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AbstractDelay in construction projects is a major concern. Research was conducted to find the construction delay causes and mitigation measures. Literature reveals that different countries experience various causes of delays and significances of these causes are different based on project types. This study explores delay causes in Kazakhstan’s construction industry and analyzes their influence on different types of construction projects. Fifty-five delay causes relevant to construction projects in Kazakhstan have been identified through literature review and primary interviews with selected construction professionals. Afterwards, a comprehensive survey was conducted among the industry professionals. The survey results show that different delay causes have different importance based on the project types (industrial, residential, commercial, etc). Moreover, project parties (client, contractor and consultant) have different views on the delay causes. Accordingly, the study ranks delay causes based on project parties and project types and compares their correlations. Finally, recommendations for the most prominent delay causes have been provided. This study provides better understanding on delay causes and gives important guideline for stakeholders of Kazakhstani construction industry and other construction professionals in the world to control their projects. Similar studies can be conducted in other countries to identify causes and remedial measures for delays.

Calcium-based stabilizing materials (CBSMs) such as lime and fly ash are extensively used in subgrade primarily to enhance mechanical strength and improve resistance to chemical attack, resulting in more durable roadway. The soluble sulfate phase contained in some soils, however, can react with CBSMs and form ettringite minerals. If the soil is compacted before the end of this reaction, large, unstable, and volumetric swelling can occur. Among several methods to control sulfate-induced swelling, a “mellowing” approach is typically used because of its efficient, economical, and practical benefits when dealing with calcium-based stabilization of soils with significant soluble sulfate contents. Although the mellowing method is one of the frequently used methods, little data is available on the characterization of the specified mellowing process in the high-sulfate-bearing soil during the mellowing period. A research program investigated key factors influencing the mellowing process during the mellowing period, explaining how stabilizer type and content, remixing interval, mellowing period, and temperature play a role in reducing soluble sulfate content. Moreover, for selected mixtures, the 3-dimensional volumetric expansion and retained strength were measured after the mellowing process. Laboratory test results have revealed that a single mellowing process with higher lime content and daily remixing at high temperature leads to the rapid reduction of sulfate content in the soil. Moreover, after the mellowing process, additional soil treatment with fly ash or a combination of lime and fly ash leads to lower expansion and higher retained unconfined compressive strength of the soil mixture.

Ordinary Portland cement (OPC) is one of the most widely used construction materials in civil engineering infrastructure construction but it is susceptible to sulfate attack. One of the ways to improve the sulfate resistance of an OPC mortar/concrete is to replace a certain amount of OPC with different pozzolanic materials such as ground granulated blast furnace slag (GGBFS) and metakaolin. The use of pozzolanic materials to mortar/concrete not only enhances durability but also reduces carbon dioxide (CO2) emission due to the less usage of OPC at the initial construction state. As considering these aspects, limestone calcined clay cement (LC3) has been developed in recent decades. However, the influence of LC3 on sulfate attack resistance has not been fully evaluated. Therefore, this study investigated the efficiency of LC3 mortar mixtures against sulfate attack at an early age (approximately 4.5 months) after two different curing periods, namely 1-day and 3-day curing, since the strength of the LC3 mixture is lower than OPC mixtures. To evaluate the synergistic effect of a combination of LC3 and GGBFS on the sulfate resistance, the LC3 and OPC mixtures containing 25% GGBFS were also assessed in terms of density, porosity, compressive strength, volumetric expansion, and weight changes. The experiment results show that the expansion of the LC3 mixture regardless of the addition of GGBFS and an initial curing strength made a plateau after a rapid increase up to 7 days, while the expansion of the OPC mixture kept increasing throughout the period. Furthermore, the addition of GGBFS to OPC or LC3 mixture provides the synergistic effect on reducing the expansion due to sulfate attack. Therefore, if LC3 mixture has high initial strength (min. 15 MPa) and dense microstructure to minimize the penetration of sulfate ion into the mixture, it is expected that LC3 mixture is more efficient than OPC mixture against the sulfate attack.