On this page you will find updated results from our analyses. In the graphs below, the data represent concrete core samples taken from homes. In the majority of cases, there are two individual data points (i.e two cores) per home.
Figure 1: Total Sulfur vs. Magnetic Susceptibility for all houses sampled as of 5/17/21 (444 homes). We classify all samples into three categories: 1) Green Squares – Samples that test negative for pyrrhotite (0 value for magnetic susceptibility loss) or return a trace of pyrrhotite (values between 0 and 5 magnetic susceptibility loss); 2) Gold Diamonds – Samples that test positive for pyrrhotite (>5 magnetic susceptibility loss), but there is no evidence or reports of map cracking in the concrete at the time of sample coring; 3) Red Circles – samples that test positive for pyrrhotite and there is evidence or reports of map cracking at the time of sample coring.
Figure 2: Percent of samples showing Map Cracking at varying levels of Magnetic Susceptibility Loss (compiled 5/17/21).
Figure 3: Distribution of total sulfur for all pyrrhotite-free (clean) samples. All concrete contains some sulfur due to sulfur minerals within the cement portion of the concrete mix, and generally ranges from approximately 0.1% – 0.2% by weight. The average of all clean samples has consistently been about 0.14%. As of 6/25/21, we have tested 420 clean samples. The average amount of sulfur from all clean samples was 0.14%, the mode was 0.14%, the median was 0.14%, and the standard deviation was 0.03.