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Corrosion of steel reinforcement in underwater concrete structures continues to be a problem in the modern era. The possibility of employing pultruded glass fibre reinforced polymer (GRFP) I beams to replace traditional steel reinforcement in an encased beam is still being explored. The purpose of this research is to further investigate the effects of incorporating treated recycled concrete aggregate (RCA) and discrete synthetic fibres, specifically Polyolefin (PO) and Fibrillated Polypropylene (PP) fibres, in the production of concrete beam reinforced with GFRP I beam for underwater construction. Five beams were constructed and tested in this investigation using a four-point loading arrangement. The load–deflection curve, stress–strain curve, and initial and ultimate fracture loads are all included in the test parameter set. The results indicate that treating RCA and fibres greatly increases the flexural capacity of modified recycle aggregate concrete (RAC) beams compared to unmodified RAC beams.

High molar mass materials (nano-silica slurry [NSS] and aggregate of steel furnace slag [ASFS]) can improve concrete shielding properties. However, only a few studies have been reported in this regard. Hence, this paper aims to determine the effect of NSS and ASFS on the properties of the resulting steel slag heavyweight concrete (SSHWC). The use of NSS in this study is a novel contribution. Furthermore, the maximum percentage of NSS to be introduced into the concrete for maximum effect was also optimized. This study also implemented an investigation program with six concrete mixtures prepared using ASFS as the primary by-product aggregate. The engineering, X-ray, and γ-ray attenuation characteristics of the SSHWC were evaluated. The results showed that the addition of NSS in SSHWC at the optimal content of 3% by weight of cement improved the X-ray shielding by 6.4%. Besides, all the concrete’s engineering and γ-rays’ properties were enhanced correspondingly.

This paper presents a study that aimed to assess the chloride penetration depth of recycled aggregate concrete (RAC) modified by using treated coarse recycled concrete aggregate (RCA), adding polyolefin (PO) or polypropylene (PP) fibre and comparing with normal concrete. The coupling effects of the treated RCA and fibres on the chloride penetration of RAC were analysed after two different curing regimes (i.e. normal and seawater) and tested at different curing ages (i.e. 90, 180 and 300 days). Results showed that the inclusion of treated coarse RCA can reduce porosity, thereby decreasing the chloride penetration of RAC. However, the coupling effects of treated coarse RCA and fibre, especially on the use of PO fibre, can enhance the results.

This study also investigates the effectiveness of multiple surface modification of recycled concrete aggregate (RCA) with respect to mechanical properties of the resultant recycled aggregate concrete (RAC) when exposed to various curing conditions, namely, normal water (Nw) and seawater (Sw). The properties included compressive and flexural strength and impact resistance. Findings show that effect inclusion of the treated coarse RCA is significant in enhancing the mechanical properties of RAC. The exposure to Sw appears to affect the degradation of the compressive strength of RAC remarkably in a marine environment. In this case, however, using of treated RCA is found beneficial in decreasing the deterioration in the compressive strength of RAC.

Promoting concrete quality is a logical inevitable choice for humanity in global revolutionary development. This study highlights one of the most important types of concrete, namely, the high density concrete, which is used widely in nuclear power plants and many other modern scientific and industrial applications. It can efficiently absorb and attenuate the dangerous types of radiation. It is low cost. These features make this type of concrete important in many relevant fields and applications. It is used as partition walls for rooms of examination in hospitals, laboratories and others. The attenuation degree of the biologically dangerous types of radiation (such as gamma rays, alpha rays, beta rays and X-ray) during the propagation of these rays through the mass of the shielding materials is in proportion with the atomic mass of the shielding material. Some of these rays can be stopped easily by a piece of paper (like α) or a thin layer of aluminium (such as β-ray). However, some of them (such as gamma rays) has ultrapenetration ability and can penetrate through the living bodies and cause destructive ionisation to biological cells. Thus, the concrete material that can properly shield from such rays is important and is the primary focus of discussion of this review. An overview of the works conducted to produce high density concrete for various engineering and radiation attenuation applications is provided. The important aspects are described in detail, such as the high-density concrete properties, materials used, physical and chemical material’s properties, mechanical properties and durability and the effect of the interfacial transition zone’s density on the properties of heavy weight concrete. The major advantages and contributions of this study are not restricted to the comprehensive review of the past works that led to the development this important type of concrete. The knowledge gap in this field of work is highlighted. An extensive review of literature reveals the difficulties related to the scarcity of work on the drastic reduction of the water/cement ratio to achieve high density concrete with reasonable workability using modern chemical admixtures, the approach of promoting high-density concrete through hybridisations of fibres and the reduction of their permeability by using the nanomaterials as mineral admixtures.

Cementitious composites are the most used man-made materials in the world with a global annual production quantum of 25 billion tonnes worldwide, contributing approximately 5% to the global greenhouse gas emissions. In the initiative to reduce the carbon footprint of cementitious composite production, are growing interests in the large volume reuse of industrial by products such as ground granulated blast-furnace slag (GGBS), pulverized fuel ash (PFA) and granite quarry dust (GQD) in cementitious composites production. Such an approach offers a two-fold solution towards addressing the waste management problem related to those industry by-products. At the same time however; reduction of carbon footprints of cementitious composite materials exists. However, in order to enable scalable applications of such a recycling approach, a comprehensive body of knowledge on the mechanical strength and durability performance of the cementitious composite products containing a large volume of the materials needs to be established. Hence, it is the primary aim of the study to report a comprehensive assessment on the mechanical strength and durability properties of high strength cementitious composites. These materials are produced with a large volume of the aforementioned materials as the primary binder and aggregate phase. Throughout the investigation, high strength cementitious composites mixes were produced with a large volume of PFA and GGBS binder. Then phase coupled with ordinary Portland cement (OPC). GQD was used as the fine aggregate phase in substitution of natural river sand at various level of substitution ranging between 0 and 100% by volume. The cementitious composites were characterized in terms of its fresh cementitious composites. Its flowability and hardened cementitious composites properties mainly bulk density, compressive strength, flexural strength, and Ultrasonic Pulse Velocity were also assessed. In addition, the durability properties such as water absorptivity and porosity were also covered in this experimental program. Pore continuity was assessed in terms of air permeability and capillary absorption of the hardened specimens according to the testing age. This paper has also covered the dimensional stability assessment in terms of drying shrinkage. Besides, a comprehensive microstructural assessment was also performed to examine the microstructure morphology. From the results, we found full incorporation of GQD as NRS without significant impairment to the mechanical, durability and length change performance. Thus, the production of sustainable high strength cementitious composites with large volume recycling of GQD is feasible which in turn reduces the depletion on the natural river sand resources.

