A research at Oxford university finds:
More than half of Chinese infrastructure investments have “destroyed, not generated” economic value as the costs have been larger than the benefits
One argument has always been that infrastructure investment has been a major driver of Chinese economic growth over the past 35 years,
especially given the fact that recently China relies on state enterprises as policy tool to stimulate economic but been seen as thwarts effort to boost efficiency 
The aim is surely to prevent a sharp slowdown.
This time differs from the stimulus launched in 2008, which focused on using credit expansion to fund construction of new factories -> that included an investment boom by private companies, which account for 88 per cent of all manufacturing investment.
By contrast, 72 per cent of infrastructure investment comes from SOEs.
And this is all because currency policy no longer works
But there are also some defenses:
“Strong state-led infrastructure investment does not aggravate overcapacity,” “By creating final demand, it helps digest the inventory of industrial goods, as well as buffering overall investment and GDP growth. “
while “sliding private and manufacturing investment suggests the country has been on the right track of cutting excess capacity”
Therefore a debate is needed over the viability of China’s infrastructure-led growth model.
The favorite criticize for westerns has always been the debt:
Although some still insist “At the current rate of expansion, it is only a matter of time before some banks find themselves unable to fund all their assets safely,”
But over long years many have given up an acute financial crisis, rather predict a chronic, Japan-style malaise in which growth slows for years or even decades. 
Case of Japan seems somehow convincible
“The most obvious example is Japan after 1990. It had too much debt, all of which was domestic, and as a consequence its growth collapsed.”
Thus, many are now concerned that China’s debt could lead to a so-called balance-sheet recession — a term coined by Richard Koo of Nomura to describe Japan’s stagnation in the 1990s and 2000s.
When corporate debt reaches very high levels, conventional monetary policy loses its effectiveness because companies focus on paying down debt and refuse to borrow even at rock-bottom interest rates.
Let’s turn back to the paper
The core of the paper is an examination of the performance of individual infrastructure projects in China, which the authors compare to projects undertaken in other countries.
They find that infrastructure projects in China often cost more and take longer to complete than expected, and that planners often do not accurately forecast demand for the completed projects.
The basic ideas are:
“Far from being an engine of economic growth, the typical infrastructure investment fails to deliver a positive risk-adjusted return”
Hypothesis 1. Due to a propensity to cost overruns and benefit shortfalls, the typical infrastructure investment destroys economic value.
“Poorly managed infrastructure investments are a main explanation of surfacing economic and financial problems in China. We predict that, unless China shifts to a lower level of higher-quality infrastructure investments, the country is headed for an infrastructure-led national financial and economic crisis.”
“It is a myth that China grew thanks largely to heavy infrastructure investment. It grew due to bold economic liberalisation and institutional reforms, and this growth is now threatened by over-investment in low-grade infrastructure” 
Three quarters of all projects suffered a cost overrun, which has exacerbated the debt problem
They estimate three quarters of all projects suffered a cost overrun, which has exacerbated the debt problem -> a third of China’s $28.2tn debt load is attributable to such overruns.
“China’s relatively low official government debt-to-GDP ratio understates the actual debt burden the government carries for the following two reasons: corporate borrowing (125 per cent of China’s GDP) and financial institution borrowing (65 per cent of China’s GDP) are dominated by state-owned or state-controlled entities. The liabilities of these state-linked entities are ultimately governmental in nature if a liquidity crisis were to manifest.”
Ok no more debt, let’s check the infra itself
“The study is based on a sample of 95 road and rail infrastructure projects in China between 1984 and 2008. “
Here’s a big but basic problem that one could dissent: they are roads and rails!
“Even if an infrastructure project does not directly generate enough cash flow to cover its financing costs, they argue, positive externalities can spur enough economic activity that makes the project worthwhile.“
“For most of the past few decades, the bulk of Chinese infrastructure investment has served the overall economy reasonably well. If you compare China with most other developing countries, they would love to be in China’s shoes in terms of having all that infrastructure”
But one can still accuse for diminishing returns from additional infrastructure, as well as problems with excessive and wasteful infrastructure investment,
though a crisis looks less likely
“The authors’ data on individual infrastructure projects tell us that China is basically no worse and no better than the rest of the world in terms of managing infrastructure projects — just like everywhere else, they often run behind schedule and over budget”
And we actually have more attacks to this paper from economists:
“if China is no better and no worse than the rest of the world at planning and executing infrastructure projects, it is hard to see how this would lead it into an infrastructure-driven financial crisis. The problem must therefore surely be that China is spending far too much on infrastructure”
“But they don’t. In fact they present absolutely no statistical information about the level or growth rate of infrastructure spending in China. Instead they present the usual numbers about the rapid growth of total investment and debt in China, such as the figures on gross fixed capital formation in the national accounts. It should hardly need pointing out that gross fixed capital formation is not the same thing as infrastructure spending; infrastructure is only one component of gross fixed capital formation, most of which is housing and business capital expenditure.” 
Rather, a real issue should be:
Chinese infrastructure projects generate low financial returns, but have to repay debts at interest rates that are far too high.
the average return on assets of state-owned enterprises in infrastructure sectors is around 2%
the average interest rate that state-owned enterprises pay on their debt is around 5%.
the magnitude is sizable: 6-7 trillion yuan a year
By channeling a lot of essentially public-sector borrowing through financing channels normally used by private companies, China has created a large financial problem.
-> if the government does not want the projects to default then it needs to restructure the debt into lower-cost government obligations 
Many analysts now believe the best hope for dealing with inefficient SOEs is not to change them from the inside but to shrink their relative share of the economy. That means opening up protected industries to competition from private business and reducing the many advantages SOEs enjoy, especially access to finance.
“I don’t think SOEs can be ‘reformed’. They can only be downsized,” “Within China’s system of state capitalism, you can have less ‘state’ and more ‘capitalism’.”
They believe the People’s Bank of China will retain its ability to ward off crisis. By flooding the banking system with cash, the PBoC can ensure that banks remain liquid, even if non-performing loans rise sharply.
The greater risk from excess debt, they argue, is the Japan scenario: a “lost decade” of slow growth and deflation.
This is [a] ‘China myth’—that the country grew thanks largely to its heavy investment in infrastructure.
<- In the 1980s, China had poor infrastructure but turned in a superb economic performance. China built its infrastructure after—rather than before— many years of economic growth and accumulation of financial resources. The ‘China miracle’ happened not because it had glittering skyscrapers and modern highways but because bold economic liberalization and institutional reforms— especially agricultural reforms in the early 1980s—created competition and nurtured private entrepreneurship.
According to estimates by the former OECD economist Richard Herd, government and infrastructure sectors have usually accounted for 20-30% of gross fixed capital formation over the past couple of decades.
since infrastructure investment is still growing by around 20% annually, and returns on infrastructure investment could plausibly fall even further (capacity utilization at thermal power plants is already at a 20-year low due to excess capacity)