This article examines the effect of total substitution of siliceous sand by crushed limestone sand in mortar and concrete with regard to durability. Crushed limestone sand is a by-product of quarries containing a significant amount of fines characterised by a ‘spread out’ grain size distribution having a maximum diameter of around 5 mm. An extensive laboratory program was planned to achieve the objectives of this study. Effect of sand replacement on transport mechanism was analysed for two different water/cement ratio by pure diffusion and accelerated migration tests conducted on mortar and concrete samples, respectively. Gas permeability, resistance to strength development under saline curing, carbonation and corrosion tests were also done. The results have indicated the suppression of chloride diffusion coefficients in both mortar and concrete specimens for crushed sand as compared to the siliceous sand. For a given water to cement ratio, the gas permeability coefficients have reduced more than twice for crushed sand as compared to siliceous sand. In addition, the crushed sand concrete has shown better resistance against the strength development in saline curing conditions and corrosion. However, the carbonation depth was observed to be on the higher side for crushed sand as compared to the siliceous sand.

This paper investigates the performance of cement mortar with the addition of various percentages of nano-silica (3%, 5% and 10%) at constant water-to-cement ratio. Early age properties of mortar along with the hydration mechanism were determined using flow test, setting time test, micro calorimetry and thermo-gravimetric analysis tests. In addition, hardened and durability-related properties using migration resistance and thermal conductivity tests were evaluated. It was observed that the workability and the setting time decreased largely according to the increase in the percentage of nano-silica as compared to the reference mortar. This finding is confirmed by micro calorimetry results, which indicate a significant increase for the heat evaluation in the presence of nano additives. The thermo-gravimetric analysis indicated the acceleration of the hydration reaction and continuation of the prolonged pozzolanic reaction, which results in the densification of the microstructure confirmed by the increase of compressive strength by 21% at 112 days for 10% addition of nano-silica as compared to the reference mortar. Moreover, the incorporation of nano-silica had also improved the durability of the mortars by reducing the effective diffusion coefficient and thermal conductivity by 46% and 40%, respectively, especially for mortar containing 10% nano-silica.

Enhancing the strength of fly ash (FA)-based geopolymer by increasing the alkaline activator content is a costly and unsustainable technique. Therefore, this work was designed to reduce the activator by employing the pressured catalysis (PC) technique, coupled with the use of minerals that have filler and occupying effects. The main objective was to enhance the strength of the mix with a lower alkaline-to-precursor (A/P) ratio and create a sustainable, load-bearing building block from it. Initially, the compressive strength of the FA-based geopolymer was investigated experimentally by varying sodium silicate to sodium hydroxide and A/P ratios with ambient and hot curing. Afterward, PC was applied to the optimized proportion of constituents, and a significant increase in strength (9.6 to 20.0 Mpa) was observed at a 0.25 A/P ratio. By adding clay and dune sand (DS), the compressive strength was 19.5 and 40.4 Mpa at an A/P of 0.25 and 0.16, respectively. The strength gain mechanism was evaluated at the molecular and micro levels by conducting FTIR and SEM analyses. The environmental and economic indices and strength indicated the high sustainability of DS-based geopolymers compared to analogous blocks. The environmental and economic benefits of 23.9% reduced CO₂ emissions and 24.2% less cost were provided by the DS-based block compared to the FA–clay-based block. A DS-based geopolymer obtains strength at a low A/P due to its occupying effect and results in sustainable building blocks.

Safety management is important throughout the world specifically on building projects, which are prone to accidents due to their unique operations, dynamic and ever-changing nature. In every country, contractors implement safety management systems (SMSs) to avoid accidents and comply with applicable laws, regulations and to provide safe work environments for their workers. Nonetheless, accidents still happen on many building projects in the country. The objective of this work is to measure safety management as perceived on building projects by employing a proactive approach in the Kingdom of Saudi Arabia to improve site safety. A survey instrument is utilized to gather data from building projects. Another questionnaire is used to conduct interviews with the key managers on the same projects. Analysis of the questionnaire survey is performed after entering the data into SPSS software by applying factor analysis and multiple linear regression. Factor analysis extracted two significant factors, including “management commitment, employee involvement, and safety training”—factor 1, and “project safety plan, safety committee, and safe use of equipment”—factor 2, which proactively measure the implementation of safety management on the building projects. The safety model obtained by multiple regression analysis identifies two significant contributors to the performance of the SMS. Analysis of the interviews complemented and validated the results of the questionnaire survey. The findings provide in-depth understanding of proactively measuring safety management on building projects for the construction industry practitioners to make project sites safer.