This paper reviews several key issues related to the use of natural aggregate (NA) for concrete production, in view of the high demand for materials to meet the rapid construction development in Malaysia. The current paper aims to discuss the potential of recycling waste concrete to generate recycled aggregates (RA) that may be used as alternative aggregate sources in the production of concrete. Moreover, several major challenges to the use of RA for concrete production are also highlighted. This paper also provides an action plan to encourage the construction industry’s wide usage of RA to achieve sustainable construction.  Keywords: construction; recycled aggregate; sustainable; waste concreteeISSN 2398-4279 © 2018. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open-access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia.Â

Heavy weight concrete (HWC) is one of the most used artificial materials for the embodiment of special infrastructures such as nuclear power, medical, nuclear science and industrial facilities. The review highlights the main aspects of HWC covering the general concept of radiation physics, fundamental of geometrical design for radiation attenuation and recent advances of HWC technology. An overview of recent research and development of HWC for various applications in engineering and radiation attenuation is elaborated. Besides, the primary industrial applications, future challenges and current limitations of research and development of HWC are also deliberated. Recent works had established that the degree of attenuation of biologically harmful forms of radiation, such as gamma-rays and X-rays, is proportional to the atomic mass (Z) of the shielding material. The high penetration power enables the radiations to penetrates the living bodies and causes harmful ionization of the biological cells. Therefore, the concrete material capable of effective attenuation of these rays plays a critical role in ensuring the safety and health of personnel in nuclear facilities. A comprehensive analysis of the literature shows the limitations in the present body of knowledge associated with the use of more than one type of nano-materials to achieve a virtually impervious HWCs. Besides, a significant gap was identified on the method of improving the cost efficiency of HWC by the use of byproduct heavyweight aggregates or by adding more than one type of aggregate and inclusion of heavyweight fiber. The review had established several critical areas for future works covering cost optimization in the formulation of high-quality HWC, reactive powder and geopolymer HWC, combinations of nano-materials, crack control and elevating Z-value of HWC to improve harmful radiation attenuation performance.

This paper examines the mechanical and durability properties of concrete incorporated with treated recycled concrete aggregate (RCA) under different curing conditions. Three different curing regimes were applied, namely, continuous normal water curing (NW), initial water curing for 28 days before exposure to an open air environment (OA), and initial water curing for 28 days before exposure to seawater (SW). Two concrete mixes were produced by replacing 60% of the coarse aggregate using treated and untreated RCA with one control specimen (100% natural coarse aggregate) to examine the mechanical strength (compressive and flexural strength) and durability (water absorption, oxygen permeability, and also porosity) properties of the concrete. Meanwhile, the microstructure of these mixes was studied via scanning electron microscopy (SEM). The inclusion of untreated RCA generally reduces the mechanical strength and durability of the concrete regardless of the curing conditions. The compressive strength of the concrete containing untreated RCA is more detrimental in SW than in the other two curing conditions. Moreover, the concrete with RCA have poor intrinsic air permeability and porosity because their intrinsic porosity and effect are more significant when the curing is performed in OA than in the other curing conditions. Incorporating the treated RCA helps limit the reduction in the mechanical strength and durability of the concrete particularly under a prolonged curing period.

The compressive strength and durability potentials of hybrid cementitious composites (HCC) that contain metakaolin (MK), produced in the laboratory using raw kaolin, nanosilica and epoxy resin was the main focus of this research study. The HCC specimens contain 10% metakaolin (MK), 1% colloidal nanosilica (CNS) and 1% epoxy resins and the specimens were examined for early ages of 7, 28, and 90 days of exposure in both water and seawater. The durability properties investigated in this research study comprise of water absorption, intrinsic air permeability, chloride penetration and porosity. All tests were conducted to assess the influence of MK, CNS and epoxy on the compressive strength and the durability properties of the HCC specimens. The result showed that HCC specimens with 10% MK, 1% CNS was durable relative to all the properties. Nevertheless, the addition of both natural fibers (coconut and oil palm fruit bunch fibers) and synthetic fiber (bar chip fiber) has a slight negative impact on the durability properties of HCC specimens. Conclusively, the results showed that the menace of water, liquid and gas transportation by water absorption, capillary suction, porosity, chloride penetration, and intrinsic air permeability of HCC were lesser than that of control specimen.

The reuse of pulverised fuel ash (PFA) and high calcium wood ash (HCWA) offers a two folds solution towards addressing the waste management problem and reduce the carbon footprint of concrete material. In order to enable sizeable application of such recycling method to produce block work for the construction industry, a comprehensive framework of knowledge on the mechanical strength performance of the concrete product containing large volume of PFA and HCWA needs to be established. Hence, it is the primary aim of the study to report a comprehensive assessment on the mechanical strength performance of concrete block work produced with the sole use of PFA and HCWA as the primary binder phase. The PFA and HCWA binder phase with small dosage of sodium silicate was characterized in terms of its standard consistency and setting times. Besides, a thorough assessment on the mechanical strength of block work produced with PFA-HCWA binder was conducted. Mechanical strength assessment covers the compressive strength, flexural strength and velocity of ultrasonic pulse propagation through the material. Besides, the fourier transformed infrared (FTIR) assessment was also performed to characterize the aluminosilicate bonds of the primary binder phase. The increasing mass ratio of HCWA was found to raise the water demand of the HCWA-PFA binder paste. Besides, the HCWA:PFA combination ratio of 50:50 and 40:60 has been found to exhibit the optimal flexural and compressive strength performance. It has also been established that the block work produced using HCWA:PFA combination ratio between 30:70 up to 90:10 meets the California Concrete Masonry Technical Committee requirement as class N concrete block work unit.

As concern regarding global environmental issue grows, there is an emerging interest to substitute conventional ordinary Portland cement by using geopolymer composite as binder matrix in concrete. However, there are two main components that become a barrier in industrialization of geopolymer are the high content of chemical activator and requirement for post fabrication heat treatment which is an energy intensive process. The study investigate the hybridization of three industrial byproducts namely Ground Granulated Blast Furnace Slag, High Calcium Wood Ash and Pulverized Fly Ash activated with reduced level of alkaline activator and produced without any thermal treatment and possesses adequate mechanical performance mortar for industrial application. Besides, the properties of low energy hybrid geopolymer mortar were assessed based on the mechanical and microstructure aspects. Test specimens were evaluated in terms of standard consistency, setting times, compressive strength, flexural strength, ultrasonic pulse velocity, dynamic modulus of elastic, and microstructure development. The inclusion of Pulverized Fly Ash at the content of 10–60% by binder weight does reduce the water demand and significantly prolonged the setting times of hybrid geopolymer paste. Enhanced modulus of elasticity, ultrasonic pulse velocity, compressive and flexural strength were observed for hybrid geopolymer concrete with Pulverized Fly Ash content of 40–80% by binder weight compare to control mixture, 0% PFA. Besides, from Scanning Electron Microscope micrograph and Energy Dispersive X-ray analysis geopolymer paste matrix indicated the formation of geopolymeric products of C-A-S-H and N-A-S-H that contributes to the early strength development on geopolymer mixture contains 0% up to 60% percentage of Pulverized Fly Ash.

