ACA vs MLM: Which Is the Better Buy in 2026?
Last updated August 2026
Short answer
MLM is the larger of the two ($31.54B market cap): the incumbent the market prices for continued execution (23.38x forward earnings, beta 1.10). ACA is the smaller challenger ($7.11B), actually pricier on forward earnings (28.29x): more room to run, but more to prove. The real question is which set of drivers you believe, and whether owning one (or both) leaves you over-concentrated.
ACA vs MLM: the tie-breaker metrics
Same yardstick, side by side (as of August 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.
| Metric | ACA | MLM | What it tells you |
|---|---|---|---|
| Market cap | $7.11B | $31.54B | Size. The larger name is the incumbent; the smaller has more room to grow and more to prove. |
| Forward P/E | 28.29 | 23.38 | Valuation on next year's expected earnings, the same yardstick for both. Lower is cheaper for that growth; higher means the market is paying up. |
| Trailing P/E | 32.33 | 34.12 | Valuation on the last 12 months. A big drop from trailing to forward means the market expects earnings to jump, so more growth is already in the price. |
| Beta | 1.07 | 1.10 | Volatility vs the market. Above 1 swings harder than the index; below 1 is steadier. Higher beta means bigger drawdowns to hold through. |
| Price vs 52-week range | 96% of range | 1% of range | Where today's price sits between the 52-week low and high. Near the high is momentum with less margin of safety; near the low is out of favor or a discount, depending on why. |
| Price / book | 2.70 | 2.79 | How much you pay over book value. Very high can signal an asset-light, high-return business or a rich price. |
Reading it: MLM is the cheaper of the two on forward earnings, but cheaper is not the same as better. Pair the valuation with growth (how far the forward P/E sits below the trailing P/E) and risk (beta) before you decide.
Before you buy: how ACA and MLM affect your concentration
The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. ACA and MLM share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.
This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined ACA and MLM exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.
What does Arcosa (ACA) do?
Arcosa was spun out of Trinity Industries in late 2018 and has spent the years since reshaping itself from a diversified industrial into an infrastructure materials company. It now reports two segments. Construction Products sells aggregates, specialty materials such as recycled asphalt and lightweight aggregate, and construction site support, and generated roughly $357.0 million of revenue in the second quarter of 2026. Engineered Structures builds utility poles and steel structures, wind towers, telecom and traffic structures, and storage tanks, and generated roughly $301.7 million. The portfolio pruning has been aggressive: the steel components business went in 2025, and the barge business was sold on April 1, 2026 for approximately $450 million, producing a pre-tax gain of roughly $359.7 million and moving barge results into discontinued operations. On the other side of the ledger, the roughly $1.2 billion Stavola acquisition in late 2024 added asphalt and aggregates positions in the New York and New Jersey metro market.
What does Martin Marietta Materials (MLM) do?
Martin Marietta Materials is the second-largest construction aggregates producer in the United States, behind Vulcan Materials. The aggregates business model is identical to Vulcan: heavy aggregates products with high transport costs create local pricing power within each quarry's service area. Martin Marietta operates approximately 350 aggregates facilities across the US with concentration in Texas, Colorado, the Carolinas, and other high-growth states.
ACA vs MLM: how do they differ?
Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.
- ACA drivers: The CRH merger sets the price; Aggregates pricing over volume.
- MLM drivers: Federal infrastructure tailwind; Texas cement franchise.
Which fits which kind of investor
A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: The largest risk is deal failure. For MLM, construction cycle volatility.
ACA or MLM: which should you pick?
Growth-minded investors who believe the theme has years to run tend to accept the richer multiple for more upside; value-minded investors lean toward the cheaper forward earnings and steadier profile. Pick ACA if you believe its drivers more; MLM if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the ACA and MLM guides.
ACA vs MLM: the full fundamentals
ACA. Trailing net income of roughly $491 million and trailing EPS near $9.98 are inflated by the roughly $359.7 million pre-tax gain on the April 2026 barge sale, which makes the trailing P/E near 32x misleading as an operating multiple. Fiscal 2025 is the cleaner reference point: revenue of roughly $2.88 billion, operating income of roughly $341.9 million and EPS of about $4.24. The dividend is nominal at $0.20 a share, a yield near 0.14 percent, and full-year 2026 guidance has been withdrawn because of the merger.
