Adjusted EBITDA, which excludes the gain on sale from our reclaimed quarry in California, was $244 million, up 22% compared to last year.
This strong growth was driven in part by a 3% increase in aggregate shipments.
Freight-adjusted aggregates pricing increased by 2% in the quarter.
Adjusted for mix, the increase was 1.3%.
Aggregate total cost of sales per ton was 2% lower than last year's first quarter.
And cash cost of sales per ton declined by 3%.
Aggregates, cash gross profit per ton, increased by 9%.
Overall, our operating results this quarter, helped drive a 90 basis point improvement in our return on invested capital.
According to Dodge, 90% of the growth in this sector will occur in Vulcan-served markets.
As a result, we've upgraded our aggregates volume guidance for 2021 to a range of 1% to 4% growth compared to 2020.
Excluding the gain on the sale of the California property, we now expect full year adjusted EBITDA of between $1.38 billion and $1.46 billion.
Our aggregates gross profit per ton increased by 12% to $4.82.
Over the past three years our compound annual growth rate for gross profit per ton was 7%.
As Tom mentioned, the 90 basis point improvement in the quarter pushed our return to 14.8% for the trailing 12 months ended March 31.
As an example, the first quarter's ROIC gain was comprised of a 1% increase in invested capital and a 7% increase in adjusted EBITDA.
Over the past three years, our trailing 12 months ROIC has improved by 280 basis points, driven by a 4% compound annual growth rate in invested capital and an 11% compound annual growth rate in adjusted EBITDA.
Our net debt to adjusted EBITDA ratio is 1.4 times, and we have nearly $900 million of cash on the balance sheet.
Our debt has a weighted average maturity of 15 years, with no significant maturities in the near-term.
The sale generated $182 million of net proceeds and a pre-tax gain of $115 million.
Gross profit in those segments collectively was $5.6 million in the quarter or $2 million less than last year.
For the full year, we now anticipate that the cost of diesel fuel will be a headwind of approximately $25 million, reflecting higher prices since the start of the year.
The last time we spoke with you we expected that our effective tax rate for 2021 would be 21%.
We now expect the full year rate to be between 23% and 24%, following a 27% rate in the first quarter.
And as a result, we recorded a $14 million charge in the first quarter.

Summary:
Aggregate total cost of sales per ton was 2% lower than last year's first quarter.
As a result, we've upgraded our aggregates volume guidance for 2021 to a range of 1% to 4% growth compared to 2020.