The research project aimed to explore the feasibility of activating fly-ash based geopolymer by the hybridization of fly-ash (FA) with high calcium wood ash (HCWA), a by-product from timber manufacturing industry, without the addition of conventional alkaline activators and post heat treatment curing regime. The raw materials namely FA and HCWA were characterized in term of their chemical and mineralogical phases by X-ray diffraction (XRD) and X-ray fluorescence (XRF). FA was substituted by HCWA at high replacement level of 50% to 100% at 10% incremental, by binder weight. Hardened geopolymer mortars samples were subjected to water curing and tested on the age of 7, 28 and 7 days + 24 hours hydrothermal treatment. Mechanical performance of the geopolymer mortars were assessed in term of compressive, flexural strength, ultrasonic pulse velocity (UPV) and dynamic modulus. Durability properties namely water absorption, vacuum porosity and capillary absorption were also investigated. Results were positive on the viability of hybridizing FA with HCWA to produce novel self-activating geopolymer mortars as mixtures with PFA replacement level of 50% and 60% showed enhanced mechanical and durability performance at all curing ages in comparison with other HCWA-PFA geopolymer mortar mixtures. Early strength development of HCWA-PFA geopolymer mortars was mainly contributed by the combination of hydraulic reaction of HCWA and geopolymerization of FA. On prolonged curing, strength development was due to the aforementioned reactions, plus pozzolanic reaction between the reactive silica from FA and portlandite formed from HCWA, producing additional secondary C-S-H gels. This experimental program showed positive findings in incorporating highly alkaline materials i.e. HCWA (12% K2O) towards activating FA based geopolymer, thus eliminating the needs of external alkaline activator in conventional geopolymer mix design.

In this study, the mechanical properties and flexural behaviour of the fibrous cementitious composites containing hybrid, kenaf and barchip fibres cured in cyclic exposure were investigated. Waste or by-product materials such as pulverized fuel ash (PFA) and ground granulated blast-furnace slag (GGBS) were used as a binder or supplementary cementitious to replace cement. Barchip and kenaf fibre were added to enhance the mechanical properties and flexural behaviour of the composites. A seven mix design of the composites containing hybrid, kenaf and barchip fibre mortar were fabricated with PFA-GGBS at 50% with hybridization of barchip and kenaf fibre between 0.5% and 2.0% by total volume weight. The composites were fabricated using 50 × 50 × 50 mm, 40 × 40 × 160 mm and 350 × 125 × 30 mm steel mould. The flexural behaviour and mechanical performance of the PFA-GGBS mortar specimens were assessed in terms of load-deflection response, load compressive response, and crack development, compressive and flexural strength after cyclic exposure for 28 days. The results showed that specimen HBK 1 (0.5% kenaf fibre and 2.0% barchip fibre) and HBK 2 (1.0% kenaf fibre and 1.5% barchip fibre) possessed good mechanical performance and flexural behaviour. As conclusion, the effect of fibres was proven to enhance the characteristics of concrete or mortar by reducing shrinkage, micro crack and additional C-S-H gel precipitated from the pozzolanic reaction acted to fill pores of the cement paste matrix and cement paste aggregate interface zone between mortar matrix and fibre bonding.

Due to the growing nuclear energy sector worldwide, it has been a global interest among researchers to improve the harmful radiation isolation properties of concrete for preserving both environment and human safety in nuclear power plant applications. While nano zinc oxide, nano-silica and steel furnace slag have high molar mass and favorable physical properties to improve high energy radiation attenuation properties of the concrete, scarce body of literature on the subject matter was reported. Hence, the study was aimed to investigate the suitability of the addition of nanomaterials such as nano-silica and nano zinc oxide for improving the mechanical, fluid transport and gamma-ray attenuation properties of heavyweight concrete (HWC) containing aggregate of steel furnace slag (ASFS). A new contribution of this study was the use of nano zinc oxide and nano-silica in concrete binder formulation to enhance the gamma ray shielding ability of concrete. A method was established for the optimization of the nano zinc oxide content used in combination with a constant amount of nano-silica to improve the various performance of heavy weight concrete. An investigation program was implemented with six concrete mixes which were prepared by utilizing ASFS with the addition of a superplasticizer, 3% of nano-silica in combination with (0.5–2.5%) of nano zinc oxide as an additive to produce high strength heavy weight concrete. The mechanical properties, fluid transport characteristics and γ-ray shielding performance were evaluated for hardened concrete samples. The inclusion of 1.5% nano zinc and 3% of nano-silica enhances the gamma-ray shielding and compressive strength by 16.3 and 6.6%, respectively, at 28 days as compared to the control mix (without nanomaterials). Besides, all the mechanical and fluid transport properties of the concrete were improved correspondingly. In conclusion, the combined use of nano-silica and nano zinc oxide is suitable to enhance mechanical strength, fluid transport and high energy radiation attenuation performance of steel furnace-slag heavyweight concrete (SSHWC).

The use of Ground Granulated Blast Furnace Slag (GGBFS) as binder for concrete had been reviewed extensively in previous reviews. However, the influence of various types of alkali activators on the behavior of GGBFS based concrete had yet to be consolidated in a comprehensive review. Hence, this paper presented a comprehensive review of the effect of various commercial and by-product types of alkali activators on the fresh properties, mechanical properties, and durability of Ground Granulated Blast Furnace Slag-based concrete. Commercial alkali activators prescribed are those hydroxide-based, silicate-based activators, carbonate-based and oxide-based alkali activators. By-product activators can be obtained directly or derived from the industrial by-product. The by-product derived sodium silicate yielded almost similar mechanical properties to GGBS as compared to commercial sodium silicate. Lime kiln dust had similar properties as oxide and carbonate-based alkali activators in alkali activation of alkali-activated materials.

