6TH International Congress on Technology - Engineering - Kuala Lumpur3 - Malaysia (2018-07-19)

Durability Investigation Of Building Stones Against Salt Crystallization Using Non-destructive Tests

Iran is among the countries with a great potentials and capabilities in the production of sedimentary, igneous and metamorphic building stones. Durability is regarded to be a major characteristic of building stones in sustainable architecture. Crystallization of soluble salts has been known to damage building stones. For this reason, durability of the two sedimentary stones (yellow and red travertine) and two igneous stones (Shirkouh monzogarnite and Solulan wehrlite) from Iran were investigated against sodium sulfate crystallization test. Petrographic, dry and saturated density, effective porosity, water absorption by weight, dry P and S-waves velocity and uniaxial compressive strength of fresh quarried stones were determined in the laboratory, and then salt crystallization test was carried out using sodium sulphate (Na2SO4) solution up to 30 cycles. Durability estimation was carried out using non-destructive tests (dry weight loss (DWL) and P- and S waves velocity). Compared with the uniaxial compression test, DWL and wave velocity test have the advantages of being non-destructive and they yield continuous measurement. Variation in DWL, P- and S waves velocity was recorded every 10 cycles. The results showed that fresh travertine samples have higher effective porosity (more than 4.5%) and water absorption (>1.5%) than fresh igneous stones (< 1% and 0.3%, respectively). Fresh igneous stones have higher density, waves velocity and uniaxial compressive strength than fresh travertine samples. Red travertine is more porous than yellow one and Solulan wehrlite has greater strength than Shirkouh monzogranite. After salt crystallization test, the red travertine and Solulan wehrlite showed highest and lowest decline in both waves velocity, respectively. Solulan wehrlite showed 0.94% and 1.78% loss in in P and S-waves velocity at the end of test. Dry weight measurement during salt cycles showed that the red travertine is the most prone to disintegration by salt crystallization pressure than other samples. Yellow travertine exhibited 4.78% loss in dry weight after salt cycles. It was not recorded any loss in dry weight for Solulan wehrlite. Of course, travertine samples show weight increment at the earlier cycles (cycle 10th) due to deposition of salt within pores space. Based on results, dry weight loss (DWL) is not a sensitive indicator estimating durability of high strength rock such as high strength stones such as Shirkouh monzogranite and wehrlite stones. Measurement of waves velocity was found to be a suitable test for estimating durability of stones. It was found that effective porosity and rock strength are key parameters controlling durability of stones. Among sthe studied samples, red travertine and Solulan wehrlite showed lowest and highest quality and durability, respectively.
Ahmad Zalooli, Mashalah Khamehchiyan, Mohammad Reza Nikudel