Effect of Expansive Agent and Temperature on the Quality of Pre-cast Concrete Products

Maruyama, Takayoshi; Karasawa, Hideaki; Hashimoto, Shinichiro; Date, Shigeyuki

doi:10.1007/s40999-016-0080-8

Cited by 11 publications

(4 citation statements)

References 7 publications

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“…Labor productivity is a dynamic entity, affected by many elements, and associated with performance of time, cost and quality [12,13]. Owing to its substantial impact on overall project success, there is a strong need to assess the performance of labor in order to address the productivity issues.…”

Section: Introductionmentioning

confidence: 99%

Labor Productivity Assessment Using Activity Analysis on Semi High-Rise Building Projects in Pakistan

Sheikh¹,

Ullah²,

Ayub³

et al. 2017

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Abstract. Construction organizations strive to increase their competitiveness by reducing the project costs especially labor cost. Optimizing labor productivity will ensure value for money. In the face of no guidelines available for local construction industry, research must be directed to benchmark construction labor productivity in building projects of Pakistan. Based on a thorough review of established productivity assessment methods, Activity Analysis is performed on five local semi high-rise building projects. Statistical analysis is carried out to identify labor productivity trends in seven standard areas. Further, sensitivity analysis is carried out to characterize the positive and negative influencers. It is revealed that labor spends a little more than one-third of working time in direct and support activities each, and one-quarter in delay activities. Furthermore, delay and support activities are correlated with direct work. Direct work is observed at its peak during midday hours, and lowest during the start and end of workday. The study is an original effort in benchmarking the labor productivity in construction projects of Pakistan. Based on the findings, productivity improvement strategies are proposed from which projects can benefit in the form of optimized costs and schedules. Results are of relevance towards understanding the labor productivity in developing countries.

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Section: Introductionmentioning

confidence: 99%

Labor Productivity Assessment Using Activity Analysis on Semi High-Rise Building Projects in Pakistan

Sheikh¹,

Ullah²,

Ayub³

et al. 2017

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“…This technology combines the advantages of the straightforward and feasible construction of unbonded prestressed structures with the excellent force transmission mechanism of bonded prestressed structures. [4][5][6][7] In the system, the construction of retard-bonded prestressed tendon differs from that of the conventional one. It consists of three parts: steel strand, epoxy adhesive, and high-density polyethylene sheath with ribs, as displayed in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…Then in the 1990s, a novel prestressed technology, namely retard‐bonded prestressed technology, was first developed based on both bonded and unbonded prestressing systems in Japan. This technology combines the advantages of the straightforward and feasible construction of unbonded prestressed structures with the excellent force transmission mechanism of bonded prestressed structures 4–7 . In the system, the construction of retard‐bonded prestressed tendon differs from that of the conventional one.…”

Section: Introductionmentioning

confidence: 99%

The effect of curing temperature on hardening, thermal, and mechanical characteristics of adhesive for retard‐bonded prestressed tendon

Li,

Jiang,

Zhang

et al. 2024

J of Applied Polymer Sci

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The effect of curing temperature on hardening, thermal, and mechanical characteristics of adhesive for retard‐bonded prestressed systems is investigated in detail. To evaluate the degree of hardening of the adhesive, the cone penetration and Shore hardness of two samples are tested throughout the curing process under conditions of 25, 35, 45, 55, and 65°C. The thermal performance and curing reaction are characterized using differential scanning calorimetry and Fourier transform infrared spectroscopy, respectively. The mechanical properties with respect to the cure temperatures are characterized by compression strength tests. Experimental results present that after curing under conditions ranging from 25 to 65°C, the hardness of the samples reached its maximum values (85–90 D). As the temperature increased from 25 to 65°C, there was a greater degree of curing cross‐linking, resulting in an increase in compressive strength from 55 to 72 MPa. Based on Shore hardness–time experimental data, a logarithmic model is proposed for predicting the hardness of adhesives at any given time for engineering applications. Additionally, the time–temperature superposition principle is utilized to extrapolate the curing time of the adhesive under low‐temperature conditions. The research findings are of significant importance for the assessment of adhesive hardening.

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“…Another method involves increasing the maximum temperature of steam curing. However, it has been reported that thick products easily crack because of the thermal stress arising from the large temperature difference between the concrete and ambient atmosphere just after demolding [12]. Moreover, an increase in the rate of temperature rise decreases the reaction rates of alite (C 3 S) and belite (C 2 S) at the early stage and the production volume of C-S-H [13].…”

Section: Introductionmentioning

confidence: 99%

Effect of Type of Cement and Expansive Agent on the Hardening of Steam-Cured Concrete

Maruyama¹,

Karasawa²,

Date

2017

KEM

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Pre-cast concrete products are sometimes manufactured in two cycles daily. It is ensured that they have the required strength at an early stage of demolding by increasing the steam curing temperature to reduce cost or increase productivity. However, the reduction in durability because of cracking due to thermal stress is a topic of concern. On the other hand, it has been known that fine blast-furnace-slag powder and expansive agents show high temperature dependence. Although they are used even in precast concrete products, the effect of steam curing on these materials is not known. Thus, in this study, the expression of compressive strength and expansion that are critical in improving the quality and productivity of precast concrete products was investigated, using high early-strength cement and two types of expansive agents, namely, ettringite-based and lime-based agents. Consequently, the strength expression was accelerated by the addition of expansive agent to ordinary cement and high early-strength cement. The extent of restrained expansion is greater for the lime-based expansive agent than for the ettringite-based expansive agent, and when an expansive agent is added to high early-strength cement, the extent of restrained expansion falls to a level lower than that in the case of ordinary cement.

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Effect of Expansive Agent and Temperature on the Quality of Pre-cast Concrete Products

Cited by 11 publications

References 7 publications

Labor Productivity Assessment Using Activity Analysis on Semi High-Rise Building Projects in Pakistan

Labor Productivity Assessment Using Activity Analysis on Semi High-Rise Building Projects in Pakistan

The effect of curing temperature on hardening, thermal, and mechanical characteristics of adhesive for retard‐bonded prestressed tendon

Effect of Type of Cement and Expansive Agent on the Hardening of Steam-Cured Concrete

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