As the nuclear energy sector continues to grow worldwide, the improvement of concrete’s radioactive isolation properties for preserving both the environment and human lives in nuclear power plant applications has received a global interest among researchers. Although nano-silica, nano-calcium carbonate, and steel furnace slag have high molar mass and favorable physical properties to improve the concrete’s radioactive insulation properties, scarce literature on the subject matter has been published. The goal of this study is to investigate the appropriateness of using nanomaterials such as nano-silica slurry and nano-calcium carbonate as additives for the production of steel furnace slag (aggregate of steel furnace slag: ASFS)-based heavyweight concrete (HWC) with improved durability, mechanical strength, and gamma (γ)-ray attenuation properties. A new contribution of the study is the use of nano-SiO2 slurry and nano-CaCO3 in concrete binder formulation to enhance concrete gamma-ray shielding capability. An optimized content was developed for the nano calcium carbonate, in combination with a constant amount of nano-silica slurry, to improve the performance of the HWC. An investigation program was implemented with eight concrete mixes, which were prepared by utilizing ASFS as the main aggregate with 3% of nano-silica slurry in combination with (0–3%) of nano-calcium carbonate as additives to produce high strength HWC. The hardened concrete samples were evaluated for mechanical strength, fluid transport and γ-ray shielding properties. The effect of 3% nano-SiO2 slurry and 2.0% nano-CaCO3 on the compressive strength and gamma-ray shielding increased by 10.3 and 3.4%, respectively, at 28 days as compared to the control mix without nanomaterials additives. The other mechanical and fluid transport properties of the concrete were also improved significantly. In conclusion, the combined use of nano-silica slurry and nano-calcium carbonate would enhance the mechanical strength, fluid transport and γ-ray shielding properties of steel furnace-slag heavyweight concrete.

The high consumption of Portland cement in concrete production had contributed to a significant carbon dioxide emission to the environment. The application aluminosilicate rich waste material in the manufacturing of Portland cement as partial replacement material has become an alternative to minimize the carbon dioxide emission and at the same time to solve waste management problems through recycling of industrial waste material. The study is mainly aimed to maximize the level of cement replacement of ground granulated blast furnace slag (GGBS) and pulverized fuel ash (PFA) in the production of cement mortar through hybridization and mechanical activation. The laboratory testing program includes bulk density test, compressive strength test, flexural strength test, ultrasonic pulse velocity test (UPV) and dynamic modulus test from 7 days of curing age up to 90 days. Besides, scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy test (EDX) have been performed in order to determine the microstructure development of the paste sample. It is observed that the inter-grinding activation method is able to further enhance the reactivity of the geopolymer material from the aspect of increase in mechanical strength and improve in durability performance.

In this study, the potency of using laboratory produced metakaolin as partial replacement of cement in the evolution of a hybrid cementitious composites (HCC) was investigated. Some chemical composition and phases of metakaolin were appraised with the aid of X-ray fluorescence (XRF) and X-ray diffraction. Particle size analyzer was used to study the physical properties of metakaolin produced in the laboratory from purified Kaolin. Early age mechanical strength and shrinkage properties of structural grade HCC developed by replacing fly ash in the original ECC M45 design with metakaolin (MK), colloidal nanosilica (CNS) and epoxy were examined. The designed mixtures consist of five mixtures with the control and base mix exposed to water and seawater. The control mix consists of only the fine aggregate and cement while the base mix consists of cement, fine aggregate, 10% MK and CNS with epoxy resin at 1% each by weight of the binder. Synthetic barchip fibres and some natural fibres namely, oil palm fruit bunch and coconut fibres were incorporated. The water cement ratio was designed as 0.30 for all mix ratios. The result reveals that the inclusion of MK, CNS and epoxy have a significant effect on the fresh properties of the HCC and at early age of 7, 28 and 90 days. The mechanical strengths were better improved than the standardized M45 ECC at these early ages.

The building industry has been acknowledged as being vital in stimulating societal change toward sustainable development in a global context. From a theoretical perspective, this study extends leadership competencies and transformational leadership qualities as hierarchical, reflective constructs, integrating ten associated components. The research analysis was completed using a sample population of 70 project managers in sustainable building projects. The model shows that leadership competencies, as well as the transformational leadership qualities of project managers as second-order reflective constructs experience a direct impact on the success criteria for sustainable buildings. In addition, the results indicate that the intellectual competence of project managers plays the most significant role in sustainable building achievements. In general, the present study extends some of the significant components from leadership assessment in the context of construction project managers in sustainable building projects and has generated a new model to facilitate the process of sustainability in the industry.

Polymer-modified materials provide numerable enhancements to cementitious composites. However, the curing/hardening conditions for cementitious and polymeric materials differ significantly, although they are mixed to form a single entity. Cement requires a moist environment for the hydration process to occur, while polymers require a hot and dry environment. Consequently, the polymer-modified composite exhibits lower compressive strength than the ordinary cementitious product. The objective of the present study was to resolve this issue by using accelerated curing regimens, following the fundamental concept that the dominant contribution to the toughness of the composite matrix is from the cement system, while polymer films refine the microstructure. Hygrothermal treatment for plain mortar was first developed in order to achieve 100% of the 28-day strength after treatment is completed. The hot + dry treatment required for the formation of polymer film was studied in the second phase of this study, together with an investigation of the microstructure using scanning electron microscopy. The results show that, after being subjected to the hygrothermal and hot + dry treatment, polymer-modified mortar can achieve low intrinsic permeability without compromising the compressive strength. A 15% polymer loading in styrene–butadiene rubber- and epoxy-modified mortar led to 46% and 18% higher compressive strengths, and 660% and 460% lower intrinsic permeabilities, compared with unmodified mortar, respectively.

An extensive review of literature on heavyweight concrete (HWC) reveals that this material is not economical to produce due to the required use of expensive special heavyweight aggregates and high water-to-cement (W/C) ratios. This study aimed to develop the utilization of steel furnace slag (SFS), as an aggregate to produce high-strength HWC with optimized water content for gamma (γ) ray shielding. A method was established for the optimization of the volumetric ratio of fine and coarse SFS aggregates and their influence on the cement content. Meanwhile, the optimum W/C ratio was determined to improve the performance of concrete. Thirteen concrete mixes were prepared by utilizing SFS as fine and coarse aggregates with the addition of a superplasticizer very-high-range water reducer admixture [VHRWRA] as a modern chemical admixture to achieve high strength after extensive mix design development. An investigation program was implemented in two parts. Firstly, compressive strength and density were determined after 7, 28, 56 and 90 days for the first six mixes with various W/C ratios between 0.2 and 0.45. Secondly, the properties of concrete mixes with different binder and aggregate ratios (C1S2G4, C1S1.5G3, C1S2G3, C1S2.5G3, C1S2.5G2.5, C1S2.5G2, and C1S3G2) were examined in terms of fresh density and workability in fresh concrete. The mechanical strength, durability and γ-ray shielding properties of the hardened concrete were also evaluated. Results showed that the use of third-generation VHRWRA reduced the W/C ratio to 0.23 whilst maintaining desirable workability. The concrete's compressive strength reached 106 MPa at 28 days, and all of the concretes' mechanical, durability and the γ-ray attenuation properties were improved. These observations show SFS is suitable to be used as aggregates (fine and coarse) in HWC to provide protection from radioactive rays.

