دانلود رایگان مقاله انگلیسی عملکرد اسلب های بتن سبک با استفاده از پومیس و اسکوریای آندزیت بازالتی با پتاسیم متوسط - اشپرینگر 2018

Abstract

An investigation was conducted on bending tests of 24 reinforced lightweight concrete one-way slabs using medium-K basaltic andesite pumice and scoria and 1 reinforced normal concrete slab as a control. The compressive strengths and reinforcement ratios were varied to evaluate their flexural behaviors. The ultimate bending moment at failure, midspan deflections and maximum crack widths at assumed service, cracking patterns and failure modes were evaluated to indicate their performance. The results showed that medium-K basaltic andesite pumice and scoria as coarse aggregates can be used to produce pumice and scoria concrete one-way slabs with a relative satisfactory performance. Both behaved typically as reinforced concrete beams with first cracking load, ultimate load and stiffness were lower than the control. The reinforcement ratio was an important factor that influenced significantly the observed parameters compared to compressive strength and type of coarse aggregates. Theoretically, the ultimate bending moment can be estimated accurately by provision compared to midspan deflection and maximum crack width. Cracking patterns were a typical flexural crack, while failure modes were a reinforcement yielding without spalling on compressive concrete zone.

Conclusions

This study proved that the medium-K basaltic andesite pumice and scoria as coarse aggregates can be used to produce lightweight concrete one-way concrete slabs with a relative satisfactory performance. From the experimental investigations reported on this paper, the following conclusions may be drawn:

1. All pumice and scoria lightweight concrete one-way slabs indicate typically the flexural behavior as reinforced concrete beams, while initial crack loads, ultimate loads and stiffness are lower than normal concrete one-way slabs as the control.

2. The reinforcement ratio is the most significant factor affecting the flexural behavior compared to the type of coarse aggregates and compressive strength.

3. Ultimate bending moment may be well predicted by theoretical calculations based on ACI 318-08 code.

4. The theoretical calculation of the instantaneous deflection based on ACI 318-08 code tends to underestimate with 14.95% maximum difference.

5. The theoretical calculation of the maximum crack width based on the Gergely–Lutz formula tends to underestimate with 21.71% maximum difference.

6. All one-way slabs show the cracking patterns due to flexure according to the design conducted previously, whereas the failure modes are indicated by reinforcement yielding at the first time and then crushing concrete without any spalling on the concrete compressive zone.