 49.3% lower carbon dioxide emission compared to traditional cement

Synthesis and characterization of shelf-healing mortar with modified strength

Cementitious materials being the most prospective building blocks achieving their absolute strength to avoid the deterioration in the early stage of service life is ever-demanding. Minimizing the labor and capital-intensive maintenance and repair cost is a critical challenge. Thus, self-healing mortars with modified strength are proposed. Lately, self-healing of micro-cracks by introducing bacteria during the formation of mortar or concrete became attractive. Self-healing with polymeric admixtures is considered to be relatively more durable and faster process. Certainly, the self-healing of synthetic polymeric materials is inspired by biological systems, where the damage triggers an autonomic healing response. This emerging and fascinating research initiative may significantly improve the durability and the safety limit of the polymeric components potential for assorted applications. In this work, using epoxy resin (diglycidyl ether of bisphenol A) without any hardener as admixture polymeric-cementitious materials is prepared. These epoxy-modified mortars are synthesized with various polymer-cement ratios subjected to initial wet/dry curing (WDC) together with long term dry curing (DC). Their self-healing function and hardening effects are evaluated via preloading and drying of the specimens, chemical analysis, and ultrasonic pulse velocity testing. It is demonstrated that 10% of polymer is the best proportion for polymer-cement ratio. Furthermore, the wet/dry curing is established to be superior process for healing hairline cracks present in the mortar. The excellent features of the results suggest that our novel method may constitute a basis for improving the compressive strength and self-healing features of mortars

Mechanical, thermal and durable performance of wastes sawdust as coarse aggregate replacement in conventional concrete

Wood yields a number of by-products and Sawdust is as useful as others. Sawdust is regarded as a waste material and is effectively utilised as sawdust concrete in the construction of buildings. It is capable to be utilised as light-weight concrete and holds the quality of long duration heat transfer. In this study, three different ratios (1:1, 1:2 and 1:3) volume mix proportions of cement to sawdust were adopted to make sawdust concrete. At varied intervals of 7, 28 and 56 days of air curing, thermal and mechanical properties like workability, density, elastic modulus, strength and heat transfer were probed of mentioned sawdust concrete proportions. The resistance to elevated temperatures was also evaluated after 28 days of age; weight loss, residual compressive strength, surface texture and ultrasonic pulse velocity were considered in evaluation process. The findings showed that increase in sawdust volume affected to decrease the workability, strength and elevated temperatures resistance. However, the concrete having higher proportion of sawdust performed competently and well in terms of thermal conductivity. Moreover, a decrease in the heat transfer of sawdust was also observed. Examining the all-embracing mechanical and physical properties, sawdust can be effectively utilised in the construction of buildings

Enduring performance of alkali-activated mortars with metakaolin as granulated blast furnace slag replacement

In the construction industries worldwide, improving the materials durability and achieving sustainability are the main goal. Owing to their excellent strength performance various alkali-activated binders can be one of the alternative solutions to the polluting traditional cement. Currently, ground blast furnace slag (GBFS) is the major base material used in the alkali-activated binders. High drying shrinkage and low resistance to sulfuric acid attack affect negatively the durability performance and life span of alkali-activated paste, mortars, and concretes made from GBFS. Thus, a series of alkali-activated mortars (AAMs) were designed with various contents (5, 10, 15, 20 and 25, mass%) of metakaolin (MK) as GBFS replacement to improve their strength performance. In addition, the strength and durability performance of the designed mixes were compared with the control mixture prepared using 100% of GBFS. The impact of varying MK level on the long-term performance such as compressive strength, porosity, resistance to sulfuric acid attacks, wet-dry cycles, drying shrinkage, and carbonation were evaluated. Various recommended standards were followed to cast the specimens in different shapes (cubes, cylinders, and prisms) and sizes. Mortar containing 10% of MK as GBFS replacement showed the highest compressive strength (63.4 MPa) at 28 days of curing age. Furthermore, the inclusion of MK as GBFS replacement was shown to improve the AAMs durability performance wherein the drying shrinkage was reduced and the resistance to aggressive environments was increased. The specimens containing 5% and 10% of MK revealed a lower porosity and carbonation depth compared to the control specimen. It was concluded that the proposed AAMs due to their long-term stability can be the sustainable and potential substitutes to the traditional construction materials

Experimental and informational modeling study of sustainable self-compacting geopolymer concrete

Self-compacting concrete (SCC) became a strong candidate for various construction applications owing to its excellent workability, low labor demand, and enhanced finish-ability, and because it provides a solution to the problem of mechanical vibration and related noise pollution in urban settings. However, the production of Portland cement (PC) as a primary constituent of SCC is energy-intensive, contributing to about 7% of global carbon dioxide (CO2 ) emissions. Conversely, the use of alternative geopolymer binders (GBs) in concrete can significantly reduce the energy consumption and CO2 emissions. In addition, using GBs in SCC can produce unique sustainable concrete with unparallel engineering properties. In this outlook, this work investigated the development of some eco-efficient self-compacting geopolymer concretes (SCGCs) obtained by incorporating different dosages of fly ash (FA) and ground blast furnace slag (GBFS). The structural, morphological, and mechanical traits of these SCGCs were examined via non-destructive tests like X-ray diffraction (XRD) and scanning electron microscopy (SEM). The workability and mechanical properties of six SCGC mixtures were examined using various measurements, and the obtained results were analyzed and discussed. Furthermore, an optimized hybrid artificial neural network (ANN) coupled with a metaheuristic Bat optimization algorithm was developed to estimate the compressive strength (CS) of these SCGCs. The results demonstrated that it is possible to achieve appropriate workability and mechanical strength through 50% partial replacement of GBFS with FA in the SCGC precursor binder. It is established that the proposed Bat-ANN model can offer an effective intelligent method for estimating the mechanical properties of various SCGC mixtures with superior reliability and accuracy via preventing the need for laborious, costly, and time-consuming laboratory trial batches that are responsible for substantial materials wastage