This study investigates the effect of inclusion of polyolefin and polypropylene fibers at various volume fractions in single and hybrid forms on the mechanical properties of recycled aggregate concrete (RAC) mix that consists of treated coarse recycled concrete aggregate (RCA). Testing parameters, such as compressive strength, flexural strength, static modulus of elasticity, and impact load resistance, are utilized to evaluate the mechanical strength of specimens. The various properties of the modified RAC are also analyzed and compared with those of normal concrete and unmodified RAC specimens. Findings indicate that the mechanical strength properties of RAC mixture using treated RCA were significantly enhanced by adding fibers. The overall optimized mechanical strength results could be obtained in RAC mixtures with fiber in hybrid form, where their compressive strength at long-term curing age, can be significantly improved by 7% upto 11% higher than normal concrete. In addition, RAC mix with hybrid fibers produced the highest flexural strength and impact load resistance by an increase of 5% and 175%, respectively as compared with the control concrete.

In this study, the flexural behavior of the fibrous cementitious composites containing hybrid fibers was investigated. Waste materials or by product materials such as pulverized fuel ash (PFA) and ground granulated blast-furnace slag (GGBS) was used as supplementary cement replacement. In addition, barchip and kenaf fiber will be used as additional materials for enhance the flexural behavior of cementitious composites. A seven mix design of fibrous cementitious composites containing hybrid fiber mortar were fabricated with PFA-GGBS as cement replacement at 50% with hybridization of barchip and kenaf fiber between 0.5% and 2.0% by total volume weight. The FCC with hybrid fibers mortar will be fabricated by using 50 × 50 × 50 mm, 40 × 40 × 160 mm and 350 × 125 × 30 mm steel mold for assessment of mechanical performances and flexural behavior characteristics. The flexural behavior and mechanical performance of the PFA-GGBS with hybrid fiber mortar block was assessed in terms of load deflection response, stress-strain response, crack development, compressive and flexural strength after water curing for 28 days. Moreover, the specimen HBK 1 and HBK 2 was observed equivalent or better in mechanical performance and flexural behavior as compared to control mortar.

The durability of the alkali-resistant (AR) glass fiber reinforced concrete (GFRC) in three simulated aggresive environments, namely tropical climate, cyclic air and seawater and seawater immersion was investigated. Durability examinations include chloride diffusion, gas permeability, X-ray diffraction (XRD) and scanning electron microscopy examination (SEM). The fiber content is in the range of 0.6 % to 2.4 %. Results reveal that the specimen containing highest AR glass fiber content suffered severe strength loss in seawater environment and relatively milder strength loss under cyclic conditions. The permeability property was found to be more inferior with the increase in the fiber content of the concrete. This suggests that the AR glass fiber is not suitable for use as the fiber reinforcement in concrete is exposed to seawater. However, in both the tropical climate and cyclic wetting and drying, the incorporation of AR glass fiber prevents a drastic increase in permeability. Este trabajo se centra en el estudio de la durabilidad de hormigón reforzado con fibra de vidrio resistente a álcalis (CRFVRA) en tres ambientes agresivos simulados como son, condiciones de clima tropical, ciclos de aire y agua de mar e inmersión marina. Los tests de durabilidad incluyeron la difusión de cloruros, permeabilidad de gas, difracción de rayos X (XRD) y evaluacion por microscopía electrónica de barrido (SEM). Los contenidos de fibra evaluados estuvieron en el rango desde 0.6% hasta 2.4%. Los resultados revelan que la muestra que contiene el mayor porcentaje de fibra sufre una severa pérdida de resistencia en condiciones de agua de mar, y una menor disminución de resistencia bajo condiciones cíclicas. Su permeabilidad disminuyó al incrementar el contenido de fibras en el hormigón. Lo anterior sugiere que el refuerzo con fibra resistente a alcalinos no es adecuado para su uso en hormigón en ambiente de agua de mar. Sin embargo, bajo condiciones de clima tropical, y en ciclos humedad/secado, la incorporación de dichas fibras previene un incremento drástico de la permeabilidad.

The limited application of conventional geopolymer in the construction industry is due to the requirement of high chemical activator dosage, the consequence handling problem associated with the high alkalinity of the material, post forming treatment at elevated temperature which resulted in high manufacturing cost and a material with high embodied energy. The study prescribed herewith proposes the ash hybridization approach between high calcium wood ash (HCWA) and Class F pulverised fuel ash (PFA) and pressurized forming technique to fabricate a low alkalinity geopolymer mortar with adequate mechanical and durability performance for industrial application. A total of eight different mix designs of geopolymer mortar were fabricated with HCWA–PFA hybridization ratio of 100:0, 70:30, 60:40 and 50:50 using two different water/binder ratios of 0.30 and 0.35. The mechanical performance of the HCWA–PFA mortar block was assessed in terms of compressive strength, flexural strength and secant modulus after a given duration of curing at ambient temperature. The durability assessments performed include tests on water absorption and total porosity. The mineralogical, elemental phase and microstructural changes of the binder phase at early age and extended curing duration were also examined. Results are indicative that a hardened binder phase consisting of a combination of potassium polysialate and gehlenite framework can be produced by the hybridization of HCWA and PFA. Moreover, the hybridization of HCWA and PFA at mass ratio of 70:30, 60:40 and 50:50 can be suitably implemented for the fabrication of mortar block with adequate mechanical strength, stiffness and durability performance to be classified as load bearing masonry unit for building construction.