MLM. Martin Marietta trades at a premium similar to (slightly below) Vulcan, reflecting the same durable aggregates pricing model, the federal infrastructure tailwind, and the Texas cement franchise. The valuation has expanded with the broader infrastructure thesis.
Headline figures (approximate, August 2026): ACA shows revenue (ttm) ~$2.9B, q2 2026 revenue (continuing ops) ~$658.7M, up ~2% year over year, q2 2026 adjusted ebitda ~$145.9M, ~22.1% margin, market cap / enterprise value ~$7.1B / ~$8.2B; MLM shows revenue (ttm) ~$6.7 billion, operating margin ~22%, net income (ttm) ~$1 billion, eps (ttm) ~$17.00.
The bottom line: ACA vs MLM
ACA and MLM are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined ACA and MLM exposure against your real portfolio. It is not an investment adviser.
Wondering how ACA or MLM fits the portfolio you already own? Walnut is an AI investing app that connects your brokerage read-only and answers questions like that about your actual holdings: overlap, concentration, and how each position tracks the S&P 500. Compare the best AI portfolio analyzers or see the best AI investing apps in 2026.
Investing in Arcosa with AI
Connect the broker you already use and ask Walnut's AI how ACA fits what you actually hold: whether you own it already through a fund, what it would do to your concentration, and how it has tracked the S&P 500. Read-only by default, and you approve anything before it reaches your broker.
FAQ
What is the difference between ACA and MLM?
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Arcosa was spun out of Trinity Industries in late 2018 and has spent the years since reshaping itself from a diversified industrial into an infrastructure materials company. Martin Marietta Materials is the second-largest construction aggregates producer in the United States, behind Vulcan Materials. They show up together because they share investment themes, but they are different businesses, so the better fit depends on which thesis you are expressing.
Is ACA or MLM the better stock?
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Neither is universally better. MLM is the larger incumbent; ACA is the smaller challenger and looks pricier on forward earnings. Walnut is informational, not investment advice. Compare what each does, the tie-breaker metrics above, and the risks, then decide which fits your thesis and what you already own.
Which is cheaper, ACA or MLM?
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On forward P/E (as of August 2026), ACA trades at 28.29x and MLM at 23.38x, so MLM is the cheaper of the two on next year's expected earnings. A lower multiple is not automatically the better buy: a richer valuation can be justified by faster growth, and a lower one can reflect real risk. Weigh the multiple against how fast each business is compounding.
Should you own both ACA and MLM?
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Because they share themes, owning both concentrates you in that theme. That can be intentional (a focused bet) or accidental (less diversification than it looks). Walnut can show your combined exposure across both, and whether adding either over-concentrates you, before you buy.
What are the risks of ACA vs MLM?
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ACA: The largest risk is deal failure. If the CRH transaction does not close, whether through the stockholder vote, antitrust review of overlapping aggregates positions, or a financing or regulatory delay past the expected first-quarter 2027 close, the share price would no longer be supported by the $150 offer and could revert toward where it traded before June 2026, well under the current level. Plaintiffs' firms including Monteverde & Associates have publicized investigations of the merger process; as of August 2026 those are solicitations rather than a filed securities-fraud complaint, but merger-related disclosure suits are common and can add noise. Underlying business risks remain: heavy exposure to Texas and Southwest construction weather and cycles, wind tower demand that depends on federal incentives and utility procurement, and leverage carried since the roughly $1.2 billion Stavola acquisition. Trailing earnings are also distorted by the roughly $359.7 million pre-tax barge gain, so headline trailing EPS and the trailing P/E overstate ongoing profitability. MLM: Construction cycle volatility. Energy costs affect operating margins. Texas market concentration creates regional exposure. Reserve permitting is increasingly difficult.
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Walnut is informational, not investment advice. This page is descriptive and not a recommendation to buy or sell ACA or MLM; figures are approximate and dated (as of August 2026). Verify current data before investing.