Flexural behavior of reinforced concrete beams under instantaneous loading: Effects of recycled ceramic as cement and aggregates replacement

The flexural behavior of five reinforced concrete beams containing recycled ceramic as cement and aggregate replacement subjected to a monotonic static load up to failure was studied. A full-scale, four-point load test was conducted on these beams for 28 days. The experimental results were compared with the conventional concrete as a control specimen. The cross-section and effective span of these beams were (160 × 200 mm) and 2200 mm, respectively. The data recorded during the tests were the ultimate load at failure, steel-reinforcement bar strain, the strain of concrete, cracking history, and mode of failure. The beam containing 100% recycled aggregates displayed an ultimate load of up to 99% of the control beam specimen. In addition, the first crack load was almost similar for both specimens (about 14 kN). The deflection of the beam composed of 100% of the recycled aggregates was reduced by 43% compared to the control specimen. Regardless of the recycled ceramic aggregates ratio, quantities such as service, yield, and ultimate load of the proposed beams exhibited a comparable trend. It was asserted that the ceramic wastes might be of potential use in producing high-performance concrete needed by the structural industry. It might be an effective strategy to decrease the pressure on the environment, thus reducing the amount of natural resources usage

Physical, chemical and morphology characterisation of nano ceramic powder as bitumen modification

The physical, chemical and morphology characteristics of the ceramic source enable its waste to be a novel modifier for bitumen. This study employed the top-down approach via dry grinding in a mechanical ball mill to generate a nanoceramic powder (NCP). As a result, NCP was successfully generated with an optimum duration of 15 h and optimum Ball-to-Powder Ratio (BPR) of 10:1. The results also indicated that the particle size of NCP was significantly decreased to less than 100 nm. XRD pattern and Scanning Electron Microscopy (SEM) of the NCP-modified bitumen (NCPMB) indicated good dispersion of the NCP within the bitumen matrix. This improvement led, in turn, to decrease in the penetration and to increase in softening point and rutting resistance factor (G*/sin δ) of the NCPMB. In addition, the contact angle results indicated that the presence of NCP increased the number of heteroatoms and, hence, the polarity of the modified bitumen, thereby improving the adhesion of bitumen toward the aggregate. A small difference in softening point between the top and bottom is an indicator of NCPMB with good high-temperature storage stability. Asphalt Pavement Analyser (APA) outcomes reaffirmed the structural improvement of the modified asphalt mixture and rutting resistance was increased

A Review on Concrete Composites Modified with Nanoparticles

Recently, various nanomaterials have extensively been used to achieve sustainability goals in the construction sector. Thus, this paper presents a state-of-the-art review involving the uses of different nanomaterials for production of high-performance cementitious, geopolymer, and alkali-activated concrete composites. The effects of nanomaterials on the fresh properties, mechanical properties, and durability of diverse nanoparticle-modified concrete composites are analyzed. The past developments, recent trends, environmental impact, sustainability, notable benefits, and demerits of various nanomaterial-based concrete production are emphasized. It is demonstrated that nanomaterials including SiO2, Al2O3, TiO2, and Fe2O3, etc., can be used effectively to enhance the microstructures and mechanical characteristics (such as compressive strength, flexural, and splitting tensile strengths) of the modified concrete composites, thus improving their anti-erosion, anti-chloride penetration, and other durability traits. In short, this communication may provide deep insight into the role of diverse nanoparticle inclusion in concrete composites to improve their overall attributes

Potential Applications of Core-Shell Nanoparticles in Construction Industry Revisited

The demand of high performance and environmentally sustainable construction materials is ever-increasing in the construction industry worldwide. The rapid growth of nanotechnology and diverse nanomaterials’ accessibility has provided an impulse for the uses of smart construction components like nano-alumina, nano-silica, nano-kaolin, nano-titanium, and so forth Amongst various nanostructures, the core-shell nanoparticles (NPs) have received much interests for wide applications in the field of phase change materials, energy storage, high performance pigments, coating agents, self-cleaning and self-healing systems, etc., due to their distinct properties. Through the fine-tuning of the shells and cores of NPS, various types of functional materials with tailored properties can be achieved, indicating their great potential for the construction applications. In this perception, this paper overviewed the past, present and future of core-shell NPs-based materials that are viable for the construction sectors. In addition, several other applications of the core-shell NPs in the construction industries are emphasized and discussed. Considerable benefits of the core-shell NPs for pigments, phase change components, polymer composites, and self-cleaning glasses with enhanced properties are also underlined. Effect of high performance core-shell NPs type, size and content on the construction materials sustainability are highlighted