The enormous amount of industrial waste ash generated by power generation industry, timber manufacturing industry, iron and steel making industry, rice milling industry, mining industry etc have posed the aforementioned industry players a great challenge when it comes to the disposal of these ash materials due to the environmental, health, scarcity of lands and other issues. The best approach in overcoming the aforementioned waste management problems is to promote large volume recycling/reuse of these waste materials. In recent years, the rapid growth in research and development related to geopolymer binders has indeed indicated that the use of geopolymer offers the greatest potential in solving not only the waste management problems related to the aluminosilicate solid waste materials generated from various industries, but also the environmental degradation related to the use of OPC as primary binder material in the construction industry. Results of recent studies are indicative that geopolymer concrete fabricated using various industrial by-products exhibited similar or better mechanical, physical and durability properties as compared to OPC concrete. This paper presents a concise review of the current studies on the utilization of industrial by-products as the primary binder materials in the fabrication of geopolymer concrete. The effects of a number of major factors such as the use of chemical activator, post fabrication curing regime, particle size distribution of source materials, and aggressive environment exposure on the mechanical strength, physical properties, microstructures and durability properties of the geopolymer concrete are exhaustively deliberated. Besides, the current material design, fabrication procedures and post fabrication treatment procedures were rigorously reviewed to identify the limitations of the current geopolymer technology which impede its wide implementation in the construction industry. It has been identified that the high alkaline content in the material design and requirement for elevated temperature treatment of the contemporary geopolymeric binder are among the major technical challenges which resulted in the limited use of the material in the construction industry. Based upon that, numerous strategies were proposed to overcome the current limitations of the geopolymer technology towards promoting a large scale implementation of the technology in the production of construction materials.

Metakaolin is a produce from Kaolinite. Meanwhile, Kaolinite is a natural clay mineral that consists of so many mineral materials, metakaolin inclusive, that can be used in many areas of life and hence sustainable in contents if process adequately. The issue of global warming coupled with a general belief of greenhouse gas emission through the production and usage of cement, a main building and infrastructures construction materials, necessitate for the substitution of cement in building materials most especially concrete. This study focused on the effect of metakaolin on the early day's strength of sandwich engineered cementitious concrete modified with nanosilica particles. The nanosilica in this mix served two purposes, one as a cementitious substitute and secondly as to increase the silica content of the normal sand used. The fresh and engineering properties of samples with 12% weight replacement of ordinary Portland cement with metakaolin was also evaluated. The surface area of metakaolin used in this experiment was 25.4m2/g. The result shows that the sandwich ECC samples modified with nanosilica produced higher strength compared with the base standard M45 ECC.

Curing is a process aimed at keeping concrete saturated or nearly saturated, so as to ensure complete hydration process of cement. For curing to be done properly, the temperature, duration and condition remain key factors. The rate of hydration is usually controlled by the quality and quantities of the cementitious materials present in the mix as well as the moisture availability and environmental temperature. Lightweight foamed concrete is regarded as a sustainable construction material in the construction industry. Some well known major setbacks such as low tensile and compressive strength, low flexural strength, fractural toughness and increase shrinkage as the ages grows, have been reported with this type of concrete. This work is directed at potential ways of increasing the compressive strength of this material by varying the curing method. Therefore, observing the effects of these variables on the eventual compressive strength of the samples in the early-ages of the concrete. The study was conducted using foamed concrete of 1200kg/m 3 1600kg/m 3 density and at the water cement ratio of 0.45. No additives or admixtures Original Research Article Richard and Ramli; AIR, 3(6): 548-557, 2015; Article no.AIR.2015.050 549 were used in this study. The samples were cured using three methods i. e. Water, air and moisture. At the end of the study, the compressive strength of the samples was analysed and the result shows that the samples cured by moisture has the highest compressive strength at 28 days.

The high embodied energy of conventional geopolymer production, which resulted from the necessity of high alkaline activator content and heat curing, hinders the transition of geopolymer technology toward industrial applications. This paper introduces a novel geopolymer system based on hybridization between high calcium wood ash (HCWA) and pulverized fuel ash (PFA), which use a low percentage of alkaline activator (5% of binder weight), ambient temperature curing, and a pressurized forming method for the fabrication of load bearing masonry unit. The elimination of alkali hydroxide was made possible by the Arcanite mineral (approximately 12%), which is inherently present in HCWA. The HCWA-PFA geopolymer mortar blocks with various sodium silicate content (0–5%) and curing regime (water and moist curing) were assessed in terms of mechanical (compressive, flexural, and UPV) and durability performance (water absorption, total porosity, and intrinsic air permeability) over a curing period of up to 90 da...

Providing affordable housing is the most critical problem in many of the developing countries. Using earth materials in building construction is one of the feasible methods to address this issue and it can be a way towards sustainable construction as well. However, the published information on the stabilized soil blocks is limited. Therefore, the present study is conducted to examine the characterization of the soils and engineering properties of the stabilized soil blocks. Four types of stabilizer were used in the study, namely; cement, slaked lime, bitumen emulsion and calcium silicate. Cement and slaked lime were added at different percentages in the range of 5% to 15%, with interval of 2.5%. The percentage was determined based on weight of soil. Meanwhile, bitumen emulsion and calcium silicate were incorporated at various percentages together with 10% of cement. Dosage of bitumen emulsion is in the range of 2% to 10% at interval of 2% while calcium silicate was incorporated at 0.50%, 0.75%, 1.00%, 1.2...

Purpose – A need for effective leadership and adequate managing the personnel is vital for every construction organization. Meanwhile, the dynamic and complex environments of the industry may be caused that not much research has been conducted on leadership practices in the industry. The purpose of this paper is to study the leadership style of the construction leaders in Iran and explore the correlation of transformational leadership practices with teamwork improvement in the construction companies. Design/methodology/approach – The research analysis was completed on a sample population of 107 managers within nominated construction firms in Iran. The analysis methods in this research were mainly descriptive and regression-based analyses and the type of investigation was a co-relational study. Findings – The research found the level of the leaders’ orientation for people and task in their leadership style, their transformational leadership qualities, and the relationship of transformational leadership with teamwork improvement in the respondents’ companies. Originality/value – The study is the first to investigate the leadership style of the construction leaders in Iran, and weather transformational leadership practices effects on teamwork improvement in the industry.

In recycling concrete, the crushing process leaves weak mortar particles and surface cracks throughout the recycled concrete aggregates (RCA). Thus, the process is detrimental, resulting in inferior aggregate properties. This experimental study presents a method to improve the properties of coarse RCA by modifying their surface structure through the combination of two different surface treatment methods. In this study, coarse RCA are first treated by soaking in hydrochloric (HCl) acid at 0.5 mol (M) concentration. They are then impregnated with calcium metasilicate (CM) solution to coat their surface with CM particles. The effects of both surface treatments on the properties of RCA before and after treatment are determined. Moreover, the effect of the replacement of natural coarse aggregates with 60% treated coarse RCA on the mechanical strength of concrete is evaluated. The findings of this study show that the effect of the combination of these two surface treatment methods is beneficial, as the combined methods not only modify RCA surface but also enhance RCA properties. More specifically, after treatment, the particle density, water absorption, and mechanical strength of RCA are significantly improved. Consequently, the incorporation of treated RCA in concrete results in a mechanical strength that approximates concrete prepared with natural aggregates and surpasses the strength of concrete prepared with untreated RCA. In addition, the effect use of treated RCA tends to reduce the drying shrinkage of concrete.

