A building faces several challenges across its lifecycle stages. Challenges such as production inefficiency and inadequate waste management hinder advancement in the construction industry. Furthermore, the sector has emerged as one of the largest producers of waste in the world, which can lead to detrimental impacts on the economy and the environment. Conventional approaches are insufficient to eradicate these concerns. Thus, practitioners have sought to implement novel methods to ameliorate the construction process. In this regard, design for manufacturing and assembly (DfMA) and design for deconstruction (DfD) have gained prominence, as studies have elucidated the methods’ unprecedented potential to wholly transform the construction process and mitigate the unwanted impacts brought about by the industry. This study identified the applications and benefits of DfMA and DfD in construction, as well as recent developments and research gaps, through a literature review, using Scopus as the primary database and MATLAB for conducting data text analytics. The current body of knowledge necessitates a further assessment of the following research gaps: (1) development of standard construction-oriented DfMA guidelines; (2) corroboration of the developed DfMA tools through practical application; (3) integration of these holistic design approaches with emerging technologies, such as additive manufacturing and digital fabrication; (4) comparison of structures constructed using DfMA and DfD with structures built with conventional approaches; (5) comprehensive application of DfD guidelines to structural systems; (6) integration of DfMA and DfD; (7) execution of sustainability assessment studies to evaluate the impact of DfMA and DfD; and (8) identification of solutions to the barriers to DfMA and DfD uptake in construction.

Drying shrinkage in mortar produces cracks and micro-cracks which affect the durability of a structure. The effects of seawater as a substitute to freshwater and fly ash as a partial replacement for cement were investigated in this study in order to address the predicted water shortage by 2025 and the increasing carbon footprint from carbon dioxide emissions worldwide. Moreover, these materials are also more economical alternatives to freshwater and cement. Rectangular prism specimens with varying fly ash content (10%, 15%, 20%, 25%, and 30%) were cast to measure the drying shrinkage in mortar while 50-mm cube mortar specimens were prepared to determine the compressive strength. This study investigated whether the addition of fly ash and seawater reduced the drying shrinkage of mortar. From the results, it was found that mortar specimens with 20% fly ash replacement achieved the highest early and late strengths. Partial substitution of fly ash would result to shrinkage in mortar while substitution of seawater to freshwater counteracts the effects of fly ash, thus producing less shrinkage. Fly ash content between 20%-25% combined with seawater produces the least shrinkage value without compromising the minimum required compressive strength.

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ABSTRACT:The effects of seawater on the strength performance of reinforced concrete (RC) beams were investigated. Four RC beams measuring 150 x 200 x 800 mm were constructed. Two beams were constructed with concrete mixed with freshwater and the other two were constructed with seawater. Center point loading test was conducted on the beams specimens. Load, deflection, and strain of each beam were monitored and recorded. It was found that the difference between the strength test values obtained by using freshwater and seawater were minimal. However, formation of rust in steel when seawater was used was very evident. Hence, the effects of seawater on the corrosion behavior of steel were investigated. Mortar specimens with cold-joint were used as medium to facilitate the investigation of corrosion. Ordinary Portland cement (OPC) Type 1 was used as binder for the mortar and was partially replaced with fly ash at 30% and 50%. Rectangular prism specimens of dimensions 40mm by 40mm by 160mm were cast for macrocell corrosion measurements and compressive strength determination. From the test results, the following were observed: (a) Specimens with fly ash were observed to have lower corrosion rates compared with the ones without fly ash; (b) Specimens mixed with freshwater resulted to the higher strength both at 7th-day age and 28th-day age; (c) Regardless of the type of water used in making the mortar, specimens cured in seawater achieved higher later strength values.

Reinforced concrete comprising of deformed steel bars is the common structural material in construction. The problem of this composite material is the corrosion of deformed steel bars inside the concrete that weakens the structure over time. In this paper, investigation on the two types of reinforced concrete were used: alkali-activated concrete (AAC) and ordinary Portland cement (OPC) concrete beams. In addition, Impressed Current Technique (ICT) was made to accelerate corrosion before performing flexural bending test. The use of a non-destructive test which is the digital image correlation (DIC) technique during the flexural loading test on the two types of beam were considered to monitor the strain values against load. It was concluded that AAC mixture 1:1:2 (coal fly ash: fine aggregate: coarse aggregate) with 12M Molarity and water binder ratio of 0.52 produced the lowest corrosion rate over time for all the beams. In addition, the strain values of the AAC mixture produced ductile behavior with strain softening effect on the third point bending load test where the location of the force was applied.