Concrete, Lightweight Aggregate

Concrete, Lightweight Aggregate 

the most common type of concrete, in which lightweight aggregate is used as the coarse filler, cement (more rarely, gypsum, lime, synthetic resins) is used as the binder, and open sand or compact sand (for example, quartz sand) is used as the fine aggregate. In terms of the degree of porosity of the concrete, lightweight aggregate concrete is classified as compact, large-pore (sand-free), or aerated. In terms of purpose, it is classified as thermally insulating, structurally insulating, or structural.

Thermally insulating lightweight aggregate concrete of varying structure is used in buildings basically as a warmth-retaining material in sandwich enclosures. Its density (dry) is between 350 kg per cu m (for example, in large-pore lightweight aggregate concrete with synthetic resins) and 600 kg per cu m. Its compressive strength is 0.5–2.5 meganewtons (MN) per sq m (l MN per sq m = 10 kg-force per sq cm). Its coefficient of thermal conductivity is 0.11–0.17 watts per (m.°K), or 0.10–0.15 kilocalories per (m · hr · °C).

Structurally insulating lightweight aggregate concrete is used chiefly for single-ply wall paneling and large units. Its density is 700–1,200 kg per cu m. Its compressive strength is 3.5–10 MN per sq m. Its coefficient of thermal conductivity is 0.21–0.46 W per (m · °K), or 0.18–0.40 kcal per (m · hr · °C). Its cold resistance is 15–100 Mrz (from 15 to 100 alternating freezing-thawing cycles).

Structural lightweight aggregate concrete is designed for the various supporting structures of buildings and engineering installations (for example, bridges). It has a density of 1,400–1,800 kg per cu m. Its compressive strength is 10–50 MN per sq m. Its cold resistance is up to 500 Mrz. The use of structural light-weight aggregate concrete (instead of ordinary heavy concrete) in large-scale reinforced-concrete structures makes it possible to reduce the weight and cost of the structures substantially. High-grade structural concrete is also used in shipbuilding (for example, for the hulls of riverboats and seagoing vessels).

REFERENCES

Stroitel’nye materialy. Edited by M. I. Khigerovich. Moscow, 1970.
Buzhevich, G. A. Legkie betony na poristykh zapolniteliakh. Moscow, 1970.

G. A. BUZHEVICH