DUBLIN (Reuters) - Irish building materials group CRH is likely to hold back on major acquisition activity for the rest of 2018 as it digests last year's deals, CEO Albert Manifold said on Thursday.

CRH committed to 5 billion euros (4.36 billion pounds) of deals last year, including the 3 billion euro purchase of Ash Grove Cement Co, which is due to close shortly.

The need for a pause to integrate the new businesses was one of the reasons CRH gave for opting instead to hand 1 billion euros back to shareholders in its first share buyback programme in a decade announced on Wednesday.

"If things go extremely well and extremely quickly (with the integration), I'd say you could be back there in the third quarter, fourth quarter... but I'd say pretty much for the remainder of this year," Manifold told reporters following the companies annual shareholder meeting, referring to the pause on major deals.

But he said smaller deals would still continue after CRH spent 150 million euros on six such transactions in the first quarter.

"The bolt-ons just come through, you'll do between 500 and 1 billion euros this year," Manifold said, referring to the smaller firms CRH routinely purchases. "But there will be no big stuff happening because all our focus and resources have to be focused on delivering that 5 billion," he said referring to the amount spent on deals last year.

(Reporting by Padraic Halpin; Editing by David Goodman and Jane Merriman)