Pirozhkova died Sept. 12 of natural causes at her home in Sarasota, Fla., said her grandson, Andrei Malaev-Babel.
Until her book, "At His Side: The Last Years of Isaac Babel," was published in English in 1996, he was perhaps more famous for how he died than how he had lived. Arrested by the Russian secret police during one of Josef Stalin's campaigns of terror against intellectuals, Babel was executed in 1940. He was 45.
Before the Jewish writer was imprisoned, he had the good fortune to spend his last seven years with Pirozhkova, whose "account of Babel's arrest and disappearance is so moving because she first makes Babel so fantastically alive," Richard Lourie wrote in 1996 in the New York Times.
The "tender memoir" brought him to life "as we could not otherwise have known him: as a jokester, a mimic, a man of boundless curiosity," New York's Buffalo News said in 1996.
"The anguish of loss never leaves me," Pirozhkova wrote near the end of the memoir, which recounts how the couple sat holding hands while officers ransacked their home searching for his papers. She never remarried.
Barely mentioned in the book are her accomplishments. A civil engineer, she helped design Moscow's palatial subway system and worked on intimidating projects in the mountainous Caucasus region.
At 23, she met the 38-year-old Babel, already a famous writer of short stories, at a dinner party. Babel courted her for two years and they lived together as common-law husband and wife for five years, until his arrest in 1939, her grandson said.
Babel never divorced his first wife, who lived in Paris with their daughter. He also had a son from a long-term relationship with another woman in Russia. In 1937, Babel and Pirozhkova had a daughter, Lidiya, who became an architect.
Born in a Siberian village on July 1, 1909, Pirozhkova attended what is now Tomsk Polytechnic University. In 1930, she earned a civil engineering degree and worked in that field until 1965.
For 15 years after Babel's arrest, she tried to find out what had happened to him. She was officially informed of his death in 1954, the same year he was pronounced "rehabilitated" in the eyes of the Soviet regime.
In the 1980s, Pirozhkova oversaw the publication of Babel's "Diary of 1920" and in 1990 finished editing a two-volume definitive collection of his works.
When she felt her husband's reputation had been properly restored, she moved with her daughter to Silver Spring, Md., in 1996 to live with her grandson. The extended family relocated to Florida in 2005.
Shortly before Pirozhkova died, she completed a memoir about her life that her grandson said he plans to get published.
In her late 80s, she had once shared her "rules" for a long and happy life. They included eating less and having "good character."
In addition to her daughter and grandson, Pirozhkova is survived by a great-grandson.