A high-performance construction workplace invests in its human resources and facilitates their technical and innovation skills through team development. Though team development has been explored in many studies, to date, little research has disentangled how team development and compensation methods enhance team performance in construction companies. Accordingly, team development as a hierarchical, reflective construct, incorporating six associated components was extended and the variables of the model in a nomological network analysed using partial least squares (PLS). As a result, with the help of PLS path modelling, a hierarchical team development construct with the mediating effects of compensation on the relationship between team development and team performance was developed. The research analysis was completed on a sample population of 128 construction design teams and the results lead to the development of a model that shows team development has a significant direct and indirect impact on team perf...

High Calcium Wood Ash (HCWA) and Pulverised Fuel Ash (PFA) are by-products from the wood biomass and coal energy production which are produced in la rge quantity with combined annual production of 500 million tonnes. This poses a serious problem for di sposal of the waste material especially at places w here land is scarce. The prescribed study was aimed to examine the mineralogical phases and their respective amount present in the industrial wastes which gover ns the hydration mechanism towards self-sustained solidification of the ashes when used in combinatio n. Besides, the influence of various forming pressu re and hydrothermal treatment temperature on mechanical strength performance of HCWA-PFA cementless mortar blocks was also examined. In the study, the mechani cal strength of the HCWA-PFA cementless mortar block produced using various forming pressure and h ydrothermal treatment temperature was assessed in terms of compressive strength and dynamic modulus. The results of the study are indicative that HCWA i s rich in calcium oxide and potassium oxide content. This enables the hybridization of HCWA with the amorphous silica and alumina rich PFA to form a sol id geopolymer binder matrix for fabrication of cementless mortar block. Throughout the study, dime nsionally and mechanically stable HCWA-PFA geopolymer mortar blocks were successfully produced by press forming and hydrothermal treatment method. Based on statistical analysis, the hydrothe rmal treatment temperature has a statistically insignificant effect on the mechanical strength of the HCWA-PFA cementless mortar blocks. The dominant factor which governs the mechanical strength of the HCWA-PFA cementless mortar blocks was found to be the hydraulic forming pressure. Moreover, it was fo und that hybridized HCWA-PFA can be recycled as the sole binder for fabrication of cementless concrete block which is a useful construction material.

In addition to being exposed to chloride and sulphate attacks, marine structures are subject to seismic and impact loads resulting from waves, impact with solid objects, and water transports. Therefore, the flexural behaviour and impact resistance of Fibre-Reinforced Concrete (FRC) in marine environment must be elucidated. However, such information is scarcely reported. Therefore, this study aims to explore the effects of simulated aggressive environments on flexural strength and impact resistance of FRC and to identify the relationship between the two parameters. Three types of fibres, namely, coconut fibre, Barchip fibre (BF), and alkali-resistant glass fibre, were used in this study. The fibre dosage ranged from 0.6% to 2.4% of the binder volume. All mixes have constant water/binder ratio of 0.37 and their compressive strengths were all exceeding 60 MPa. The specimens were prepared and exposed to three different aggressive exposure environments, namely, tropical climate, cyclic air and seawater conditions, and seawater environment for up to 180 days. Results indicate that flexural strength and impact resistance of FRC have a direct relationship with fibre content. Nonetheless, change in fibre type is more significant than increasing fibre dosage in enhancing flexural strength but alteration in both matters would significantly impact the impact resistance. Tensile strength of an individual BF (640 MPa) is much higher than the flexural strength of the BFRC composite. Thus, failure of concrete matrix was observed to occur prior to the rupture of the fibre which in turn resulted in fibre pull out from the concrete matrix. Among the various FRC examined, FRC containing the highest BF content (2.4%) demonstrated the best flexural strength performance. The flexural strength of the Barchip FRC was observed to be increased by 11–13% in all exposure environments after 180 days. The pre-crack energy absorptions, which were determined through impact load test were found to increase by 60–63% as compared to the control concrete, which exhibited no post-crack energy absorption. Meanwhile, the post-crack energy absorptions of the 2.4BF were found to range between 3.67 J and 3.71 J for various environmental exposure conditions. Analysis of variance (ANOVA) results showed that flexural strengths were significantly increased after six months of exposure to the various aggressive environment conditions, especially in seawater. This could be due to formation of salt crystals which contributed towards enhancing the fibre/matrix frictional bond. However, the exposure environments have no significant effect on impact resistance performance. A logarithmic relationship was found between flexural strength and total impact energy absorption.

This study first investigates the optimization of different percentages of steel fiber (0–2%) and the hybridization of the steel fiber and palm fiber as 2% volumetric fractions on the high strength flowing concrete and determine the density, compressive strength, flexural strength and toughness indices for the mixes. The results show that the use of 1.0% mono steel fiber increases the compressive strength by about 10%, while the inclusion of more than 0.5% of palm fiber in hybrid fiber mixes reduces the compressive strength. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fiber with palm fiber can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fiber (1.5 steel fiber + 0.5% palm fiber) in specimens increases significantly the toughness indices and thus, the use of hybrid fiber combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances.

The maintenance and the repair of concrete structures have become more needed in the field of Civil Engineering. The selection of repair materials for concrete structures requires an understanding of the material behavior. Therefore, this research is conducted to provide a clear indication and understanding of the behavior and structural performance in engineering construction. The combined system of substrate concrete with different mix proportions of flowable high strength system reinforced by hybrid fibers was used to study its mechanical properties. The experimental tests are: compressive strength, splitting tensile strength, flexural strength and pull-out test. It was found that the high strength flowing concrete (HSFC) provides the best performance when the compressive strength of the repaired system is needed, whereas the high strength flowable mortar (HSFM) has the best performance when the tensile strength of repaired system is required. The best value of pull out test was obtained from using the flowable high strength mortar reinforced with 1.5% steel fiber +0.25% palm fiber +0.25% Barchip fiber as the repair material, whereas, the least value of pull-out test was obtained from samples using epoxy.

