Ma Xiao, 53, can vividly remember his experience helping build the Cacuaco Social Housing Project in Angola 17 years ago, as workers lived in tents surrounded by uncleared land mines, swarms of mosquitoes, venomous serpents and mice coming and going at will.

Ma, an employee from Fifth Engineering of China Railway No 4 Engineering Group, was sent in May 2008 to work as the Party chief representing his firm in building 102 five-storey buildings in a project in the municipality of Cacuaco, Luanda province.

Angola's 27-year civil war ended in 2002, but mines laid during the conflict remained a pressing problem in some areas.

"I arrived with three other colleagues in May 2008, and later spent $100 to get a big pot from a Chinese company to start our meals," Ma said.

Earlier, in November 2007, CREC4 signed a contract with the Angolan government to build a social welfare housing project in Cacuaco, with the first phase ushering in nearly 10,000 apartments in 424 buildings, some government buildings and infrastructure, costing some $700 million. Construction began in 2008 and was completed in 2012.

"In order to start construction as soon as possible, our group started setting up tents in a desolate and rough wilderness," he said.

After seeing that vegetables were extremely expensive, they decided to plant vegetables by themselves, as the soil in Angola is very fertile and its climate is suitable for such crops.

In less than a year, some 1.1 hectares of land were cleared and planted with a variety of vegetables.

"I selected an experienced vegetable farmer from our team to lead several Angolan employees to tend to the crops," Ma said.

"Later on, we also raised sheep and chickens, and our 'vegetable garden' became famous," Ma said.

"In order to avoid venomous snakes, our technicians walked on stilts for surveying work and laying out lines. They could only move within designated safe areas, as they were surrounded by uncleared landmines," he said.

"We finally had a home," he said, adding that this lasted for some years, until the employees from CREC4 Fifth Engineering finally left Angola in October 2017 upon completing all their work.

"I can still remember our first Mid-Autumn Festival in Angola in the year 2008. We made our own moon cakes, and as the bright moon shone over our camps, everyone gathered on the playground for a get-together party to share our homesickness and our friendship," he said.

With the rapid development of the project, Ma's team members expanded fast, with dozens of professional teams, and 12 canteens for Chinese staff and 13 canteens for some 700 Angolan workers.

The construction work was very difficult, as at that time, Angola was seriously short of goods and materials, and the company had to ship most of the construction materials, including cement and steel, from China.

On Oct 31, 2012, the 2,240 units of 102 buildings undertaken by Ma's company were delivered for inspection on schedule.

"Upon delivery of the houses to the Angolans and seeing the joy of residents living in good homes, my heart was deeply moved and proud," Ma recalled.

While Ma had a rich experience in the scorching weather in the southern hemisphere, his colleague Wang Xiangzhou had a different one in the northern hemisphere.

Wang, now 51, helped build the Nalaikh-Choyr section of the 700-kilometer second highway in Mongolia 20 years ago.

Funded by the Asian Development Bank and running from Ulan Bator, the Mongolian capital, to Ereenhot in China's Inner Mongolia autonomous region, the second highway was the largest construction project in Mongolia at that time, and dubbed a "road of friendship" as a north-south artery.

The Nalaikh-Choyr section, undertaken by Wang's firm, cost $21.93 million. It started construction in March 2002 and was completed in September 2005, slashing the travel time between Ulan Bator and Choyr from the previous five hours to less than two hours.

"Our pressure was immense, as the work covered over 3 million cubic meters of roadbed earthwork, over 1 million cubic meters of sub-base and graded crushed stone, over 70,000 cubic meters of asphalt concrete, 171 culverts and three small bridges," recalled Wang.

"Since the construction work officially started, the CREC4 Fifth Engineering sent more than 400 excellent technical and management personnel, and provided over 200 units of advanced construction machinery and equipment for the job," he said.

But the conditions were harsh, as Mongolia can have temperatures as low as -40 C, he said, noting that snow begins in mid-September each year and stops in mid-June, leaving only some four months as a golden window for construction.

"Most of our living sites were temporarily built with wooden boards, so in our rooms, it's cold in winter and hot in summer, and we relied on coal stoves for heating in winter," he said, noting that every time they met a sandstorm, their blankets and tables would be covered with a thick layer of sand.

"Due to water shortages, water for daily use had to be supplied by truck. As the highway is located in the desolate Gobi Desert, we had beef and mutton all year round, with carrots, radishes and other vegetables being quite rare," Wang said.

"At that time, communications were underdeveloped and it was very hard to keep in touch with our family members," he noted.

"Once, we saw a heavy snowfall. Our truck, which was transporting construction materials, could not move as the road was covered in heavy snow and it was difficult to see where we were amid the sweeping wind," he recalled.

"Outside the truck cab, it was freezing with temperatures as low as — 30 C, and we really felt fear," Wang said, adding that fortunately, when the wind slowly abated around 2 pm, they finally returned to their campsites around 10 pm.

After spending four years in such an environment, Wang and his team members successfully completed their job.

"Although the work was arduous, it was also a blessing for my work and life, as we had solidified our friendships among us, and they can last a lifetime," he said.

At 6 pm on Sept 24, 2005, as the sunset cast a golden glow on the beautiful Mongolian grasslands, a completion ceremony of the Nalaikh-Choyr section was held with a large number of project participants.

The then Mongolian prime minister delivered a speech and expressed his gratitude for the hard work of the road builders, saying the government would continue to support Chinese companies to invest in and undertake projects in Mongolia.