It has been demonstrated in several past studies that high calcium wood ash (HCWA) can be effectively used in combination with densified silica fume (DSF) as supplementary binder material to enhance the mechanical performance of concrete. The experimental investigation was conducted to study the effect of the inclusion of HCWA and DSF on the durability properties of high strength cement mortar produced. A total of twelve different mix designs of mortar were fabricated with the use of HCWA at various cement replacement levels of 0–20% in combination with 7.5% densified silica fume (DSF) and subjected to various durability tests. The durability assessments performed include tests on water absorption, air permeability, porosity and degree of carbonation. A significantly lower degree of water absorption, porosity and carbonation was observed for cement mortars with HCWA contents of 2–8% used in combination with 7.5% DSF by weight of binder as compared to an equivalent pure cement mortar.

This paper presents an investigation on the feasibility of inclusion of biomass wood ash (BWA) as a partial replacement material for fly ash (FA) in preparation of blended BWA-FA geopolymer mortars. The blended mortar systems for this study were prepared at three replacement ratios of FA by BWA of 10%, 20% and 30% by binder mass. The engineering properties of the BWA-FA geopolymer mortars were evaluated using compressive strength, flexural strength, water absorption and total porosity measurements. Microstructural and phase composition analysis were also conducted to assess the obtained results and compared with a control mortar mix containing 100% FA at different ages of 3, 7 and 28 days. The results showed the inclusion of BWA up to 20% resulted in higher strength and porosity characteristics than the control mix at age of 3 and 7 days. However, at age of 28 days, the geopolymer contains 10% BWA of the total binder was the only blended mixture that exhibited higher compressive strength and lower total porosity than the control mix. The phase composition results of the blended mixtures at 28 days confirmed the formation of calcium polysialate and calcium silicate hydrate gels coexisted with sodium polysialate phase.

The porosity and pore size distributions are pore structure parameters which have a direct effect on the permeability of cement paste as well as its durability. This paper is based on laboratory programs comparing the porosity, pore size distributions and water absorption with varying ageing processes of three commercial polymer-modified mortars (SBR, PAE and VAE) as well as unmodified conventional mortar mixes exposed to different curing conditions. It was found that an increase in polymer loading has resulted in a significant reduce in porosity and water absorption in polymer-modified mortars. Furthermore, the SBR3 mix exhibited the most superior properties of the study in all conditions at different ages of curing.

Fiber reinforced polymer (FRP) is an ideal reinforcing material for marine structures because of its chemical stability. It is normally used in rod form to substitute the conventional steel bars in marine structures. However, the FRP bar reinforced concrete structure tends to fail with limited ductility. Thus, the safety of its application is greatly affected. This study aimed to enhance the ductility of FRP reinforced structure by proposing a novel FRP encased beam design. Structural behaviors of different encased beams were studied under four point flexural loading. Four types of encased beams were tested, namely, the plain FRP I-beam, the FRP I-beam with studs, the FRP I-beam with links and studs, and the FRP I-beam with studs and Barchip fiber. The results suggested that the FRP in the I-beam form could enhance the ductility performance of the FRP reinforced concrete beam, to a level that satisfies the ductility requirements as stated in the Canadian Highway Bridge Design Code, i.e. ductility index should exceed 4.0. However, shear studs should have to install on the FRP I-beam and this is also useful in preventing bond slip problem. Addition of Barchip fibers in the mixing concrete could further enhance the first crack load by 25.4%, while addition of stirrups enhanced the ultimate load carrying capacity by another 18.2%. However, both of these methods were not recommended since they would reduce the ductility of the beam, as opposed to the primary objective of the proposed design.

The trouble of sea water attacks in marine structures has suffered the engineers for decades. Until present, the most popular approach used to minimize the detrimental effects resulted by the sea water is the applications of high strength high performance concrete. The binary or ternary blended cement system is applied to improve the impermeability properties of the resulting concrete. Nonetheless, the sulphate attacks and the expansions and shrinkages caused by the environments would induce cracks at the structures. Once the cracks are initiated, it allows the penetration of harmful substances and ultimately reduces the durability of the structure in a substantial manner. In this experiment, a mechanical approach is employed to improvise the concrete in the aspects of strength and durability properties. The barchip fibre that is non-corrosive, short and discrete is introduced into high strength concrete so as to provide localize reinforcing effects to restrain the cracks development in the matrix. The specimens were exposed to three types of aggressive environments; namely tropical climate (A-series), alternate air and sea water in a 14-day cycle (4 days in sea water + 10 days in air) (N-series) and continuous immersion in the sea water (W-series). Parameters like the compressive strength, permeability, porosity, chloride penetration were examined. The mineralogical and microstructures were studied by the means of X-ray diffraction (XRD) and scanning electron microscope (SEM) examination, respectively. The findings in these studies solidify the justifications provided in the discussions. The results verify that 1.8% would be the optimum dosage of barchip fibre that could provide greatest enhancements to the concrete. When the exposure period is prolonged, the increments in the compressive strength were above 12% and the permeability was also reduced. Together with other improvements, it could be concluded that the incorporation of barchip fibre has successfully suppressed the damaging effects that arise from the aggressive environments.

This study was performed with the aim to assess the structural behaviour of ferrocement–reinforced concrete composite slab system with high calcium wood ash (HCWA) high strength mortar used as the compression zone. The proposed slab system consisted of conventional reinforced concrete slab topped with a layer of high strength ferrocement composite containing various contents of HCWA by total weight of binder. A total of six numbers of one-way composite slab prototypes were subjected to four point flexural load test to ultimate failure. The main parameters of the study include serviceability moment, ultimate moment capacity, flexural stiffness in serviceability and post cracked conditions, crack width development, crack spacing and failure mode. Results of the investigation indicate a significant enhancement in the first crack load and ultimate failure load of the composite slab system with the use of HCWA in the mortar layer at cement replacement level of 2% to 8% by binder weight. In addition, the inclusion of HCWA at various replacement levels also contributed to a reduction in the magnitude of average crack width at a given flexural load.

One method to promote and encourage maximum recycled concrete aggregate (RCA) utilisation for structural concrete applications is to minimise the adverse effects of RCA on concrete performance. The formulation of an appropriate recycling process in RCA production with improved properties is desirable. This study aims to develop a potential treatment of RCA by using low-concentration acid as an alternative method to produce high quality RCA for structural concrete applications. This work aims to study the effect of using different molarities of acid solvent and age of treatment (soaking) on properties of RCA, as well as the influence of using this treated aggregate on the properties of concrete. The results show that the use of different acid molarities to remove or minimise loose mortar particles attached on the surfaces of RCA can significantly improves its physical and mechanical properties. In addition, the reduction of loose mortar that covers RCA particles can significantly improves surface contact between the new cement paste and the aggregate which subsequently resulted in a significant improvement in the strength of concrete mechanical. However, the effectiveness of these treatment methods remains dependent on several factors that require further consideration.